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| <div class="titlepage"><div><div><h3 class="title"> |
| <a name="boost_asio.reference.io_service"></a><a class="link" href="io_service.html" title="io_service">io_service</a> |
| </h3></div></div></div> |
| <p> |
| Provides core I/O functionality. |
| </p> |
| <pre class="programlisting"><span class="keyword">class</span> <span class="identifier">io_service</span> <span class="special">:</span> |
| <span class="identifier">noncopyable</span> |
| </pre> |
| <a name="boost_asio.reference.io_service.types"></a><h5> |
| <a name="id1155597"></a> |
| <a class="link" href="io_service.html#boost_asio.reference.io_service.types">Types</a> |
| </h5> |
| <div class="informaltable"><table class="table"> |
| <colgroup> |
| <col> |
| <col> |
| </colgroup> |
| <thead><tr> |
| <th> |
| <p> |
| Name |
| </p> |
| </th> |
| <th> |
| <p> |
| Description |
| </p> |
| </th> |
| </tr></thead> |
| <tbody> |
| <tr> |
| <td> |
| <p> |
| <a class="link" href="io_service__id.html" title="io_service::id"><span class="bold"><strong>id</strong></span></a> |
| </p> |
| </td> |
| <td> |
| <p> |
| Class used to uniquely identify a service. |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <a class="link" href="io_service__service.html" title="io_service::service"><span class="bold"><strong>service</strong></span></a> |
| </p> |
| </td> |
| <td> |
| <p> |
| Base class for all io_service services. |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <a class="link" href="io_service__strand.html" title="io_service::strand"><span class="bold"><strong>strand</strong></span></a> |
| </p> |
| </td> |
| <td> |
| <p> |
| Provides serialised handler execution. |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <a class="link" href="io_service__work.html" title="io_service::work"><span class="bold"><strong>work</strong></span></a> |
| </p> |
| </td> |
| <td> |
| <p> |
| Class to inform the io_service when it has work to do. |
| </p> |
| </td> |
| </tr> |
| </tbody> |
| </table></div> |
| <a name="boost_asio.reference.io_service.member_functions"></a><h5> |
| <a name="id1155765"></a> |
| <a class="link" href="io_service.html#boost_asio.reference.io_service.member_functions">Member Functions</a> |
| </h5> |
| <div class="informaltable"><table class="table"> |
| <colgroup> |
| <col> |
| <col> |
| </colgroup> |
| <thead><tr> |
| <th> |
| <p> |
| Name |
| </p> |
| </th> |
| <th> |
| <p> |
| Description |
| </p> |
| </th> |
| </tr></thead> |
| <tbody> |
| <tr> |
| <td> |
| <p> |
| <a class="link" href="io_service/dispatch.html" title="io_service::dispatch"><span class="bold"><strong>dispatch</strong></span></a> |
| </p> |
| </td> |
| <td> |
| <p> |
| Request the io_service to invoke the given handler. |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <a class="link" href="io_service/io_service.html" title="io_service::io_service"><span class="bold"><strong>io_service</strong></span></a> |
| </p> |
| </td> |
| <td> |
| <p> |
| Constructor. |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <a class="link" href="io_service/poll.html" title="io_service::poll"><span class="bold"><strong>poll</strong></span></a> |
| </p> |
| </td> |
| <td> |
| <p> |
| Run the io_service object's event processing loop to execute ready |
| handlers. |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <a class="link" href="io_service/poll_one.html" title="io_service::poll_one"><span class="bold"><strong>poll_one</strong></span></a> |
| </p> |
| </td> |
| <td> |
| <p> |
| Run the io_service object's event processing loop to execute one |
| ready handler. |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <a class="link" href="io_service/post.html" title="io_service::post"><span class="bold"><strong>post</strong></span></a> |
| </p> |
| </td> |
| <td> |
| <p> |
| Request the io_service to invoke the given handler and return immediately. |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <a class="link" href="io_service/reset.html" title="io_service::reset"><span class="bold"><strong>reset</strong></span></a> |
| </p> |
| </td> |
| <td> |
| <p> |
| Reset the io_service in preparation for a subsequent run() invocation. |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <a class="link" href="io_service/run.html" title="io_service::run"><span class="bold"><strong>run</strong></span></a> |
| </p> |
| </td> |
| <td> |
| <p> |
| Run the io_service object's event processing loop. |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <a class="link" href="io_service/run_one.html" title="io_service::run_one"><span class="bold"><strong>run_one</strong></span></a> |
| </p> |
| </td> |
| <td> |
| <p> |
| Run the io_service object's event processing loop to execute at |
| most one handler. |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <a class="link" href="io_service/stop.html" title="io_service::stop"><span class="bold"><strong>stop</strong></span></a> |
| </p> |
| </td> |
| <td> |
| <p> |
| Stop the io_service object's event processing loop. |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <a class="link" href="io_service/wrap.html" title="io_service::wrap"><span class="bold"><strong>wrap</strong></span></a> |
| </p> |
| </td> |
| <td> |
| <p> |
| Create a new handler that automatically dispatches the wrapped |
| handler on the io_service. |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <a class="link" href="io_service/_io_service.html" title="io_service::~io_service"><span class="bold"><strong>~io_service</strong></span></a> |
| </p> |
| </td> |
| <td> |
| <p> |
| Destructor. |
| </p> |
| </td> |
| </tr> |
| </tbody> |
| </table></div> |
| <a name="boost_asio.reference.io_service.friends"></a><h5> |
| <a name="id1156148"></a> |
| <a class="link" href="io_service.html#boost_asio.reference.io_service.friends">Friends</a> |
| </h5> |
| <div class="informaltable"><table class="table"> |
| <colgroup> |
| <col> |
| <col> |
| </colgroup> |
| <thead><tr> |
| <th> |
| <p> |
| Name |
| </p> |
| </th> |
| <th> |
| <p> |
| Description |
| </p> |
| </th> |
| </tr></thead> |
| <tbody> |
| <tr> |
| <td> |
| <p> |
| <a class="link" href="io_service/add_service.html" title="io_service::add_service"><span class="bold"><strong>add_service</strong></span></a> |
| </p> |
| </td> |
| <td> |
| <p> |
| Add a service object to the io_service. |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <a class="link" href="io_service/has_service.html" title="io_service::has_service"><span class="bold"><strong>has_service</strong></span></a> |
| </p> |
| </td> |
| <td> |
| <p> |
| Determine if an io_service contains a specified service type. |
| </p> |
| </td> |
| </tr> |
| <tr> |
| <td> |
| <p> |
| <a class="link" href="io_service/use_service.html" title="io_service::use_service"><span class="bold"><strong>use_service</strong></span></a> |
| </p> |
| </td> |
| <td> |
| <p> |
| Obtain the service object corresponding to the given type. |
| </p> |
| </td> |
| </tr> |
| </tbody> |
| </table></div> |
| <p> |
| The <a class="link" href="io_service.html" title="io_service"><code class="computeroutput"><span class="identifier">io_service</span></code></a> |
| class provides the core I/O functionality for users of the asynchronous I/O |
| objects, including: |
| </p> |
| <div class="itemizedlist"><ul class="itemizedlist" type="disc"> |
| <li class="listitem"> |
| <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">asio</span><span class="special">::</span><span class="identifier">ip</span><span class="special">::</span><span class="identifier">tcp</span><span class="special">::</span><span class="identifier">socket</span></code> |
| </li> |
| <li class="listitem"> |
| <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">asio</span><span class="special">::</span><span class="identifier">ip</span><span class="special">::</span><span class="identifier">tcp</span><span class="special">::</span><span class="identifier">acceptor</span></code> |
| </li> |
| <li class="listitem"> |
| <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">asio</span><span class="special">::</span><span class="identifier">ip</span><span class="special">::</span><span class="identifier">udp</span><span class="special">::</span><span class="identifier">socket</span></code> |
| </li> |
| <li class="listitem"> |
| <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">asio</span><span class="special">::</span><span class="identifier">deadline_timer</span></code>. |
| </li> |
| </ul></div> |
| <p> |
| The <a class="link" href="io_service.html" title="io_service"><code class="computeroutput"><span class="identifier">io_service</span></code></a> |
| class also includes facilities intended for developers of custom asynchronous |
| services. |
| </p> |
| <a name="boost_asio.reference.io_service.thread_safety"></a><h5> |
| <a name="id1156524"></a> |
| <a class="link" href="io_service.html#boost_asio.reference.io_service.thread_safety">Thread Safety</a> |
| </h5> |
| <p> |
| <span class="bold"><strong>Distinct</strong></span> <span class="bold"><strong>objects:</strong></span> |
| Safe. |
| </p> |
| <p> |
| <span class="bold"><strong>Shared</strong></span> <span class="bold"><strong>objects:</strong></span> |
| Safe, with the exception that calling <code class="computeroutput"><span class="identifier">reset</span><span class="special">()</span></code> while there are unfinished <code class="computeroutput"><span class="identifier">run</span><span class="special">()</span></code>, |
| <code class="computeroutput"><span class="identifier">run_one</span><span class="special">()</span></code>, |
| <code class="computeroutput"><span class="identifier">poll</span><span class="special">()</span></code> |
| or <code class="computeroutput"><span class="identifier">poll_one</span><span class="special">()</span></code> |
| calls results in undefined behaviour. |
| </p> |
| <a name="boost_asio.reference.io_service.synchronous_and_asynchronous_operations"></a><h5> |
| <a name="id1156651"></a> |
| <a class="link" href="io_service.html#boost_asio.reference.io_service.synchronous_and_asynchronous_operations">Synchronous |
| and asynchronous operations</a> |
| </h5> |
| <p> |
| Synchronous operations on I/O objects implicitly run the <a class="link" href="io_service.html" title="io_service"><code class="computeroutput"><span class="identifier">io_service</span></code></a> object for an individual |
| operation. The <a class="link" href="io_service.html" title="io_service"><code class="computeroutput"><span class="identifier">io_service</span></code></a> functions <code class="computeroutput"><span class="identifier">run</span><span class="special">()</span></code>, |
| <code class="computeroutput"><span class="identifier">run_one</span><span class="special">()</span></code>, |
| <code class="computeroutput"><span class="identifier">poll</span><span class="special">()</span></code> |
| or <code class="computeroutput"><span class="identifier">poll_one</span><span class="special">()</span></code> |
| must be called for the <a class="link" href="io_service.html" title="io_service"><code class="computeroutput"><span class="identifier">io_service</span></code></a> to perform asynchronous |
| operations on behalf of a C++ program. Notification that an asynchronous |
| operation has completed is delivered by invocation of the associated handler. |
| Handlers are invoked only by a thread that is currently calling any overload |
| of <code class="computeroutput"><span class="identifier">run</span><span class="special">()</span></code>, |
| <code class="computeroutput"><span class="identifier">run_one</span><span class="special">()</span></code>, |
| <code class="computeroutput"><span class="identifier">poll</span><span class="special">()</span></code> |
| or <code class="computeroutput"><span class="identifier">poll_one</span><span class="special">()</span></code> |
| for the <a class="link" href="io_service.html" title="io_service"><code class="computeroutput"><span class="identifier">io_service</span></code></a>. |
| </p> |
| <a name="boost_asio.reference.io_service.effect_of_exceptions_thrown_from_handlers"></a><h5> |
| <a name="id1156864"></a> |
| <a class="link" href="io_service.html#boost_asio.reference.io_service.effect_of_exceptions_thrown_from_handlers">Effect |
| of exceptions thrown from handlers</a> |
| </h5> |
| <p> |
| If an exception is thrown from a handler, the exception is allowed to propagate |
| through the throwing thread's invocation of <code class="computeroutput"><span class="identifier">run</span><span class="special">()</span></code>, <code class="computeroutput"><span class="identifier">run_one</span><span class="special">()</span></code>, <code class="computeroutput"><span class="identifier">poll</span><span class="special">()</span></code> or <code class="computeroutput"><span class="identifier">poll_one</span><span class="special">()</span></code>. No other threads that are calling any |
| of these functions are affected. It is then the responsibility of the application |
| to catch the exception. |
| </p> |
| <p> |
| After the exception has been caught, the <code class="computeroutput"><span class="identifier">run</span><span class="special">()</span></code>, <code class="computeroutput"><span class="identifier">run_one</span><span class="special">()</span></code>, <code class="computeroutput"><span class="identifier">poll</span><span class="special">()</span></code> or <code class="computeroutput"><span class="identifier">poll_one</span><span class="special">()</span></code> call may be restarted <span class="bold"><strong>without</strong></span> |
| the need for an intervening call to <code class="computeroutput"><span class="identifier">reset</span><span class="special">()</span></code>. This allows the thread to rejoin the |
| <a class="link" href="io_service.html" title="io_service"><code class="computeroutput"><span class="identifier">io_service</span></code></a> |
| object's thread pool without impacting any other threads in the pool. |
| </p> |
| <p> |
| For example: |
| </p> |
| <pre class="programlisting"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">asio</span><span class="special">::</span><span class="identifier">io_service</span> <span class="identifier">io_service</span><span class="special">;</span> |
| <span class="special">...</span> |
| <span class="keyword">for</span> <span class="special">(;;)</span> |
| <span class="special">{</span> |
| <span class="keyword">try</span> |
| <span class="special">{</span> |
| <span class="identifier">io_service</span><span class="special">.</span><span class="identifier">run</span><span class="special">();</span> |
| <span class="keyword">break</span><span class="special">;</span> <span class="comment">// run() exited normally |
| </span> <span class="special">}</span> |
| <span class="keyword">catch</span> <span class="special">(</span><span class="identifier">my_exception</span><span class="special">&</span> <span class="identifier">e</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="comment">// Deal with exception as appropriate. |
| </span> <span class="special">}</span> |
| <span class="special">}</span> |
| </pre> |
| <a name="boost_asio.reference.io_service.stopping_the_io_service_from_running_out_of_work"></a><h5> |
| <a name="id1157221"></a> |
| <a class="link" href="io_service.html#boost_asio.reference.io_service.stopping_the_io_service_from_running_out_of_work">Stopping |
| the io_service from running out of work</a> |
| </h5> |
| <p> |
| Some applications may need to prevent an <a class="link" href="io_service.html" title="io_service"><code class="computeroutput"><span class="identifier">io_service</span></code></a> object's <code class="computeroutput"><span class="identifier">run</span><span class="special">()</span></code> call |
| from returning when there is no more work to do. For example, the <a class="link" href="io_service.html" title="io_service"><code class="computeroutput"><span class="identifier">io_service</span></code></a> may be being run in a |
| background thread that is launched prior to the application's asynchronous |
| operations. The <code class="computeroutput"><span class="identifier">run</span><span class="special">()</span></code> |
| call may be kept running by creating an object of type <a class="link" href="io_service__work.html" title="io_service::work"><code class="computeroutput"><span class="identifier">io_service</span><span class="special">::</span><span class="identifier">work</span></code></a>: |
| </p> |
| <pre class="programlisting"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">asio</span><span class="special">::</span><span class="identifier">io_service</span> <span class="identifier">io_service</span><span class="special">;</span> |
| <span class="identifier">boost</span><span class="special">::</span><span class="identifier">asio</span><span class="special">::</span><span class="identifier">io_service</span><span class="special">::</span><span class="identifier">work</span> <span class="identifier">work</span><span class="special">(</span><span class="identifier">io_service</span><span class="special">);</span> |
| <span class="special">...</span> |
| </pre> |
| <p> |
| To effect a shutdown, the application will then need to call the <a class="link" href="io_service.html" title="io_service"><code class="computeroutput"><span class="identifier">io_service</span></code></a> object's <code class="computeroutput"><span class="identifier">stop</span><span class="special">()</span></code> |
| member function. This will cause the <a class="link" href="io_service.html" title="io_service"><code class="computeroutput"><span class="identifier">io_service</span></code></a> <code class="computeroutput"><span class="identifier">run</span><span class="special">()</span></code> call to return as soon as possible, abandoning |
| unfinished operations and without permitting ready handlers to be dispatched. |
| </p> |
| <p> |
| Alternatively, if the application requires that all operations and handlers |
| be allowed to finish normally, the work object may be explicitly destroyed. |
| </p> |
| <pre class="programlisting"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">asio</span><span class="special">::</span><span class="identifier">io_service</span> <span class="identifier">io_service</span><span class="special">;</span> |
| <span class="identifier">auto_ptr</span><span class="special"><</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">asio</span><span class="special">::</span><span class="identifier">io_service</span><span class="special">::</span><span class="identifier">work</span><span class="special">></span> <span class="identifier">work</span><span class="special">(</span> |
| <span class="keyword">new</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">asio</span><span class="special">::</span><span class="identifier">io_service</span><span class="special">::</span><span class="identifier">work</span><span class="special">(</span><span class="identifier">io_service</span><span class="special">));</span> |
| <span class="special">...</span> |
| <span class="identifier">work</span><span class="special">.</span><span class="identifier">reset</span><span class="special">();</span> <span class="comment">// Allow run() to exit. |
| </span></pre> |
| <a name="boost_asio.reference.io_service.the_io_service_class_and_i_o_services"></a><h5> |
| <a name="id1157678"></a> |
| <a class="link" href="io_service.html#boost_asio.reference.io_service.the_io_service_class_and_i_o_services">The |
| io_service class and I/O services</a> |
| </h5> |
| <p> |
| Class <a class="link" href="io_service.html" title="io_service"><code class="computeroutput"><span class="identifier">io_service</span></code></a> |
| implements an extensible, type-safe, polymorphic set of I/O services, indexed |
| by service type. An object of class <a class="link" href="io_service.html" title="io_service"><code class="computeroutput"><span class="identifier">io_service</span></code></a> must be initialised before |
| I/O objects such as sockets, resolvers and timers can be used. These I/O |
| objects are distinguished by having constructors that accept an <code class="computeroutput"><span class="identifier">io_service</span><span class="special">&</span></code> |
| parameter. |
| </p> |
| <p> |
| I/O services exist to manage the logical interface to the operating system |
| on behalf of the I/O objects. In particular, there are resources that are |
| shared across a class of I/O objects. For example, timers may be implemented |
| in terms of a single timer queue. The I/O services manage these shared resources. |
| </p> |
| <p> |
| Access to the services of an <a class="link" href="io_service.html" title="io_service"><code class="computeroutput"><span class="identifier">io_service</span></code></a> is via three function |
| templates, <code class="computeroutput"><span class="identifier">use_service</span><span class="special">()</span></code>, |
| <code class="computeroutput"><span class="identifier">add_service</span><span class="special">()</span></code> |
| and <code class="computeroutput"><span class="identifier">has_service</span><span class="special">()</span></code>. |
| </p> |
| <p> |
| In a call to <code class="computeroutput"><span class="identifier">use_service</span><span class="special"><</span><span class="identifier">Service</span><span class="special">>()</span></code>, the type argument chooses a service, |
| making available all members of the named type. If <code class="computeroutput"><span class="identifier">Service</span></code> |
| is not present in an <a class="link" href="io_service.html" title="io_service"><code class="computeroutput"><span class="identifier">io_service</span></code></a>, an object of type <code class="computeroutput"><span class="identifier">Service</span></code> is created and added to the <a class="link" href="io_service.html" title="io_service"><code class="computeroutput"><span class="identifier">io_service</span></code></a>. |
| A C++ program can check if an <a class="link" href="io_service.html" title="io_service"><code class="computeroutput"><span class="identifier">io_service</span></code></a> implements a particular |
| service with the function template <code class="computeroutput"><span class="identifier">has_service</span><span class="special"><</span><span class="identifier">Service</span><span class="special">>()</span></code>. |
| </p> |
| <p> |
| Service objects may be explicitly added to an <a class="link" href="io_service.html" title="io_service"><code class="computeroutput"><span class="identifier">io_service</span></code></a> using the function template |
| <code class="computeroutput"><span class="identifier">add_service</span><span class="special"><</span><span class="identifier">Service</span><span class="special">>()</span></code>. |
| If the <code class="computeroutput"><span class="identifier">Service</span></code> is already |
| present, the <a class="link" href="service_already_exists.html" title="service_already_exists"><code class="computeroutput"><span class="identifier">service_already_exists</span></code></a> exception |
| is thrown. If the owner of the service is not the same object as the <a class="link" href="io_service.html" title="io_service"><code class="computeroutput"><span class="identifier">io_service</span></code></a> |
| parameter, the <a class="link" href="invalid_service_owner.html" title="invalid_service_owner"><code class="computeroutput"><span class="identifier">invalid_service_owner</span></code></a> exception |
| is thrown. |
| </p> |
| <p> |
| Once a service reference is obtained from an <a class="link" href="io_service.html" title="io_service"><code class="computeroutput"><span class="identifier">io_service</span></code></a> object by calling <code class="computeroutput"><span class="identifier">use_service</span><span class="special">()</span></code>, |
| that reference remains usable as long as the owning <a class="link" href="io_service.html" title="io_service"><code class="computeroutput"><span class="identifier">io_service</span></code></a> object exists. |
| </p> |
| <p> |
| All I/O service implementations have <a class="link" href="io_service__service.html" title="io_service::service"><code class="computeroutput"><span class="identifier">io_service</span><span class="special">::</span><span class="identifier">service</span></code></a> as a public base class. |
| Custom I/O services may be implemented by deriving from this class and then |
| added to an <a class="link" href="io_service.html" title="io_service"><code class="computeroutput"><span class="identifier">io_service</span></code></a> using the facilities |
| described above. |
| </p> |
| <a name="boost_asio.reference.io_service.requirements"></a><h5> |
| <a name="id1158151"></a> |
| <a class="link" href="io_service.html#boost_asio.reference.io_service.requirements">Requirements</a> |
| </h5> |
| <p> |
| <span class="bold"><strong>Header: </strong></span><code class="literal">boost/asio/io_service.hpp</code> |
| </p> |
| <p> |
| <span class="bold"><strong>Convenience header: </strong></span><code class="literal">boost/asio.hpp</code> |
| </p> |
| </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 © 2003 - 2010 Christopher M. Kohlhoff<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> |
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