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| <div class="titlepage"><div><div><h4 class="title"> |
| <a name="boost_asio.reference.async_read.overload3"></a><a class="link" href="overload3.html" title="async_read (3 of 4 overloads)">async_read |
| (3 of 4 overloads)</a> |
| </h4></div></div></div> |
| <p> |
| Start an asynchronous operation to read a certain amount of data from a |
| stream. |
| </p> |
| <pre class="programlisting"><span class="keyword">template</span><span class="special"><</span> |
| <span class="keyword">typename</span> <a class="link" href="../AsyncReadStream.html" title="Buffer-oriented asynchronous read stream requirements">AsyncReadStream</a><span class="special">,</span> |
| <span class="keyword">typename</span> <span class="identifier">Allocator</span><span class="special">,</span> |
| <span class="keyword">typename</span> <a class="link" href="../ReadHandler.html" title="Read handler requirements">ReadHandler</a><span class="special">></span> |
| <span class="keyword">void</span> <span class="identifier">async_read</span><span class="special">(</span> |
| <span class="identifier">AsyncReadStream</span> <span class="special">&</span> <span class="identifier">s</span><span class="special">,</span> |
| <span class="identifier">basic_streambuf</span><span class="special"><</span> <span class="identifier">Allocator</span> <span class="special">></span> <span class="special">&</span> <span class="identifier">b</span><span class="special">,</span> |
| <span class="identifier">ReadHandler</span> <span class="identifier">handler</span><span class="special">);</span> |
| </pre> |
| <p> |
| This function is used to asynchronously read a certain number of bytes |
| of data from a stream. The function call always returns immediately. The |
| asynchronous operation will continue until one of the following conditions |
| is true: |
| </p> |
| <div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"> |
| An error occurred. |
| </li></ul></div> |
| <p> |
| This operation is implemented in terms of zero or more calls to the stream's |
| async_read_some function, and is known as a <span class="bold"><strong>composed |
| operation</strong></span>. The program must ensure that the stream performs |
| no other read operations (such as async_read, the stream's async_read_some |
| function, or any other composed operations that perform reads) until this |
| operation completes. |
| </p> |
| <a name="boost_asio.reference.async_read.overload3.parameters"></a><h6> |
| <a name="id872470"></a> |
| <a class="link" href="overload3.html#boost_asio.reference.async_read.overload3.parameters">Parameters</a> |
| </h6> |
| <div class="variablelist"> |
| <p class="title"><b></b></p> |
| <dl> |
| <dt><span class="term">s</span></dt> |
| <dd><p> |
| The stream from which the data is to be read. The type must support |
| the AsyncReadStream concept. |
| </p></dd> |
| <dt><span class="term">b</span></dt> |
| <dd><p> |
| A <a class="link" href="../basic_streambuf.html" title="basic_streambuf"><code class="computeroutput"><span class="identifier">basic_streambuf</span></code></a> object into |
| which the data will be read. Ownership of the streambuf is retained |
| by the caller, which must guarantee that it remains valid until the |
| handler is called. |
| </p></dd> |
| <dt><span class="term">handler</span></dt> |
| <dd> |
| <p> |
| The handler to be called when the read operation completes. Copies |
| will be made of the handler as required. The function signature of |
| the handler must be: |
| </p> |
| <pre class="programlisting"><span class="keyword">void</span> <span class="identifier">handler</span><span class="special">(</span> |
| <span class="keyword">const</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">system</span><span class="special">::</span><span class="identifier">error_code</span><span class="special">&</span> <span class="identifier">error</span><span class="special">,</span> <span class="comment">// Result of operation. |
| </span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span> <span class="identifier">bytes_transferred</span> <span class="comment">// Number of bytes copied into the |
| </span> <span class="comment">// buffers. If an error occurred, |
| </span> <span class="comment">// this will be the number of |
| </span> <span class="comment">// bytes successfully transferred |
| </span> <span class="comment">// prior to the error. |
| </span><span class="special">);</span> |
| </pre> |
| <p> |
| Regardless of whether the asynchronous operation completes immediately |
| or not, the handler will not be invoked from within this function. |
| Invocation of the handler will be performed in a manner equivalent |
| to using <code class="computeroutput"><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">post</span><span class="special">()</span></code>. |
| </p> |
| </dd> |
| </dl> |
| </div> |
| <a name="boost_asio.reference.async_read.overload3.remarks"></a><h6> |
| <a name="id872733"></a> |
| <a class="link" href="overload3.html#boost_asio.reference.async_read.overload3.remarks">Remarks</a> |
| </h6> |
| <p> |
| This overload is equivalent to calling: |
| </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">async_read</span><span class="special">(</span> |
| <span class="identifier">s</span><span class="special">,</span> <span class="identifier">b</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">transfer_all</span><span class="special">(),</span> |
| <span class="identifier">handler</span><span class="special">);</span> |
| </pre> |
| </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> |
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