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| <a name="chrono.users_guide"></a><a class="link" href="users_guide.html" title="User's Guide">User's Guide</a> |
| </h2></div></div></div> |
| <div class="toc"><dl class="toc"> |
| <dt><span class="section"><a href="users_guide.html#chrono.users_guide.getting_started">Getting Started</a></span></dt> |
| <dt><span class="section"><a href="users_guide.html#chrono.users_guide.tutorial">Tutorial</a></span></dt> |
| <dt><span class="section"><a href="users_guide.html#chrono.users_guide.examples">Examples</a></span></dt> |
| <dt><span class="section"><a href="users_guide.html#chrono.users_guide.ext_references">External Resources</a></span></dt> |
| </dl></div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h3 class="title"> |
| <a name="chrono.users_guide.getting_started"></a><a class="link" href="users_guide.html#chrono.users_guide.getting_started" title="Getting Started">Getting Started</a> |
| </h3></div></div></div> |
| <div class="toc"><dl class="toc"> |
| <dt><span class="section"><a href="users_guide.html#chrono.users_guide.getting_started.install">Installing |
| Chrono</a></span></dt> |
| <dt><span class="section"><a href="users_guide.html#chrono.users_guide.getting_started.hello_world__">Hello |
| World! </a></span></dt> |
| </dl></div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h4 class="title"> |
| <a name="chrono.users_guide.getting_started.install"></a><a class="link" href="users_guide.html#chrono.users_guide.getting_started.install" title="Installing Chrono">Installing |
| Chrono</a> |
| </h4></div></div></div> |
| <h6> |
| <a name="chrono.users_guide.getting_started.install.h0"></a> |
| <span class="phrase"><a name="chrono.users_guide.getting_started.install.getting__emphasis_role__bold__boost_chrono__emphasis__"></a></span><a class="link" href="users_guide.html#chrono.users_guide.getting_started.install.getting__emphasis_role__bold__boost_chrono__emphasis__">Getting |
| <span class="bold"><strong>Boost.Chrono</strong></span> </a> |
| </h6> |
| <p> |
| <span class="bold"><strong>Boost.Chrono</strong></span> is in the latest Boost release |
| in the folder <code class="computeroutput"><span class="special">/</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">chrono</span></code>. |
| Documentation, tests and examples folder are at <code class="computeroutput"><span class="identifier">boost</span><span class="special">/</span><span class="identifier">libs</span><span class="special">/</span><span class="identifier">chrono</span><span class="special">/</span></code>. |
| </p> |
| <p> |
| You can also access the latest (unstable?) state from the <a href="https://svn.boost.org/svn/boost-trunk" target="_top">Boost |
| trunk</a> directories boost/chrono and libs/chrono. Just go to <a href="http://svn.boost.org/trac/boost/wiki/BoostSubversion" target="_top">here</a> |
| and follow the instructions there for anonymous SVN access. |
| </p> |
| <h6> |
| <a name="chrono.users_guide.getting_started.install.h1"></a> |
| <span class="phrase"><a name="chrono.users_guide.getting_started.install.where_to_install_boost_chrono__"></a></span><a class="link" href="users_guide.html#chrono.users_guide.getting_started.install.where_to_install_boost_chrono__">Where |
| to install Boost.Chrono? </a> |
| </h6> |
| <p> |
| The simple way is to decompress (or checkout from SVN) the files in your |
| BOOST_ROOT directory. |
| </p> |
| <h6> |
| <a name="chrono.users_guide.getting_started.install.h2"></a> |
| <span class="phrase"><a name="chrono.users_guide.getting_started.install.building_boost_chrono_"></a></span><a class="link" href="users_guide.html#chrono.users_guide.getting_started.install.building_boost_chrono_">Building |
| Boost.Chrono </a> |
| </h6> |
| <p> |
| <span class="bold"><strong>Boost.Chrono</strong></span> can be configured as a header-only |
| library defining <a class="link" href="reference.html#chrono.reference.cpp0x.chrono_chrono_hpp.conf.header_only" title="How to Build Boost.Chrono as a Header Only Library?"><code class="computeroutput"><span class="identifier">BOOST_CHRONO_HEADER_ONLY</span></code></a>. However |
| Boost.Chrono depends on the non header-only library Boost.System, so that |
| you will need to link with boost_system. |
| </p> |
| <p> |
| Boost.System has an undocumented feature (use of macro BOOST_ERROR_CODE_HEADER_ONLY) |
| to make it header only. |
| </p> |
| <p> |
| If <a class="link" href="reference.html#chrono.reference.cpp0x.chrono_chrono_hpp.conf.header_only" title="How to Build Boost.Chrono as a Header Only Library?"><code class="computeroutput"><span class="identifier">BOOST_CHRONO_HEADER_ONLY</span></code></a> is not |
| defined you need to compile it and build the library before use, for example |
| using: |
| </p> |
| <pre class="programlisting"><span class="identifier">bjam</span> <span class="identifier">libs</span><span class="special">/</span><span class="identifier">chrono</span><span class="special">/</span><span class="identifier">build</span> |
| </pre> |
| <h6> |
| <a name="chrono.users_guide.getting_started.install.h3"></a> |
| <span class="phrase"><a name="chrono.users_guide.getting_started.install.requirements"></a></span><a class="link" href="users_guide.html#chrono.users_guide.getting_started.install.requirements">Requirements</a> |
| </h6> |
| <p> |
| In particular, <span class="bold"><strong>Boost.Chrono</strong></span> depends on: |
| </p> |
| <div class="variablelist"> |
| <p class="title"><b></b></p> |
| <dl class="variablelist"> |
| <dt><span class="term"><a href="http://www.boost.org/libs/config" target="_top"><span class="bold"><strong>Boost.Config</strong></span></a></span></dt> |
| <dd><p> |
| for configuration purposes, ... |
| </p></dd> |
| <dt><span class="term"><a href="http://www.boost.org/libs/exception" target="_top"><span class="bold"><strong>Boost.Exception</strong></span></a></span></dt> |
| <dd><p> |
| for throw_exception, ... |
| </p></dd> |
| <dt><span class="term"><a href="http://www.boost.org/libs/integer" target="_top"><span class="bold"><strong>Boost.Integer</strong></span></a></span></dt> |
| <dd><p> |
| for cstdint conformance, ... |
| </p></dd> |
| <dt><span class="term"><a href="http://www.boost.org/libs/mpl" target="_top"><span class="bold"><strong>Boost.MPL</strong></span></a></span></dt> |
| <dd><p> |
| for MPL Assert and bool, logical ... |
| </p></dd> |
| <dt><span class="term"><a href="http://www.boost.org/libs/operators" target="_top"><span class="bold"><strong>Boost.Operators</strong></span></a></span></dt> |
| <dd><p> |
| for operators, ... |
| </p></dd> |
| <dt><span class="term"><a href="http://www.boost.org/libs/ratio" target="_top"><span class="bold"><strong>Boost.Ratio</strong></span></a></span></dt> |
| <dd><p> |
| for ratio, milli, micro, ... |
| </p></dd> |
| <dt><span class="term"><a href="http://www.boost.org/libs/system" target="_top"><span class="bold"><strong>Boost.System</strong></span></a></span></dt> |
| <dd><p> |
| for error_code, ... |
| </p></dd> |
| <dt><span class="term"><a href="http://www.boost.org/libs/type_traits" target="_top"><span class="bold"><strong>Boost.TypeTraits</strong></span></a></span></dt> |
| <dd><p> |
| for is_base, is_convertible, common_type, ... |
| </p></dd> |
| <dt><span class="term"><a href="http://www.boost.org/libs/utility" target="_top"><span class="bold"><strong>Boost.Utility/EnableIf</strong></span></a></span></dt> |
| <dd><p> |
| for enable_if, ... |
| </p></dd> |
| </dl> |
| </div> |
| <h6> |
| <a name="chrono.users_guide.getting_started.install.h4"></a> |
| <span class="phrase"><a name="chrono.users_guide.getting_started.install.building_an_executable_that_uses_boost_chrono_"></a></span><a class="link" href="users_guide.html#chrono.users_guide.getting_started.install.building_an_executable_that_uses_boost_chrono_">Building |
| an Executable that Uses Boost.Chrono </a> |
| </h6> |
| <p> |
| In addition to link with the <span class="bold"><strong>Boost.Chrono</strong></span> |
| library you need also to link with the <span class="bold"><strong>Boost.System</strong></span> |
| library. If <span class="bold"><strong>Boost.System</strong></span> is configured |
| defining BOOST_ERROR_CODE_HEADER_ONLY you will no need to link with it |
| as the dependent part is header only then. |
| </p> |
| <h6> |
| <a name="chrono.users_guide.getting_started.install.h5"></a> |
| <span class="phrase"><a name="chrono.users_guide.getting_started.install.exception_safety_"></a></span><a class="link" href="users_guide.html#chrono.users_guide.getting_started.install.exception_safety_">Exception |
| safety </a> |
| </h6> |
| <p> |
| All functions in the library are exception-neutral and provide strong guarantee |
| of exception safety as long as the underlying parameters provide it. |
| </p> |
| <h6> |
| <a name="chrono.users_guide.getting_started.install.h6"></a> |
| <span class="phrase"><a name="chrono.users_guide.getting_started.install.thread_safety_"></a></span><a class="link" href="users_guide.html#chrono.users_guide.getting_started.install.thread_safety_">Thread |
| safety </a> |
| </h6> |
| <p> |
| All functions in the library are thread-unsafe except when noted explicitly. |
| </p> |
| <p> |
| As Boost.Chrono doesn't use mutable global variables the thread-safety |
| analysis is limited to the access to each instance variable. It is not |
| thread safe to use a function that modifies the access to a user variable |
| if another can be reading or writing it. |
| </p> |
| <h6> |
| <a name="chrono.users_guide.getting_started.install.h7"></a> |
| <span class="phrase"><a name="chrono.users_guide.getting_started.install.tested_compilers_"></a></span><a class="link" href="users_guide.html#chrono.users_guide.getting_started.install.tested_compilers_">Tested |
| compilers </a> |
| </h6> |
| <p> |
| The implementation will eventually work with most C++03 conforming compilers. |
| Currently I use to test with on: |
| </p> |
| <p> |
| Windows with |
| </p> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> |
| MSVC 10.0 |
| </li></ul></div> |
| <p> |
| MinGW with |
| </p> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| GCC 4.5.0 |
| </li> |
| <li class="listitem"> |
| GCC 4.5.0 -std=c++0x |
| </li> |
| <li class="listitem"> |
| GCC 4.5.2 |
| </li> |
| <li class="listitem"> |
| GCC 4.5.2 -std=c++0x |
| </li> |
| <li class="listitem"> |
| GCC 4.6.0 |
| </li> |
| <li class="listitem"> |
| GCC 4.6.0 -std=c++0x |
| </li> |
| <li class="listitem"> |
| GCC 4.8.0 |
| </li> |
| <li class="listitem"> |
| GCC 4.8.0 -std=c++0x |
| </li> |
| </ul></div> |
| <p> |
| Ubuntu with * GCC 4.4.6 * GCC 4.4.6 -std=c++0x * GCC 4.5.4 * GCC 4.5.4 |
| -std=c++0x * GCC 4.6.1 * GCC 4.6.1 -std=c++0x * Intel 12.1.3 * Intel 12.1.3 |
| -std=c++0x |
| </p> |
| <p> |
| OsX with |
| </p> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| GCC 4.1.2 |
| </li> |
| <li class="listitem"> |
| GCC 4.6.2 |
| </li> |
| <li class="listitem"> |
| GCC 4.6.2 -std=c++0x |
| </li> |
| <li class="listitem"> |
| GCC 4.7.0 |
| </li> |
| <li class="listitem"> |
| GCC 4.7.0 -std=c++0x |
| </li> |
| <li class="listitem"> |
| GCC 4.7.1 |
| </li> |
| <li class="listitem"> |
| GCC 4.7.1 -std=c++0x |
| </li> |
| <li class="listitem"> |
| GCC 4.7.2 |
| </li> |
| <li class="listitem"> |
| GCC 4.7.2 -std=c++0x |
| </li> |
| <li class="listitem"> |
| GCC 4.8.0 |
| </li> |
| <li class="listitem"> |
| GCC 4.8.0 -std=c++0x |
| </li> |
| <li class="listitem"> |
| GCC 4.8.1 |
| </li> |
| <li class="listitem"> |
| GCC 4.8.1 -std=c++0x |
| </li> |
| <li class="listitem"> |
| clang 3.1 |
| </li> |
| <li class="listitem"> |
| clang 3.1 -std=c++0x -stdlib=libc++ |
| </li> |
| <li class="listitem"> |
| clang 3.2 |
| </li> |
| <li class="listitem"> |
| clang 3.2 -std=c++11 -stdlib=libc++ |
| </li> |
| </ul></div> |
| <p> |
| The committed code is tested with much more compilers. There are two compilers |
| (VACPP and Borland) that don't provide the needed features. Other as Intel |
| and Sun have some issues with i/o. While everything compiles and link correctly, |
| there are some runtime issues I have not cached yet. See the regression |
| tests for details. |
| </p> |
| <div class="note"><table border="0" summary="Note"> |
| <tr> |
| <td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../doc/src/images/note.png"></td> |
| <th align="left">Note</th> |
| </tr> |
| <tr><td align="left" valign="top"><p> |
| Please let us know how this works on other platforms/compilers. |
| </p></td></tr> |
| </table></div> |
| <div class="note"><table border="0" summary="Note"> |
| <tr> |
| <td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../doc/src/images/note.png"></td> |
| <th align="left">Note</th> |
| </tr> |
| <tr><td align="left" valign="top"><p> |
| Please send any questions, comments and bug reports to boost <at> |
| lists <dot> boost <dot> org. |
| </p></td></tr> |
| </table></div> |
| </div> |
| <div class="section"><div class="titlepage"><div><div><h4 class="title"> |
| <a name="chrono.users_guide.getting_started.hello_world__"></a><a class="link" href="users_guide.html#chrono.users_guide.getting_started.hello_world__" title="Hello World!">Hello |
| World! </a> |
| </h4></div></div></div></div> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h3 class="title"> |
| <a name="chrono.users_guide.tutorial"></a><a class="link" href="users_guide.html#chrono.users_guide.tutorial" title="Tutorial">Tutorial</a> |
| </h3></div></div></div> |
| <div class="toc"><dl class="toc"> |
| <dt><span class="section"><a href="users_guide.html#chrono.users_guide.tutorial.duration">Duration</a></span></dt> |
| <dt><span class="section"><a href="users_guide.html#chrono.users_guide.tutorial.clocks">Clocks</a></span></dt> |
| <dt><span class="section"><a href="users_guide.html#chrono.users_guide.tutorial.time_point">Time Point</a></span></dt> |
| <dt><span class="section"><a href="users_guide.html#chrono.users_guide.tutorial.specific_clocks">Specific |
| Clocks</a></span></dt> |
| <dt><span class="section"><a href="users_guide.html#chrono.users_guide.tutorial.i_o">I/O</a></span></dt> |
| </dl></div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h4 class="title"> |
| <a name="chrono.users_guide.tutorial.duration"></a><a class="link" href="users_guide.html#chrono.users_guide.tutorial.duration" title="Duration">Duration</a> |
| </h4></div></div></div> |
| <div class="toc"><dl class="toc"> |
| <dt><span class="section"><a href="users_guide.html#chrono.users_guide.tutorial.duration.so_what_exactly_is_a__duration__and_how_do_i_use_one_">So |
| What Exactly is a <code class="computeroutput"><span class="identifier">duration</span></code> |
| and How Do I Use One?</a></span></dt> |
| <dt><span class="section"><a href="users_guide.html#chrono.users_guide.tutorial.duration.what_happens_if_i_assign__m3___us3__to__minutes__instead_of__microseconds__">What |
| Happens if I Assign <code class="computeroutput"><span class="identifier">m3</span> <span class="special">+</span> <span class="identifier">us3</span></code> |
| to <code class="computeroutput"><span class="identifier">minutes</span></code> Instead of |
| <code class="computeroutput"><span class="identifier">microseconds</span></code>?</a></span></dt> |
| <dt><span class="section"><a href="users_guide.html#chrono.users_guide.tutorial.duration.but_what_if_the_truncation_behavior_is_what_i_want_to_do_">But |
| What if the Truncation Behavior is What I Want to Do?</a></span></dt> |
| <dt><span class="section"><a href="users_guide.html#chrono.users_guide.tutorial.duration.round">Rounding |
| functions</a></span></dt> |
| <dt><span class="section"><a href="users_guide.html#chrono.users_guide.tutorial.duration.trafficking_in_floating_point_durations">Trafficking |
| in floating-point Durations</a></span></dt> |
| <dt><span class="section"><a href="users_guide.html#chrono.users_guide.tutorial.duration.how_expensive_is_all_of_this_">How |
| Expensive is All of this?</a></span></dt> |
| <dt><span class="section"><a href="users_guide.html#chrono.users_guide.tutorial.duration.how_complicated_is_it_to_build_a_function_taking_a__duration__parameter_">How |
| Complicated is it to Build a Function Taking a <code class="computeroutput"><span class="identifier">duration</span></code> |
| Parameter?</a></span></dt> |
| <dt><span class="section"><a href="users_guide.html#chrono.users_guide.tutorial.duration.is_it_possible_for_the_user_to_pass_a___duration_to_a_function_with_the_units_being_ambiguous_">Is |
| it possible for the user to pass a <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> to a function with the |
| units being ambiguous?</a></span></dt> |
| <dt><span class="section"><a href="users_guide.html#chrono.users_guide.tutorial.duration.can_durations_overflow_">Can |
| Durations Overflow?</a></span></dt> |
| </dl></div> |
| <p> |
| The <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> is the heart of this |
| library. The interface that the user will see in everyday use is nearly |
| identical to that of <span class="bold"><strong>Boost.DateTime</strong></span> time |
| <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>s authored by Jeff Garland, |
| both in syntax and in behavior. This has been a very popular boost library |
| for 7 years. There is an enormous positive history with this interface. |
| </p> |
| <p> |
| The library consists of six units of time <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>: |
| </p> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">hours</span></code></a> |
| </li> |
| <li class="listitem"> |
| <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">minutes</span></code></a> |
| </li> |
| <li class="listitem"> |
| <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">seconds</span></code></a> |
| </li> |
| <li class="listitem"> |
| <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">milliseconds</span></code></a> |
| </li> |
| <li class="listitem"> |
| <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">microseconds</span></code></a> |
| </li> |
| <li class="listitem"> |
| <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">nanoseconds</span></code></a> |
| </li> |
| </ul></div> |
| <p> |
| These units were chosen as a subset of the boost library because they are |
| the most common units used when sleeping, waiting on a condition variable, |
| or waiting to obtain the lock on a mutex. Each of these units is nothing |
| but a thin wrapper around a signed integral count. That is, when you construct |
| <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">minutes</span></code></a><code class="computeroutput"><span class="special">(</span><span class="number">3</span><span class="special">)</span></code>, all that |
| happens is a <code class="computeroutput"><span class="number">3</span></code> is stored inside |
| <code class="computeroutput"><span class="identifier">minutes</span></code>. When you construct |
| <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">microseconds</span></code></a><code class="computeroutput"><span class="special">(</span><span class="number">3</span><span class="special">)</span></code>, all that |
| happens is a <code class="computeroutput"><span class="number">3</span></code> is stored inside |
| <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">microseconds</span></code></a>. |
| </p> |
| <p> |
| The only context in which these different types differ is when being converted |
| to one another. At this time, unit-specific compile-time conversion constants |
| are used to convert the source unit to the target unit. Only conversions |
| from coarser units to finer units are allowed (in Boost). This restriction |
| ensures that all conversions are always exact. That is, <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">microseconds</span></code></a> can always represent |
| any value <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">minutes</span></code></a> has. |
| </p> |
| <p> |
| In <span class="bold"><strong>Boost.DateTime</strong></span>, these units are united |
| via inheritance. <span class="bold"><strong>Boost.Chrono</strong></span> instead |
| unites these units through the class template <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>. That is, in <span class="bold"><strong>Boost.Chrono</strong></span> all six of the above units are nothing |
| but typedefs to different instantiations of <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>. This change from Boost.DateTime |
| has a far reaching positive impact, while not changing the syntax of the |
| everyday use at all. |
| </p> |
| <p> |
| The most immediate positive impact is that the library can immediately |
| generate any unit, with any precision it needs. This is sometimes necessary |
| when doing comparisons or arithmetic between <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>s of differing precision, |
| assuming one wants the comparison and arithmetic to be exact. |
| </p> |
| <p> |
| A secondary benefit is that by publishing the class template <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> interface, user code |
| can very easily create <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>s with any precision they |
| desire. The <code class="computeroutput"><span class="identifier">ratio</span></code> utility |
| is used to specify the precision, so as long as the precision can be expressed |
| by a rational constant with respect to seconds, this framework can exactly |
| represent it (one third of a second is no problem, and neither is one third |
| of a <code class="computeroutput"><span class="identifier">femto</span></code> second). All |
| of this utility and flexibility comes at no cost just by making use of |
| the no-run-time-overhead <code class="computeroutput"><span class="identifier">ratio</span></code> |
| facility. |
| </p> |
| <p> |
| In Boost.DateTime, <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">hours</span></code></a> does not have the same representation |
| as <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">nanoseconds</span></code></a>. The former is usually |
| represented with a <code class="computeroutput"><span class="keyword">long</span></code> whereas |
| a <code class="computeroutput"><span class="keyword">long</span> <span class="keyword">long</span></code> |
| is required for the latter. The reason for this is simply range. You don't |
| need many hours to cover an extremely large range of time. But this isn't |
| true of nanoseconds. Being able to reduce the sizeof overhead for some |
| units when possible, can be a significant performance advantage. |
| </p> |
| <p> |
| <span class="bold"><strong>Boost.Chrono</strong></span> continues, and generalizes |
| that philosophy. Not only can one specify the precision of a <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>, one can also specify |
| its representation. This can be any integral type, or even a floating-point |
| type. Or it can be a user-defined type which emulates an arithmetic type. |
| The six predefined units all use signed integral types as their representation. |
| And they all have a minimum range of ± 292 years. <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">nanoseconds</span></code></a> needs 64 bits to cover |
| that range. <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">hours</span></code></a> needs only 23 bits to cover |
| that range. |
| </p> |
| <div class="section"> |
| <div class="titlepage"><div><div><h5 class="title"> |
| <a name="chrono.users_guide.tutorial.duration.so_what_exactly_is_a__duration__and_how_do_i_use_one_"></a><a class="link" href="users_guide.html#chrono.users_guide.tutorial.duration.so_what_exactly_is_a__duration__and_how_do_i_use_one_" title="So What Exactly is a duration and How Do I Use One?">So |
| What Exactly is a <code class="computeroutput"><span class="identifier">duration</span></code> |
| and How Do I Use One?</a> |
| </h5></div></div></div> |
| <p> |
| A <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> has a representation |
| and a tick period (precision). |
| </p> |
| <pre class="programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">Rep</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Period</span> <span class="special">=</span> <code class="computeroutput"><span class="identifier">ratio</span></code><span class="special"><</span><span class="number">1</span><span class="special">></span> <span class="special">></span> <span class="keyword">class</span> <span class="identifier">duration</span><span class="special">;</span> |
| </pre> |
| <p> |
| The representation is simply any arithmetic type, or an emulation of |
| such a type. The representation stores a count of ticks. This count is |
| the only data member stored in a <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>. If the representation |
| is floating-point, it can store fractions of a tick to the precision |
| of the representation. The tick period is represented by a <code class="computeroutput"><span class="identifier">ratio</span></code> and is encoded into the <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>'s type, instead of |
| stored. The tick period only has an impact on the behavior of the <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> when a conversion between |
| different <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>s is attempted. The |
| tick period is completely ignored when simply doing arithmetic among |
| like <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>s. |
| </p> |
| <p> |
| <span class="bold"><strong>Example:</strong></span> |
| </p> |
| <pre class="programlisting"><span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a><span class="special"><</span><span class="keyword">long</span><span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">ratio</span><span class="special"><</span><span class="number">60</span><span class="special">></span> <span class="special">></span> <span class="identifier">minutes</span><span class="special">;</span> |
| <span class="identifier">minutes</span> <span class="identifier">m1</span><span class="special">(</span><span class="number">3</span><span class="special">);</span> <span class="comment">// m1 stores 3</span> |
| <span class="identifier">minutes</span> <span class="identifier">m2</span><span class="special">(</span><span class="number">2</span><span class="special">);</span> <span class="comment">// m2 stores 2</span> |
| <span class="identifier">minutes</span> <span class="identifier">m3</span> <span class="special">=</span> <span class="identifier">m1</span> <span class="special">+</span> <span class="identifier">m2</span><span class="special">;</span> <span class="comment">// m3 stores 5</span> |
| |
| <span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a><span class="special"><</span><span class="keyword">long</span> <span class="keyword">long</span><span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">micro</span><span class="special">></span> <span class="identifier">microseconds</span><span class="special">;</span> |
| <span class="identifier">microseconds</span> <span class="identifier">us1</span><span class="special">(</span><span class="number">3</span><span class="special">);</span> <span class="comment">// us1 stores 3</span> |
| <span class="identifier">microseconds</span> <span class="identifier">us2</span><span class="special">(</span><span class="number">2</span><span class="special">);</span> <span class="comment">// us2 stores 2</span> |
| <span class="identifier">microseconds</span> <span class="identifier">us3</span> <span class="special">=</span> <span class="identifier">us1</span> <span class="special">+</span> <span class="identifier">us2</span><span class="special">;</span> <span class="comment">// us3 stores 5</span> |
| |
| <span class="identifier">microseconds</span> <span class="identifier">us4</span> <span class="special">=</span> <span class="identifier">m3</span> <span class="special">+</span> <span class="identifier">us3</span><span class="special">;</span> <span class="comment">// us4 stores 300000005</span> |
| </pre> |
| <p> |
| In the final line of code above, there is an implicit conversion from |
| minutes to microseconds, resulting in a relatively large number of microseconds. |
| </p> |
| <p> |
| If you need to access the tick count within a <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>, there is a member |
| <code class="computeroutput"><span class="identifier">count</span><span class="special">()</span></code> |
| which simply returns the stored tick count. |
| </p> |
| <pre class="programlisting"><span class="keyword">long</span> <span class="keyword">long</span> <span class="identifier">tc</span> <span class="special">=</span> <span class="identifier">us4</span><span class="special">.</span><span class="identifier">count</span><span class="special">();</span> <span class="comment">// tc is 300000005</span> |
| </pre> |
| <p> |
| These <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>'s have very simple, |
| very predictable, and very observable behavior. After all, this is really |
| nothing but the time-tested interface of Jeff's boost time <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> library (unified with |
| templates instead of inheritance). |
| </p> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h5 class="title"> |
| <a name="chrono.users_guide.tutorial.duration.what_happens_if_i_assign__m3___us3__to__minutes__instead_of__microseconds__"></a><a class="link" href="users_guide.html#chrono.users_guide.tutorial.duration.what_happens_if_i_assign__m3___us3__to__minutes__instead_of__microseconds__" title="What Happens if I Assign m3 + us3 to minutes Instead of microseconds?">What |
| Happens if I Assign <code class="computeroutput"><span class="identifier">m3</span> <span class="special">+</span> <span class="identifier">us3</span></code> |
| to <code class="computeroutput"><span class="identifier">minutes</span></code> Instead of |
| <code class="computeroutput"><span class="identifier">microseconds</span></code>?</a> |
| </h5></div></div></div> |
| <pre class="programlisting"><span class="identifier">minutes</span> <span class="identifier">m4</span> <span class="special">=</span> <span class="identifier">m3</span> <span class="special">+</span> <span class="identifier">us3</span><span class="special">;</span> |
| </pre> |
| <p> |
| It won't compile! The rationale is that implicit truncation error should |
| not be allowed to happen. If this were to compile, then <code class="computeroutput"><span class="identifier">m4</span></code> would hold <code class="computeroutput"><span class="number">5</span></code>, |
| the same value as <code class="computeroutput"><span class="identifier">m3</span></code>. |
| The value associated with <code class="computeroutput"><span class="identifier">us3</span></code> |
| has been effectively ignored. This is similar to the problem of assigning |
| a double to an <code class="computeroutput"><span class="keyword">int</span></code>: the |
| fractional part gets silently discarded. |
| </p> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h5 class="title"> |
| <a name="chrono.users_guide.tutorial.duration.but_what_if_the_truncation_behavior_is_what_i_want_to_do_"></a><a class="link" href="users_guide.html#chrono.users_guide.tutorial.duration.but_what_if_the_truncation_behavior_is_what_i_want_to_do_" title="But What if the Truncation Behavior is What I Want to Do?">But |
| What if the Truncation Behavior is What I Want to Do?</a> |
| </h5></div></div></div> |
| <p> |
| There is a <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_cast" title="Non-Member Function duration_cast(duration)"><code class="computeroutput"><span class="identifier">duration_cast</span></code></a> facility to explicitly |
| ask for this behavior: |
| </p> |
| <pre class="programlisting"><span class="identifier">minutes</span> <span class="identifier">m4</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_cast" title="Non-Member Function duration_cast(duration)"><code class="computeroutput"><span class="identifier">duration_cast</span></code></a><span class="special"><</span><span class="identifier">minutes</span><span class="special">>(</span><span class="identifier">m3</span> <span class="special">+</span> <span class="identifier">us3</span><span class="special">);</span> <span class="comment">// m4.count() == 5</span> |
| </pre> |
| <p> |
| In general, one can perform <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> arithmetic at will. |
| If <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_cast" title="Non-Member Function duration_cast(duration)"><code class="computeroutput"><span class="identifier">duration_cast</span></code></a> isn't used, and |
| it compiles, the arithmetic is exact. If one wants to override this exact |
| arithmetic behavior, <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_cast" title="Non-Member Function duration_cast(duration)"><code class="computeroutput"><span class="identifier">duration_cast</span></code></a> can be used to |
| explicitly specify that desire. The <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_cast" title="Non-Member Function duration_cast(duration)"><code class="computeroutput"><span class="identifier">duration_cast</span></code></a> has the same efficiency |
| as the implicit conversion, and will even be exact as often as it can. |
| </p> |
| <p> |
| You can use <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_cast" title="Non-Member Function duration_cast(duration)"><code class="computeroutput"><span class="identifier">duration_cast</span></code></a><code class="computeroutput"><span class="special"><></span></code> |
| to convert the <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> into whatever units |
| you desire. This facility will round down (truncate) if an exact conversion |
| is not possible. For example: |
| </p> |
| <pre class="programlisting"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">nanoseconds</span></code></a> <span class="identifier">start</span><span class="special">;</span> |
| <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">nanoseconds</span></code></a> <span class="identifier">end</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">milliseconds</span></code></a> <span class="identifier">ms</span><span class="special">;</span> |
| <span class="identifier">ms</span> <span class="identifier">d</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_cast" title="Non-Member Function duration_cast(duration)"><code class="computeroutput"><span class="identifier">duration_cast</span></code></a><span class="special"><</span><span class="identifier">ms</span><span class="special">>(</span><span class="identifier">end</span> <span class="special">-</span> <span class="identifier">start</span><span class="special">);</span> |
| |
| <span class="comment">// d now holds the number of milliseconds from start to end.</span> |
| |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">ms</span><span class="special">.</span><span class="identifier">count</span><span class="special">()</span> <span class="special"><<</span> <span class="string">"ms\n"</span><span class="special">;</span> |
| </pre> |
| <p> |
| We can convert to <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">nanoseconds</span></code></a>, or some integral-based |
| duration which <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">nanoseconds</span></code></a> will always exactly |
| convert to, then <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_cast" title="Non-Member Function duration_cast(duration)"><code class="computeroutput"><span class="identifier">duration_cast</span></code></a><code class="computeroutput"><span class="special"><></span></code> |
| is unnecessary: |
| </p> |
| <pre class="programlisting"><span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">nanoseconds</span></code></a> <span class="identifier">ns</span><span class="special">;</span> |
| <span class="identifier">ns</span> <span class="identifier">d</span> <span class="special">=</span> <span class="identifier">end</span> <span class="special">-</span> <span class="identifier">start</span><span class="special">;</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">ns</span><span class="special">.</span><span class="identifier">count</span><span class="special">()</span> <span class="special"><<</span> <span class="string">"ns\n"</span><span class="special">;</span> |
| </pre> |
| <p> |
| If you need seconds with a floating-point representation you can also |
| eliminate the <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_cast" title="Non-Member Function duration_cast(duration)"><code class="computeroutput"><span class="identifier">duration_cast</span></code></a><code class="computeroutput"><span class="special"><></span></code>: |
| </p> |
| <pre class="programlisting"><span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a><span class="special"><</span><span class="keyword">double</span><span class="special">></span> <span class="identifier">sec</span><span class="special">;</span> <span class="comment">// seconds, stored with a double</span> |
| <span class="identifier">sec</span> <span class="identifier">d</span> <span class="special">=</span> <span class="identifier">end</span> <span class="special">-</span> <span class="identifier">start</span><span class="special">;</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">sec</span><span class="special">.</span><span class="identifier">count</span><span class="special">()</span> <span class="special"><<</span> <span class="string">"s\n"</span><span class="special">;</span> |
| </pre> |
| <p> |
| If you're not sure if you need <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_cast" title="Non-Member Function duration_cast(duration)"><code class="computeroutput"><span class="identifier">duration_cast</span></code></a><code class="computeroutput"><span class="special"><></span></code> |
| or not, feel free to try it without. If the conversion is exact, or if |
| the destination has a floating-point representation, it will compile: |
| else it will not compile. |
| </p> |
| <p> |
| If you need to use <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_cast" title="Non-Member Function duration_cast(duration)"><code class="computeroutput"><span class="identifier">duration_cast</span></code></a><code class="computeroutput"><span class="special"><></span></code>, |
| but want to round up, instead of down when the conversion is inexact, |
| here is a handy little helper function to do so. Writing it is actually |
| a good starter project for understanding <span class="bold"><strong>Boost.Chrono</strong></span>: |
| </p> |
| <pre class="programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">ToDuration</span></code></a><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Rep</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Period</span><span class="special">></span> |
| <span class="identifier">ToDuration</span> |
| <span class="identifier">round_up</span><span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a><span class="special"><</span><span class="identifier">Rep</span><span class="special">,</span> <span class="identifier">Period</span><span class="special">></span> <span class="identifier">d</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="comment">// first round down</span> |
| <span class="identifier">ToDuration</span> <span class="identifier">result</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_cast" title="Non-Member Function duration_cast(duration)"><code class="computeroutput"><span class="identifier">duration_cast</span></code></a><span class="special"><</span><span class="identifier">ToDuration</span><span class="special">>(</span><span class="identifier">d</span><span class="special">);</span> |
| <span class="keyword">if</span> <span class="special">(</span><span class="identifier">result</span> <span class="special"><</span> <span class="identifier">d</span><span class="special">)</span> <span class="comment">// comparisons are *always* exact</span> |
| <span class="special">++</span><span class="identifier">result</span><span class="special">;</span> <span class="comment">// increment by one tick period</span> |
| <span class="keyword">return</span> <span class="identifier">result</span><span class="special">;</span> |
| <span class="special">}</span> |
| |
| <span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">milliseconds</span></code></a> <span class="identifier">ms</span><span class="special">;</span> |
| <span class="identifier">ms</span> <span class="identifier">d</span> <span class="special">=</span> <span class="identifier">round_up</span><span class="special"><</span><span class="identifier">ms</span><span class="special">>(</span><span class="identifier">end</span> <span class="special">-</span> <span class="identifier">start</span><span class="special">);</span> |
| <span class="comment">// d now holds the number of milliseconds from start to end, rounded up.</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">ms</span><span class="special">.</span><span class="identifier">count</span><span class="special">()</span> <span class="special"><<</span> <span class="string">"ms\n"</span><span class="special">;</span> |
| </pre> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h5 class="title"> |
| <a name="chrono.users_guide.tutorial.duration.round"></a><a class="link" href="users_guide.html#chrono.users_guide.tutorial.duration.round" title="Rounding functions">Rounding |
| functions</a> |
| </h5></div></div></div> |
| <p> |
| <span class="bold"><strong>Boost.Chrono</strong></span> provides few simple rounding |
| utility functions for working with durations. |
| </p> |
| <pre class="programlisting"><span class="comment">// round down</span> |
| <span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">To</span></code></a><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Rep</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Period</span><span class="special">></span> |
| <span class="identifier">To</span> |
| <span class="identifier">floor</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">duration</span><span class="special"><</span><span class="identifier">Rep</span><span class="special">,</span> <span class="identifier">Period</span><span class="special">>&</span> <span class="identifier">d</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="keyword">return</span> <span class="identifier">duration_cast</span><span class="special"><</span><span class="identifier">To</span><span class="special">>(</span><span class="identifier">d</span><span class="special">);</span> |
| <span class="special">}</span> |
| |
| <span class="comment">// round to nearest, to even on tie</span> |
| <span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">To</span></code></a><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Rep</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Period</span><span class="special">></span> |
| <span class="identifier">To</span> |
| <span class="identifier">round</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">duration</span><span class="special"><</span><span class="identifier">Rep</span><span class="special">,</span> <span class="identifier">Period</span><span class="special">>&</span> <span class="identifier">d</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="identifier">To</span> <span class="identifier">t0</span> <span class="special">=</span> <span class="identifier">duration_cast</span><span class="special"><</span><span class="identifier">To</span><span class="special">>(</span><span class="identifier">d</span><span class="special">);</span> |
| <span class="identifier">To</span> <span class="identifier">t1</span> <span class="special">=</span> <span class="identifier">t0</span><span class="special">;</span> |
| <span class="special">++</span><span class="identifier">t1</span><span class="special">;</span> |
| <span class="identifier">BOOST_AUTO</span><span class="special">(</span><span class="identifier">diff0</span><span class="special">,</span> <span class="identifier">d</span> <span class="special">-</span> <span class="identifier">t0</span><span class="special">);</span> |
| <span class="identifier">BOOST_AUTO</span><span class="special">(</span><span class="identifier">diff1</span><span class="special">,</span> <span class="identifier">t1</span> <span class="special">-</span> <span class="identifier">d</span><span class="special">);</span> |
| <span class="keyword">if</span> <span class="special">(</span><span class="identifier">diff0</span> <span class="special">==</span> <span class="identifier">diff1</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="keyword">if</span> <span class="special">(</span><span class="identifier">t0</span><span class="special">.</span><span class="identifier">count</span><span class="special">()</span> <span class="special">&</span> <span class="number">1</span><span class="special">)</span> |
| <span class="keyword">return</span> <span class="identifier">t1</span><span class="special">;</span> |
| <span class="keyword">return</span> <span class="identifier">t0</span><span class="special">;</span> |
| <span class="special">}</span> |
| <span class="keyword">else</span> <span class="keyword">if</span> <span class="special">(</span><span class="identifier">diff0</span> <span class="special"><</span> <span class="identifier">diff1</span><span class="special">)</span> |
| <span class="keyword">return</span> <span class="identifier">t0</span><span class="special">;</span> |
| <span class="keyword">return</span> <span class="identifier">t1</span><span class="special">;</span> |
| <span class="special">}</span> |
| <span class="comment">// round up</span> |
| <span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">To</span></code></a><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Rep</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Period</span><span class="special">></span> |
| <span class="identifier">To</span> |
| <span class="identifier">ceil</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">duration</span><span class="special"><</span><span class="identifier">Rep</span><span class="special">,</span> <span class="identifier">Period</span><span class="special">>&</span> <span class="identifier">d</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="identifier">To</span> <span class="identifier">t</span> <span class="special">=</span> <span class="identifier">duration_cast</span><span class="special"><</span><span class="identifier">To</span><span class="special">>(</span><span class="identifier">d</span><span class="special">);</span> |
| <span class="keyword">if</span> <span class="special">(</span><span class="identifier">t</span> <span class="special"><</span> <span class="identifier">d</span><span class="special">)</span> |
| <span class="special">++</span><span class="identifier">t</span><span class="special">;</span> |
| <span class="keyword">return</span> <span class="identifier">t</span><span class="special">;</span> |
| <span class="special">}</span> |
| </pre> |
| <p> |
| The beauty of the chrono library is the ease and accuracy with which |
| such conversions can be made. For example to convert from <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">milliseconds</span></code></a> (<code class="computeroutput"><span class="number">1</span><span class="special">/</span><span class="number">1000</span></code> |
| of a second), to <code class="computeroutput"><span class="number">1</span><span class="special">/</span><span class="number">30</span></code> of a second, one must multiply the milliseconds |
| by <code class="computeroutput"><span class="number">0.03</span></code>. It is common knowledge |
| that you can't exactly represent <code class="computeroutput"><span class="number">0.03</span></code> |
| in a computer. Nevertheless round will exactly (with no round off error) |
| detect a tie and round to even when this happens. The differences <code class="computeroutput"><span class="identifier">diff0</span></code> and <code class="computeroutput"><span class="identifier">diff1</span></code> |
| are not approximate, but exact differences, even when <code class="computeroutput"><span class="identifier">d</span></code> |
| has the units of millisecond and <code class="computeroutput"><span class="identifier">To</span></code> |
| is <code class="computeroutput"><span class="number">1</span><span class="special">/</span><span class="number">30</span></code> of a second. The unit of <code class="computeroutput"><span class="identifier">diff0</span></code> and <code class="computeroutput"><span class="identifier">diff1</span></code> |
| is <code class="computeroutput"><span class="number">1</span><span class="special">/</span><span class="number">3000</span></code> of a second which both millisecond |
| and <code class="computeroutput"><span class="number">1</span><span class="special">/</span><span class="number">30</span></code> of a second exactly convert to (with |
| no truncation error). |
| </p> |
| <p> |
| Similarly, the comparison <code class="computeroutput"><span class="identifier">t</span> |
| <span class="special"><</span> <span class="identifier">d</span></code> |
| in <a class="link" href="reference.html#chrono.reference.round.ceil_hpp" title="Header <boost/chrono/ceil.hpp>"><code class="computeroutput"><span class="identifier">ceil</span></code></a> |
| is exact, even when there is no exact conversion between <code class="computeroutput"><span class="identifier">t</span></code> and <code class="computeroutput"><span class="identifier">d</span></code>. |
| Example use of rounding functions |
| </p> |
| <pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">iostream</span><span class="special">></span> |
| <span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">chrono</span><span class="special">/</span><span class="identifier">chrono_io</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> |
| <span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">chrono</span><span class="special">/</span><span class="identifier">floor</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> |
| <span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">chrono</span><span class="special">/</span><span class="identifier">round</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> |
| <span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">chrono</span><span class="special">/</span><span class="identifier">ceil</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> |
| |
| <span class="keyword">int</span> <span class="identifier">main</span><span class="special">()</span> |
| <span class="special">{</span> |
| <span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">;</span> |
| <span class="identifier">milliseconds</span> <span class="identifier">ms</span><span class="special">(</span><span class="number">2500</span><span class="special">);</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">floor</span><span class="special"><</span><span class="identifier">seconds</span><span class="special">>(</span><span class="identifier">ms</span><span class="special">)</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">round</span><span class="special"><</span><span class="identifier">seconds</span><span class="special">>(</span><span class="identifier">ms</span><span class="special">)</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">ceil</span><span class="special"><</span><span class="identifier">seconds</span><span class="special">>(</span><span class="identifier">ms</span><span class="special">)</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> |
| <span class="identifier">ms</span> <span class="special">=</span> <span class="identifier">milliseconds</span><span class="special">(</span><span class="number">2516</span><span class="special">);</span> |
| <span class="keyword">typedef</span> <span class="identifier">duration</span><span class="special"><</span><span class="keyword">long</span><span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">ratio</span><span class="special"><</span><span class="number">1</span><span class="special">,</span> <span class="number">30</span><span class="special">></span> <span class="special">></span> <span class="identifier">frame_rate</span><span class="special">;</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">floor</span><span class="special"><</span><span class="identifier">frame_rate</span><span class="special">>(</span><span class="identifier">ms</span><span class="special">)</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">round</span><span class="special"><</span><span class="identifier">frame_rate</span><span class="special">>(</span><span class="identifier">ms</span><span class="special">)</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">ceil</span><span class="special"><</span><span class="identifier">frame_rate</span><span class="special">>(</span><span class="identifier">ms</span><span class="special">)</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> |
| |
| <span class="keyword">return</span> <span class="number">0</span><span class="special">;</span> |
| <span class="special">}</span> |
| </pre> |
| <p> |
| The output of this program should be |
| </p> |
| <pre class="programlisting"><span class="number">2</span> <span class="identifier">seconds</span> |
| <span class="number">2</span> <span class="identifier">seconds</span> |
| <span class="number">3</span> <span class="identifier">seconds</span> |
| <span class="number">75</span> <span class="special">[</span><span class="number">1</span><span class="special">/</span><span class="number">30</span><span class="special">]</span><span class="identifier">seconds</span> |
| <span class="number">75</span> <span class="special">[</span><span class="number">1</span><span class="special">/</span><span class="number">30</span><span class="special">]</span><span class="identifier">seconds</span> |
| <span class="number">76</span> <span class="special">[</span><span class="number">1</span><span class="special">/</span><span class="number">30</span><span class="special">]</span><span class="identifier">seconds</span> |
| </pre> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h5 class="title"> |
| <a name="chrono.users_guide.tutorial.duration.trafficking_in_floating_point_durations"></a><a class="link" href="users_guide.html#chrono.users_guide.tutorial.duration.trafficking_in_floating_point_durations" title="Trafficking in floating-point Durations">Trafficking |
| in floating-point Durations</a> |
| </h5></div></div></div> |
| <p> |
| I don't want to deal with writing <code class="computeroutput"><span class="identifier">duration_cast</span></code> |
| all over the place. I'm content with the precision of my floating-point |
| representation. |
| </p> |
| <p> |
| Not a problem. When the destination of a conversion has floating-point |
| representation, all conversions are allowed to happen implicitly. |
| </p> |
| <pre class="programlisting"><span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a><span class="special"><</span><span class="keyword">double</span><span class="special">,</span> <code class="computeroutput"><span class="identifier">ratio</span></code><span class="special"><</span><span class="number">60</span><span class="special">></span> <span class="special">></span> <span class="identifier">dminutes</span><span class="special">;</span> |
| <span class="identifier">dminutes</span> <span class="identifier">dm4</span> <span class="special">=</span> <span class="identifier">m3</span> <span class="special">+</span> <span class="identifier">us3</span><span class="special">;</span> <span class="comment">// dm4.count() == 5.000000083333333</span> |
| </pre> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h5 class="title"> |
| <a name="chrono.users_guide.tutorial.duration.how_expensive_is_all_of_this_"></a><a class="link" href="users_guide.html#chrono.users_guide.tutorial.duration.how_expensive_is_all_of_this_" title="How Expensive is All of this?">How |
| Expensive is All of this?</a> |
| </h5></div></div></div> |
| <p> |
| If you were writing these conversions by hand, you could not make it |
| more efficient. The use of <code class="computeroutput"><span class="identifier">ratio</span></code> |
| ensures that all conversion constants are simplified as much as possible |
| at compile-time. This usually results in the numerator or denominator |
| of the conversion factor simplifying to <code class="computeroutput"><span class="number">1</span></code>, |
| and being subsequently ignored in converting the run-time values of the |
| tick counts. |
| </p> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h5 class="title"> |
| <a name="chrono.users_guide.tutorial.duration.how_complicated_is_it_to_build_a_function_taking_a__duration__parameter_"></a><a class="link" href="users_guide.html#chrono.users_guide.tutorial.duration.how_complicated_is_it_to_build_a_function_taking_a__duration__parameter_" title="How Complicated is it to Build a Function Taking a duration Parameter?">How |
| Complicated is it to Build a Function Taking a <code class="computeroutput"><span class="identifier">duration</span></code> |
| Parameter?</a> |
| </h5></div></div></div> |
| <p> |
| There are several options open to the user: |
| </p> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> |
| If the author of the function wants to accept any <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>, and is willing |
| to work in floating-point <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>s, he can simply |
| use any floating-point <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> as the parameter: |
| </li></ul></div> |
| <pre class="programlisting"><span class="keyword">void</span> <span class="identifier">f</span><span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">duration</span><span class="special"><</span><span class="keyword">double</span><span class="special">></span> <span class="identifier">d</span><span class="special">)</span> <span class="comment">// accept floating-point seconds</span> |
| <span class="special">{</span> |
| <span class="comment">// d.count() == 3.e-6 when passed boost::chrono::microseconds(3)</span> |
| <span class="special">}</span> |
| |
| <span class="identifier">f</span><span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">microseconds</span><span class="special">(</span><span class="number">3</span><span class="special">));</span> |
| </pre> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> |
| If the author of the function wants to traffic only in integral |
| <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>s, and is content |
| with handling nothing finer than say nanoseconds (just as an example), |
| he can simply specify nanoseconds as the parameter: |
| </li></ul></div> |
| <pre class="programlisting"><span class="keyword">void</span> <span class="identifier">f</span><span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">nanoseconds</span> <span class="identifier">d</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="comment">// d.count() == 3000 when passed boost::chrono::microseconds(3)</span> |
| <span class="special">}</span> |
| |
| <span class="identifier">f</span><span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">microseconds</span><span class="special">(</span><span class="number">3</span><span class="special">));</span> |
| </pre> |
| <p> |
| In this design, if the client wants to pass in a floating-point <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>, or a <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> of finer precision |
| than nanoseconds, then the client is responsible for choosing his own |
| rounding mode in the conversion to nanoseconds. |
| </p> |
| <pre class="programlisting"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a><span class="special"><</span><span class="keyword">double</span><span class="special">></span> <span class="identifier">s</span><span class="special">(</span><span class="number">1.</span><span class="special">/</span><span class="number">3</span><span class="special">);</span> <span class="comment">// 1/3 of a second</span> |
| <span class="identifier">f</span><span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">duration_cast</span><span class="special"><</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">nanoseconds</span><span class="special">>(</span><span class="identifier">s</span><span class="special">));</span> <span class="comment">// round towards zero in conversion to nanoseconds</span> |
| </pre> |
| <p> |
| In the example above, the client of f has chosen "round towards |
| zero" as the desired rounding mode to nanoseconds. If the client |
| has a <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> that won't exactly |
| convert to nanoseconds, and fails to choose how the conversion will take |
| place, the compiler will refuse the call: |
| </p> |
| <pre class="programlisting"><span class="identifier">f</span><span class="special">(</span><span class="identifier">s</span><span class="special">);</span> <span class="comment">// does not compile</span> |
| </pre> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> |
| If the author of the function wants to accept any <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>, but wants to work |
| with integral representations and wants to control the rounding mode |
| internally, then he can template the function: |
| </li></ul></div> |
| <pre class="programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">Rep</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Period</span><span class="special">></span> |
| <span class="keyword">void</span> <span class="identifier">f</span><span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a><span class="special"><</span><span class="identifier">Rep</span><span class="special">,</span> <span class="identifier">Period</span><span class="special">></span> <span class="identifier">d</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="comment">// convert d to nanoseconds, rounding up if it is not an exact conversion</span> |
| <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">nanoseconds</span> <span class="identifier">ns</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">duration_cast</span><span class="special"><</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">nanoseconds</span><span class="special">>(</span><span class="identifier">d</span><span class="special">);</span> |
| <span class="keyword">if</span> <span class="special">(</span><span class="identifier">ns</span> <span class="special"><</span> <span class="identifier">d</span><span class="special">)</span> |
| <span class="special">++</span><span class="identifier">ns</span><span class="special">;</span> |
| <span class="comment">// ns.count() == 333333334 when passed 1/3 of a floating-point second</span> |
| <span class="special">}</span> |
| |
| <span class="identifier">f</span><span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a><span class="special"><</span><span class="keyword">double</span><span class="special">>(</span><span class="number">1.</span><span class="special">/</span><span class="number">3</span><span class="special">));</span> |
| </pre> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> |
| If the author in the example does not want to accept floating-point |
| based <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>s, he can enforce |
| that behavior like so: |
| </li></ul></div> |
| <pre class="programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">Period</span><span class="special">></span> |
| <span class="keyword">void</span> <span class="identifier">f</span><span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a><span class="special"><</span><span class="keyword">long</span> <span class="keyword">long</span><span class="special">,</span> <span class="identifier">Period</span><span class="special">></span> <span class="identifier">d</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="comment">// convert d to nanoseconds, rounding up if it is not an exact conversion</span> |
| <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">nanoseconds</span> <span class="identifier">ns</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">duration_cast</span><span class="special"><</span><span class="identifier">nanoseconds</span><span class="special">>(</span><span class="identifier">d</span><span class="special">);</span> |
| <span class="keyword">if</span> <span class="special">(</span><span class="identifier">ns</span> <span class="special"><</span> <span class="identifier">d</span><span class="special">)</span> |
| <span class="special">++</span><span class="identifier">ns</span><span class="special">;</span> |
| <span class="comment">// ns.count() == 333333334 when passed 333333333333 picoseconds</span> |
| <span class="special">}</span> |
| <span class="comment">// About 1/3 of a second worth of picoseconds</span> |
| <span class="identifier">f</span><span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a><span class="special"><</span><span class="keyword">long</span> <span class="keyword">long</span><span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">pico</span><span class="special">>(</span><span class="number">333333333333</span><span class="special">));</span> |
| </pre> |
| <p> |
| Clients with floating-point <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>s who want to use f |
| will now have to convert to an integral <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> themselves before passing |
| the result to f. |
| </p> |
| <p> |
| In summary, the author of f has quite a bit of flexibility and control |
| in the interface he wants to provide his clients with, and easy options |
| for manipulating that <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> internal to his function. |
| </p> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h5 class="title"> |
| <a name="chrono.users_guide.tutorial.duration.is_it_possible_for_the_user_to_pass_a___duration_to_a_function_with_the_units_being_ambiguous_"></a><a class="link" href="users_guide.html#chrono.users_guide.tutorial.duration.is_it_possible_for_the_user_to_pass_a___duration_to_a_function_with_the_units_being_ambiguous_" title="Is it possible for the user to pass a duration to a function with the units being ambiguous?">Is |
| it possible for the user to pass a <code class="computeroutput"><span class="identifier">duration</span></code> to a function with the |
| units being ambiguous?</a> |
| </h5></div></div></div> |
| <p> |
| No. No matter which option the author of <code class="computeroutput"><span class="identifier">f</span></code> |
| chooses above, the following client code will not compile: |
| </p> |
| <pre class="programlisting"><span class="identifier">f</span><span class="special">(</span><span class="number">3</span><span class="special">);</span> <span class="comment">// Will not compile, 3 is not implicitly convertible to any __duration</span> |
| </pre> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h5 class="title"> |
| <a name="chrono.users_guide.tutorial.duration.can_durations_overflow_"></a><a class="link" href="users_guide.html#chrono.users_guide.tutorial.duration.can_durations_overflow_" title="Can Durations Overflow?">Can |
| Durations Overflow?</a> |
| </h5></div></div></div> |
| <p> |
| This depend on the representation. The default typedefs uses a representation |
| that don't handle overflows. The user can define his own representation |
| that manage overflow as required by its application. |
| </p> |
| </div> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h4 class="title"> |
| <a name="chrono.users_guide.tutorial.clocks"></a><a class="link" href="users_guide.html#chrono.users_guide.tutorial.clocks" title="Clocks">Clocks</a> |
| </h4></div></div></div> |
| <p> |
| While <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>s only have precision |
| and representation to concern themselves, clocks and <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a>s are intimately related |
| and refer to one another. Because clocks are simpler to explain, we will |
| do so first without fully explaining <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a>s. Once clocks are introduced, |
| it will be easier to then fill in what a <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a> is. |
| </p> |
| <p> |
| A clock is a concept which bundles 3 things: |
| </p> |
| <div class="orderedlist"><ol class="orderedlist" type="1"> |
| <li class="listitem"> |
| A concrete <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> type. |
| </li> |
| <li class="listitem"> |
| A concrete <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a> type. |
| </li> |
| <li class="listitem"> |
| A function called now() which returns the concrete <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a>. |
| </li> |
| </ol></div> |
| <p> |
| The standard defines three system-wide clocks that are associated to the |
| computer time. |
| </p> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.system_clock" title="Class system_clock"><code class="computeroutput"><span class="identifier">system_clock</span></code></a> represents system-wide |
| realtime clock that can be synchronized with an external clock. |
| </li> |
| <li class="listitem"> |
| <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.steady_clock" title="Class steady_clock"><code class="computeroutput"><span class="identifier">steady_clock</span></code></a> can not be changed |
| explicitly and the time since the initial epoch increase in a steady |
| way. |
| </li> |
| <li class="listitem"> |
| <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.high_resolution_clock" title="Class high_resolution_clock"><code class="computeroutput"><span class="identifier">high_resolution_clock</span></code></a> intend |
| to use the system-wide clock provided by the platform with the highest |
| resolution. |
| </li> |
| </ul></div> |
| <p> |
| <span class="bold"><strong>Boost.Chrono</strong></span> provides them when supported |
| by the underlying platform. A given platform may not be able to supply |
| all three of these clocks. |
| </p> |
| <p> |
| The library adds some clocks that are specific to a process or a thread, |
| that is there is a clock per process or per thread. |
| </p> |
| <p> |
| The user is also able to easily create more clocks. |
| </p> |
| <p> |
| Given a clock named Clock, it will have: |
| </p> |
| <pre class="programlisting"><span class="keyword">class</span> <span class="identifier">Clock</span> <span class="special">{</span> |
| <span class="keyword">public</span><span class="special">:</span> |
| <span class="keyword">typedef</span> <span class="identifier">an</span> <span class="identifier">arithmetic</span><span class="special">-</span><span class="identifier">like</span> <span class="identifier">type</span> <span class="identifier">rep</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="identifier">an</span> <span class="identifier">instantiation</span> <span class="identifier">of</span> <span class="identifier">ratio</span> <span class="identifier">period</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a><span class="special"><</span><span class="identifier">rep</span><span class="special">,</span> <span class="identifier">period</span><span class="special">></span> <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a><span class="special"><</span><a class="link" href="reference.html#chrono.reference.cpp0x.clock" title="Clock Requirements"><code class="computeroutput"><span class="identifier">Clock</span></code></a><span class="special">></span> <span class="identifier">time_point</span><span class="special">;</span> |
| <span class="keyword">static</span> <span class="keyword">constexpr</span> <span class="keyword">bool</span> <span class="identifier">is_steady</span> <span class="special">=</span> <span class="keyword">true</span> <span class="keyword">or</span> <span class="keyword">false</span><span class="special">;</span> |
| |
| <span class="keyword">static</span> <span class="identifier">time_point</span> <span class="identifier">now</span><span class="special">();</span> |
| <span class="special">};</span> |
| </pre> |
| <p> |
| One can get the current time from Clock with: |
| </p> |
| <pre class="programlisting"><span class="identifier">Clock</span><span class="special">::</span><span class="identifier">time_point</span> <span class="identifier">t1</span> <span class="special">=</span> <span class="identifier">Clock</span><span class="special">::</span><span class="identifier">now</span><span class="special">();</span> |
| </pre> |
| <p> |
| And one can get the time <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> between two <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a>s associated with Clock |
| with: |
| </p> |
| <pre class="programlisting"><span class="identifier">Clock</span><span class="special">::</span><span class="identifier">duration</span> <span class="identifier">d</span> <span class="special">=</span> <span class="identifier">Clock</span><span class="special">::</span><span class="identifier">now</span><span class="special">()</span> <span class="special">-</span> <span class="identifier">t1</span><span class="special">;</span> |
| </pre> |
| <p> |
| And one can specify a past or future <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a> with: |
| </p> |
| <pre class="programlisting"><span class="identifier">Clock</span><span class="special">::</span><span class="identifier">time_point</span> <span class="identifier">t2</span> <span class="special">=</span> <span class="identifier">Clock</span><span class="special">::</span><span class="identifier">now</span><span class="special">()</span> <span class="special">+</span> <span class="identifier">d</span><span class="special">;</span> |
| </pre> |
| <p> |
| Note how even if a particular clock becomes obsolete, the next clock in |
| line will have the same API. There is no new learning curve to come up. |
| The only source code changes will be simply changing the type of the clock. |
| The same <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> and <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a> framework continues |
| to work as new clocks are introduced. And multiple clocks are safely and |
| easily handled within the same program. |
| </p> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h4 class="title"> |
| <a name="chrono.users_guide.tutorial.time_point"></a><a class="link" href="users_guide.html#chrono.users_guide.tutorial.time_point" title="Time Point">Time Point</a> |
| </h4></div></div></div> |
| <div class="toc"><dl class="toc"><dt><span class="section"><a href="users_guide.html#chrono.users_guide.tutorial.time_point.so_what_exactly_is_a__time_point__and_how_do_i_use_one_">So |
| What Exactly is a <code class="computeroutput"><span class="identifier">time_point</span></code> |
| and How Do I Use One?</a></span></dt></dl></div> |
| <p> |
| A <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a> represents a point |
| in time, as opposed to a <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> of time. Another way |
| of saying the same thing, is that a <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a> represents an epoch |
| plus or minus a <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>. Examples of <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a>s include: |
| </p> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| 3 minutes after the computer booted. |
| </li> |
| <li class="listitem"> |
| 03:14:07 UTC on Tuesday, January 19, 2038 |
| </li> |
| <li class="listitem"> |
| 20 milliseconds after I started that timer. |
| </li> |
| </ul></div> |
| <p> |
| In each of the examples above, a different epoch is implied. Sometimes |
| an epoch has meaning for several millennia. Other times the meaning of |
| an epoch is lost after a while (such as the start of a timer, or when the |
| computer booted). However, if two <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a>s are known to share |
| the same epoch, they can be subtracted, yielding a valid <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>, even if the definition |
| of the epoch no longer has meaning. |
| </p> |
| <p> |
| In <span class="bold"><strong>Boost.Chrono</strong></span>, an epoch is a purely |
| abstract and unspecified concept. There is no type representing an epoch. |
| It is simply an idea that relates (or doesn't) <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a>s to a clock, and in |
| the case that they share a clock, <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a>s to one another. <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a>s associated with different |
| clocks are generally not interoperable unless the relationship between |
| the epochs associated with each clock is known. |
| </p> |
| <div class="section"> |
| <div class="titlepage"><div><div><h5 class="title"> |
| <a name="chrono.users_guide.tutorial.time_point.so_what_exactly_is_a__time_point__and_how_do_i_use_one_"></a><a class="link" href="users_guide.html#chrono.users_guide.tutorial.time_point.so_what_exactly_is_a__time_point__and_how_do_i_use_one_" title="So What Exactly is a time_point and How Do I Use One?">So |
| What Exactly is a <code class="computeroutput"><span class="identifier">time_point</span></code> |
| and How Do I Use One?</a> |
| </h5></div></div></div> |
| <p> |
| A <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a> has a clock and a |
| <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>. |
| </p> |
| <pre class="programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <a class="link" href="reference.html#chrono.reference.cpp0x.clock" title="Clock Requirements"><code class="computeroutput"><span class="identifier">Clock</span></code></a><span class="special">,</span> <span class="keyword">class</span> <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">Duration</span></code></a> <span class="special">=</span> <span class="keyword">typename</span> <span class="identifier">Clock</span><span class="special">::</span><span class="identifier">duration</span><span class="special">></span> <span class="keyword">class</span> <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a><span class="special">;</span> |
| </pre> |
| <p> |
| The <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a>'s clock is not stored. |
| It is simply embedded into the <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a>'s type and serves |
| two purposes: |
| </p> |
| <div class="orderedlist"><ol class="orderedlist" type="1"> |
| <li class="listitem"> |
| Because <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a>s originating |
| from different clocks have different types, the compiler can be instructed |
| to fail if incompatible <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a>s are used in |
| inappropriate ways. |
| </li> |
| <li class="listitem"> |
| Given a <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a>, one often needs |
| to compare that <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a> to "now". |
| This is very simple as long as the <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a> knows what clock |
| it is defined with respect to. |
| </li> |
| </ol></div> |
| <p> |
| A <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a>'s <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> is stored as the only |
| data member of the <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a>. Thus <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a>s and their corresponding |
| <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> have exactly the same |
| layout. But they have very different meanings. For example, it is one |
| thing to say I want to sleep for 3 minutes. It is a completely different |
| thing to say I want to sleep until 3 minutes past the time I started |
| that timer (unless you just happened to start that timer now). Both meanings |
| (and options for sleeping) have great practical value in common use cases |
| for sleeping, waiting on a condition variable, and waiting for a mutex's |
| lock. These same concepts and tools are found (for example) in Ada. |
| </p> |
| <p> |
| A timer example: |
| </p> |
| <pre class="programlisting"><span class="keyword">void</span> <span class="identifier">f</span><span class="special">()</span> |
| <span class="special">{</span> |
| <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">steady_clock</span><span class="special">::</span><span class="identifier">time_point</span> <span class="identifier">start</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">steady_clock</span><span class="special">::</span><span class="identifier">now</span><span class="special">();</span> |
| <span class="identifier">g</span><span class="special">();</span> |
| <span class="identifier">h</span><span class="special">();</span> |
| <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a><span class="special"><</span><span class="keyword">double</span><span class="special">></span> <span class="identifier">sec</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">steady_clock</span><span class="special">::</span><span class="identifier">now</span><span class="special">()</span> <span class="special">-</span> <span class="identifier">start</span><span class="special">;</span> |
| <span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"f() took "</span> <span class="special"><<</span> <span class="identifier">sec</span><span class="special">.</span><span class="identifier">count</span><span class="special">()</span> <span class="special"><<</span> <span class="string">" seconds\n"</span><span class="special">;</span> |
| <span class="special">}</span> |
| </pre> |
| <p> |
| Note that if one is using the <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> between two clock |
| <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a>s in a way where the |
| precision of the <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> matters, it is good |
| practice to convert the clock's <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> to a known <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>. This insulates the |
| code from future changes which may be made to the clock's precision in |
| the future. For example <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.steady_clock" title="Class steady_clock"><code class="computeroutput"><span class="identifier">steady_clock</span></code></a> could easily be |
| based on the clock speed of the cpu. When you upgrade to a faster machine, |
| you do not want your code that assumed a certain tick period of this |
| clock to start experiencing run-time failures because your timing code |
| has silently changed meaning. |
| </p> |
| <p> |
| A delay loop example: |
| </p> |
| <pre class="programlisting"><span class="comment">// delay for at least 500 nanoseconds:</span> |
| <span class="keyword">auto</span> <span class="identifier">go</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">steady_clock</span><span class="special">::</span><span class="identifier">now</span><span class="special">()</span> <span class="special">+</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">nanoseconds</span><span class="special">(</span><span class="number">500</span><span class="special">);</span> |
| <span class="keyword">while</span> <span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">steady_clock</span><span class="special">::</span><span class="identifier">now</span><span class="special">()</span> <span class="special"><</span> <span class="identifier">go</span><span class="special">)</span> |
| <span class="special">;</span> |
| </pre> |
| <p> |
| The above code will delay as close as possible to half a microsecond, |
| no matter what the precision of <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.steady_clock" title="Class steady_clock"><code class="computeroutput"><span class="identifier">steady_clock</span></code></a> is. The more precise |
| <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.steady_clock" title="Class steady_clock"><code class="computeroutput"><span class="identifier">steady_clock</span></code></a> becomes, the more |
| accurate will be the delay to 500 nanoseconds. |
| </p> |
| </div> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h4 class="title"> |
| <a name="chrono.users_guide.tutorial.specific_clocks"></a><a class="link" href="users_guide.html#chrono.users_guide.tutorial.specific_clocks" title="Specific Clocks">Specific |
| Clocks</a> |
| </h4></div></div></div> |
| <div class="toc"><dl class="toc"> |
| <dt><span class="section"><a href="users_guide.html#chrono.users_guide.tutorial.specific_clocks.system_clock">system_clock</a></span></dt> |
| <dt><span class="section"><a href="users_guide.html#chrono.users_guide.tutorial.specific_clocks.steady_clock">steady_clock</a></span></dt> |
| <dt><span class="section"><a href="users_guide.html#chrono.users_guide.tutorial.specific_clocks.high_resolution_clock">high_resolution_clock</a></span></dt> |
| <dt><span class="section"><a href="users_guide.html#chrono.users_guide.tutorial.specific_clocks.process_cpu_clock">process_cpu_clock</a></span></dt> |
| <dt><span class="section"><a href="users_guide.html#chrono.users_guide.tutorial.specific_clocks.thread_clock">thread_clock</a></span></dt> |
| </dl></div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h5 class="title"> |
| <a name="chrono.users_guide.tutorial.specific_clocks.system_clock"></a><a class="link" href="users_guide.html#chrono.users_guide.tutorial.specific_clocks.system_clock" title="system_clock">system_clock</a> |
| </h5></div></div></div> |
| <p> |
| <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.system_clock" title="Class system_clock"><code class="computeroutput"><span class="identifier">system_clock</span></code></a> is useful when |
| you need to correlate the time with a known epoch so you can convert |
| it to a calendar time. Note the specific functions in the <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.system_clock" title="Class system_clock"><code class="computeroutput"><span class="identifier">system_clock</span></code></a> class. |
| </p> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h5 class="title"> |
| <a name="chrono.users_guide.tutorial.specific_clocks.steady_clock"></a><a class="link" href="users_guide.html#chrono.users_guide.tutorial.specific_clocks.steady_clock" title="steady_clock">steady_clock</a> |
| </h5></div></div></div> |
| <p> |
| <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.steady_clock" title="Class steady_clock"><code class="computeroutput"><span class="identifier">steady_clock</span></code></a> is useful when |
| you need to wait for a specific amount of time. <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.steady_clock" title="Class steady_clock"><code class="computeroutput"><span class="identifier">steady_clock</span></code></a> time can not be |
| reset. As other steady clocks, it is usually based on the processor tick. |
| </p> |
| <p> |
| Here is a polling solution, but it will probably be too inefficient: |
| </p> |
| <pre class="programlisting"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.steady_clock" title="Class steady_clock"><code class="computeroutput"><span class="identifier">steady_clock</span></code></a><span class="special">::</span><span class="identifier">time_point</span> <span class="identifier">start</span><span class="special">=</span> <span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.steady_clock" title="Class steady_clock"><code class="computeroutput"><span class="identifier">steady_clock</span></code></a><span class="special">::</span><span class="identifier">now</span><span class="special">();</span> |
| <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.steady_clock" title="Class steady_clock"><code class="computeroutput"><span class="identifier">steady_clock</span></code></a><span class="special">::</span><span class="identifier">duration</span> <span class="identifier">delay</span><span class="special">=</span> <span class="identifier">chrono</span><span class="special">::</span><span class="identifier">seconds</span><span class="special">(</span><span class="number">5</span><span class="special">);</span> |
| <span class="keyword">while</span> <span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.steady_clock" title="Class steady_clock"><code class="computeroutput"><span class="identifier">steady_clock</span></code></a><span class="special">::</span><span class="identifier">now</span><span class="special">()</span> <span class="special">-</span> <span class="identifier">start</span> <span class="special"><=</span> <span class="identifier">delay</span><span class="special">)</span> <span class="special">{}</span> |
| </pre> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h5 class="title"> |
| <a name="chrono.users_guide.tutorial.specific_clocks.high_resolution_clock"></a><a class="link" href="users_guide.html#chrono.users_guide.tutorial.specific_clocks.high_resolution_clock" title="high_resolution_clock">high_resolution_clock</a> |
| </h5></div></div></div> |
| <p> |
| When available, <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.high_resolution_clock" title="Class high_resolution_clock"><code class="computeroutput"><span class="identifier">high_resolution_clock</span></code></a> is usually |
| more expensive than the other system-wide clocks, so they are used only |
| when the provided resolution is required to the application. |
| </p> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h5 class="title"> |
| <a name="chrono.users_guide.tutorial.specific_clocks.process_cpu_clock"></a><a class="link" href="users_guide.html#chrono.users_guide.tutorial.specific_clocks.process_cpu_clock" title="process_cpu_clock">process_cpu_clock</a> |
| </h5></div></div></div> |
| <p> |
| Process and thread clocks are used usually to measure the time spent |
| by code blocks, as a basic time-spent profiling of different blocks of |
| code (Boost.Chrono.Stopwatch is a clear example of this use). |
| </p> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h5 class="title"> |
| <a name="chrono.users_guide.tutorial.specific_clocks.thread_clock"></a><a class="link" href="users_guide.html#chrono.users_guide.tutorial.specific_clocks.thread_clock" title="thread_clock">thread_clock</a> |
| </h5></div></div></div> |
| <p> |
| You can use <a class="link" href="reference.html#chrono.reference.other_clocks.thread_clock_hpp.thread_clock" title="Class thread_clock"><code class="computeroutput"><span class="identifier">thread_clock</span></code></a> whenever you want |
| to measure the time spent by the current thread. For example: |
| </p> |
| <pre class="programlisting"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.other_clocks.thread_clock_hpp.thread_clock" title="Class thread_clock"><code class="computeroutput"><span class="identifier">thread_clock</span></code></a><span class="special">::</span><span class="identifier">time_point</span> <span class="identifier">start</span><span class="special">=</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.other_clocks.thread_clock_hpp.thread_clock" title="Class thread_clock"><code class="computeroutput"><span class="identifier">thread_clock</span></code></a><span class="special">::</span><span class="identifier">now</span><span class="special">();</span> |
| <span class="comment">// ... do something ...</span> |
| |
| <span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">milliseconds</span></code></a> <span class="identifier">ms</span><span class="special">;</span> |
| <span class="identifier">ms</span> <span class="identifier">d</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.other_clocks.thread_clock_hpp.thread_clock" title="Class thread_clock"><code class="computeroutput"><span class="identifier">thread_clock</span></code></a><span class="special">::</span><span class="identifier">now</span><span class="special">()</span> <span class="special">-</span> <span class="identifier">start</span><span class="special">;</span> |
| <span class="comment">// d now holds the number of milliseconds from start to end.</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">ms</span><span class="special">.</span><span class="identifier">count</span><span class="special">()</span> <span class="special"><<</span> <span class="string">"ms\n"</span><span class="special">;</span> |
| </pre> |
| <p> |
| If you need seconds with a floating-point representation you can do: |
| </p> |
| <pre class="programlisting"><span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a><span class="special"><</span><span class="keyword">double</span><span class="special">></span> <span class="identifier">sec</span><span class="special">;</span> <span class="comment">// seconds, stored with a double.</span> |
| <span class="identifier">sec</span> <span class="identifier">d</span> <span class="special">=</span> <span class="identifier">end</span> <span class="special">-</span> <span class="identifier">start</span><span class="special">;</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">sec</span><span class="special">.</span><span class="identifier">count</span><span class="special">()</span> <span class="special"><<</span> <span class="string">"s\n"</span><span class="special">;</span> |
| </pre> |
| <p> |
| If you would like to programmatically inspect <code class="computeroutput"><a class="link" href="reference.html#chrono.reference.other_clocks.thread_clock_hpp.thread_clock" title="Class thread_clock"><code class="computeroutput"><span class="identifier">thread_clock</span></code></a><span class="special">::</span><span class="identifier">duration</span></code>, you can get the representation |
| type with <code class="computeroutput"><a class="link" href="reference.html#chrono.reference.other_clocks.thread_clock_hpp.thread_clock" title="Class thread_clock"><code class="computeroutput"><span class="identifier">thread_clock</span></code></a><span class="special">::</span><span class="identifier">rep</span></code>, and the tick period with <code class="computeroutput"><a class="link" href="reference.html#chrono.reference.other_clocks.thread_clock_hpp.thread_clock" title="Class thread_clock"><code class="computeroutput"><span class="identifier">thread_clock</span></code></a><span class="special">::</span><span class="identifier">period</span></code> (which should be a type <code class="computeroutput"><span class="identifier">ratio</span></code> which has nested values <code class="computeroutput"><code class="computeroutput"><span class="identifier">ratio</span></code><span class="special">::</span><span class="identifier">num</span></code> and <code class="computeroutput"><code class="computeroutput"><span class="identifier">ratio</span></code><span class="special">::</span><span class="identifier">den</span></code>). |
| The tick period of <a class="link" href="reference.html#chrono.reference.other_clocks.thread_clock_hpp.thread_clock" title="Class thread_clock"><code class="computeroutput"><span class="identifier">thread_clock</span></code></a> is <code class="computeroutput"><a class="link" href="reference.html#chrono.reference.other_clocks.thread_clock_hpp.thread_clock" title="Class thread_clock"><code class="computeroutput"><span class="identifier">thread_clock</span></code></a><span class="special">::</span><span class="identifier">period</span><span class="special">::</span><span class="identifier">num</span> <span class="special">/</span> <a class="link" href="reference.html#chrono.reference.other_clocks.thread_clock_hpp.thread_clock" title="Class thread_clock"><code class="computeroutput"><span class="identifier">thread_clock</span></code></a><span class="special">::</span><span class="identifier">period</span><span class="special">::</span><span class="identifier">den</span></code> seconds: <code class="computeroutput"><span class="number">1</span><span class="special">/</span><span class="number">1000000000</span></code> |
| in this case (<code class="computeroutput"><span class="number">1</span></code> billionth |
| of a second), stored in a <code class="computeroutput"><span class="keyword">long</span> |
| <span class="keyword">long</span></code>. |
| </p> |
| </div> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h4 class="title"> |
| <a name="chrono.users_guide.tutorial.i_o"></a><a class="link" href="users_guide.html#chrono.users_guide.tutorial.i_o" title="I/O">I/O</a> |
| </h4></div></div></div> |
| <div class="toc"><dl class="toc"> |
| <dt><span class="section"><a href="users_guide.html#chrono.users_guide.tutorial.i_o.duration_io">duration</a></span></dt> |
| <dt><span class="section"><a href="users_guide.html#chrono.users_guide.tutorial.i_o.system_clock_time_point_io"><code class="computeroutput"><span class="identifier">system_clock</span><span class="special">::</span><span class="identifier">time_point</span></code></a></span></dt> |
| <dt><span class="section"><a href="users_guide.html#chrono.users_guide.tutorial.i_o.other_clocks_time_point_io">Other |
| clocks time_point</a></span></dt> |
| <dt><span class="section"><a href="users_guide.html#chrono.users_guide.tutorial.i_o.low_level_i_o">Low |
| level I/O</a></span></dt> |
| </dl></div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h5 class="title"> |
| <a name="chrono.users_guide.tutorial.i_o.duration_io"></a><a class="link" href="users_guide.html#chrono.users_guide.tutorial.i_o.duration_io" title="duration">duration</a> |
| </h5></div></div></div> |
| <p> |
| Any <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> can be streamed out |
| to a <code class="computeroutput"><span class="identifier">basic_ostream</span></code>. The |
| run-time value of the <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> is formatted according |
| to the rules and current format settings for <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a><code class="computeroutput"><span class="special">::</span><span class="identifier">rep</span></code> get_duration_style and the durationpunct |
| facet. |
| </p> |
| <p> |
| the format is either |
| </p> |
| <pre class="programlisting"><span class="special"><</span><span class="identifier">value</span><span class="special">></span> <span class="special"><</span><span class="identifier">unit</span><span class="special">></span> |
| </pre> |
| <p> |
| or |
| </p> |
| <pre class="programlisting"><span class="special"><</span><span class="identifier">unit</span><span class="special">></span> <span class="special"><</span><span class="identifier">value</span><span class="special">></span> |
| </pre> |
| <div class="warning"><table border="0" summary="Warning"> |
| <tr> |
| <td rowspan="2" align="center" valign="top" width="25"><img alt="[Warning]" src="../../../doc/src/images/warning.png"></td> |
| <th align="left">Warning</th> |
| </tr> |
| <tr><td align="left" valign="top"> |
| <p> |
| Need to be changed This is followed by a single space and then the |
| compile-time unit name of the <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>. This unit name is |
| built on the string returned from <code class="computeroutput"><span class="identifier">ratio_string</span><span class="special"><></span></code> and the data used to construct |
| the <a class="link" href="reference.html#chrono.reference.io_v1.chrono_io_hpp.duration_punct" title="Template Class duration_punct<>"><code class="computeroutput"><span class="identifier">duration_punct</span></code></a> which was inserted |
| into the stream's locale. If a <a class="link" href="reference.html#chrono.reference.io_v1.chrono_io_hpp.duration_punct" title="Template Class duration_punct<>"><code class="computeroutput"><span class="identifier">duration_punct</span></code></a> has not been |
| inserted into the stream's locale, a default constructed <a class="link" href="reference.html#chrono.reference.io_v1.chrono_io_hpp.duration_punct" title="Template Class duration_punct<>"><code class="computeroutput"><span class="identifier">duration_punct</span></code></a> will be added |
| to the stream's locale. |
| </p> |
| <p> |
| <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> unit names come in |
| two varieties: long(prefix) and short(symbol). The default constructed |
| <a class="link" href="reference.html#chrono.reference.io_v1.chrono_io_hpp.duration_punct" title="Template Class duration_punct<>"><code class="computeroutput"><span class="identifier">duration_punct</span></code></a> provides names |
| in the long(prefix) format. These names are English descriptions. Other |
| languages are supported by constructing a <a class="link" href="reference.html#chrono.reference.io_v1.chrono_io_hpp.duration_punct" title="Template Class duration_punct<>"><code class="computeroutput"><span class="identifier">duration_punct</span></code></a> with the proper |
| spellings for "hours", "minutes" and "seconds", |
| and their abbreviations (for the short format). The short or long format |
| can be easily chosen by streaming a <code class="computeroutput"><span class="identifier">duration_short</span><span class="special">()</span></code> or <code class="computeroutput"><span class="identifier">duration_long</span><span class="special">()</span></code> manipulator respectively or using |
| the parameterized manipulator <code class="computeroutput"><span class="identifier">duration_fmt</span><span class="special">(</span><span class="identifier">duration_style</span><span class="special">::</span><span class="identifier">prefix</span><span class="special">)</span></code> or <code class="computeroutput"><span class="identifier">duration_fmt</span><span class="special">(</span><span class="identifier">duration_style</span><span class="special">::</span><span class="identifier">symbol</span><span class="special">)</span></code>. |
| </p> |
| </td></tr> |
| </table></div> |
| <p> |
| <span class="bold"><strong>Example:</strong></span> |
| </p> |
| <pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">iostream</span><span class="special">></span> |
| <span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">chrono</span><span class="special">/</span><span class="identifier">chrono_io</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> |
| |
| <span class="keyword">int</span> <span class="identifier">main</span><span class="special">()</span> |
| <span class="special">{</span> |
| <span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">std</span><span class="special">;</span> |
| <span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">boost</span><span class="special">;</span> |
| |
| <span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"milliseconds(1) = "</span> |
| <span class="special"><<</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">milliseconds</span><span class="special">(</span><span class="number">1</span><span class="special">)</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> |
| |
| <span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"milliseconds(3) + microseconds(10) = "</span> |
| <span class="special"><<</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">milliseconds</span><span class="special">(</span><span class="number">3</span><span class="special">)</span> <span class="special">+</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">microseconds</span><span class="special">(</span><span class="number">10</span><span class="special">)</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> |
| |
| <span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"hours(3) + minutes(10) = "</span> |
| <span class="special"><<</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">hours</span><span class="special">(</span><span class="number">3</span><span class="special">)</span> <span class="special">+</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">minutes</span><span class="special">(</span><span class="number">10</span><span class="special">)</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> |
| |
| <span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">duration</span><span class="special"><</span><span class="keyword">long</span> <span class="keyword">long</span><span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">ratio</span><span class="special"><</span><span class="number">1</span><span class="special">,</span> <span class="number">2500000000</span><span class="special">></span> <span class="special">></span> <span class="identifier">ClockTick</span><span class="special">;</span> |
| <span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"ClockTick(3) + boost::chrono::nanoseconds(10) = "</span> |
| <span class="special"><<</span> <span class="identifier">ClockTick</span><span class="special">(</span><span class="number">3</span><span class="special">)</span> <span class="special">+</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">nanoseconds</span><span class="special">(</span><span class="number">10</span><span class="special">)</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> |
| |
| <span class="comment">// ...</span> |
| <span class="keyword">return</span> <span class="number">0</span><span class="special">;</span> |
| <span class="special">}</span> |
| </pre> |
| <p> |
| The output could be |
| </p> |
| <pre class="programlisting"><span class="identifier">milliseconds</span><span class="special">(</span><span class="number">1</span><span class="special">)</span> <span class="special">=</span> <span class="number">1</span> <span class="identifier">microsecond</span> |
| <span class="identifier">milliseconds</span><span class="special">(</span><span class="number">3</span><span class="special">)</span> <span class="special">+</span> <span class="identifier">microseconds</span><span class="special">(</span><span class="number">10</span><span class="special">)</span> <span class="special">=</span> <span class="number">3010</span> <span class="identifier">microseconds</span> |
| <span class="identifier">hours</span><span class="special">(</span><span class="number">3</span><span class="special">)</span> <span class="special">+</span> <span class="identifier">minutes</span><span class="special">(</span><span class="number">10</span><span class="special">)</span> <span class="special">=</span> <span class="number">190</span> <span class="identifier">minutes</span> |
| <span class="identifier">ClockTick</span><span class="special">(</span><span class="number">3</span><span class="special">)</span> <span class="special">+</span> <span class="identifier">nanoseconds</span><span class="special">(</span><span class="number">10</span><span class="special">)</span> <span class="special">=</span> <span class="number">56</span> <span class="special">[</span><span class="number">1</span><span class="special">/</span><span class="number">5000000000</span><span class="special">]</span><span class="identifier">seconds</span> |
| |
| <span class="identifier">Set</span> <span class="identifier">cout</span> <span class="identifier">to</span> <span class="identifier">use</span> <span class="keyword">short</span> <span class="identifier">names</span><span class="special">:</span> |
| <span class="identifier">milliseconds</span><span class="special">(</span><span class="number">3</span><span class="special">)</span> <span class="special">+</span> <span class="identifier">microseconds</span><span class="special">(</span><span class="number">10</span><span class="special">)</span> <span class="special">=</span> <span class="number">3010</span> μs |
| <span class="identifier">hours</span><span class="special">(</span><span class="number">3</span><span class="special">)</span> <span class="special">+</span> <span class="identifier">minutes</span><span class="special">(</span><span class="number">10</span><span class="special">)</span> <span class="special">=</span> <span class="number">190</span> <span class="identifier">m</span> |
| <span class="identifier">ClockTick</span><span class="special">(</span><span class="number">3</span><span class="special">)</span> <span class="special">+</span> <span class="identifier">nanoseconds</span><span class="special">(</span><span class="number">10</span><span class="special">)</span> <span class="special">=</span> <span class="number">56</span> <span class="special">[</span><span class="number">1</span><span class="special">/</span><span class="number">5000000000</span><span class="special">]</span><span class="identifier">s</span> |
| |
| <span class="identifier">system_clock</span><span class="special">::</span><span class="identifier">now</span><span class="special">()</span> <span class="special">=</span> <span class="number">129387415616250000</span> <span class="special">[</span><span class="number">1</span><span class="special">/</span><span class="number">10000000</span><span class="special">]</span><span class="identifier">s</span> <span class="identifier">since</span> <span class="identifier">Jan</span> <span class="number">1</span><span class="special">,</span> <span class="number">1970</span> |
| <span class="identifier">monotonic_clock</span><span class="special">::</span><span class="identifier">now</span><span class="special">()</span> <span class="special">=</span> <span class="number">37297387636417</span> <span class="identifier">ns</span> <span class="identifier">since</span> <span class="identifier">boot</span> |
| |
| <span class="identifier">Set</span> <span class="identifier">cout</span> <span class="identifier">to</span> <span class="identifier">use</span> <span class="keyword">long</span> <span class="identifier">names</span><span class="special">:</span> |
| <span class="identifier">high_resolution_clock</span><span class="special">::</span><span class="identifier">now</span><span class="special">()</span> <span class="special">=</span> <span class="number">37297387655134</span> <span class="identifier">nanoseconds</span> <span class="identifier">since</span> <span class="identifier">boot</span> |
| </pre> |
| <p> |
| As can be seen, each duration type can be streamed without having to |
| manually stream the compile-time units after the run-time value. And |
| when the compile-time unit is known to be a "common unit", |
| English names are used. For "uncommon units" a unit name is |
| composed from the reduced numerator and denominator of the associated |
| <code class="computeroutput"><span class="identifier">ratio</span></code>. Whatever stream/locale |
| settings are set for <code class="computeroutput"><span class="identifier">duration</span><span class="special">::</span><span class="identifier">rep</span></code> |
| are used for the value. Additionally, when the value is 1, singular forms |
| for the units are used. |
| </p> |
| <p> |
| Sometimes it is desired to shorten these names by using the SI symbols |
| instead of SI prefixes. This can be accomplished with the use of the |
| <a class="link" href="reference.html#chrono.reference.io.duration_io_hpp.manipulators.symbol_format" title="Non Member Function symbol_format(ios_base&)"><code class="computeroutput"><span class="identifier">symbol_format</span></code></a> manipulator <a href="#ftn.chrono.users_guide.tutorial.i_o.duration_io.f0" class="footnote" name="chrono.users_guide.tutorial.i_o.duration_io.f0"><sup class="footnote">[1]</sup></a>: |
| </p> |
| <pre class="programlisting"><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"\nSet cout to use short names:\n"</span><span class="special">;</span> |
| <span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">symbol_format</span><span class="special">;</span> |
| |
| <span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"milliseconds(3) + microseconds(10) = "</span> |
| <span class="special"><<</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">milliseconds</span><span class="special">(</span><span class="number">3</span><span class="special">)</span> <span class="special">+</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">microseconds</span><span class="special">(</span><span class="number">10</span><span class="special">)</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> |
| |
| <span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"hours(3) + minutes(10) = "</span> |
| <span class="special"><<</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">hours</span><span class="special">(</span><span class="number">3</span><span class="special">)</span> <span class="special">+</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">minutes</span><span class="special">(</span><span class="number">10</span><span class="special">)</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> |
| |
| <span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"ClockTick(3) + nanoseconds(10) = "</span> |
| <span class="special"><<</span> <span class="identifier">ClockTick</span><span class="special">(</span><span class="number">3</span><span class="special">)</span> <span class="special">+</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">nanoseconds</span><span class="special">(</span><span class="number">10</span><span class="special">)</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> |
| </pre> |
| <p> |
| The output could be |
| </p> |
| <pre class="programlisting"><span class="identifier">Set</span> <span class="identifier">cout</span> <span class="identifier">to</span> <span class="identifier">use</span> <span class="keyword">short</span> <span class="identifier">names</span><span class="special">:</span> |
| <span class="identifier">milliseconds</span><span class="special">(</span><span class="number">3</span><span class="special">)</span> <span class="special">+</span> <span class="identifier">microseconds</span><span class="special">(</span><span class="number">10</span><span class="special">)</span> <span class="special">=</span> <span class="number">3010</span> μs |
| <span class="identifier">hours</span><span class="special">(</span><span class="number">3</span><span class="special">)</span> <span class="special">+</span> <span class="identifier">minutes</span><span class="special">(</span><span class="number">10</span><span class="special">)</span> <span class="special">=</span> <span class="number">190</span> <span class="identifier">m</span> |
| <span class="identifier">ClockTick</span><span class="special">(</span><span class="number">3</span><span class="special">)</span> <span class="special">+</span> <span class="identifier">nanoseconds</span><span class="special">(</span><span class="number">10</span><span class="special">)</span> <span class="special">=</span> <span class="number">56</span> <span class="special">[</span><span class="number">1</span><span class="special">/</span><span class="number">5000000000</span><span class="special">]</span><span class="identifier">s</span> |
| |
| <span class="identifier">system_clock</span><span class="special">::</span><span class="identifier">now</span><span class="special">()</span> <span class="special">=</span> <span class="number">129387415616250000</span> <span class="special">[</span><span class="number">1</span><span class="special">/</span><span class="number">10000000</span><span class="special">]</span><span class="identifier">s</span> <span class="identifier">since</span> <span class="identifier">Jan</span> <span class="number">1</span><span class="special">,</span> <span class="number">1970</span> |
| <span class="identifier">monotonic_clock</span><span class="special">::</span><span class="identifier">now</span><span class="special">()</span> <span class="special">=</span> <span class="number">37297387636417</span> <span class="identifier">ns</span> <span class="identifier">since</span> <span class="identifier">boot</span> |
| |
| <span class="identifier">Set</span> <span class="identifier">cout</span> <span class="identifier">to</span> <span class="identifier">use</span> <span class="keyword">long</span> <span class="identifier">names</span><span class="special">:</span> |
| <span class="identifier">high_resolution_clock</span><span class="special">::</span><span class="identifier">now</span><span class="special">()</span> <span class="special">=</span> <span class="number">37297387655134</span> <span class="identifier">nanoseconds</span> <span class="identifier">since</span> <span class="identifier">boot</span> |
| </pre> |
| <p> |
| The μ for microsecond is specified to be U+00B5, encoded as UTF-8, UTF-16 |
| or UTF-32 as appropriate for the stream's character size. |
| </p> |
| <p> |
| When the format decision is taken at runtime, it could be better to use |
| the parameterized manipulator <a class="link" href="reference.html#chrono.reference.io.duration_io_hpp.manipulators.duration_fmt" title="Template Class duration_fmt"><code class="computeroutput"><span class="identifier">duration_fmt</span></code></a> as in |
| </p> |
| <pre class="programlisting"><span class="identifier">duration_style</span> <span class="identifier">style</span><span class="special">;</span> |
| <span class="comment">//...</span> |
| <span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">duration_fmt</span><span class="special">(</span><span class="identifier">style</span><span class="special">);</span> |
| </pre> |
| <p> |
| Parsing a <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> follows rules analogous |
| to the <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> converting constructor. |
| A value and a unit (SI symbol or prefixed) are read from the <code class="computeroutput"><span class="identifier">basic_istream</span></code>. If the <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> has an integral representation, |
| then the value parsed must be exactly representable in the target <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> (after conversion to |
| the target <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> units), else <code class="computeroutput"><span class="identifier">failbit</span></code> is set. <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>s based on floating-point |
| representations can be parsed using any units that do not cause overflow. |
| </p> |
| <p> |
| For example a stream containing "5000 milliseconds" can be |
| parsed into seconds, but if the stream contains "3001 ms", |
| parsing into <code class="computeroutput"><span class="identifier">seconds</span></code> |
| will cause <code class="computeroutput"><span class="identifier">failbit</span></code> to |
| be set. |
| </p> |
| <p> |
| <span class="bold"><strong>Example:</strong></span> |
| </p> |
| <pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">chrono</span><span class="special">/</span><span class="identifier">chrono_io</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> |
| <span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">sstream</span><span class="special">></span> |
| <span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">cassert</span><span class="special">></span> |
| |
| <span class="keyword">int</span> <span class="identifier">main</span><span class="special">()</span> |
| <span class="special">{</span> |
| <span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">std</span><span class="special">;</span> |
| |
| <span class="identifier">istringstream</span> <span class="identifier">in</span><span class="special">(</span><span class="string">"5000 milliseconds 4000 ms 3001 ms"</span><span class="special">);</span> |
| <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">seconds</span> <span class="identifier">d</span><span class="special">(</span><span class="number">0</span><span class="special">);</span> |
| <span class="identifier">in</span> <span class="special">>></span> <span class="identifier">d</span><span class="special">;</span> |
| <span class="identifier">assert</span><span class="special">(</span><span class="identifier">in</span><span class="special">.</span><span class="identifier">good</span><span class="special">());</span> |
| <span class="identifier">assert</span><span class="special">(</span><span class="identifier">d</span> <span class="special">==</span> <span class="identifier">seconds</span><span class="special">(</span><span class="number">5</span><span class="special">));</span> |
| <span class="identifier">in</span> <span class="special">>></span> <span class="identifier">d</span><span class="special">;</span> |
| <span class="identifier">assert</span><span class="special">(</span><span class="identifier">in</span><span class="special">.</span><span class="identifier">good</span><span class="special">());</span> |
| <span class="identifier">assert</span><span class="special">(</span><span class="identifier">d</span> <span class="special">==</span> <span class="identifier">seconds</span><span class="special">(</span><span class="number">4</span><span class="special">));</span> |
| <span class="identifier">in</span> <span class="special">>></span> <span class="identifier">d</span><span class="special">;</span> |
| <span class="identifier">assert</span><span class="special">(</span><span class="identifier">in</span><span class="special">.</span><span class="identifier">fail</span><span class="special">());</span> |
| <span class="identifier">assert</span><span class="special">(</span><span class="identifier">d</span> <span class="special">==</span> <span class="identifier">seconds</span><span class="special">(</span><span class="number">4</span><span class="special">));</span> |
| |
| <span class="keyword">return</span> <span class="number">0</span><span class="special">;</span> |
| <span class="special">}</span> |
| </pre> |
| <p> |
| Note that a <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> failure may occur late |
| in the parsing process. This means that the characters making up the |
| failed parse in the stream are usually consumed despite the failure to |
| successfully parse. |
| </p> |
| <p> |
| Sometimes in templated code it is difficult to know what the unit of |
| your duration is. It is all deterministic, and inspect-able. But it can |
| be inconvenient to do so, especially if you just need to print out a |
| "debugging" statement. For example: |
| </p> |
| <pre class="programlisting"><span class="comment">// round to nearest, to even on tie</span> |
| <span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">To</span></code></a><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Rep</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Period</span><span class="special">></span> |
| <span class="identifier">To</span> |
| <span class="identifier">round</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">duration</span><span class="special"><</span><span class="identifier">Rep</span><span class="special">,</span> <span class="identifier">Period</span><span class="special">>&</span> <span class="identifier">d</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="identifier">To</span> <span class="identifier">t0</span> <span class="special">=</span> <span class="identifier">duration_cast</span><span class="special"><</span><span class="identifier">To</span><span class="special">>(</span><span class="identifier">d</span><span class="special">);</span> |
| <span class="identifier">To</span> <span class="identifier">t1</span> <span class="special">=</span> <span class="identifier">t0</span><span class="special">;</span> |
| <span class="special">++</span><span class="identifier">t1</span><span class="special">;</span> |
| <span class="keyword">auto</span> <span class="identifier">diff0</span> <span class="special">=</span> <span class="identifier">d</span> <span class="special">-</span> <span class="identifier">t0</span><span class="special">;</span> |
| <span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"diff0 = "</span> <span class="special"><<</span> <span class="identifier">diff0</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> |
| <span class="keyword">auto</span> <span class="identifier">diff1</span> <span class="special">=</span> <span class="identifier">t1</span> <span class="special">-</span> <span class="identifier">d</span><span class="special">;</span> |
| <span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"diff1 = "</span> <span class="special"><<</span> <span class="identifier">diff1</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> |
| <span class="keyword">if</span> <span class="special">(</span><span class="identifier">diff0</span> <span class="special">==</span> <span class="identifier">diff1</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="keyword">if</span> <span class="special">(</span><span class="identifier">t0</span><span class="special">.</span><span class="identifier">count</span><span class="special">()</span> <span class="special">&</span> <span class="number">1</span><span class="special">)</span> |
| <span class="keyword">return</span> <span class="identifier">t1</span><span class="special">;</span> |
| <span class="keyword">return</span> <span class="identifier">t0</span><span class="special">;</span> |
| <span class="special">}</span> |
| <span class="keyword">else</span> <span class="keyword">if</span> <span class="special">(</span><span class="identifier">diff0</span> <span class="special"><</span> <span class="identifier">diff1</span><span class="special">)</span> |
| <span class="keyword">return</span> <span class="identifier">t0</span><span class="special">;</span> |
| <span class="keyword">return</span> <span class="identifier">t1</span><span class="special">;</span> |
| <span class="special">}</span> |
| </pre> |
| <p> |
| This is where I/O for duration really shines. The compiler knows what |
| the type of diff0 is and with this proposal that type (with proper units) |
| will automatically be printed out for you. For example: |
| </p> |
| <pre class="programlisting"><span class="identifier">milliseconds</span> <span class="identifier">ms</span> <span class="special">=</span> <span class="identifier">round</span><span class="special"><</span><span class="identifier">milliseconds</span><span class="special">>(</span><span class="identifier">nanoseconds</span><span class="special">(</span><span class="number">123</span><span class="special">));</span> <span class="comment">// diff0 = 123 nanoseconds</span> |
| <span class="comment">// diff1 = 999877 nanoseconds</span> |
| <span class="identifier">milliseconds</span> <span class="identifier">ms</span> <span class="special">=</span> <span class="identifier">round</span><span class="special"><</span><span class="identifier">milliseconds</span><span class="special">>(</span><span class="identifier">Ticks</span><span class="special">(</span><span class="number">44</span><span class="special">));</span> <span class="comment">// diff0 = 2 [1/3000]seconds</span> |
| <span class="comment">// diff1 = 1 [1/3000]second</span> |
| </pre> |
| <p> |
| This simple I/O will make duration so much more accessible to programmers. |
| </p> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h5 class="title"> |
| <a name="chrono.users_guide.tutorial.i_o.system_clock_time_point_io"></a><a class="link" href="users_guide.html#chrono.users_guide.tutorial.i_o.system_clock_time_point_io" title="system_clock::time_point"><code class="computeroutput"><span class="identifier">system_clock</span><span class="special">::</span><span class="identifier">time_point</span></code></a> |
| </h5></div></div></div> |
| <p> |
| <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.system_clock" title="Class system_clock"><code class="computeroutput"><span class="identifier">system_clock</span></code></a> is special. It |
| is the only clock that has conversions between its <code class="computeroutput"><span class="identifier">time_point</span></code> |
| and <code class="computeroutput"><span class="identifier">time_t</span></code>. C subsequently |
| relates time_t to the <a href="http://en.wikipedia.org/wiki/Gregorian_calendar" target="_top">Gregorian |
| calendar</a> via <code class="computeroutput"><span class="identifier">ctime</span></code>, |
| <code class="computeroutput"><span class="identifier">gmtime</span></code>, <code class="computeroutput"><span class="identifier">localtime</span></code>, and <code class="computeroutput"><span class="identifier">strftime</span></code>. |
| Neither C, nor POSIX relate <code class="computeroutput"><span class="identifier">time_t</span></code> |
| to any calendar other than the <a href="http://en.wikipedia.org/wiki/Gregorian_calendar" target="_top">Gregorian |
| calendar</a>. ISO 8601 is specified only in terms of the <a href="http://en.wikipedia.org/wiki/Gregorian_calendar" target="_top">Gregorian |
| calendar</a>. |
| </p> |
| <p> |
| <span class="bold"><strong>Boost.Chrono</strong></span> provides <code class="computeroutput"><span class="identifier">system_clock</span><span class="special">::</span><span class="identifier">time_point</span></code> I/O in terms of the Gregorian |
| calendar, and no other calendar. However as <code class="computeroutput"><span class="identifier">system_clock</span><span class="special">::</span><span class="identifier">time_point</span></code> |
| remains convertible with <code class="computeroutput"><span class="identifier">time_t</span></code>, |
| it is possible for clients to create other calendars which interoperate |
| with <code class="computeroutput"><span class="identifier">time_t</span></code> and subsequently |
| <code class="computeroutput"><span class="identifier">system_clock</span><span class="special">::</span><span class="identifier">time_point</span></code>. |
| </p> |
| <p> |
| Furthermore, it is existing practice for all major hosted operating systems |
| to store system time in a format which facilitates display as <a href="http://en.wikipedia.org/wiki/Coordinated_Universal_Time" target="_top">Coordinated |
| Universal Time</a> (UTC). Therefore <span class="bold"><strong>Boost.Chrono</strong></span> |
| provides that the default output for <code class="computeroutput"><span class="identifier">system_clock</span><span class="special">::</span><span class="identifier">time_point</span></code> |
| be in a format that represents a point in time with respect to UTC. |
| </p> |
| <pre class="programlisting"><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">system_clock</span><span class="special">::</span><span class="identifier">now</span><span class="special">()</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> |
| </pre> |
| <p> |
| could output |
| </p> |
| <pre class="programlisting"><span class="number">2011</span><span class="special">-</span><span class="number">09</span><span class="special">-</span><span class="number">15</span> <span class="number">18</span><span class="special">:</span><span class="number">36</span><span class="special">:</span><span class="number">59.325132</span> <span class="special">+</span><span class="number">0000</span> |
| </pre> |
| <p> |
| This format is strongly influenced by ISO 8601, but places a ' ' between |
| the date and time instead of a 'T'. The former appears to more accurately |
| represent existing practice. A fully numeric format was chosen so as |
| to be understandable to as large a group of human readers as possible. |
| A 24 hour format was chosen for the same reasons. |
| </p> |
| <p> |
| Of the referenced standards, only ISO 8601 discusses the output of fractional |
| seconds. Neither C nor POSIX have built-in functionality for this. However |
| it appears to be universal (as of this writing) that <code class="computeroutput"><span class="identifier">system_clock</span><span class="special">::</span><span class="identifier">period</span></code> |
| is sub-second. And it seems desirable that if you stream out a <code class="computeroutput"><span class="identifier">system_clock</span><span class="special">::</span><span class="identifier">time_point</span></code>, you ought to be able to |
| stream it back in and get the same value. Therefore the streaming of |
| fractional seconds (at least by default) appears to be unavoidable. |
| </p> |
| <p> |
| Finally the trailing " +0000" disambiguates the UTC-formatted |
| <code class="computeroutput"><span class="identifier">system_clock</span><span class="special">::</span><span class="identifier">time_point</span></code> from one formatted with |
| respect to the local time zone of the computer. The latter can easily |
| be achieved with: |
| </p> |
| <pre class="programlisting"><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">time_fmt</span><span class="special">(</span><span class="identifier">local</span><span class="special">)</span> <span class="special"><<</span> <span class="identifier">system_clock</span><span class="special">::</span><span class="identifier">now</span><span class="special">()</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> |
| </pre> |
| <p> |
| that could result in |
| </p> |
| <pre class="programlisting"><span class="number">2011</span><span class="special">-</span><span class="number">09</span><span class="special">-</span><span class="number">15</span> <span class="number">14</span><span class="special">:</span><span class="number">36</span><span class="special">:</span><span class="number">59.325132</span> <span class="special">-</span><span class="number">0400</span> |
| </pre> |
| <p> |
| Note that <code class="computeroutput"><span class="identifier">system_clock</span><span class="special">::</span><span class="identifier">time_point</span></code> |
| itself is neither UTC, nor the local time. However in practice, <code class="computeroutput"><span class="identifier">system_clock</span><span class="special">::</span><span class="identifier">time_point</span></code> is a count of ticks beyond |
| some epoch which is synchronized with UTC. So as a mobile computer moves |
| across time zones, the time zone traversal does not impact the value |
| of a <code class="computeroutput"><span class="identifier">system_clock</span><span class="special">::</span><span class="identifier">time_point</span></code> produced by <code class="computeroutput"><span class="identifier">system_clock</span><span class="special">::</span><span class="identifier">now</span><span class="special">()</span></code>. |
| And it is only in formatting it for human consumption that one can choose |
| UTC or the local time zone. C and POSIX treat <code class="computeroutput"><span class="identifier">time_t</span></code> |
| just as <span class="bold"><strong>Boost.Chrono</strong></span> treats <code class="computeroutput"><span class="identifier">system_clock</span><span class="special">::</span><span class="identifier">time_point</span></code>: |
| </p> |
| <pre class="programlisting"><span class="identifier">tm</span><span class="special">*</span> <span class="identifier">gmtime</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">time_t</span><span class="special">*</span> <span class="identifier">timer</span><span class="special">)</span> <span class="special">-></span> <span class="identifier">UTC</span> |
| <span class="identifier">tm</span><span class="special">*</span> <span class="identifier">localtime</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">time_t</span><span class="special">*</span> <span class="identifier">timer</span><span class="special">)</span> <span class="special">-></span> <span class="identifier">local</span> <span class="identifier">time</span> |
| </pre> |
| <p> |
| This proposal simply extends the C/POSIX <code class="computeroutput"><span class="identifier">time_t</span></code> |
| functionality to C++ syntax and <code class="computeroutput"><span class="identifier">system_clock</span><span class="special">::</span><span class="identifier">time_point</span></code>. |
| </p> |
| <p> |
| The <code class="computeroutput"><span class="identifier">time_fmt</span><span class="special">()</span></code> |
| manipulator is "sticky". It will remain in effect until the |
| stream destructs or until it is changed. The stream can be reset to its |
| default state with: |
| </p> |
| <pre class="programlisting"><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">time_fmt</span><span class="special">(</span><span class="identifier">utc</span><span class="special">);</span> |
| </pre> |
| <p> |
| And the formatting can be further customized by using the time format |
| sequences. For example: |
| </p> |
| <pre class="programlisting"><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">time_fmt</span><span class="special">(</span><span class="identifier">local</span><span class="special">,</span> <span class="string">"%A %B %e, %Y %r"</span><span class="special">);</span> |
| <span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">system_clock</span><span class="special">::</span><span class="identifier">now</span><span class="special">()</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> <span class="comment">// Sunday April 24, 2011 02:36:59 PM</span> |
| </pre> |
| <p> |
| When specifying formatting manipulators for wide streams, use wide strings. |
| </p> |
| <p> |
| You can use the same manipulators with istreams to specify parsing sequences. |
| </p> |
| <p> |
| Unfortunately there are no formatting/parsing sequences which indicate |
| fractional seconds. <span class="bold"><strong>Boost.Chrono</strong></span> does |
| not provide such sequences. In the meantime, one can format and parse |
| fractional seconds for <code class="computeroutput"><span class="identifier">system_clock</span><span class="special">::</span><span class="identifier">time_point</span></code> |
| by defaulting the format, or by using an empty string in <code class="computeroutput"><span class="identifier">time_fmt</span><span class="special">()</span></code>. |
| </p> |
| <p> |
| The stream's current locale may impact the parsing/format sequences supplied |
| to the <code class="computeroutput"><span class="identifier">system_clock</span><span class="special">::</span><span class="identifier">time_point</span></code> manipulators (e.g. names |
| of days of the week, and names of months). |
| </p> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h5 class="title"> |
| <a name="chrono.users_guide.tutorial.i_o.other_clocks_time_point_io"></a><a class="link" href="users_guide.html#chrono.users_guide.tutorial.i_o.other_clocks_time_point_io" title="Other clocks time_point">Other |
| clocks time_point</a> |
| </h5></div></div></div> |
| <p> |
| Unlike <code class="computeroutput"><span class="identifier">system_clock</span><span class="special">::</span><span class="identifier">time_point</span></code>, the other clocks have no |
| conversion with <code class="computeroutput"><span class="identifier">time_t</span></code>. |
| There is likely no relationship between steady_clock::time_point and |
| UTC at all (UTC is not steady). |
| </p> |
| <p> |
| In general a <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a> is formatted by outputting |
| its internal <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> followed by a string |
| that describes the <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a><code class="computeroutput"><span class="special">::</span><span class="identifier">clock</span></code> epoch. This string will vary |
| for each distinct clock, and for each implementation of the supplied |
| clocks. |
| </p> |
| <pre class="programlisting"><span class="preprocessor">#ifdef</span> <span class="identifier">BOOST_CHRONO_HAS_CLOCK_STEADY</span> |
| <span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"steady_clock::now() = "</span> <span class="special"><<</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">steady_clock</span><span class="special">::</span><span class="identifier">now</span><span class="special">()</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> |
| <span class="preprocessor">#endif</span> |
| <span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"\nSet cout to use long names:\n"</span> |
| <span class="special"><<</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">duration_long</span> |
| <span class="special"><<</span> <span class="string">"high_resolution_clock::now() = "</span> |
| <span class="special"><<</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">high_resolution_clock</span><span class="special">::</span><span class="identifier">now</span><span class="special">()</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> |
| </pre> |
| <p> |
| The output could be |
| </p> |
| <pre class="programlisting"><span class="identifier">steady_clock</span><span class="special">::</span><span class="identifier">now</span><span class="special">()</span> <span class="special">=</span> <span class="number">37297387636417</span> <span class="identifier">ns</span> <span class="identifier">since</span> <span class="identifier">boot</span> |
| |
| <span class="identifier">Set</span> <span class="identifier">cout</span> <span class="identifier">to</span> <span class="identifier">use</span> <span class="keyword">long</span> <span class="identifier">names</span><span class="special">:</span> |
| <span class="identifier">high_resolution_clock</span><span class="special">::</span><span class="identifier">now</span><span class="special">()</span> <span class="special">=</span> <span class="number">37297387655134</span> <span class="identifier">nanoseconds</span> <span class="identifier">since</span> <span class="identifier">boot</span> |
| </pre> |
| <p> |
| Parsing a <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a> involves first parsing |
| a <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> and then parsing the |
| epoch string. If the epoch string does not match that associated with |
| <code class="computeroutput"><span class="identifier">time_point</span><span class="special">::</span><span class="identifier">clock</span></code> then failbit will be set. |
| </p> |
| <p> |
| <span class="bold"><strong>Example:</strong></span> |
| </p> |
| <pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">chrono</span><span class="special">/</span><span class="identifier">chrono_io</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> |
| <span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">sstream</span><span class="special">></span> |
| <span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">iostream</span><span class="special">></span> |
| <span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">cassert</span><span class="special">></span> |
| |
| <span class="keyword">int</span> <span class="identifier">main</span><span class="special">()</span> |
| <span class="special">{</span> |
| <span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">std</span><span class="special">;</span> |
| |
| <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">high_resolution_clock</span><span class="special">::</span><span class="identifier">time_point</span> <span class="identifier">t0</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">high_resolution_clock</span><span class="special">::</span><span class="identifier">now</span><span class="special">();</span> |
| <span class="identifier">stringstream</span> <span class="identifier">io</span><span class="special">;</span> |
| <span class="identifier">io</span> <span class="special"><<</span> <span class="identifier">t0</span><span class="special">;</span> |
| <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">high_resolution_clock</span><span class="special">::</span><span class="identifier">time_point</span> <span class="identifier">t1</span><span class="special">;</span> |
| <span class="identifier">io</span> <span class="special">>></span> <span class="identifier">t1</span><span class="special">;</span> |
| <span class="identifier">assert</span><span class="special">(!</span><span class="identifier">io</span><span class="special">.</span><span class="identifier">fail</span><span class="special">());</span> |
| <span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">io</span><span class="special">.</span><span class="identifier">str</span><span class="special">()</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> |
| <span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">t0</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> |
| <span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">t1</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> |
| <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">high_resolution_clock</span><span class="special">::</span><span class="identifier">time_point</span> <span class="identifier">t</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">high_resolution_clock</span><span class="special">::</span><span class="identifier">now</span><span class="special">();</span> |
| <span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">t</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> |
| |
| <span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"That took "</span> <span class="special"><<</span> <span class="identifier">t</span> <span class="special">-</span> <span class="identifier">t0</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> |
| <span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"That took "</span> <span class="special"><<</span> <span class="identifier">t</span> <span class="special">-</span> <span class="identifier">t1</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> |
| |
| <span class="keyword">return</span> <span class="number">0</span><span class="special">;</span> |
| <span class="special">}</span> |
| </pre> |
| <p> |
| The output could be: |
| </p> |
| <pre class="programlisting"><span class="number">50908679121461</span> <span class="identifier">nanoseconds</span> <span class="identifier">since</span> <span class="identifier">boot</span> |
| <span class="identifier">That</span> <span class="identifier">took</span> <span class="number">649630</span> <span class="identifier">nanoseconds</span> |
| </pre> |
| <p> |
| Here's a simple example to find out how many hours the computer has been |
| up (on this platform): |
| </p> |
| <pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">chrono</span><span class="special">/</span><span class="identifier">chrono_io</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> |
| <span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">iostream</span><span class="special">></span> |
| |
| <span class="keyword">int</span> <span class="identifier">main</span><span class="special">()</span> |
| <span class="special">{</span> |
| <span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">std</span><span class="special">;</span> |
| <span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">boost</span><span class="special">;</span> |
| |
| <span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">time_point</span><span class="special"><</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">steady_clock</span><span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">duration</span><span class="special"><</span><span class="keyword">double</span><span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">ratio</span><span class="special"><</span><span class="number">3600</span><span class="special">></span> <span class="special">></span> <span class="special">></span> <span class="identifier">T</span><span class="special">;</span> |
| <span class="identifier">T</span> <span class="identifier">tp</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">steady_clock</span><span class="special">::</span><span class="identifier">now</span><span class="special">();</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">tp</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> |
| <span class="keyword">return</span> <span class="number">0</span><span class="special">;</span> |
| <span class="special">}</span> |
| </pre> |
| <p> |
| The output could be: |
| </p> |
| <pre class="programlisting"><span class="number">17.8666</span> <span class="identifier">hours</span> <span class="identifier">since</span> <span class="identifier">boot</span> |
| </pre> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h5 class="title"> |
| <a name="chrono.users_guide.tutorial.i_o.low_level_i_o"></a><a class="link" href="users_guide.html#chrono.users_guide.tutorial.i_o.low_level_i_o" title="Low level I/O">Low |
| level I/O</a> |
| </h5></div></div></div> |
| <p> |
| The I/O interface described in the preceding I/O sections were at the |
| user level. These services are based on low level services that are useful |
| when writing libraries. The low level services are related to access |
| to the associated ios state and locale facets. The design follows the |
| C++ IOStreams standard design: |
| </p> |
| <p> |
| The library encapsulate the locale-dependent parsing and formatting of |
| <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> into a new facet class. |
| Let's focus on formatting in this example. The concerned facet class |
| is <a class="link" href="reference.html#chrono.reference.io.duration_put_hpp.duration_put" title="Template Class duration_put"><code class="computeroutput"><span class="identifier">duration_put</span></code></a>, analogous to time_put, |
| money_put, etc. |
| </p> |
| <p> |
| The use of this facet is similar to the time_put facet. |
| </p> |
| </div> |
| </div> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h3 class="title"> |
| <a name="chrono.users_guide.examples"></a><a class="link" href="users_guide.html#chrono.users_guide.examples" title="Examples">Examples</a> |
| </h3></div></div></div> |
| <div class="toc"><dl class="toc"> |
| <dt><span class="section"><a href="users_guide.html#chrono.users_guide.examples.duration">Duration</a></span></dt> |
| <dt><span class="section"><a href="users_guide.html#chrono.users_guide.examples.clocks">Clocks</a></span></dt> |
| <dt><span class="section"><a href="users_guide.html#chrono.users_guide.examples.time_point">Time Point</a></span></dt> |
| <dt><span class="section"><a href="users_guide.html#chrono.users_guide.examples.io">IO</a></span></dt> |
| </dl></div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h4 class="title"> |
| <a name="chrono.users_guide.examples.duration"></a><a class="link" href="users_guide.html#chrono.users_guide.examples.duration" title="Duration">Duration</a> |
| </h4></div></div></div> |
| <div class="toc"><dl class="toc"> |
| <dt><span class="section"><a href="users_guide.html#chrono.users_guide.examples.duration.how_you_override_the_duration_s_default_constructor">How |
| you Override the Duration's Default Constructor</a></span></dt> |
| <dt><span class="section"><a href="users_guide.html#chrono.users_guide.examples.duration.saturating">Saturating</a></span></dt> |
| <dt><span class="section"><a href="users_guide.html#chrono.users_guide.examples.duration.xtime_conversions">xtime |
| Conversions</a></span></dt> |
| </dl></div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h5 class="title"> |
| <a name="chrono.users_guide.examples.duration.how_you_override_the_duration_s_default_constructor"></a><a class="link" href="users_guide.html#chrono.users_guide.examples.duration.how_you_override_the_duration_s_default_constructor" title="How you Override the Duration's Default Constructor">How |
| you Override the Duration's Default Constructor</a> |
| </h5></div></div></div> |
| <p> |
| Next we show how to override the <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>'s default constructor |
| to do anything you want (in this case set it to zero). All we need to |
| do is to change the representation |
| </p> |
| <pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">I_dont_like_the_default_duration_behavior</span> <span class="special">{</span> |
| |
| <span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">R</span><span class="special">></span> |
| <span class="keyword">class</span> <span class="identifier">zero_default</span> |
| <span class="special">{</span> |
| <span class="keyword">public</span><span class="special">:</span> |
| <span class="keyword">typedef</span> <span class="identifier">R</span> <span class="identifier">rep</span><span class="special">;</span> |
| |
| <span class="keyword">private</span><span class="special">:</span> |
| <span class="identifier">rep</span> <span class="identifier">rep_</span><span class="special">;</span> |
| <span class="keyword">public</span><span class="special">:</span> |
| <span class="identifier">zero_default</span><span class="special">(</span><span class="identifier">rep</span> <span class="identifier">i</span> <span class="special">=</span> <span class="number">0</span><span class="special">)</span> <span class="special">:</span> <span class="identifier">rep_</span><span class="special">(</span><span class="identifier">i</span><span class="special">)</span> <span class="special">{}</span> |
| <span class="keyword">operator</span> <span class="identifier">rep</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">{</span><span class="keyword">return</span> <span class="identifier">rep_</span><span class="special">;}</span> |
| |
| <span class="identifier">zero_default</span><span class="special">&</span> <span class="keyword">operator</span><span class="special">+=(</span><span class="identifier">zero_default</span> <span class="identifier">x</span><span class="special">)</span> <span class="special">{</span><span class="identifier">rep_</span> <span class="special">+=</span> <span class="identifier">x</span><span class="special">.</span><span class="identifier">rep_</span><span class="special">;</span> <span class="keyword">return</span> <span class="special">*</span><span class="keyword">this</span><span class="special">;}</span> |
| <span class="identifier">zero_default</span><span class="special">&</span> <span class="keyword">operator</span><span class="special">-=(</span><span class="identifier">zero_default</span> <span class="identifier">x</span><span class="special">)</span> <span class="special">{</span><span class="identifier">rep_</span> <span class="special">-=</span> <span class="identifier">x</span><span class="special">.</span><span class="identifier">rep_</span><span class="special">;</span> <span class="keyword">return</span> <span class="special">*</span><span class="keyword">this</span><span class="special">;}</span> |
| <span class="identifier">zero_default</span><span class="special">&</span> <span class="keyword">operator</span><span class="special">*=(</span><span class="identifier">zero_default</span> <span class="identifier">x</span><span class="special">)</span> <span class="special">{</span><span class="identifier">rep_</span> <span class="special">*=</span> <span class="identifier">x</span><span class="special">.</span><span class="identifier">rep_</span><span class="special">;</span> <span class="keyword">return</span> <span class="special">*</span><span class="keyword">this</span><span class="special">;}</span> |
| <span class="identifier">zero_default</span><span class="special">&</span> <span class="keyword">operator</span><span class="special">/=(</span><span class="identifier">zero_default</span> <span class="identifier">x</span><span class="special">)</span> <span class="special">{</span><span class="identifier">rep_</span> <span class="special">/=</span> <span class="identifier">x</span><span class="special">.</span><span class="identifier">rep_</span><span class="special">;</span> <span class="keyword">return</span> <span class="special">*</span><span class="keyword">this</span><span class="special">;}</span> |
| |
| <span class="identifier">zero_default</span> <span class="keyword">operator</span><span class="special">+</span> <span class="special">()</span> <span class="keyword">const</span> <span class="special">{</span><span class="keyword">return</span> <span class="special">*</span><span class="keyword">this</span><span class="special">;}</span> |
| <span class="identifier">zero_default</span> <span class="keyword">operator</span><span class="special">-</span> <span class="special">()</span> <span class="keyword">const</span> <span class="special">{</span><span class="keyword">return</span> <span class="identifier">zero_default</span><span class="special">(-</span><span class="identifier">rep_</span><span class="special">);}</span> |
| <span class="identifier">zero_default</span><span class="special">&</span> <span class="keyword">operator</span><span class="special">++()</span> <span class="special">{++</span><span class="identifier">rep_</span><span class="special">;</span> <span class="keyword">return</span> <span class="special">*</span><span class="keyword">this</span><span class="special">;}</span> |
| <span class="identifier">zero_default</span> <span class="keyword">operator</span><span class="special">++(</span><span class="keyword">int</span><span class="special">)</span> <span class="special">{</span><span class="keyword">return</span> <span class="identifier">zero_default</span><span class="special">(</span><span class="identifier">rep_</span><span class="special">++);}</span> |
| <span class="identifier">zero_default</span><span class="special">&</span> <span class="keyword">operator</span><span class="special">--()</span> <span class="special">{--</span><span class="identifier">rep_</span><span class="special">;</span> <span class="keyword">return</span> <span class="special">*</span><span class="keyword">this</span><span class="special">;}</span> |
| <span class="identifier">zero_default</span> <span class="keyword">operator</span><span class="special">--(</span><span class="keyword">int</span><span class="special">)</span> <span class="special">{</span><span class="keyword">return</span> <span class="identifier">zero_default</span><span class="special">(</span><span class="identifier">rep_</span><span class="special">--);}</span> |
| |
| <span class="keyword">friend</span> <span class="identifier">zero_default</span> <span class="keyword">operator</span><span class="special">+(</span><span class="identifier">zero_default</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">zero_default</span> <span class="identifier">y</span><span class="special">)</span> <span class="special">{</span><span class="keyword">return</span> <span class="identifier">x</span> <span class="special">+=</span> <span class="identifier">y</span><span class="special">;}</span> |
| <span class="keyword">friend</span> <span class="identifier">zero_default</span> <span class="keyword">operator</span><span class="special">-(</span><span class="identifier">zero_default</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">zero_default</span> <span class="identifier">y</span><span class="special">)</span> <span class="special">{</span><span class="keyword">return</span> <span class="identifier">x</span> <span class="special">-=</span> <span class="identifier">y</span><span class="special">;}</span> |
| <span class="keyword">friend</span> <span class="identifier">zero_default</span> <span class="keyword">operator</span><span class="special">*(</span><span class="identifier">zero_default</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">zero_default</span> <span class="identifier">y</span><span class="special">)</span> <span class="special">{</span><span class="keyword">return</span> <span class="identifier">x</span> <span class="special">*=</span> <span class="identifier">y</span><span class="special">;}</span> |
| <span class="keyword">friend</span> <span class="identifier">zero_default</span> <span class="keyword">operator</span><span class="special">/(</span><span class="identifier">zero_default</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">zero_default</span> <span class="identifier">y</span><span class="special">)</span> <span class="special">{</span><span class="keyword">return</span> <span class="identifier">x</span> <span class="special">/=</span> <span class="identifier">y</span><span class="special">;}</span> |
| |
| <span class="keyword">friend</span> <span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">==(</span><span class="identifier">zero_default</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">zero_default</span> <span class="identifier">y</span><span class="special">)</span> <span class="special">{</span><span class="keyword">return</span> <span class="identifier">x</span><span class="special">.</span><span class="identifier">rep_</span> <span class="special">==</span> <span class="identifier">y</span><span class="special">.</span><span class="identifier">rep_</span><span class="special">;}</span> |
| <span class="keyword">friend</span> <span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">!=(</span><span class="identifier">zero_default</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">zero_default</span> <span class="identifier">y</span><span class="special">)</span> <span class="special">{</span><span class="keyword">return</span> <span class="special">!(</span><span class="identifier">x</span> <span class="special">==</span> <span class="identifier">y</span><span class="special">);}</span> |
| <span class="keyword">friend</span> <span class="keyword">bool</span> <span class="keyword">operator</span><span class="special"><</span> <span class="special">(</span><span class="identifier">zero_default</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">zero_default</span> <span class="identifier">y</span><span class="special">)</span> <span class="special">{</span><span class="keyword">return</span> <span class="identifier">x</span><span class="special">.</span><span class="identifier">rep_</span> <span class="special"><</span> <span class="identifier">y</span><span class="special">.</span><span class="identifier">rep_</span><span class="special">;}</span> |
| <span class="keyword">friend</span> <span class="keyword">bool</span> <span class="keyword">operator</span><span class="special"><=(</span><span class="identifier">zero_default</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">zero_default</span> <span class="identifier">y</span><span class="special">)</span> <span class="special">{</span><span class="keyword">return</span> <span class="special">!(</span><span class="identifier">y</span> <span class="special"><</span> <span class="identifier">x</span><span class="special">);}</span> |
| <span class="keyword">friend</span> <span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">></span> <span class="special">(</span><span class="identifier">zero_default</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">zero_default</span> <span class="identifier">y</span><span class="special">)</span> <span class="special">{</span><span class="keyword">return</span> <span class="identifier">y</span> <span class="special"><</span> <span class="identifier">x</span><span class="special">;}</span> |
| <span class="keyword">friend</span> <span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">>=(</span><span class="identifier">zero_default</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">zero_default</span> <span class="identifier">y</span><span class="special">)</span> <span class="special">{</span><span class="keyword">return</span> <span class="special">!(</span><span class="identifier">x</span> <span class="special"><</span> <span class="identifier">y</span><span class="special">);}</span> |
| <span class="special">};</span> |
| |
| <span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a><span class="special"><</span><span class="identifier">zero_default</span><span class="special"><</span><span class="keyword">long</span> <span class="keyword">long</span><span class="special">>,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">nano</span> <span class="special">></span> <span class="identifier">nanoseconds</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a><span class="special"><</span><span class="identifier">zero_default</span><span class="special"><</span><span class="keyword">long</span> <span class="keyword">long</span><span class="special">>,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">micro</span> <span class="special">></span> <span class="identifier">microseconds</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a><span class="special"><</span><span class="identifier">zero_default</span><span class="special"><</span><span class="keyword">long</span> <span class="keyword">long</span><span class="special">>,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">milli</span> <span class="special">></span> <span class="identifier">milliseconds</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a><span class="special"><</span><span class="identifier">zero_default</span><span class="special"><</span><span class="keyword">long</span> <span class="keyword">long</span><span class="special">></span> <span class="special">></span> <span class="identifier">seconds</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a><span class="special"><</span><span class="identifier">zero_default</span><span class="special"><</span><span class="keyword">long</span> <span class="keyword">long</span><span class="special">>,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">ratio</span><span class="special"><</span><span class="number">60</span><span class="special">></span> <span class="special">></span> <span class="identifier">minutes</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a><span class="special"><</span><span class="identifier">zero_default</span><span class="special"><</span><span class="keyword">long</span> <span class="keyword">long</span><span class="special">>,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">ratio</span><span class="special"><</span><span class="number">3600</span><span class="special">></span> <span class="special">></span> <span class="identifier">hours</span><span class="special">;</span> |
| <span class="special">}</span> |
| </pre> |
| <p> |
| Usage |
| </p> |
| <pre class="programlisting"><span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">I_dont_like_the_default_duration_behavior</span><span class="special">;</span> |
| |
| <span class="identifier">milliseconds</span> <span class="identifier">ms</span><span class="special">;</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">ms</span><span class="special">.</span><span class="identifier">count</span><span class="special">()</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> |
| </pre> |
| <p> |
| <span class="emphasis"><em>See the source file <a href="../../../libs/chrono/example/i_dont_like_the_default_duration_behavior.cpp" target="_top">example/i_dont_like_the_default_duration_behavior.cpp</a></em></span> |
| </p> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h5 class="title"> |
| <a name="chrono.users_guide.examples.duration.saturating"></a><a class="link" href="users_guide.html#chrono.users_guide.examples.duration.saturating" title="Saturating">Saturating</a> |
| </h5></div></div></div> |
| <p> |
| A "saturating" signed integral type is developed. This type |
| has +/- infinity and a NaN (like IEEE floating-point) but otherwise obeys |
| signed integral arithmetic. This class is subsequently used as the template |
| parameter Rep in boost::chrono::<a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> to demonstrate a duration |
| class that does not silently ignore overflow. |
| </p> |
| <p> |
| <span class="emphasis"><em>See the source file <a href="../../../libs/chrono/example/saturating.cpp" target="_top">example/saturating.cpp</a></em></span> |
| </p> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h5 class="title"> |
| <a name="chrono.users_guide.examples.duration.xtime_conversions"></a><a class="link" href="users_guide.html#chrono.users_guide.examples.duration.xtime_conversions" title="xtime Conversions">xtime |
| Conversions</a> |
| </h5></div></div></div> |
| <p> |
| Example round_up utility: converts d to To, rounding up for inexact conversions |
| Being able to <span class="bold"><strong>easily</strong></span> write this function |
| is a major feature! |
| </p> |
| <pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">chrono</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> |
| <span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">type_traits</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> |
| |
| <span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">iostream</span><span class="special">></span> |
| |
| <span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">To</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Rep</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Period</span><span class="special">></span> |
| <span class="identifier">To</span> |
| <span class="identifier">round_up</span><span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">duration</span><span class="special"><</span><span class="identifier">Rep</span><span class="special">,</span> <span class="identifier">Period</span><span class="special">></span> <span class="identifier">d</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="identifier">To</span> <span class="identifier">result</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">duration_cast</span><span class="special"><</span><span class="identifier">To</span><span class="special">>(</span><span class="identifier">d</span><span class="special">);</span> |
| <span class="keyword">if</span> <span class="special">(</span><span class="identifier">result</span> <span class="special"><</span> <span class="identifier">d</span><span class="special">)</span> |
| <span class="special">++</span><span class="identifier">result</span><span class="special">;</span> |
| <span class="keyword">return</span> <span class="identifier">result</span><span class="special">;</span> |
| <span class="special">}</span> |
| </pre> |
| <p> |
| To demonstrate interaction with an xtime-like facility: |
| </p> |
| <pre class="programlisting"><span class="keyword">struct</span> <span class="identifier">xtime</span> |
| <span class="special">{</span> |
| <span class="keyword">long</span> <span class="identifier">sec</span><span class="special">;</span> |
| <span class="keyword">unsigned</span> <span class="keyword">long</span> <span class="identifier">usec</span><span class="special">;</span> |
| <span class="special">};</span> |
| |
| <span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">Rep</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Period</span><span class="special">></span> |
| <span class="identifier">xtime</span> |
| <span class="identifier">to_xtime_truncate</span><span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a><span class="special"><</span><span class="identifier">Rep</span><span class="special">,</span> <span class="identifier">Period</span><span class="special">></span> <span class="identifier">d</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="identifier">xtime</span> <span class="identifier">xt</span><span class="special">;</span> |
| <span class="identifier">xt</span><span class="special">.</span><span class="identifier">sec</span> <span class="special">=</span> <span class="keyword">static_cast</span><span class="special"><</span><span class="keyword">long</span><span class="special">>(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_cast" title="Non-Member Function duration_cast(duration)"><code class="computeroutput"><span class="identifier">duration_cast</span></code></a><span class="special"><</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">seconds</span></code></a><span class="special">>(</span><span class="identifier">d</span><span class="special">).</span><span class="identifier">count</span><span class="special">());</span> |
| <span class="identifier">xt</span><span class="special">.</span><span class="identifier">usec</span> <span class="special">=</span> <span class="keyword">static_cast</span><span class="special"><</span><span class="keyword">long</span><span class="special">>(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_cast" title="Non-Member Function duration_cast(duration)"><code class="computeroutput"><span class="identifier">duration_cast</span></code></a><span class="special"><</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">microseconds</span></code></a><span class="special">>(</span><span class="identifier">d</span> <span class="special">-</span> <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">seconds</span></code></a><span class="special">(</span><span class="identifier">xt</span><span class="special">.</span><span class="identifier">sec</span><span class="special">)).</span><span class="identifier">count</span><span class="special">());</span> |
| <span class="keyword">return</span> <span class="identifier">xt</span><span class="special">;</span> |
| <span class="special">}</span> |
| |
| <span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">Rep</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Period</span><span class="special">></span> |
| <span class="identifier">xtime</span> |
| <span class="identifier">to_xtime_round_up</span><span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a><span class="special"><</span><span class="identifier">Rep</span><span class="special">,</span> <span class="identifier">Period</span><span class="special">></span> <span class="identifier">d</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="identifier">xtime</span> <span class="identifier">xt</span><span class="special">;</span> |
| <span class="identifier">xt</span><span class="special">.</span><span class="identifier">sec</span> <span class="special">=</span> <span class="keyword">static_cast</span><span class="special"><</span><span class="keyword">long</span><span class="special">>(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_cast" title="Non-Member Function duration_cast(duration)"><code class="computeroutput"><span class="identifier">duration_cast</span></code></a><span class="special"><</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">seconds</span></code></a><span class="special">>(</span><span class="identifier">d</span><span class="special">).</span><span class="identifier">count</span><span class="special">());</span> |
| <span class="identifier">xt</span><span class="special">.</span><span class="identifier">usec</span> <span class="special">=</span> <span class="keyword">static_cast</span><span class="special"><</span><span class="keyword">unsigned</span> <span class="keyword">long</span><span class="special">>(</span><span class="identifier">round_up</span><span class="special"><</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">microseconds</span></code></a><span class="special">>(</span><span class="identifier">d</span> <span class="special">-</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">seconds</span></code></a><span class="special">(</span><span class="identifier">xt</span><span class="special">.</span><span class="identifier">sec</span><span class="special">)).</span><span class="identifier">count</span><span class="special">());</span> |
| <span class="keyword">return</span> <span class="identifier">xt</span><span class="special">;</span> |
| <span class="special">}</span> |
| |
| <span class="identifier">microseconds</span> |
| <span class="identifier">from_xtime</span><span class="special">(</span><span class="identifier">xtime</span> <span class="identifier">xt</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="keyword">return</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">seconds</span></code></a><span class="special">(</span><span class="identifier">xt</span><span class="special">.</span><span class="identifier">sec</span><span class="special">)</span> <span class="special">+</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">microseconds</span></code></a><span class="special">(</span><span class="identifier">xt</span><span class="special">.</span><span class="identifier">usec</span><span class="special">);</span> |
| <span class="special">}</span> |
| |
| <span class="keyword">void</span> <span class="identifier">print</span><span class="special">(</span><span class="identifier">xtime</span> <span class="identifier">xt</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="char">'{'</span> <span class="special"><<</span> <span class="identifier">xt</span><span class="special">.</span><span class="identifier">sec</span> <span class="special"><<</span> <span class="char">','</span> <span class="special"><<</span> <span class="identifier">xt</span><span class="special">.</span><span class="identifier">usec</span> <span class="special"><<</span> <span class="string">"}\n"</span><span class="special">;</span> |
| <span class="special">}</span> |
| </pre> |
| <p> |
| Usage |
| </p> |
| <pre class="programlisting"><span class="identifier">xtime</span> <span class="identifier">xt</span> <span class="special">=</span> <span class="identifier">to_xtime_truncate</span><span class="special">(</span><span class="identifier">seconds</span><span class="special">(</span><span class="number">3</span><span class="special">)</span> <span class="special">+</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">milliseconds</span></code></a><span class="special">(</span><span class="number">251</span><span class="special">));</span> |
| <span class="identifier">print</span><span class="special">(</span><span class="identifier">xt</span><span class="special">);</span> |
| <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">milliseconds</span> <span class="identifier">ms</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_cast" title="Non-Member Function duration_cast(duration)"><code class="computeroutput"><span class="identifier">duration_cast</span></code></a><span class="special"><</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">milliseconds</span></code></a><span class="special">>(</span><span class="identifier">from_xtime</span><span class="special">(</span><span class="identifier">xt</span><span class="special">));</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">ms</span><span class="special">.</span><span class="identifier">count</span><span class="special">()</span> <span class="special"><<</span> <span class="string">" milliseconds\n"</span><span class="special">;</span> |
| <span class="identifier">xt</span> <span class="special">=</span> <span class="identifier">to_xtime_round_up</span><span class="special">(</span><span class="identifier">ms</span><span class="special">);</span> |
| <span class="identifier">print</span><span class="special">(</span><span class="identifier">xt</span><span class="special">);</span> |
| <span class="identifier">xt</span> <span class="special">=</span> <span class="identifier">to_xtime_truncate</span><span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">seconds</span><span class="special">(</span><span class="number">3</span><span class="special">)</span> <span class="special">+</span> <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">nanoseconds</span></code></a><span class="special">(</span><span class="number">999</span><span class="special">));</span> |
| <span class="identifier">print</span><span class="special">(</span><span class="identifier">xt</span><span class="special">);</span> |
| <span class="identifier">xt</span> <span class="special">=</span> <span class="identifier">to_xtime_round_up</span><span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">seconds</span><span class="special">(</span><span class="number">3</span><span class="special">)</span> <span class="special">+</span> <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">nanoseconds</span></code></a><span class="special">(</span><span class="number">999</span><span class="special">));</span> |
| <span class="identifier">print</span><span class="special">(</span><span class="identifier">xt</span><span class="special">);</span> |
| </pre> |
| <p> |
| <span class="emphasis"><em>See the source file <a href="../../../libs/chrono/example/xtime.cpp" target="_top">xtime.cpp</a></em></span> |
| </p> |
| </div> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h4 class="title"> |
| <a name="chrono.users_guide.examples.clocks"></a><a class="link" href="users_guide.html#chrono.users_guide.examples.clocks" title="Clocks">Clocks</a> |
| </h4></div></div></div> |
| <div class="toc"><dl class="toc"> |
| <dt><span class="section"><a href="users_guide.html#chrono.users_guide.examples.clocks.cycle_count">Cycle |
| count</a></span></dt> |
| <dt><span class="section"><a href="users_guide.html#chrono.users_guide.examples.clocks.xtime_clock">xtime_clock</a></span></dt> |
| </dl></div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h5 class="title"> |
| <a name="chrono.users_guide.examples.clocks.cycle_count"></a><a class="link" href="users_guide.html#chrono.users_guide.examples.clocks.cycle_count" title="Cycle count">Cycle |
| count</a> |
| </h5></div></div></div> |
| <p> |
| Users can easily create their own clocks, with both points in time and |
| time durations which have a representation and precision of their own |
| choosing. For example if there is a hardware counter which simply increments |
| a count with each cycle of the cpu, one can very easily build clocks, |
| time points and durations on top of that, using only a few tens of lines |
| of code. Such systems can be used to call the time-sensitive threading |
| API's such as sleep, wait on a condition variable, or wait for a mutex |
| lock. The API proposed herein is not sensitive as to whether this is |
| a 300MHz clock (with a 3 1/3 nanosecond tick period) or a 3GHz clock |
| (with a tick period of 1/3 of a nanosecond). And the resulting code will |
| be just as efficient as if the user wrote a special purpose clock cycle |
| counter. |
| </p> |
| <pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">chrono</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> |
| <span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">type_traits</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> |
| <span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">iostream</span><span class="special">></span> |
| |
| <span class="keyword">template</span> <span class="special"><</span><span class="keyword">long</span> <span class="keyword">long</span> <span class="identifier">speed</span><span class="special">></span> |
| <span class="keyword">struct</span> <span class="identifier">cycle_count</span> |
| <span class="special">{</span> |
| <span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">__ratio_multiply__</span><span class="special"><</span><span class="identifier">boost</span><span class="special">::</span><code class="computeroutput"><span class="identifier">ratio</span></code><span class="special"><</span><span class="identifier">speed</span><span class="special">>,</span> <span class="identifier">boost</span><span class="special">::</span><code class="computeroutput"><span class="identifier">mega</span></code><span class="special">>::</span><span class="identifier">type</span> |
| <span class="identifier">frequency</span><span class="special">;</span> <span class="comment">// Mhz</span> |
| <span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">__ratio_divide__</span><span class="special"><</span><span class="identifier">boost</span><span class="special">::</span><code class="computeroutput"><span class="identifier">ratio</span></code><span class="special"><</span><span class="number">1</span><span class="special">>,</span> <span class="identifier">frequency</span><span class="special">>::</span><span class="identifier">type</span> <span class="identifier">period</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="keyword">long</span> <span class="keyword">long</span> <span class="identifier">rep</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a><span class="special"><</span><span class="identifier">rep</span><span class="special">,</span> <span class="identifier">period</span><span class="special">></span> <span class="identifier">duration</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a><span class="special"><</span><span class="identifier">cycle_count</span><span class="special">></span> <span class="identifier">time_point</span><span class="special">;</span> |
| |
| <span class="keyword">static</span> <span class="identifier">time_point</span> <span class="identifier">now</span><span class="special">()</span> |
| <span class="special">{</span> |
| <span class="keyword">static</span> <span class="keyword">long</span> <span class="keyword">long</span> <span class="identifier">tick</span> <span class="special">=</span> <span class="number">0</span><span class="special">;</span> |
| <span class="comment">// return exact cycle count</span> |
| <span class="keyword">return</span> <span class="identifier">time_point</span><span class="special">(</span><span class="identifier">duration</span><span class="special">(++</span><span class="identifier">tick</span><span class="special">));</span> <span class="comment">// fake access to clock cycle count</span> |
| <span class="special">}</span> |
| <span class="special">};</span> |
| |
| <span class="keyword">template</span> <span class="special"><</span><span class="keyword">long</span> <span class="keyword">long</span> <span class="identifier">speed</span><span class="special">></span> |
| <span class="keyword">struct</span> <span class="identifier">approx_cycle_count</span> |
| <span class="special">{</span> |
| <span class="keyword">static</span> <span class="keyword">const</span> <span class="keyword">long</span> <span class="keyword">long</span> <span class="identifier">frequency</span> <span class="special">=</span> <span class="identifier">speed</span> <span class="special">*</span> <span class="number">1000000</span><span class="special">;</span> <span class="comment">// MHz</span> |
| <span class="keyword">typedef</span> <span class="identifier">nanoseconds</span> <span class="identifier">duration</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="identifier">duration</span><span class="special">::</span><span class="identifier">rep</span> <span class="identifier">rep</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="identifier">duration</span><span class="special">::</span><span class="identifier">period</span> <span class="identifier">period</span><span class="special">;</span> |
| <span class="keyword">static</span> <span class="keyword">const</span> <span class="keyword">long</span> <span class="keyword">long</span> <span class="identifier">nanosec_per_sec</span> <span class="special">=</span> <span class="identifier">period</span><span class="special">::</span><span class="identifier">den</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a><span class="special"><</span><span class="identifier">approx_cycle_count</span><span class="special">></span> <span class="identifier">time_point</span><span class="special">;</span> |
| |
| <span class="keyword">static</span> <span class="identifier">time_point</span> <span class="identifier">now</span><span class="special">()</span> |
| <span class="special">{</span> |
| <span class="keyword">static</span> <span class="keyword">long</span> <span class="keyword">long</span> <span class="identifier">tick</span> <span class="special">=</span> <span class="number">0</span><span class="special">;</span> |
| <span class="comment">// return cycle count as an approximate number of nanoseconds</span> |
| <span class="comment">// compute as if nanoseconds is only duration in the std::lib</span> |
| <span class="keyword">return</span> <span class="identifier">time_point</span><span class="special">(</span><span class="identifier">duration</span><span class="special">(++</span><span class="identifier">tick</span> <span class="special">*</span> <span class="identifier">nanosec_per_sec</span> <span class="special">/</span> <span class="identifier">frequency</span><span class="special">));</span> |
| <span class="special">}</span> |
| <span class="special">};</span> |
| </pre> |
| <p> |
| <span class="emphasis"><em>See the source file <a href="../../../libs/chrono/example/cycle_count.cpp" target="_top">cycle_count.cpp</a></em></span> |
| </p> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h5 class="title"> |
| <a name="chrono.users_guide.examples.clocks.xtime_clock"></a><a class="link" href="users_guide.html#chrono.users_guide.examples.clocks.xtime_clock" title="xtime_clock">xtime_clock</a> |
| </h5></div></div></div> |
| <p> |
| This example demonstrates the use of a timeval-like struct to be used |
| as the representation type for both <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> and <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a>. |
| </p> |
| <pre class="programlisting"><span class="keyword">class</span> <span class="identifier">xtime</span> <span class="special">{</span> |
| <span class="keyword">private</span><span class="special">:</span> |
| <span class="keyword">long</span> <span class="identifier">tv_sec</span><span class="special">;</span> |
| <span class="keyword">long</span> <span class="identifier">tv_usec</span><span class="special">;</span> |
| |
| <span class="keyword">void</span> <span class="identifier">fixup</span><span class="special">()</span> <span class="special">{</span> |
| <span class="keyword">if</span> <span class="special">(</span><span class="identifier">tv_usec</span> <span class="special"><</span> <span class="number">0</span><span class="special">)</span> <span class="special">{</span> |
| <span class="identifier">tv_usec</span> <span class="special">+=</span> <span class="number">1000000</span><span class="special">;</span> |
| <span class="special">--</span><span class="identifier">tv_sec</span><span class="special">;</span> |
| <span class="special">}</span> |
| <span class="special">}</span> |
| |
| <span class="keyword">public</span><span class="special">:</span> |
| <span class="keyword">explicit</span> <span class="identifier">xtime</span><span class="special">(</span><span class="keyword">long</span> <span class="identifier">sec</span><span class="special">,</span> <span class="keyword">long</span> <span class="identifier">usec</span><span class="special">)</span> <span class="special">{</span> |
| <span class="identifier">tv_sec</span> <span class="special">=</span> <span class="identifier">sec</span><span class="special">;</span> |
| <span class="identifier">tv_usec</span> <span class="special">=</span> <span class="identifier">usec</span><span class="special">;</span> |
| <span class="keyword">if</span> <span class="special">(</span><span class="identifier">tv_usec</span> <span class="special"><</span> <span class="number">0</span> <span class="special">||</span> <span class="identifier">tv_usec</span> <span class="special">>=</span> <span class="number">1000000</span><span class="special">)</span> <span class="special">{</span> |
| <span class="identifier">tv_sec</span> <span class="special">+=</span> <span class="identifier">tv_usec</span> <span class="special">/</span> <span class="number">1000000</span><span class="special">;</span> |
| <span class="identifier">tv_usec</span> <span class="special">%=</span> <span class="number">1000000</span><span class="special">;</span> |
| <span class="identifier">fixup</span><span class="special">();</span> |
| <span class="special">}</span> |
| <span class="special">}</span> |
| |
| <span class="keyword">explicit</span> <span class="identifier">xtime</span><span class="special">(</span><span class="keyword">long</span> <span class="keyword">long</span> <span class="identifier">usec</span><span class="special">)</span> <span class="special">{</span> |
| <span class="identifier">tv_usec</span> <span class="special">=</span> <span class="keyword">static_cast</span><span class="special"><</span><span class="keyword">long</span><span class="special">>(</span><span class="identifier">usec</span> <span class="special">%</span> <span class="number">1000000</span><span class="special">);</span> |
| <span class="identifier">tv_sec</span> <span class="special">=</span> <span class="keyword">static_cast</span><span class="special"><</span><span class="keyword">long</span><span class="special">>(</span><span class="identifier">usec</span> <span class="special">/</span> <span class="number">1000000</span><span class="special">);</span> |
| <span class="identifier">fixup</span><span class="special">();</span> |
| <span class="special">}</span> |
| |
| <span class="comment">// explicit</span> |
| <span class="keyword">operator</span> <span class="keyword">long</span> <span class="keyword">long</span><span class="special">()</span> <span class="keyword">const</span> <span class="special">{</span><span class="keyword">return</span> <span class="keyword">static_cast</span><span class="special"><</span><span class="keyword">long</span> <span class="keyword">long</span><span class="special">>(</span><span class="identifier">tv_sec</span><span class="special">)</span> <span class="special">*</span> <span class="number">1000000</span> <span class="special">+</span> <span class="identifier">tv_usec</span><span class="special">;}</span> |
| |
| <span class="identifier">xtime</span><span class="special">&</span> <span class="keyword">operator</span> <span class="special">+=</span> <span class="special">(</span><span class="identifier">xtime</span> <span class="identifier">rhs</span><span class="special">)</span> <span class="special">{</span> |
| <span class="identifier">tv_sec</span> <span class="special">+=</span> <span class="identifier">rhs</span><span class="special">.</span><span class="identifier">tv_sec</span><span class="special">;</span> |
| <span class="identifier">tv_usec</span> <span class="special">+=</span> <span class="identifier">rhs</span><span class="special">.</span><span class="identifier">tv_usec</span><span class="special">;</span> |
| <span class="keyword">if</span> <span class="special">(</span><span class="identifier">tv_usec</span> <span class="special">>=</span> <span class="number">1000000</span><span class="special">)</span> <span class="special">{</span> |
| <span class="identifier">tv_usec</span> <span class="special">-=</span> <span class="number">1000000</span><span class="special">;</span> |
| <span class="special">++</span><span class="identifier">tv_sec</span><span class="special">;</span> |
| <span class="special">}</span> |
| <span class="keyword">return</span> <span class="special">*</span><span class="keyword">this</span><span class="special">;</span> |
| <span class="special">}</span> |
| |
| <span class="identifier">xtime</span><span class="special">&</span> <span class="keyword">operator</span> <span class="special">-=</span> <span class="special">(</span><span class="identifier">xtime</span> <span class="identifier">rhs</span><span class="special">)</span> <span class="special">{</span> |
| <span class="identifier">tv_sec</span> <span class="special">-=</span> <span class="identifier">rhs</span><span class="special">.</span><span class="identifier">tv_sec</span><span class="special">;</span> |
| <span class="identifier">tv_usec</span> <span class="special">-=</span> <span class="identifier">rhs</span><span class="special">.</span><span class="identifier">tv_usec</span><span class="special">;</span> |
| <span class="identifier">fixup</span><span class="special">();</span> |
| <span class="keyword">return</span> <span class="special">*</span><span class="keyword">this</span><span class="special">;</span> |
| <span class="special">}</span> |
| |
| <span class="identifier">xtime</span><span class="special">&</span> <span class="keyword">operator</span> <span class="special">%=</span> <span class="special">(</span><span class="identifier">xtime</span> <span class="identifier">rhs</span><span class="special">)</span> <span class="special">{</span> |
| <span class="keyword">long</span> <span class="keyword">long</span> <span class="identifier">t</span> <span class="special">=</span> <span class="identifier">tv_sec</span> <span class="special">*</span> <span class="number">1000000</span> <span class="special">+</span> <span class="identifier">tv_usec</span><span class="special">;</span> |
| <span class="keyword">long</span> <span class="keyword">long</span> <span class="identifier">r</span> <span class="special">=</span> <span class="identifier">rhs</span><span class="special">.</span><span class="identifier">tv_sec</span> <span class="special">*</span> <span class="number">1000000</span> <span class="special">+</span> <span class="identifier">rhs</span><span class="special">.</span><span class="identifier">tv_usec</span><span class="special">;</span> |
| <span class="identifier">t</span> <span class="special">%=</span> <span class="identifier">r</span><span class="special">;</span> |
| <span class="identifier">tv_sec</span> <span class="special">=</span> <span class="keyword">static_cast</span><span class="special"><</span><span class="keyword">long</span><span class="special">>(</span><span class="identifier">t</span> <span class="special">/</span> <span class="number">1000000</span><span class="special">);</span> |
| <span class="identifier">tv_usec</span> <span class="special">=</span> <span class="keyword">static_cast</span><span class="special"><</span><span class="keyword">long</span><span class="special">>(</span><span class="identifier">t</span> <span class="special">%</span> <span class="number">1000000</span><span class="special">);</span> |
| <span class="identifier">fixup</span><span class="special">();</span> |
| <span class="keyword">return</span> <span class="special">*</span><span class="keyword">this</span><span class="special">;</span> |
| <span class="special">}</span> |
| |
| <span class="keyword">friend</span> <span class="identifier">xtime</span> <span class="keyword">operator</span><span class="special">+(</span><span class="identifier">xtime</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">xtime</span> <span class="identifier">y</span><span class="special">)</span> <span class="special">{</span><span class="keyword">return</span> <span class="identifier">x</span> <span class="special">+=</span> <span class="identifier">y</span><span class="special">;}</span> |
| <span class="keyword">friend</span> <span class="identifier">xtime</span> <span class="keyword">operator</span><span class="special">-(</span><span class="identifier">xtime</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">xtime</span> <span class="identifier">y</span><span class="special">)</span> <span class="special">{</span><span class="keyword">return</span> <span class="identifier">x</span> <span class="special">-=</span> <span class="identifier">y</span><span class="special">;}</span> |
| <span class="keyword">friend</span> <span class="identifier">xtime</span> <span class="keyword">operator</span><span class="special">%(</span><span class="identifier">xtime</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">xtime</span> <span class="identifier">y</span><span class="special">)</span> <span class="special">{</span><span class="keyword">return</span> <span class="identifier">x</span> <span class="special">%=</span> <span class="identifier">y</span><span class="special">;}</span> |
| |
| <span class="keyword">friend</span> <span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">==(</span><span class="identifier">xtime</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">xtime</span> <span class="identifier">y</span><span class="special">)</span> |
| <span class="special">{</span> <span class="keyword">return</span> <span class="special">(</span><span class="identifier">x</span><span class="special">.</span><span class="identifier">tv_sec</span> <span class="special">==</span> <span class="identifier">y</span><span class="special">.</span><span class="identifier">tv_sec</span> <span class="special">&&</span> <span class="identifier">x</span><span class="special">.</span><span class="identifier">tv_usec</span> <span class="special">==</span> <span class="identifier">y</span><span class="special">.</span><span class="identifier">tv_usec</span><span class="special">);</span> <span class="special">}</span> |
| |
| <span class="keyword">friend</span> <span class="keyword">bool</span> <span class="keyword">operator</span><span class="special"><(</span><span class="identifier">xtime</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">xtime</span> <span class="identifier">y</span><span class="special">)</span> <span class="special">{</span> |
| <span class="keyword">if</span> <span class="special">(</span><span class="identifier">x</span><span class="special">.</span><span class="identifier">tv_sec</span> <span class="special">==</span> <span class="identifier">y</span><span class="special">.</span><span class="identifier">tv_sec</span><span class="special">)</span> |
| <span class="keyword">return</span> <span class="special">(</span><span class="identifier">x</span><span class="special">.</span><span class="identifier">tv_usec</span> <span class="special"><</span> <span class="identifier">y</span><span class="special">.</span><span class="identifier">tv_usec</span><span class="special">);</span> |
| <span class="keyword">return</span> <span class="special">(</span><span class="identifier">x</span><span class="special">.</span><span class="identifier">tv_sec</span> <span class="special"><</span> <span class="identifier">y</span><span class="special">.</span><span class="identifier">tv_sec</span><span class="special">);</span> |
| <span class="special">}</span> |
| |
| <span class="keyword">friend</span> <span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">!=(</span><span class="identifier">xtime</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">xtime</span> <span class="identifier">y</span><span class="special">)</span> <span class="special">{</span> <span class="keyword">return</span> <span class="special">!(</span><span class="identifier">x</span> <span class="special">==</span> <span class="identifier">y</span><span class="special">);</span> <span class="special">}</span> |
| <span class="keyword">friend</span> <span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">></span> <span class="special">(</span><span class="identifier">xtime</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">xtime</span> <span class="identifier">y</span><span class="special">)</span> <span class="special">{</span> <span class="keyword">return</span> <span class="identifier">y</span> <span class="special"><</span> <span class="identifier">x</span><span class="special">;</span> <span class="special">}</span> |
| <span class="keyword">friend</span> <span class="keyword">bool</span> <span class="keyword">operator</span><span class="special"><=(</span><span class="identifier">xtime</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">xtime</span> <span class="identifier">y</span><span class="special">)</span> <span class="special">{</span> <span class="keyword">return</span> <span class="special">!(</span><span class="identifier">y</span> <span class="special"><</span> <span class="identifier">x</span><span class="special">);</span> <span class="special">}</span> |
| <span class="keyword">friend</span> <span class="keyword">bool</span> <span class="keyword">operator</span><span class="special">>=(</span><span class="identifier">xtime</span> <span class="identifier">x</span><span class="special">,</span> <span class="identifier">xtime</span> <span class="identifier">y</span><span class="special">)</span> <span class="special">{</span> <span class="keyword">return</span> <span class="special">!(</span><span class="identifier">x</span> <span class="special"><</span> <span class="identifier">y</span><span class="special">);</span> <span class="special">}</span> |
| |
| <span class="keyword">friend</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">ostream</span><span class="special">&</span> <span class="keyword">operator</span><span class="special"><<(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">ostream</span><span class="special">&</span> <span class="identifier">os</span><span class="special">,</span> <span class="identifier">xtime</span> <span class="identifier">x</span><span class="special">)</span> |
| <span class="special">{</span><span class="keyword">return</span> <span class="identifier">os</span> <span class="special"><<</span> <span class="char">'{'</span> <span class="special"><<</span> <span class="identifier">x</span><span class="special">.</span><span class="identifier">tv_sec</span> <span class="special"><<</span> <span class="char">','</span> <span class="special"><<</span> <span class="identifier">x</span><span class="special">.</span><span class="identifier">tv_usec</span> <span class="special"><<</span> <span class="char">'}'</span><span class="special">;}</span> |
| <span class="special">};</span> |
| </pre> |
| <p> |
| Clock based on timeval-like struct. |
| </p> |
| <pre class="programlisting"><span class="keyword">class</span> <span class="identifier">xtime_clock</span> |
| <span class="special">{</span> |
| <span class="keyword">public</span><span class="special">:</span> |
| <span class="keyword">typedef</span> <span class="identifier">xtime</span> <span class="identifier">rep</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">micro</span> <span class="identifier">period</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">duration</span><span class="special"><</span><span class="identifier">rep</span><span class="special">,</span> <span class="identifier">period</span><span class="special">></span> <span class="identifier">duration</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">time_point</span><span class="special"><</span><span class="identifier">xtime_clock</span><span class="special">></span> <span class="identifier">time_point</span><span class="special">;</span> |
| |
| <span class="keyword">static</span> <span class="identifier">time_point</span> <span class="identifier">now</span><span class="special">()</span> |
| <span class="special">{</span> |
| <span class="preprocessor">#if</span> <span class="identifier">defined</span><span class="special">(</span><span class="identifier">BOOST_CHRONO_WINDOWS_API</span><span class="special">)</span> |
| <span class="identifier">time_point</span> <span class="identifier">t</span><span class="special">(</span><span class="identifier">duration</span><span class="special">(</span><span class="identifier">xtime</span><span class="special">(</span><span class="number">0</span><span class="special">)));</span> |
| <span class="identifier">gettimeofday</span><span class="special">((</span><span class="identifier">timeval</span><span class="special">*)&</span><span class="identifier">t</span><span class="special">,</span> <span class="number">0</span><span class="special">);</span> |
| <span class="keyword">return</span> <span class="identifier">t</span><span class="special">;</span> |
| |
| <span class="preprocessor">#elif</span> <span class="identifier">defined</span><span class="special">(</span><span class="identifier">BOOST_CHRONO_MAC_API</span><span class="special">)</span> |
| |
| <span class="identifier">time_point</span> <span class="identifier">t</span><span class="special">(</span><span class="identifier">duration</span><span class="special">(</span><span class="identifier">xtime</span><span class="special">(</span><span class="number">0</span><span class="special">)));</span> |
| <span class="identifier">gettimeofday</span><span class="special">((</span><span class="identifier">timeval</span><span class="special">*)&</span><span class="identifier">t</span><span class="special">,</span> <span class="number">0</span><span class="special">);</span> |
| <span class="keyword">return</span> <span class="identifier">t</span><span class="special">;</span> |
| |
| <span class="preprocessor">#elif</span> <span class="identifier">defined</span><span class="special">(</span><span class="identifier">BOOST_CHRONO_POSIX_API</span><span class="special">)</span> |
| <span class="comment">//time_point t(0,0);</span> |
| |
| <span class="identifier">timespec</span> <span class="identifier">ts</span><span class="special">;</span> |
| <span class="special">::</span><span class="identifier">clock_gettime</span><span class="special">(</span> <span class="identifier">CLOCK_REALTIME</span><span class="special">,</span> <span class="special">&</span><span class="identifier">ts</span> <span class="special">);</span> |
| |
| <span class="identifier">xtime</span> <span class="identifier">xt</span><span class="special">(</span> <span class="identifier">ts</span><span class="special">.</span><span class="identifier">tv_sec</span><span class="special">,</span> <span class="identifier">ts</span><span class="special">.</span><span class="identifier">tv_nsec</span><span class="special">/</span><span class="number">1000</span><span class="special">);</span> |
| <span class="keyword">return</span> <span class="identifier">time_point</span><span class="special">(</span><span class="identifier">duration</span><span class="special">(</span><span class="identifier">xt</span><span class="special">));</span> |
| |
| <span class="preprocessor">#endif</span> <span class="comment">// POSIX</span> |
| <span class="special">}</span> |
| <span class="special">};</span> |
| </pre> |
| <p> |
| Usage of xtime_clock |
| </p> |
| <pre class="programlisting"><span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"sizeof xtime_clock::time_point = "</span> <span class="special"><<</span> <span class="keyword">sizeof</span><span class="special">(</span><span class="identifier">xtime_clock</span><span class="special">::</span><span class="identifier">time_point</span><span class="special">)</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"sizeof xtime_clock::duration = "</span> <span class="special"><<</span> <span class="keyword">sizeof</span><span class="special">(</span><span class="identifier">xtime_clock</span><span class="special">::</span><span class="identifier">duration</span><span class="special">)</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"sizeof xtime_clock::rep = "</span> <span class="special"><<</span> <span class="keyword">sizeof</span><span class="special">(</span><span class="identifier">xtime_clock</span><span class="special">::</span><span class="identifier">rep</span><span class="special">)</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> |
| <span class="identifier">xtime_clock</span><span class="special">::</span><span class="identifier">duration</span> <span class="identifier">delay</span><span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">milliseconds</span><span class="special">(</span><span class="number">5</span><span class="special">));</span> |
| <span class="identifier">xtime_clock</span><span class="special">::</span><span class="identifier">time_point</span> <span class="identifier">start</span> <span class="special">=</span> <span class="identifier">xtime_clock</span><span class="special">::</span><span class="identifier">now</span><span class="special">();</span> |
| <span class="keyword">while</span> <span class="special">(</span><span class="identifier">xtime_clock</span><span class="special">::</span><span class="identifier">now</span><span class="special">()</span> <span class="special">-</span> <span class="identifier">start</span> <span class="special"><=</span> <span class="identifier">delay</span><span class="special">)</span> <span class="special">{}</span> |
| <span class="identifier">xtime_clock</span><span class="special">::</span><span class="identifier">time_point</span> <span class="identifier">stop</span> <span class="special">=</span> <span class="identifier">xtime_clock</span><span class="special">::</span><span class="identifier">now</span><span class="special">();</span> |
| <span class="identifier">xtime_clock</span><span class="special">::</span><span class="identifier">duration</span> <span class="identifier">elapsed</span> <span class="special">=</span> <span class="identifier">stop</span> <span class="special">-</span> <span class="identifier">start</span><span class="special">;</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"paused "</span> <span class="special"><<</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::::</span><span class="identifier">nanoseconds</span><span class="special">(</span><span class="identifier">elapsed</span><span class="special">).</span><span class="identifier">count</span><span class="special">()</span> <span class="special"><<</span> <span class="string">" nanoseconds\n"</span><span class="special">;</span> |
| </pre> |
| <p> |
| <span class="emphasis"><em>See the source file <a href="../../../libs/chrono/example/timeval_demo.cpp" target="_top">example/timeval_demo.cpp</a></em></span> |
| </p> |
| </div> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h4 class="title"> |
| <a name="chrono.users_guide.examples.time_point"></a><a class="link" href="users_guide.html#chrono.users_guide.examples.time_point" title="Time Point">Time Point</a> |
| </h4></div></div></div> |
| <div class="toc"><dl class="toc"> |
| <dt><span class="section"><a href="users_guide.html#chrono.users_guide.examples.time_point.min_utility">min |
| Utility</a></span></dt> |
| <dt><span class="section"><a href="users_guide.html#chrono.users_guide.examples.time_point.a_tiny_program_that_times_how_long_until_a_key_is_struck">A |
| Tiny Program that Times How Long Until a Key is Struck</a></span></dt> |
| <dt><span class="section"><a href="users_guide.html#chrono.users_guide.examples.time_point.24_hours_display">24 |
| Hours Display</a></span></dt> |
| <dt><span class="section"><a href="users_guide.html#chrono.users_guide.examples.time_point.simulated_thread_interface_demonstration_program">Simulated |
| Thread Interface Demonstration Program</a></span></dt> |
| </dl></div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h5 class="title"> |
| <a name="chrono.users_guide.examples.time_point.min_utility"></a><a class="link" href="users_guide.html#chrono.users_guide.examples.time_point.min_utility" title="min Utility">min |
| Utility</a> |
| </h5></div></div></div> |
| <p> |
| The user can define a function returning the earliest <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a> as follows: |
| </p> |
| <pre class="programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <a class="link" href="reference.html#chrono.reference.cpp0x.clock" title="Clock Requirements"><code class="computeroutput"><span class="identifier">Clock</span></code></a><span class="special">,</span> <span class="keyword">class</span> <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">Duration1</span></code></a><span class="special">,</span> <span class="keyword">class</span> <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">Duration2</span></code></a><span class="special">></span> |
| <span class="keyword">typename</span> <span class="identifier">boost</span><span class="special">::</span><code class="computeroutput"><span class="identifier">common_type</span></code><span class="special"><</span><a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a><span class="special"><</span><a class="link" href="reference.html#chrono.reference.cpp0x.clock" title="Clock Requirements"><code class="computeroutput"><span class="identifier">Clock</span></code></a><span class="special">,</span> <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">Duration1</span></code></a><span class="special">>,</span> |
| <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a><span class="special"><</span><a class="link" href="reference.html#chrono.reference.cpp0x.clock" title="Clock Requirements"><code class="computeroutput"><span class="identifier">Clock</span></code></a><span class="special">,</span> <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">Duration2</span></code></a><span class="special">></span> <span class="special">>::</span><span class="identifier">type</span> |
| <span class="identifier">min</span><span class="special">(</span><a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a><span class="special"><</span><a class="link" href="reference.html#chrono.reference.cpp0x.clock" title="Clock Requirements"><code class="computeroutput"><span class="identifier">Clock</span></code></a><span class="special">,</span> <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">Duration1</span></code></a><span class="special">></span> <span class="identifier">t1</span><span class="special">,</span> <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a><span class="special"><</span><a class="link" href="reference.html#chrono.reference.cpp0x.clock" title="Clock Requirements"><code class="computeroutput"><span class="identifier">Clock</span></code></a><span class="special">,</span> <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">Duration2</span></code></a><span class="special">></span> <span class="identifier">t2</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="keyword">return</span> <span class="identifier">t2</span> <span class="special"><</span> <span class="identifier">t1</span> <span class="special">?</span> <span class="identifier">t2</span> <span class="special">:</span> <span class="identifier">t1</span><span class="special">;</span> |
| <span class="special">}</span> |
| </pre> |
| <p> |
| Being able to <span class="bold"><strong>easily</strong></span> write this function |
| is a major feature! |
| </p> |
| <pre class="programlisting"><span class="identifier">BOOST_AUTO</span><span class="special">(</span><span class="identifier">t1</span><span class="special">,</span> <span class="identifier">system_clock</span><span class="special">::</span><span class="identifier">now</span><span class="special">()</span> <span class="special">+</span> <span class="identifier">seconds</span><span class="special">(</span><span class="number">3</span><span class="special">));</span> |
| <span class="identifier">BOOST_AUTO</span><span class="special">(</span><span class="identifier">t2</span><span class="special">,</span> <span class="identifier">system_clock</span><span class="special">::</span><span class="identifier">now</span><span class="special">()</span> <span class="special">+</span> <span class="identifier">nanoseconds</span><span class="special">(</span><span class="number">3</span><span class="special">));</span> |
| <span class="identifier">BOOST_AUTO</span><span class="special">(</span><span class="identifier">t3</span><span class="special">,</span> <span class="identifier">min</span><span class="special">(</span><span class="identifier">t1</span><span class="special">,</span> <span class="identifier">t2</span><span class="special">));</span> |
| </pre> |
| <p> |
| <span class="emphasis"><em>See the source file <a href="../../../libs/chrono/example/min_time_point.cpp" target="_top">example/min_time_point.cpp</a></em></span> |
| </p> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h5 class="title"> |
| <a name="chrono.users_guide.examples.time_point.a_tiny_program_that_times_how_long_until_a_key_is_struck"></a><a class="link" href="users_guide.html#chrono.users_guide.examples.time_point.a_tiny_program_that_times_how_long_until_a_key_is_struck" title="A Tiny Program that Times How Long Until a Key is Struck">A |
| Tiny Program that Times How Long Until a Key is Struck</a> |
| </h5></div></div></div> |
| <pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">chrono</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> |
| <span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">iostream</span><span class="special">></span> |
| <span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">iomanip</span><span class="special">></span> |
| |
| <span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">;</span> |
| |
| <span class="keyword">template</span><span class="special"><</span> <span class="keyword">class</span> <a class="link" href="reference.html#chrono.reference.cpp0x.clock" title="Clock Requirements"><code class="computeroutput"><span class="identifier">Clock</span></code></a> <span class="special">></span> |
| <span class="keyword">class</span> <span class="identifier">timer</span> |
| <span class="special">{</span> |
| <span class="keyword">typename</span> <a class="link" href="reference.html#chrono.reference.cpp0x.clock" title="Clock Requirements"><code class="computeroutput"><span class="identifier">Clock</span></code></a><span class="special">::</span><span class="identifier">time_point</span> <span class="identifier">start</span><span class="special">;</span> |
| <span class="keyword">public</span><span class="special">:</span> |
| <span class="identifier">timer</span><span class="special">()</span> <span class="special">:</span> <span class="identifier">start</span><span class="special">(</span> <a class="link" href="reference.html#chrono.reference.cpp0x.clock" title="Clock Requirements"><code class="computeroutput"><span class="identifier">Clock</span></code></a><span class="special">::</span><span class="identifier">now</span><span class="special">()</span> <span class="special">)</span> <span class="special">{}</span> |
| <span class="keyword">typename</span> <a class="link" href="reference.html#chrono.reference.cpp0x.clock" title="Clock Requirements"><code class="computeroutput"><span class="identifier">Clock</span></code></a><span class="special">::</span><span class="identifier">duration</span> <span class="identifier">elapsed</span><span class="special">()</span> <span class="keyword">const</span> |
| <span class="special">{</span> |
| <span class="keyword">return</span> <a class="link" href="reference.html#chrono.reference.cpp0x.clock" title="Clock Requirements"><code class="computeroutput"><span class="identifier">Clock</span></code></a><span class="special">::</span><span class="identifier">now</span><span class="special">()</span> <span class="special">-</span> <span class="identifier">start</span><span class="special">;</span> |
| <span class="special">}</span> |
| <span class="keyword">double</span> <span class="identifier">seconds</span><span class="special">()</span> <span class="keyword">const</span> |
| <span class="special">{</span> |
| <span class="keyword">return</span> <span class="identifier">elapsed</span><span class="special">().</span><span class="identifier">count</span><span class="special">()</span> <span class="special">*</span> <span class="special">((</span><span class="keyword">double</span><span class="special">)</span><span class="identifier">Clock</span><span class="special">::</span><span class="identifier">period</span><span class="special">::</span><span class="identifier">num</span><span class="special">/</span><span class="identifier">Clock</span><span class="special">::</span><span class="identifier">period</span><span class="special">::</span><span class="identifier">den</span><span class="special">);</span> |
| <span class="special">}</span> |
| <span class="special">};</span> |
| |
| <span class="keyword">int</span> <span class="identifier">main</span><span class="special">()</span> |
| <span class="special">{</span> |
| <span class="identifier">timer</span><span class="special"><</span><a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.system_clock" title="Class system_clock"><code class="computeroutput"><span class="identifier">system_clock</span></code></a><span class="special">></span> <span class="identifier">t1</span><span class="special">;</span> |
| <span class="identifier">timer</span><span class="special"><</span><a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.steady_clock" title="Class steady_clock"><code class="computeroutput"><span class="identifier">steady_clock</span></code></a><span class="special">></span> <span class="identifier">t2</span><span class="special">;</span> |
| <span class="identifier">timer</span><span class="special"><</span><a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.high_resolution_clock" title="Class high_resolution_clock"><code class="computeroutput"><span class="identifier">high_resolution_clock</span></code></a><span class="special">></span> <span class="identifier">t3</span><span class="special">;</span> |
| |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"Type the Enter key: "</span><span class="special">;</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">cin</span><span class="special">.</span><span class="identifier">get</span><span class="special">();</span> |
| |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">fixed</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">setprecision</span><span class="special">(</span><span class="number">9</span><span class="special">);</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"system_clock-----------: "</span> |
| <span class="special"><<</span> <span class="identifier">t1</span><span class="special">.</span><span class="identifier">seconds</span><span class="special">()</span> <span class="special"><<</span> <span class="string">" seconds\n"</span><span class="special">;</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"steady_clock--------: "</span> |
| <span class="special"><<</span> <span class="identifier">t2</span><span class="special">.</span><span class="identifier">seconds</span><span class="special">()</span> <span class="special"><<</span> <span class="string">" seconds\n"</span><span class="special">;</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"high_resolution_clock--: "</span> |
| <span class="special"><<</span> <span class="identifier">t3</span><span class="special">.</span><span class="identifier">seconds</span><span class="special">()</span> <span class="special"><<</span> <span class="string">" seconds\n"</span><span class="special">;</span> |
| |
| <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.system_clock" title="Class system_clock"><code class="computeroutput"><span class="identifier">system_clock</span></code></a><span class="special">::</span><span class="identifier">time_point</span> <span class="identifier">d4</span> <span class="special">=</span> <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.system_clock" title="Class system_clock"><code class="computeroutput"><span class="identifier">system_clock</span></code></a><span class="special">::</span><span class="identifier">now</span><span class="special">();</span> |
| <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.system_clock" title="Class system_clock"><code class="computeroutput"><span class="identifier">system_clock</span></code></a><span class="special">::</span><span class="identifier">time_point</span> <span class="identifier">d5</span> <span class="special">=</span> <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.system_clock" title="Class system_clock"><code class="computeroutput"><span class="identifier">system_clock</span></code></a><span class="special">::</span><span class="identifier">now</span><span class="special">();</span> |
| |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"\nsystem_clock latency-----------: "</span> <span class="special"><<</span> <span class="special">(</span><span class="identifier">d5</span> <span class="special">-</span> <span class="identifier">d4</span><span class="special">).</span><span class="identifier">count</span><span class="special">()</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span> |
| |
| <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.steady_clock" title="Class steady_clock"><code class="computeroutput"><span class="identifier">steady_clock</span></code></a><span class="special">::</span><span class="identifier">time_point</span> <span class="identifier">d6</span> <span class="special">=</span> <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.steady_clock" title="Class steady_clock"><code class="computeroutput"><span class="identifier">steady_clock</span></code></a><span class="special">::</span><span class="identifier">now</span><span class="special">();</span> |
| <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.steady_clock" title="Class steady_clock"><code class="computeroutput"><span class="identifier">steady_clock</span></code></a><span class="special">::</span><span class="identifier">time_point</span> <span class="identifier">d7</span> <span class="special">=</span> <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.steady_clock" title="Class steady_clock"><code class="computeroutput"><span class="identifier">steady_clock</span></code></a><span class="special">::</span><span class="identifier">now</span><span class="special">();</span> |
| |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"steady_clock latency--------: "</span> <span class="special"><<</span> <span class="special">(</span><span class="identifier">d7</span> <span class="special">-</span> <span class="identifier">d6</span><span class="special">).</span><span class="identifier">count</span><span class="special">()</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span> |
| |
| <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.high_resolution_clock" title="Class high_resolution_clock"><code class="computeroutput"><span class="identifier">high_resolution_clock</span></code></a><span class="special">::</span><span class="identifier">time_point</span> <span class="identifier">d8</span> <span class="special">=</span> <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.high_resolution_clock" title="Class high_resolution_clock"><code class="computeroutput"><span class="identifier">high_resolution_clock</span></code></a><span class="special">::</span><span class="identifier">now</span><span class="special">();</span> |
| <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.high_resolution_clock" title="Class high_resolution_clock"><code class="computeroutput"><span class="identifier">high_resolution_clock</span></code></a><span class="special">::</span><span class="identifier">time_point</span> <span class="identifier">d9</span> <span class="special">=</span> <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.high_resolution_clock" title="Class high_resolution_clock"><code class="computeroutput"><span class="identifier">high_resolution_clock</span></code></a><span class="special">::</span><span class="identifier">now</span><span class="special">();</span> |
| |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"high_resolution_clock latency--: "</span> <span class="special"><<</span> <span class="special">(</span><span class="identifier">d9</span> <span class="special">-</span> <span class="identifier">d8</span><span class="special">).</span><span class="identifier">count</span><span class="special">()</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span> |
| |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">time_t</span> <span class="identifier">now</span> <span class="special">=</span> <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.system_clock" title="Class system_clock"><code class="computeroutput"><span class="identifier">system_clock</span></code></a><span class="special">::</span><span class="identifier">to_time_t</span><span class="special">(</span><a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.system_clock" title="Class system_clock"><code class="computeroutput"><span class="identifier">system_clock</span></code></a><span class="special">::</span><span class="identifier">now</span><span class="special">());</span> |
| |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"\nsystem_clock::now() reports UTC is "</span> |
| <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">asctime</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">gmtime</span><span class="special">(&</span><span class="identifier">now</span><span class="special">))</span> <span class="special"><<</span> <span class="string">"\n"</span><span class="special">;</span> |
| |
| <span class="keyword">return</span> <span class="number">0</span><span class="special">;</span> |
| <span class="special">}</span> |
| </pre> |
| <p> |
| The output of this program run looks like this: |
| </p> |
| <p> |
| <span class="emphasis"><em>See the source file <a href="../../../libs/chrono/example/await_keystroke.cpp" target="_top">example/await_keystroke.cpp</a></em></span> |
| </p> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h5 class="title"> |
| <a name="chrono.users_guide.examples.time_point.24_hours_display"></a><a class="link" href="users_guide.html#chrono.users_guide.examples.time_point.24_hours_display" title="24 Hours Display">24 |
| Hours Display</a> |
| </h5></div></div></div> |
| <p> |
| In the example above we take advantage of the fact that <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a>s convert as long |
| as they have the same clock, and as long as their internal <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>s convert. We also take |
| advantage of the fact that a <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a> with a floating-point |
| representation will convert from anything. Finally the I/O system discovers |
| the more readable "hours" unit for our <code class="computeroutput"><span class="identifier">duration</span><span class="special"><</span><span class="keyword">double</span><span class="special">,</span> <span class="identifier">ratio</span><span class="special"><</span><span class="number">3600</span><span class="special">>></span></code>. |
| </p> |
| <p> |
| There are many other ways to format <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>s and <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a>s. For example see |
| <a href="http://en.wikipedia.org/wiki/ISO_8601#Durations" target="_top">ISO 8601</a>. |
| Instead of coding every possibility into <code class="computeroutput"><span class="keyword">operator</span><span class="special"><<</span></code>, which would lead to significant |
| code bloat for even the most trivial uses, this document seeks to inform |
| the reader how to write custom I/O when desired. |
| </p> |
| <p> |
| As an example, the function below streams arbitrary <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a>s to arbitrary <code class="computeroutput"><span class="identifier">basic_ostreams</span></code> using the format: |
| </p> |
| <pre class="programlisting"><span class="special">[-]</span><span class="identifier">d</span><span class="special">/</span><span class="identifier">hh</span><span class="special">:</span><span class="identifier">mm</span><span class="special">:</span><span class="identifier">ss</span><span class="special">.</span><span class="identifier">cc</span> |
| </pre> |
| <p> |
| Where: |
| </p> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| <code class="computeroutput"><span class="identifier">d</span></code> is the number of |
| <code class="computeroutput"><span class="identifier">days</span></code> |
| </li> |
| <li class="listitem"> |
| <code class="computeroutput"><span class="identifier">h</span></code> is the number of |
| <code class="computeroutput"><span class="identifier">hours</span></code> |
| </li> |
| <li class="listitem"> |
| <code class="computeroutput"><span class="identifier">m</span></code> is the number of |
| <code class="computeroutput"><span class="identifier">minutes</span></code> |
| </li> |
| <li class="listitem"> |
| <code class="computeroutput"><span class="identifier">ss</span><span class="special">.</span><span class="identifier">cc</span></code> is the number of <code class="computeroutput"><span class="identifier">seconds</span></code> rounded to the nearest |
| hundredth of a second |
| <div class="orderedlist"><ol class="orderedlist" type="1"> |
| <li class="listitem"> |
| include <boost/chrono/chrono_io.hpp> |
| </li> |
| <li class="listitem"> |
| include <ostream> |
| </li> |
| <li class="listitem"> |
| include <iostream> |
| </li> |
| </ol></div> |
| </li> |
| </ul></div> |
| <pre class="programlisting"><span class="comment">// format duration as [-]d/hh::mm::ss.cc</span> |
| <span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">CharT</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Traits</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Rep</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Period</span><span class="special">></span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">basic_ostream</span><span class="special"><</span><span class="identifier">CharT</span><span class="special">,</span> <span class="identifier">Traits</span><span class="special">>&</span> |
| <span class="identifier">display</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">basic_ostream</span><span class="special"><</span><span class="identifier">CharT</span><span class="special">,</span> <span class="identifier">Traits</span><span class="special">>&</span> <span class="identifier">os</span><span class="special">,</span> |
| <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">duration</span><span class="special"><</span><span class="identifier">Rep</span><span class="special">,</span> <span class="identifier">Period</span><span class="special">></span> <span class="identifier">d</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">std</span><span class="special">;</span> |
| <span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">boost</span><span class="special">;</span> |
| |
| <span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">duration</span><span class="special"><</span><span class="keyword">long</span> <span class="keyword">long</span><span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">ratio</span><span class="special"><</span><span class="number">86400</span><span class="special">></span> <span class="special">></span> <span class="identifier">days</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">duration</span><span class="special"><</span><span class="keyword">long</span> <span class="keyword">long</span><span class="special">,</span> <span class="identifier">boost</span><span class="special">:</span><span class="identifier">centi</span><span class="special">></span> <span class="identifier">centiseconds</span><span class="special">;</span> |
| |
| <span class="comment">// if negative, print negative sign and negate</span> |
| <span class="keyword">if</span> <span class="special">(</span><span class="identifier">d</span> <span class="special"><</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">duration</span><span class="special"><</span><span class="identifier">Rep</span><span class="special">,</span> <span class="identifier">Period</span><span class="special">>(</span><span class="number">0</span><span class="special">))</span> |
| <span class="special">{</span> |
| <span class="identifier">d</span> <span class="special">=</span> <span class="special">-</span><span class="identifier">d</span><span class="special">;</span> |
| <span class="identifier">os</span> <span class="special"><<</span> <span class="char">'-'</span><span class="special">;</span> |
| <span class="special">}</span> |
| <span class="comment">// round d to nearest centiseconds, to even on tie</span> |
| <span class="identifier">centiseconds</span> <span class="identifier">cs</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">duration_cast</span><span class="special"><</span><span class="identifier">centiseconds</span><span class="special">>(</span><span class="identifier">d</span><span class="special">);</span> |
| <span class="keyword">if</span> <span class="special">(</span><span class="identifier">d</span> <span class="special">-</span> <span class="identifier">cs</span> <span class="special">></span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">milliseconds</span><span class="special">(</span><span class="number">5</span><span class="special">)</span> |
| <span class="special">||</span> <span class="special">(</span><span class="identifier">d</span> <span class="special">-</span> <span class="identifier">cs</span> <span class="special">==</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">milliseconds</span><span class="special">(</span><span class="number">5</span><span class="special">)</span> <span class="special">&&</span> <span class="identifier">cs</span><span class="special">.</span><span class="identifier">count</span><span class="special">()</span> <span class="special">&</span> <span class="number">1</span><span class="special">))</span> |
| <span class="special">++</span><span class="identifier">cs</span><span class="special">;</span> |
| <span class="comment">// separate seconds from centiseconds</span> |
| <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">seconds</span> <span class="identifier">s</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">duration_cast</span><span class="special"><</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">seconds</span><span class="special">>(</span><span class="identifier">cs</span><span class="special">);</span> |
| <span class="identifier">cs</span> <span class="special">-=</span> <span class="identifier">s</span><span class="special">;</span> |
| <span class="comment">// separate minutes from seconds</span> |
| <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">minutes</span> <span class="identifier">m</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">duration_cast</span><span class="special"><</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">minutes</span><span class="special">>(</span><span class="identifier">s</span><span class="special">);</span> |
| <span class="identifier">s</span> <span class="special">-=</span> <span class="identifier">m</span><span class="special">;</span> |
| <span class="comment">// separate hours from minutes</span> |
| <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">hours</span> <span class="identifier">h</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">duration_cast</span><span class="special"><</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">hours</span><span class="special">>(</span><span class="identifier">m</span><span class="special">);</span> |
| <span class="identifier">m</span> <span class="special">-=</span> <span class="identifier">h</span><span class="special">;</span> |
| <span class="comment">// separate days from hours</span> |
| <span class="identifier">days</span> <span class="identifier">dy</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">duration_cast</span><span class="special"><</span><span class="identifier">days</span><span class="special">>(</span><span class="identifier">h</span><span class="special">);</span> |
| <span class="identifier">h</span> <span class="special">-=</span> <span class="identifier">dy</span><span class="special">;</span> |
| <span class="comment">// print d/hh:mm:ss.cc</span> |
| <span class="identifier">os</span> <span class="special"><<</span> <span class="identifier">dy</span><span class="special">.</span><span class="identifier">count</span><span class="special">()</span> <span class="special"><<</span> <span class="char">'/'</span><span class="special">;</span> |
| <span class="keyword">if</span> <span class="special">(</span><span class="identifier">h</span> <span class="special"><</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">hours</span><span class="special">(</span><span class="number">10</span><span class="special">))</span> |
| <span class="identifier">os</span> <span class="special"><<</span> <span class="char">'0'</span><span class="special">;</span> |
| <span class="identifier">os</span> <span class="special"><<</span> <span class="identifier">h</span><span class="special">.</span><span class="identifier">count</span><span class="special">()</span> <span class="special"><<</span> <span class="char">':'</span><span class="special">;</span> |
| <span class="keyword">if</span> <span class="special">(</span><span class="identifier">m</span> <span class="special"><</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">minutes</span><span class="special">(</span><span class="number">10</span><span class="special">))</span> |
| <span class="identifier">os</span> <span class="special"><<</span> <span class="char">'0'</span><span class="special">;</span> |
| <span class="identifier">os</span> <span class="special"><<</span> <span class="identifier">m</span><span class="special">.</span><span class="identifier">count</span><span class="special">()</span> <span class="special"><<</span> <span class="char">':'</span><span class="special">;</span> |
| <span class="keyword">if</span> <span class="special">(</span><span class="identifier">s</span> <span class="special"><</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">seconds</span><span class="special">(</span><span class="number">10</span><span class="special">))</span> |
| <span class="identifier">os</span> <span class="special"><<</span> <span class="char">'0'</span><span class="special">;</span> |
| <span class="identifier">os</span> <span class="special"><<</span> <span class="identifier">s</span><span class="special">.</span><span class="identifier">count</span><span class="special">()</span> <span class="special"><<</span> <span class="char">'.'</span><span class="special">;</span> |
| <span class="keyword">if</span> <span class="special">(</span><span class="identifier">cs</span> <span class="special"><</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">centiseconds</span><span class="special">(</span><span class="number">10</span><span class="special">))</span> |
| <span class="identifier">os</span> <span class="special"><<</span> <span class="char">'0'</span><span class="special">;</span> |
| <span class="identifier">os</span> <span class="special"><<</span> <span class="identifier">cs</span><span class="special">.</span><span class="identifier">count</span><span class="special">();</span> |
| <span class="keyword">return</span> <span class="identifier">os</span><span class="special">;</span> |
| <span class="special">}</span> |
| |
| <span class="keyword">int</span> <span class="identifier">main</span><span class="special">()</span> |
| <span class="special">{</span> |
| <span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">std</span><span class="special">;</span> |
| <span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">boost</span><span class="special">;</span> |
| |
| <span class="identifier">display</span><span class="special">(</span><span class="identifier">cout</span><span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">steady_clock</span><span class="special">::</span><span class="identifier">now</span><span class="special">().</span><span class="identifier">time_since_epoch</span><span class="special">()</span> |
| <span class="special">+</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">duration</span><span class="special"><</span><span class="keyword">long</span><span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">mega</span><span class="special">>(</span><span class="number">1</span><span class="special">))</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> |
| <span class="identifier">display</span><span class="special">(</span><span class="identifier">cout</span><span class="special">,</span> <span class="special">-</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">milliseconds</span><span class="special">(</span><span class="number">6</span><span class="special">))</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> |
| <span class="identifier">display</span><span class="special">(</span><span class="identifier">cout</span><span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">duration</span><span class="special"><</span><span class="keyword">long</span><span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">mega</span><span class="special">>(</span><span class="number">1</span><span class="special">))</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> |
| <span class="identifier">display</span><span class="special">(</span><span class="identifier">cout</span><span class="special">,</span> <span class="special">-</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">duration</span><span class="special"><</span><span class="keyword">long</span><span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">mega</span><span class="special">>(</span><span class="number">1</span><span class="special">))</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> |
| <span class="special">}</span> |
| </pre> |
| <p> |
| The output could be: |
| </p> |
| <pre class="programlisting"><span class="number">12</span><span class="special">/</span><span class="number">06</span><span class="special">:</span><span class="number">03</span><span class="special">:</span><span class="number">22.95</span> |
| <span class="special">-</span><span class="number">0</span><span class="special">/</span><span class="number">00</span><span class="special">:</span><span class="number">00</span><span class="special">:</span><span class="number">00</span><span class="special">.</span><span class="number">01</span> |
| <span class="number">11</span><span class="special">/</span><span class="number">13</span><span class="special">:</span><span class="number">46</span><span class="special">:</span><span class="number">40.00</span> |
| <span class="special">-</span><span class="number">11</span><span class="special">/</span><span class="number">13</span><span class="special">:</span><span class="number">46</span><span class="special">:</span><span class="number">40.00</span> |
| </pre> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h5 class="title"> |
| <a name="chrono.users_guide.examples.time_point.simulated_thread_interface_demonstration_program"></a><a class="link" href="users_guide.html#chrono.users_guide.examples.time_point.simulated_thread_interface_demonstration_program" title="Simulated Thread Interface Demonstration Program">Simulated |
| Thread Interface Demonstration Program</a> |
| </h5></div></div></div> |
| <p> |
| The C++11 standard library's multi-threading library requires the ability |
| to deal with the representation of time in a manner consistent with modern |
| C++ practices. Next is a simulation of this interface. |
| </p> |
| <p> |
| The non-member sleep functions can be emulated as follows: |
| </p> |
| <pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">boost</span> <span class="special">{</span> <span class="keyword">namespace</span> <span class="identifier">this_thread</span> <span class="special">{</span> |
| |
| <span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">Rep</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Period</span><span class="special">></span> |
| <span class="keyword">void</span> <span class="identifier">sleep_for</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a><span class="special"><</span><span class="identifier">Rep</span><span class="special">,</span> <span class="identifier">Period</span><span class="special">>&</span> <span class="identifier">d</span><span class="special">)</span> <span class="special">{</span> |
| <span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">microseconds</span></code></a> <span class="identifier">t</span> <span class="special">=</span> <span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_cast" title="Non-Member Function duration_cast(duration)"><code class="computeroutput"><span class="identifier">duration_cast</span></code></a><span class="special"><</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">microseconds</span></code></a><span class="special">>(</span><span class="identifier">d</span><span class="special">);</span> |
| <span class="keyword">if</span> <span class="special">(</span><span class="identifier">t</span> <span class="special"><</span> <span class="identifier">d</span><span class="special">)</span> |
| <span class="special">++</span><span class="identifier">t</span><span class="special">;</span> |
| <span class="keyword">if</span> <span class="special">(</span><span class="identifier">t</span> <span class="special">></span> <span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">microseconds</span></code></a><span class="special">(</span><span class="number">0</span><span class="special">))</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"sleep_for "</span> <span class="special"><<</span> <span class="identifier">t</span><span class="special">.</span><span class="identifier">count</span><span class="special">()</span> <span class="special"><<</span> <span class="string">" microseconds\n"</span><span class="special">;</span> |
| <span class="special">}</span> |
| |
| <span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <a class="link" href="reference.html#chrono.reference.cpp0x.clock" title="Clock Requirements"><code class="computeroutput"><span class="identifier">Clock</span></code></a><span class="special">,</span> <span class="keyword">class</span> <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">Duration</span></code></a><span class="special">></span> |
| <span class="keyword">void</span> <span class="identifier">sleep_until</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a><span class="special"><</span><a class="link" href="reference.html#chrono.reference.cpp0x.clock" title="Clock Requirements"><code class="computeroutput"><span class="identifier">Clock</span></code></a><span class="special">,</span> <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">Duration</span></code></a><span class="special">>&</span> <span class="identifier">t</span><span class="special">)</span> <span class="special">{</span> |
| <span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">chrono</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a><span class="special"><</span><a class="link" href="reference.html#chrono.reference.cpp0x.clock" title="Clock Requirements"><code class="computeroutput"><span class="identifier">Clock</span></code></a><span class="special">,</span> <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">Duration</span></code></a><span class="special">></span> <span class="identifier">Time</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.system_clock" title="Class system_clock"><code class="computeroutput"><span class="identifier">system_clock</span></code></a><span class="special">::</span><span class="identifier">time_point</span> <span class="identifier">SysTime</span><span class="special">;</span> |
| <span class="keyword">if</span> <span class="special">(</span><span class="identifier">t</span> <span class="special">></span> <a class="link" href="reference.html#chrono.reference.cpp0x.clock" title="Clock Requirements"><code class="computeroutput"><span class="identifier">Clock</span></code></a><span class="special">::</span><span class="identifier">now</span><span class="special">())</span> <span class="special">{</span> |
| <span class="keyword">typedef</span> <span class="keyword">typename</span> <code class="computeroutput"><span class="identifier">common_type</span></code><span class="special"><</span><span class="keyword">typename</span> <span class="identifier">Time</span><span class="special">::</span><span class="identifier">duration</span><span class="special">,</span> |
| <span class="keyword">typename</span> <span class="identifier">SysTime</span><span class="special">::</span><span class="identifier">duration</span><span class="special">>::</span><span class="identifier">type</span> <span class="identifier">D</span><span class="special">;</span> |
| <span class="comment">/* auto */</span> <span class="identifier">D</span> <span class="identifier">d</span> <span class="special">=</span> <span class="identifier">t</span> <span class="special">-</span> <a class="link" href="reference.html#chrono.reference.cpp0x.clock" title="Clock Requirements"><code class="computeroutput"><span class="identifier">Clock</span></code></a><span class="special">::</span><span class="identifier">now</span><span class="special">();</span> |
| <span class="identifier">microseconds</span> <span class="identifier">us</span> <span class="special">=</span> <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_cast" title="Non-Member Function duration_cast(duration)"><code class="computeroutput"><span class="identifier">duration_cast</span></code></a><span class="special"><</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">microseconds</span></code></a><span class="special">>(</span><span class="identifier">d</span><span class="special">);</span> |
| <span class="keyword">if</span> <span class="special">(</span><span class="identifier">us</span> <span class="special"><</span> <span class="identifier">d</span><span class="special">)</span> |
| <span class="special">++</span><span class="identifier">us</span><span class="special">;</span> |
| <span class="identifier">SysTime</span> <span class="identifier">st</span> <span class="special">=</span> <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.system_clock" title="Class system_clock"><code class="computeroutput"><span class="identifier">system_clock</span></code></a><span class="special">::</span><span class="identifier">now</span><span class="special">()</span> <span class="special">+</span> <span class="identifier">us</span><span class="special">;</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"sleep_until "</span><span class="special">;</span> |
| <span class="identifier">detail</span><span class="special">::</span><span class="identifier">print_time</span><span class="special">(</span><span class="identifier">st</span><span class="special">);</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">" which is "</span> <span class="special"><<</span> <span class="special">(</span><span class="identifier">st</span> <span class="special">-</span> <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.system_clock" title="Class system_clock"><code class="computeroutput"><span class="identifier">system_clock</span></code></a><span class="special">::</span><span class="identifier">now</span><span class="special">()).</span><span class="identifier">count</span><span class="special">()</span> <span class="special"><<</span> <span class="string">" microseconds away\n"</span><span class="special">;</span> |
| <span class="special">}</span> |
| <span class="special">}</span> |
| |
| <span class="special">}}</span> |
| </pre> |
| <p> |
| Next is the <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">thread</span><span class="special">::</span><span class="identifier">timed_mutex</span></code> modified functions |
| </p> |
| <pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">boost</span> <span class="special">{</span> |
| <span class="keyword">struct</span> <span class="identifier">timed_mutex</span> <span class="special">{</span> |
| <span class="comment">// ...</span> |
| |
| <span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">Rep</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Period</span><span class="special">></span> |
| <span class="keyword">bool</span> <span class="identifier">try_lock_for</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a><span class="special"><</span><span class="identifier">Rep</span><span class="special">,</span> <span class="identifier">Period</span><span class="special">>&</span> <span class="identifier">d</span><span class="special">)</span> <span class="special">{</span> |
| <span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">microseconds</span></code></a> <span class="identifier">t</span> <span class="special">=</span> <span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_cast" title="Non-Member Function duration_cast(duration)"><code class="computeroutput"><span class="identifier">duration_cast</span></code></a><span class="special"><</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">microseconds</span></code></a><span class="special">>(</span><span class="identifier">d</span><span class="special">);</span> |
| <span class="keyword">if</span> <span class="special">(</span><span class="identifier">t</span> <span class="special"><=</span> <span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">microseconds</span></code></a><span class="special">(</span><span class="number">0</span><span class="special">))</span> |
| <span class="keyword">return</span> <span class="identifier">try_lock</span><span class="special">();</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"try_lock_for "</span> <span class="special"><<</span> <span class="identifier">t</span><span class="special">.</span><span class="identifier">count</span><span class="special">()</span> <span class="special"><<</span> <span class="string">" microseconds\n"</span><span class="special">;</span> |
| <span class="keyword">return</span> <span class="keyword">true</span><span class="special">;</span> |
| <span class="special">}</span> |
| |
| <span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <a class="link" href="reference.html#chrono.reference.cpp0x.clock" title="Clock Requirements"><code class="computeroutput"><span class="identifier">Clock</span></code></a><span class="special">,</span> <span class="keyword">class</span> <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">Duration</span></code></a><span class="special">></span> |
| <span class="keyword">bool</span> <span class="identifier">try_lock_until</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a><span class="special"><</span><a class="link" href="reference.html#chrono.reference.cpp0x.clock" title="Clock Requirements"><code class="computeroutput"><span class="identifier">Clock</span></code></a><span class="special">,</span> <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">Duration</span></code></a><span class="special">>&</span> <span class="identifier">t</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">chrono</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a><span class="special"><</span><a class="link" href="reference.html#chrono.reference.cpp0x.clock" title="Clock Requirements"><code class="computeroutput"><span class="identifier">Clock</span></code></a><span class="special">,</span> <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">Duration</span></code></a><span class="special">></span> <span class="identifier">Time</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.system_clock" title="Class system_clock"><code class="computeroutput"><span class="identifier">system_clock</span></code></a><span class="special">::</span><span class="identifier">time_point</span> <span class="identifier">SysTime</span><span class="special">;</span> |
| <span class="keyword">if</span> <span class="special">(</span><span class="identifier">t</span> <span class="special"><=</span> <a class="link" href="reference.html#chrono.reference.cpp0x.clock" title="Clock Requirements"><code class="computeroutput"><span class="identifier">Clock</span></code></a><span class="special">::</span><span class="identifier">now</span><span class="special">())</span> |
| <span class="keyword">return</span> <span class="identifier">try_lock</span><span class="special">();</span> |
| <span class="keyword">typedef</span> <span class="keyword">typename</span> <code class="computeroutput"><span class="identifier">common_type</span></code><span class="special"><</span><span class="keyword">typename</span> <span class="identifier">Time</span><span class="special">::</span><span class="identifier">duration</span><span class="special">,</span> |
| <span class="keyword">typename</span> <a class="link" href="reference.html#chrono.reference.cpp0x.clock" title="Clock Requirements"><code class="computeroutput"><span class="identifier">Clock</span></code></a><span class="special">::</span><span class="identifier">duration</span><span class="special">>::</span><span class="identifier">type</span> <span class="identifier">D</span><span class="special">;</span> |
| <span class="comment">/* auto */</span> <span class="identifier">D</span> <span class="identifier">d</span> <span class="special">=</span> <span class="identifier">t</span> <span class="special">-</span> <a class="link" href="reference.html#chrono.reference.cpp0x.clock" title="Clock Requirements"><code class="computeroutput"><span class="identifier">Clock</span></code></a><span class="special">::</span><span class="identifier">now</span><span class="special">();</span> |
| <span class="identifier">microseconds</span> <span class="identifier">us</span> <span class="special">=</span> <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_cast" title="Non-Member Function duration_cast(duration)"><code class="computeroutput"><span class="identifier">duration_cast</span></code></a><span class="special"><</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">microseconds</span></code></a><span class="special">>(</span><span class="identifier">d</span><span class="special">);</span> |
| <span class="identifier">SysTime</span> <span class="identifier">st</span> <span class="special">=</span> <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.system_clock" title="Class system_clock"><code class="computeroutput"><span class="identifier">system_clock</span></code></a><span class="special">::</span><span class="identifier">now</span><span class="special">()</span> <span class="special">+</span> <span class="identifier">us</span><span class="special">;</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"try_lock_until "</span><span class="special">;</span> |
| <span class="identifier">detail</span><span class="special">::</span><span class="identifier">print_time</span><span class="special">(</span><span class="identifier">st</span><span class="special">);</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">" which is "</span> <span class="special"><<</span> <span class="special">(</span><span class="identifier">st</span> <span class="special">-</span> <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.system_clock" title="Class system_clock"><code class="computeroutput"><span class="identifier">system_clock</span></code></a><span class="special">::</span><span class="identifier">now</span><span class="special">()).</span><span class="identifier">count</span><span class="special">()</span> |
| <span class="special"><<</span> <span class="string">" microseconds away\n"</span><span class="special">;</span> |
| <span class="keyword">return</span> <span class="keyword">true</span><span class="special">;</span> |
| <span class="special">}</span> |
| <span class="special">};</span> |
| <span class="special">}</span> |
| </pre> |
| <p> |
| <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">thread</span><span class="special">::</span><span class="identifier">condition_variable</span></code> time related function |
| are modified as follows: |
| </p> |
| <pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">boost</span> <span class="special">{</span> |
| <span class="keyword">struct</span> <span class="identifier">condition_variable</span> |
| <span class="special">{</span> |
| <span class="comment">// ...</span> |
| |
| <span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <span class="identifier">Rep</span><span class="special">,</span> <span class="keyword">class</span> <span class="identifier">Period</span><span class="special">></span> |
| <span class="keyword">bool</span> <span class="identifier">wait_for</span><span class="special">(</span><span class="identifier">mutex</span><span class="special">&,</span> <span class="keyword">const</span> <span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a><span class="special"><</span><span class="identifier">Rep</span><span class="special">,</span> <span class="identifier">Period</span><span class="special">>&</span> <span class="identifier">d</span><span class="special">)</span> <span class="special">{</span> |
| <span class="identifier">chrono</span><span class="special">::</span><span class="identifier">microseconds</span> <span class="identifier">t</span> <span class="special">=</span> <span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_cast" title="Non-Member Function duration_cast(duration)"><code class="computeroutput"><span class="identifier">duration_cast</span></code></a><span class="special"><</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">microseconds</span><span class="special">>(</span><span class="identifier">d</span><span class="special">);</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"wait_for "</span> <span class="special"><<</span> <span class="identifier">t</span><span class="special">.</span><span class="identifier">count</span><span class="special">()</span> <span class="special"><<</span> <span class="string">" microseconds\n"</span><span class="special">;</span> |
| <span class="keyword">return</span> <span class="keyword">true</span><span class="special">;</span> |
| <span class="special">}</span> |
| |
| <span class="keyword">template</span> <span class="special"><</span><span class="keyword">class</span> <a class="link" href="reference.html#chrono.reference.cpp0x.clock" title="Clock Requirements"><code class="computeroutput"><span class="identifier">Clock</span></code></a><span class="special">,</span> <span class="keyword">class</span> <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">Duration</span></code></a><span class="special">></span> |
| <span class="keyword">bool</span> <span class="identifier">wait_until</span><span class="special">(</span><span class="identifier">mutex</span><span class="special">&,</span> <span class="keyword">const</span> <span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a><span class="special"><</span><a class="link" href="reference.html#chrono.reference.cpp0x.clock" title="Clock Requirements"><code class="computeroutput"><span class="identifier">Clock</span></code></a><span class="special">,</span> <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">Duration</span></code></a><span class="special">>&</span> <span class="identifier">t</span><span class="special">)</span> <span class="special">{</span> |
| <span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <a class="link" href="reference.html#chrono.reference.cpp0x.time_point_hpp.time_point" title="Class template time_point<>"><code class="computeroutput"><span class="identifier">time_point</span></code></a><span class="special"><</span><a class="link" href="reference.html#chrono.reference.cpp0x.clock" title="Clock Requirements"><code class="computeroutput"><span class="identifier">Clock</span></code></a><span class="special">,</span> <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">Duration</span></code></a><span class="special">></span> <span class="identifier">Time</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.system_clock" title="Class system_clock"><code class="computeroutput"><span class="identifier">system_clock</span></code></a><span class="special">::</span><span class="identifier">time_point</span> <span class="identifier">SysTime</span><span class="special">;</span> |
| <span class="keyword">if</span> <span class="special">(</span><span class="identifier">t</span> <span class="special"><=</span> <a class="link" href="reference.html#chrono.reference.cpp0x.clock" title="Clock Requirements"><code class="computeroutput"><span class="identifier">Clock</span></code></a><span class="special">::</span><span class="identifier">now</span><span class="special">())</span> |
| <span class="keyword">return</span> <span class="keyword">false</span><span class="special">;</span> |
| <span class="keyword">typedef</span> <span class="keyword">typename</span> <code class="computeroutput"><span class="identifier">common_type</span></code><span class="special"><</span><span class="keyword">typename</span> <span class="identifier">Time</span><span class="special">::</span><span class="identifier">duration</span><span class="special">,</span> |
| <span class="keyword">typename</span> <a class="link" href="reference.html#chrono.reference.cpp0x.clock" title="Clock Requirements"><code class="computeroutput"><span class="identifier">Clock</span></code></a><span class="special">::</span><span class="identifier">duration</span><span class="special">>::</span><span class="identifier">type</span> <span class="identifier">D</span><span class="special">;</span> |
| <span class="comment">/* auto */</span> <span class="identifier">D</span> <span class="identifier">d</span> <span class="special">=</span> <span class="identifier">t</span> <span class="special">-</span> <a class="link" href="reference.html#chrono.reference.cpp0x.clock" title="Clock Requirements"><code class="computeroutput"><span class="identifier">Clock</span></code></a><span class="special">::</span><span class="identifier">now</span><span class="special">();</span> |
| <span class="identifier">microseconds</span> <span class="identifier">us</span> <span class="special">=</span> <a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_cast" title="Non-Member Function duration_cast(duration)"><code class="computeroutput"><span class="identifier">duration_cast</span></code></a><span class="special"><</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">microseconds</span></code></a><span class="special">>(</span><span class="identifier">d</span><span class="special">);</span> |
| <span class="identifier">SysTime</span> <span class="identifier">st</span> <span class="special">=</span> <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.system_clock" title="Class system_clock"><code class="computeroutput"><span class="identifier">system_clock</span></code></a><span class="special">::</span><span class="identifier">now</span><span class="special">()</span> <span class="special">+</span> <span class="identifier">us</span><span class="special">;</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"wait_until "</span><span class="special">;</span> |
| <span class="identifier">detail</span><span class="special">::</span><span class="identifier">print_time</span><span class="special">(</span><span class="identifier">st</span><span class="special">);</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">" which is "</span> <span class="special"><<</span> <span class="special">(</span><span class="identifier">st</span> <span class="special">-</span> <a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.system_clock" title="Class system_clock"><code class="computeroutput"><span class="identifier">system_clock</span></code></a><span class="special">::</span><span class="identifier">now</span><span class="special">()).</span><span class="identifier">count</span><span class="special">()</span> |
| <span class="special"><<</span> <span class="string">" microseconds away\n"</span><span class="special">;</span> |
| <span class="keyword">return</span> <span class="keyword">true</span><span class="special">;</span> |
| <span class="special">}</span> |
| <span class="special">};</span> |
| <span class="special">}</span> |
| </pre> |
| <p> |
| Next follows how simple is the usage of this functions: |
| </p> |
| <pre class="programlisting"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">mutex</span> <span class="identifier">m</span><span class="special">;</span> |
| <span class="identifier">boost</span><span class="special">::</span><span class="identifier">timed_mutex</span> <span class="identifier">mut</span><span class="special">;</span> |
| <span class="identifier">boost</span><span class="special">::</span><span class="identifier">condition_variable</span> <span class="identifier">cv</span><span class="special">;</span> |
| |
| <span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">boost</span><span class="special">;</span> |
| |
| <span class="identifier">this_thread</span><span class="special">::</span><span class="identifier">sleep_for</span><span class="special">(</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">seconds</span></code></a><span class="special">(</span><span class="number">3</span><span class="special">));</span> |
| <span class="identifier">this_thread</span><span class="special">::</span><span class="identifier">sleep_for</span><span class="special">(</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">nanoseconds</span></code></a><span class="special">(</span><span class="number">300</span><span class="special">));</span> |
| <span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.system_clock" title="Class system_clock"><code class="computeroutput"><span class="identifier">system_clock</span></code></a><span class="special">::</span><span class="identifier">time_point</span> <span class="identifier">time_limit</span> <span class="special">=</span> <span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.system_clock" title="Class system_clock"><code class="computeroutput"><span class="identifier">system_clock</span></code></a><span class="special">::</span><span class="identifier">now</span><span class="special">()</span> <span class="special">+</span> <span class="identifier">chrono</span><span class="special">::</span><span class="identifier">__seconds_</span><span class="special">(</span><span class="number">4</span><span class="special">)</span> <span class="special">+</span> <span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">milliseconds</span></code></a><span class="special">(</span><span class="number">500</span><span class="special">);</span> |
| <span class="identifier">this_thread</span><span class="special">::</span><span class="identifier">sleep_until</span><span class="special">(</span><span class="identifier">time_limit</span><span class="special">);</span> |
| |
| <span class="identifier">mut</span><span class="special">.</span><span class="identifier">try_lock_for</span><span class="special">(</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">milliseconds</span></code></a><span class="special">(</span><span class="number">30</span><span class="special">));</span> |
| <span class="identifier">mut</span><span class="special">.</span><span class="identifier">try_lock_until</span><span class="special">(</span><span class="identifier">time_limit</span><span class="special">);</span> |
| |
| <span class="identifier">cv</span><span class="special">.</span><span class="identifier">wait_for</span><span class="special">(</span><span class="identifier">m</span><span class="special">,</span> <span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration_typedefs" title="duration typedefs"><code class="computeroutput"><span class="identifier">minutes</span></code></a><span class="special">(</span><span class="number">1</span><span class="special">));</span> <span class="comment">// real code would put this in a loop</span> |
| <span class="identifier">cv</span><span class="special">.</span><span class="identifier">wait_until</span><span class="special">(</span><span class="identifier">m</span><span class="special">,</span> <span class="identifier">time_limit</span><span class="special">);</span> <span class="comment">// real code would put this in a loop</span> |
| |
| <span class="comment">// For those who prefer floating-point</span> |
| <span class="identifier">this_thread</span><span class="special">::</span><span class="identifier">sleep_for</span><span class="special">(</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a><span class="special"><</span><span class="keyword">double</span><span class="special">>(</span><span class="number">0.25</span><span class="special">));</span> |
| <span class="identifier">this_thread</span><span class="special">::</span><span class="identifier">sleep_until</span><span class="special">(</span><span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.system_clocks_hpp.system_clock" title="Class system_clock"><code class="computeroutput"><span class="identifier">system_clock</span></code></a><span class="special">::</span><span class="identifier">now</span><span class="special">()</span> <span class="special">+</span> <span class="identifier">chrono</span><span class="special">::</span><a class="link" href="reference.html#chrono.reference.cpp0x.duration_hpp.duration" title="Class Template duration<>"><code class="computeroutput"><span class="identifier">duration</span></code></a><span class="special"><</span><span class="keyword">double</span><span class="special">>(</span><span class="number">1.5</span><span class="special">));</span> |
| </pre> |
| <p> |
| <span class="emphasis"><em>See the source file <a href="../../../libs/chrono/example/simulated_thread_interface_demo.cpp" target="_top">example/simulated_thread_interface_demo.cpp</a></em></span> |
| </p> |
| </div> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h4 class="title"> |
| <a name="chrono.users_guide.examples.io"></a><a class="link" href="users_guide.html#chrono.users_guide.examples.io" title="IO">IO</a> |
| </h4></div></div></div> |
| <div class="toc"><dl class="toc"><dt><span class="section"><a href="users_guide.html#chrono.users_guide.examples.io.french">French Output</a></span></dt></dl></div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h5 class="title"> |
| <a name="chrono.users_guide.examples.io.french"></a><a class="link" href="users_guide.html#chrono.users_guide.examples.io.french" title="French Output">French Output</a> |
| </h5></div></div></div> |
| <p> |
| Example use of output in French |
| </p> |
| <pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">chrono</span><span class="special">/</span><span class="identifier">chrono_io</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> |
| <span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">iostream</span><span class="special">></span> |
| <span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">locale</span><span class="special">></span> |
| |
| <span class="keyword">int</span> <span class="identifier">main</span><span class="special">()</span> |
| <span class="special">{</span> |
| <span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">std</span><span class="special">;</span> |
| <span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">boost</span><span class="special">;</span> |
| <span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">;</span> |
| |
| <span class="identifier">cout</span><span class="special">.</span><span class="identifier">imbue</span><span class="special">(</span><span class="identifier">locale</span><span class="special">(</span><span class="identifier">locale</span><span class="special">(),</span> <span class="keyword">new</span> <span class="identifier">duration_punct</span><span class="special"><</span><span class="keyword">char</span><span class="special">></span> |
| <span class="special">(</span> |
| <span class="identifier">duration_punct</span><span class="special"><</span><span class="keyword">char</span><span class="special">>::</span><span class="identifier">use_long</span><span class="special">,</span> |
| <span class="string">"secondes"</span><span class="special">,</span> <span class="string">"minutes"</span><span class="special">,</span> <span class="string">"heures"</span><span class="special">,</span> |
| <span class="string">"s"</span><span class="special">,</span> <span class="string">"m"</span><span class="special">,</span> <span class="string">"h"</span> |
| <span class="special">)));</span> |
| <span class="identifier">hours</span> <span class="identifier">h</span><span class="special">(</span><span class="number">5</span><span class="special">);</span> |
| <span class="identifier">minutes</span> <span class="identifier">m</span><span class="special">(</span><span class="number">45</span><span class="special">);</span> |
| <span class="identifier">seconds</span> <span class="identifier">s</span><span class="special">(</span><span class="number">15</span><span class="special">);</span> |
| <span class="identifier">milliseconds</span> <span class="identifier">ms</span><span class="special">(</span><span class="number">763</span><span class="special">);</span> |
| <span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">h</span> <span class="special"><<</span> <span class="string">", "</span> <span class="special"><<</span> <span class="identifier">m</span> <span class="special"><<</span> <span class="string">", "</span> <span class="special"><<</span> <span class="identifier">s</span> <span class="special"><<</span> <span class="string">" et "</span> <span class="special"><<</span> <span class="identifier">ms</span> <span class="special"><<</span> <span class="char">'\n'</span><span class="special">;</span> |
| <span class="special">}</span> |
| </pre> |
| <p> |
| Output is: |
| </p> |
| <pre class="programlisting"><span class="number">5</span> <span class="identifier">heures</span><span class="special">,</span> <span class="number">45</span> <span class="identifier">minutes</span><span class="special">,</span> <span class="number">15</span> <span class="identifier">secondes</span> <span class="identifier">et</span> <span class="number">763</span> <span class="identifier">millisecondes</span> |
| </pre> |
| <p> |
| <span class="emphasis"><em>See the source file <a href="../../../libs/chrono/example/french.cpp" target="_top">example/french.cpp</a></em></span> |
| </p> |
| </div> |
| </div> |
| </div> |
| <div class="section"> |
| <div class="titlepage"><div><div><h3 class="title"> |
| <a name="chrono.users_guide.ext_references"></a><a class="link" href="users_guide.html#chrono.users_guide.ext_references" title="External Resources">External Resources</a> |
| </h3></div></div></div> |
| <div class="variablelist"> |
| <p class="title"><b></b></p> |
| <dl class="variablelist"> |
| <dt><span class="term"><a href="http://www.open-std.org/jtc1/sc22/wg21" target="_top"><span class="bold"><strong>C++ |
| Standards Committee's current Working Paper</strong></span></a></span></dt> |
| <dd><p> |
| The most authoritative reference material for the library is the C++ |
| Standards Committee's current Working Paper (WP). 20.11 Time utilities |
| "time" |
| </p></dd> |
| <dt><span class="term"><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2008/n2661.htm" target="_top"><span class="bold"><strong>N2661 - A Foundation to Sleep On</strong></span></a></span></dt> |
| <dd><p> |
| From Howard E. Hinnant, Walter E. Brown, Jeff Garland and Marc Paterno. |
| Is very informative and provides motivation for key design decisions |
| </p></dd> |
| <dt><span class="term"><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2010/n3134.html#934" target="_top"><span class="bold"><strong>LGW 934. duration is missing operator%</strong></span></a></span></dt> |
| <dd><p> |
| From Terry Golubiewski. Is very informative and provides motivation |
| for key design decisions |
| </p></dd> |
| <dt><span class="term"><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2010/n3135.html#935" target="_top"><span class="bold"><strong>LGW 935. clock error handling needs to be specified</strong></span></a></span></dt> |
| <dd><p> |
| From Beman Dawes. This issue has been stated as NAD Future. |
| </p></dd> |
| </dl> |
| </div> |
| </div> |
| <div class="footnotes"> |
| <br><hr style="width:100; text-align:left;margin-left: 0"> |
| <div id="ftn.chrono.users_guide.tutorial.i_o.duration_io.f0" class="footnote"><p><a href="#chrono.users_guide.tutorial.i_o.duration_io.f0" class="para"><sup class="para">[1] </sup></a> |
| <a class="link" href="reference.html#chrono.reference.io_v1.chrono_io_hpp.manipulators" title="I/O Manipulators"><code class="computeroutput"><span class="identifier">duration_short</span></code></a> in V1 |
| </p></div> |
| </div> |
| </div> |
| <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> |
| <td align="left"></td> |
| <td align="right"><div class="copyright-footer">Copyright © 2008 Howard Hinnant<br>Copyright © 2006, 2008 Beman Dawes<br>Copyright © 2009-2013 Vicente J. Botet Escriba<p> |
| Distributed under the Boost Software License, Version 1.0. (See accompanying |
| file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>) |
| </p> |
| </div></td> |
| </tr></table> |
| <hr> |
| <div class="spirit-nav"> |
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