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| <h1><img src="../../../../boost.png" alt="Boost logo" align= |
| "middle" width="277" height="86">Boost.Flyweight |
| Tracking policies reference</h1> |
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| Locking policies |
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| <h2>Contents</h2> |
| |
| <ul> |
| <li><a href="#preliminary">Preliminary concepts</a></li> |
| <li><a href="#tracking">Tracking policies</a></li> |
| <li><a href="#tracking_tag_synopsis">Header |
| <code>"boost/flyweight/tracking_tag.hpp"</code> synopsis</a> |
| <ul> |
| <li><a href="#is_tracking">Class template <code>is_tracking</code></a></li> |
| <li><a href="#tracking_construct">Class template <code>tracking</code></a></li> |
| </ul> |
| </li> |
| <li><a href="#refcounted_fwd_synopsis">Header |
| <code>"boost/flyweight/refcounted_fwd.hpp"</code> synopsis</a> |
| </li> |
| <li><a href="#refcounted_synopsis">Header |
| <code>"boost/flyweight/refcounted.hpp"</code> synopsis</a> |
| <ul> |
| <li><a href="#refcounted">Class <code>refcounted</code></a></li> |
| </ul> |
| </li> |
| <li><a href="#no_tracking_fwd_synopsis">Header |
| <code>"boost/flyweight/no_tracking_fwd.hpp"</code> synopsis</a> |
| </li> |
| <li><a href="#no_tracking_synopsis">Header |
| <code>"boost/flyweight/no_tracking.hpp"</code> synopsis</a> |
| <ul> |
| <li><a href="#no_tracking">Class <code>no_tracking</code></a></li> |
| </ul> |
| </li> |
| </ul> |
| |
| <h2><a name="preliminary">Preliminary concepts</a></h2> |
| |
| <p> |
| A <i>tracking policy helper</i> provides access to some of the functionality |
| of a <a href="factories.html#factory">factory</a> so as to be used |
| in the implementation of an associated <a href="#tracking"><code>Tracking Policy</code></a>. |
| In the following table, <code>TrackingHelper</code> is a tracking policy |
| helper associated to a <a href="factories.html#factory">factory</a> type |
| <code>Factory</code> of elements of type <code>Entry</code>, <code>h</code> |
| is a value of |
| <code>Factory::handle_type</code> associated to a <code>Factory</code> <code>f</code> |
| and <code>check</code> is a value of |
| a <a href="http://www.sgi.com/tech/stl/Predicate.html"><code>Predicate</code></a> |
| type <code>Checker</code> with argument of type <code>Factory::handle_type</code>. |
| </p> |
| |
| <p align="center"> |
| <table cellspacing="0"> |
| <caption><b>Tracking Policy Helper requirements.</b></caption> |
| <tr> |
| <th align="center">expression</th> |
| <th align="center">return type</th> |
| <th align="center">assertion/note<br>pre/post-condition</th> |
| </tr> |
| <tr> |
| <td><code>TrackingHelper::entry(h);</code></td> |
| <td><code>const Entry&</code></td> |
| <td>Returns <code>f.entry(h)</code>.</td> |
| </tr> |
| <tr class="odd_tr"> |
| <td><code>TrackingHelper::erase(h,check);</code></td> |
| <td><code>void</code></td> |
| <td>If <code>check(h)</code>, invokes <code>f.erase(h)</code>.</td> |
| </tr> |
| </table> |
| </p> |
| |
| <p> |
| The execution of <code>TrackingHelper::erase</code> (including the |
| invocation of <code>check(h)</code>) is done in a |
| synchronized manner so as to prevent any other thread of execution from |
| simultaneously accessing the factory's insertion or deletion facilities. |
| </p> |
| |
| <h2><a name="tracking">Tracking policies</a></h2> |
| |
| <p> |
| A <i>tracking policy</i> defines the strategy to be followed by a |
| <a href="flyweight.html#flyweight"><code>flyweight</code></a> instantiation when |
| all the flyweight objects associated to a given value are destroyed. |
| The tracking policy contributes some type information necessary for the |
| definition of the <code>flyweight</code> internal |
| <a href="factories.html#factory">factory</a>. |
| </p> |
| |
| <p> |
| A type <code>Tracking</code> is a tracking policy if: |
| <ul> |
| <li>One of the following conditions is satisfied: |
| <ol type="a"> |
| <li><a href="#is_tracking"><code>is_tracking<Tracking>::type</code></a> is |
| <a href="../../../mpl/doc/refmanual/bool.html"><code>boost::mpl::true_</code></a>,</li> |
| <li><code>Tracking</code> is of the form |
| <a href="#tracking_construct"><code>tracking<Tracking'></code></a>.</li> |
| </ol> |
| </li> |
| <li>The expression <code>Tracking::entry_type</code> (or |
| <code>Tracking'::entry_type</code> if (b) applies) is an |
| <a href="../../../mpl/doc/refmanual/lambda-expression.html"><code>MPL Lambda |
| Expression</code></a> that resolves, when invoked with different types |
| (<code>Value</code>,<code>Key</code>) such that <code>Value</code> is |
| <a href="http://www.sgi.com/tech/stl/Assignable.html"><code>Assignable</code></a> |
| and implicitly convertible to <code>const Key&</code>, to an |
| <a href="http://www.sgi.com/tech/stl/Assignable.html"><code>Assignable</code></a> |
| type <code>Entry</code> implicitly convertible to both <code>const Value&</code> |
| and <code>const Key&</code>. |
| </li> |
| <li>The expression <code>Tracking::handle_type</code> (or |
| <code>Tracking'::handle_type</code> if (b) applies) is an |
| <a href="../../../mpl/doc/refmanual/lambda-expression.html"><code>MPL Lambda |
| Expression</code></a>; this expression, when invoked with types |
| (<code>InternalHandle</code>,<a href="#preliminary"><code>TrackingHelper</code></a>), |
| with <code>InternalHandle</code> being |
| <a href="http://www.sgi.com/tech/stl/Assignable.html"><code>Assignable</code></a> |
| and providing the nothrow guarantee for copy and assignment, |
| resolves to an |
| <a href="http://www.sgi.com/tech/stl/Assignable.html"><code>Assignable</code></a> |
| type <code>Handle</code> which also provides the nothrow guarantee for |
| copy and assignment and is constructible from and implicitly |
| convertible to <code>InternalHandle</code>. |
| <code>TrackingHelper</code> is an incomplete type at the time of |
| invocation of <code>Tracking::handle_type</code>. |
| </li> |
| </ul> |
| <code>Tracking::handle_type</code> is parameterized by a helper that provides |
| access to some of the functionality of the factory associated to the |
| tracking policy. This factory's associated entry and handle types are the types |
| <code>Entry</code> and <code>Handle</code> defined above, respectively. |
| </p> |
| |
| <h2><a name="tracking_tag_synopsis">Header |
| <a href="../../../../boost/flyweight/tracking_tag.hpp"><code>"boost/flyweight/tracking_tag.hpp"</code></a> synopsis</a></h2> |
| |
| <blockquote><pre> |
| <span class=keyword>namespace</span> <span class=identifier>boost</span><span class=special>{</span> |
| |
| <span class=keyword>namespace</span> <span class=identifier>flyweights</span><span class=special>{</span> |
| |
| <span class=keyword>struct</span> <span class=identifier>tracking_marker</span><span class=special>;</span> |
| |
| <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>T</span><span class=special>></span> |
| <span class=keyword>struct</span> <span class=identifier>is_tracking</span> |
| |
| <span class=keyword>template</span><span class=special><</span><span class=keyword>typename</span> <span class=identifier>T</span><span class=special>></span> |
| <span class=keyword>struct</span> <span class=identifier>tracking</span><span class=special>;</span> |
| |
| <span class=special>}</span> <span class=comment>// namespace boost::flyweights</span> |
| |
| <span class=special>}</span> <span class=comment>// namespace boost</span> |
| </pre></blockquote> |
| |
| <h3><a name="is_tracking">Class template <code>is_tracking</code></a></h3> |
| |
| <p> |
| Unless specialized by the user, <code>is_tracking<T>::type</code> is |
| <a href="../../../mpl/doc/refmanual/bool.html"><code>boost::mpl::true_</code></a> |
| if <code>T</code> is derived from <code>tracking_marker</code>, and it is |
| <a href="../../../mpl/doc/refmanual/bool.html"><code>boost::mpl::false_</code></a> |
| otherwise. |
| </p> |
| |
| <h3><a name="tracking_construct">Class template <code>tracking</code></a></h3> |
| |
| <p> |
| <code>tracking<T></code> is a syntactic construct meant to indicate |
| that <code>T</code> is a tracking policy without resorting to the |
| mechanisms provided by the <code>is_tracking</code> class template. |
| </p> |
| |
| <h2><a name="refcounted_fwd_synopsis">Header |
| <a href="../../../../boost/flyweight/refcounted_fwd.hpp"><code>"boost/flyweight/refcounted_fwd.hpp"</code></a> synopsis</a></h2> |
| |
| <blockquote><pre> |
| <span class=keyword>namespace</span> <span class=identifier>boost</span><span class=special>{</span> |
| |
| <span class=keyword>namespace</span> <span class=identifier>flyweights</span><span class=special>{</span> |
| |
| <span class=keyword>struct</span> <span class=identifier>refcounted</span><span class=special>;</span> |
| |
| <span class=special>}</span> <span class=comment>// namespace boost::flyweights</span> |
| |
| <span class=special>}</span> <span class=comment>// namespace boost</span> |
| </pre></blockquote> |
| |
| <p> |
| <code>refcounted_fwd.hpp</code> forward declares the class |
| <a href="#refcounted"><code>refcounted</code></a>. |
| </p> |
| |
| <h2><a name="refcounted_synopsis">Header |
| <a href="../../../../boost/flyweight/refcounted.hpp"><code>"boost/flyweight/refcounted.hpp"</code></a> synopsis</a></h2> |
| |
| <h3><a name="refcounted">Class <code>refcounted</code></a></h3> |
| |
| <p> |
| <a href="#tracking"><code>Tracking Policy</code></a> providing |
| <a href="flyweight.html#flyweight"><code>flyweight</code></a> |
| instantiations with reference counting semantics: when all the flyweight objects |
| associated to a given value are destroyed, the corresponding entry is |
| erased from <code>flyweight</code>'s internal |
| <a href="factories.html#factory">factory</a>. |
| </p> |
| |
| <h2><a name="no_tracking_fwd_synopsis">Header |
| <a href="../../../../boost/flyweight/no_tracking_fwd.hpp"><code>"boost/flyweight/no_tracking_fwd.hpp"</code></a> synopsis</a></h2> |
| |
| <blockquote><pre> |
| <span class=keyword>namespace</span> <span class=identifier>boost</span><span class=special>{</span> |
| |
| <span class=keyword>namespace</span> <span class=identifier>flyweights</span><span class=special>{</span> |
| |
| <span class=keyword>struct</span> <span class=identifier>no_tracking</span><span class=special>;</span> |
| |
| <span class=special>}</span> <span class=comment>// namespace boost::flyweights</span> |
| |
| <span class=special>}</span> <span class=comment>// namespace boost</span> |
| </pre></blockquote> |
| |
| <p> |
| <code>no_tracking_fwd.hpp</code> forward declares the class |
| <a href="#no_tracking"><code>no_tracking</code></a>. |
| </p> |
| |
| <h2><a name="no_tracking_synopsis">Header |
| <a href="../../../../boost/flyweight/no_tracking.hpp"><code>"boost/flyweight/no_tracking.hpp"</code></a> synopsis</a></h2> |
| |
| <h3><a name="no_tracking">Class <code>no_tracking</code></a></h3> |
| |
| <p> |
| Null <a href="#tracking"><code>Tracking Policy</code></a>: elements inserted |
| into <code>flyweight</code>'s internal <a href="factories.html#factory">factory</a> |
| are not erased until program termination. |
| </p> |
| |
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| |
| <br> |
| |
| <p>Revised August 18th 2008</p> |
| |
| <p>© Copyright 2006-2008 Joaquín M López Muñoz. |
| Distributed under the Boost Software |
| License, Version 1.0. (See accompanying file <a href="../../../../LICENSE_1_0.txt"> |
| LICENSE_1_0.txt</a> or copy at <a href="http://www.boost.org/LICENSE_1_0.txt"> |
| http://www.boost.org/LICENSE_1_0.txt</a>) |
| </p> |
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