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<title>Handlers</title>
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<div class="titlepage"><div><div><h3 class="title">
<a name="asio.reference.Handler"></a><a class="link" href="Handler.html" title="Handlers">Handlers</a>
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<p>
        A handler must meet the requirements of <code class="computeroutput"><span class="identifier">CopyConstructible</span></code>
        types (C++ Std, 20.1.3).
      </p>
<p>
        In the table below, <code class="computeroutput"><span class="identifier">X</span></code> denotes
        a handler class, <code class="computeroutput"><span class="identifier">h</span></code> denotes
        a value of <code class="computeroutput"><span class="identifier">X</span></code>, <code class="computeroutput"><span class="identifier">p</span></code> denotes a pointer to a block of allocated
        memory of type <code class="computeroutput"><span class="keyword">void</span><span class="special">*</span></code>,
        <code class="computeroutput"><span class="identifier">s</span></code> denotes the size for a
        block of allocated memory, and <code class="computeroutput"><span class="identifier">f</span></code>
        denotes a function object taking no arguments.
      </p>
<div class="table">
<a name="asio.reference.Handler.t0"></a><p class="title"><b>Table&#160;13.&#160;Handler requirements</b></p>
<div class="table-contents"><table class="table" summary="Handler requirements">
<colgroup>
<col>
<col>
<col>
</colgroup>
<thead><tr>
<th>
                <p>
                  expression
                </p>
              </th>
<th>
                <p>
                  return type
                </p>
              </th>
<th>
                <p>
                  assertion/note<br> pre/post-conditions
                </p>
              </th>
</tr></thead>
<tbody>
<tr>
<td>
                <p>
</p>
<pre class="programlisting"><span class="keyword">using</span> <span class="identifier">asio</span><span class="special">::</span><span class="identifier">asio_handler_allocate</span><span class="special">;</span>
<span class="identifier">asio_handler_allocate</span><span class="special">(</span><span class="identifier">s</span><span class="special">,</span> <span class="special">&amp;</span><span class="identifier">h</span><span class="special">);</span>
</pre>
<p>
                </p>
              </td>
<td>
                <p>
                  <code class="computeroutput"><span class="keyword">void</span><span class="special">*</span></code>
                </p>
              </td>
<td>
                <p>
                  Returns a pointer to a block of memory of size <code class="computeroutput"><span class="identifier">s</span></code>.
                  The pointer must satisfy the same alignment requirements as a pointer
                  returned by <code class="computeroutput"><span class="special">::</span><span class="keyword">operator</span>
                  <span class="keyword">new</span><span class="special">()</span></code>.
                  Throws <code class="computeroutput"><span class="identifier">bad_alloc</span></code>
                  on failure.<br> <br> The <code class="computeroutput"><span class="identifier">asio_handler_allocate</span><span class="special">()</span></code> function is located using argument-dependent
                  lookup. The function <code class="computeroutput"><span class="identifier">asio</span><span class="special">::</span><span class="identifier">asio_handler_allocate</span><span class="special">()</span></code> serves as a default if no user-supplied
                  function is available.
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
</p>
<pre class="programlisting"><span class="keyword">using</span> <span class="identifier">asio</span><span class="special">::</span><span class="identifier">asio_handler_deallocate</span><span class="special">;</span>
<span class="identifier">asio_handler_deallocate</span><span class="special">(</span><span class="identifier">p</span><span class="special">,</span> <span class="identifier">s</span><span class="special">,</span> <span class="special">&amp;</span><span class="identifier">h</span><span class="special">);</span>
</pre>
<p>
                </p>
              </td>
<td>
              </td>
<td>
                <p>
                  Frees a block of memory associated with a pointer <code class="computeroutput"><span class="identifier">p</span></code>, of at least size <code class="computeroutput"><span class="identifier">s</span></code>, that was previously allocated
                  using <code class="computeroutput"><span class="identifier">asio_handler_allocate</span><span class="special">()</span></code>.<br> <br> The <code class="computeroutput"><span class="identifier">asio_handler_deallocate</span><span class="special">()</span></code>
                  function is located using argument-dependent lookup. The function
                  <code class="computeroutput"><span class="identifier">asio</span><span class="special">::</span><span class="identifier">asio_handler_deallocate</span><span class="special">()</span></code>
                  serves as a default if no user-supplied function is available.
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
</p>
<pre class="programlisting"><span class="keyword">using</span> <span class="identifier">asio</span><span class="special">::</span><span class="identifier">asio_handler_invoke</span><span class="special">;</span>
<span class="identifier">asio_handler_invoke</span><span class="special">(</span><span class="identifier">f</span><span class="special">,</span> <span class="special">&amp;</span><span class="identifier">h</span><span class="special">);</span>
</pre>
<p>
                </p>
              </td>
<td>
              </td>
<td>
                <p>
                  Causes the function object <code class="computeroutput"><span class="identifier">f</span></code>
                  to be executed as if by calling <code class="computeroutput"><span class="identifier">f</span><span class="special">()</span></code>.<br> <br> The <code class="computeroutput"><span class="identifier">asio_handler_invoke</span><span class="special">()</span></code>
                  function is located using argument-dependent lookup. The function
                  <code class="computeroutput"><span class="identifier">asio</span><span class="special">::</span><span class="identifier">asio_handler_invoke</span><span class="special">()</span></code>
                  serves as a default if no user-supplied function is available.
                </p>
              </td>
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<td align="right"><div class="copyright-footer">Copyright &#169; 2003-2014 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>)
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