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| <div class="titlepage"><div><div><h4 class="title"> |
| <a name="boost_asio.reference.async_read_until.overload3"></a><a class="link" href="overload3.html" title="async_read_until (3 of 4 overloads)">async_read_until |
| (3 of 4 overloads)</a> |
| </h4></div></div></div> |
| <p> |
| Start an asynchronous operation to read data into a streambuf until some |
| part of its data matches a regular expression. |
| </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_until</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">boost</span><span class="special">::</span><span class="identifier">asio</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="keyword">const</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">regex</span> <span class="special">&</span> <span class="identifier">expr</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 data into the specified streambuf |
| until the streambuf's get area contains some data that matches a regular |
| expression. 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"> |
| A substring of the streambuf's get area matches the regular expression. |
| </li> |
| <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>. If the streambuf's get area already contains data |
| that matches the regular expression, this asynchronous operation completes |
| immediately. The program must ensure that the stream performs no other |
| read operations (such as async_read, async_read_until, 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_until.overload3.parameters"></a><h6> |
| <a name="id881201"></a> |
| <a class="link" href="overload3.html#boost_asio.reference.async_read_until.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 streambuf 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">expr</span></dt> |
| <dd><p> |
| The regular expression. |
| </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="comment">// Result of operation. |
| </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">// The number of bytes in the streambuf's get |
| </span> <span class="comment">// area up to and including the substring |
| </span> <span class="comment">// that matches the regular. expression. |
| </span> <span class="comment">// 0 if an error occurred. |
| </span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span> <span class="identifier">bytes_transferred</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_until.overload3.remarks"></a><h6> |
| <a name="id881457"></a> |
| <a class="link" href="overload3.html#boost_asio.reference.async_read_until.overload3.remarks">Remarks</a> |
| </h6> |
| <p> |
| After a successful async_read_until operation, the streambuf may contain |
| additional data beyond that which matched the regular expression. An application |
| will typically leave that data in the streambuf for a subsequent async_read_until |
| operation to examine. |
| </p> |
| <a name="boost_asio.reference.async_read_until.overload3.example"></a><h6> |
| <a name="id881487"></a> |
| <a class="link" href="overload3.html#boost_asio.reference.async_read_until.overload3.example">Example</a> |
| </h6> |
| <p> |
| To asynchronously read data into a streambuf until a CR-LF sequence is |
| encountered: |
| </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">streambuf</span> <span class="identifier">b</span><span class="special">;</span> |
| <span class="special">...</span> |
| <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">e</span><span class="special">,</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span> <span class="identifier">size</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="keyword">if</span> <span class="special">(!</span><span class="identifier">e</span><span class="special">)</span> |
| <span class="special">{</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">istream</span> <span class="identifier">is</span><span class="special">(&</span><span class="identifier">b</span><span class="special">);</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="identifier">line</span><span class="special">;</span> |
| <span class="identifier">std</span><span class="special">::</span><span class="identifier">getline</span><span class="special">(</span><span class="identifier">is</span><span class="special">,</span> <span class="identifier">line</span><span class="special">);</span> |
| <span class="special">...</span> |
| <span class="special">}</span> |
| <span class="special">}</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">async_read_until</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">regex</span><span class="special">(</span><span class="string">"\r\n"</span><span class="special">),</span> <span class="identifier">handler</span><span class="special">);</span> |
| </pre> |
| <p> |
| After the <code class="computeroutput"><span class="identifier">async_read_until</span></code> |
| operation completes successfully, the buffer <code class="computeroutput"><span class="identifier">b</span></code> |
| contains the data which matched the regular expression: |
| </p> |
| <pre class="programlisting"><span class="special">{</span> <span class="char">'a'</span><span class="special">,</span> <span class="char">'b'</span><span class="special">,</span> <span class="special">...,</span> <span class="char">'c'</span><span class="special">,</span> <span class="char">'\r'</span><span class="special">,</span> <span class="char">'\n'</span><span class="special">,</span> <span class="char">'d'</span><span class="special">,</span> <span class="char">'e'</span><span class="special">,</span> <span class="special">...</span> <span class="special">}</span> |
| </pre> |
| <p> |
| The call to <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">getline</span></code> then extracts the data up to |
| and including the match, so that the string <code class="computeroutput"><span class="identifier">line</span></code> |
| contains: |
| </p> |
| <pre class="programlisting"><span class="special">{</span> <span class="char">'a'</span><span class="special">,</span> <span class="char">'b'</span><span class="special">,</span> <span class="special">...,</span> <span class="char">'c'</span><span class="special">,</span> <span class="char">'\r'</span><span class="special">,</span> <span class="char">'\n'</span> <span class="special">}</span> |
| </pre> |
| <p> |
| The remaining data is left in the buffer <code class="computeroutput"><span class="identifier">b</span></code> |
| as follows: |
| </p> |
| <pre class="programlisting"><span class="special">{</span> <span class="char">'d'</span><span class="special">,</span> <span class="char">'e'</span><span class="special">,</span> <span class="special">...</span> <span class="special">}</span> |
| </pre> |
| <p> |
| This data may be the start of a new line, to be extracted by a subsequent |
| <code class="computeroutput"><span class="identifier">async_read_until</span></code> operation. |
| </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> |
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