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<div class="titlepage"><div><div><h4 class="title">
<a name="boost_asio.reference.async_read_until.overload1"></a><a class="link" href="overload1.html" title="async_read_until (1 of 12 overloads)">async_read_until
(1 of 12 overloads)</a>
</h4></div></div></div>
<p>
Start an asynchronous operation to read data into a dynamic buffer sequence
until it contains a specified delimiter.
</p>
<pre class="programlisting">template&lt;
typename <a class="link" href="../AsyncReadStream.html" title="Buffer-oriented asynchronous read stream requirements">AsyncReadStream</a>,
typename <a class="link" href="../DynamicBuffer_v1.html" title="Dynamic buffer requirements (version 1)">DynamicBuffer_v1</a>,
typename <a class="link" href="../ReadHandler.html" title="Read handler requirements">ReadHandler</a> = <a class="link" href="../asynchronous_operations.html#boost_asio.reference.asynchronous_operations.default_completion_tokens"><span class="emphasis"><em>DEFAULT</em></span></a>&gt;
<a class="link" href="../asynchronous_operations.html#boost_asio.reference.asynchronous_operations.automatic_deduction_of_initiating_function_return_type"><span class="emphasis"><em>DEDUCED</em></span></a> async_read_until(
AsyncReadStream &amp; s,
DynamicBuffer_v1 &amp;&amp; buffers,
char delim,
ReadHandler &amp;&amp; handler = <a class="link" href="../asynchronous_operations.html#boost_asio.reference.asynchronous_operations.default_completion_tokens"><span class="emphasis"><em>DEFAULT</em></span></a>,
typename constraint&lt; is_dynamic_buffer_v1&lt; typename decay&lt; DynamicBuffer_v1 &gt;::type &gt;::value &gt;::type = 0,
typename constraint&lt; !is_dynamic_buffer_v2&lt; typename decay&lt; DynamicBuffer_v1 &gt;::type &gt;::value &gt;::type = 0);
</pre>
<p>
This function is used to asynchronously read data into the specified dynamic
buffer sequence until the dynamic buffer sequence's get area contains the
specified delimiter. 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" style="list-style-type: disc; ">
<li class="listitem">
The get area of the dynamic buffer sequence contains the specified
delimiter.
</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="emphasis"><em>composed operation</em></span>.
If the dynamic buffer sequence's get area already contains the delimiter,
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>
<h6>
<a name="boost_asio.reference.async_read_until.overload1.h0"></a>
<span class="phrase"><a name="boost_asio.reference.async_read_until.overload1.parameters"></a></span><a class="link" href="overload1.html#boost_asio.reference.async_read_until.overload1.parameters">Parameters</a>
</h6>
<div class="variablelist">
<p class="title"><b></b></p>
<dl class="variablelist">
<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">buffers</span></dt>
<dd><p>
The dynamic buffer sequence into which the data will be read. Although
the buffers object may be copied as necessary, ownership of the underlying
memory blocks is retained by the caller, which must guarantee that
they remain valid until the handler is called.
</p></dd>
<dt><span class="term">delim</span></dt>
<dd><p>
The delimiter character.
</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">void handler(
// Result of operation.
const boost::system::error_code&amp; error,
// The number of bytes in the dynamic buffer sequence's
// get area up to and including the delimiter.
// 0 if an error occurred.
std::size_t bytes_transferred
);
</pre>
<p>
Regardless of whether the asynchronous operation completes immediately
or not, the handler will not be invoked from within this function.
On immediate completion, invocation of the handler will be performed
in a manner equivalent to using <a class="link" href="../post.html" title="post"><code class="computeroutput">post</code></a>.
</p>
</dd>
</dl>
</div>
<h6>
<a name="boost_asio.reference.async_read_until.overload1.h1"></a>
<span class="phrase"><a name="boost_asio.reference.async_read_until.overload1.remarks"></a></span><a class="link" href="overload1.html#boost_asio.reference.async_read_until.overload1.remarks">Remarks</a>
</h6>
<p>
After a successful async_read_until operation, the dynamic buffer sequence
may contain additional data beyond the delimiter. An application will typically
leave that data in the dynamic buffer sequence for a subsequent async_read_until
operation to examine.
</p>
<h6>
<a name="boost_asio.reference.async_read_until.overload1.h2"></a>
<span class="phrase"><a name="boost_asio.reference.async_read_until.overload1.example"></a></span><a class="link" href="overload1.html#boost_asio.reference.async_read_until.overload1.example">Example</a>
</h6>
<p>
To asynchronously read data into a <code class="computeroutput">std::string</code> until a newline
is encountered:
</p>
<pre class="programlisting">std::string data;
...
void handler(const boost::system::error_code&amp; e, std::size_t size)
{
if (!e)
{
std::string line = data.substr(0, n);
data.erase(0, n);
...
}
}
...
boost::asio::async_read_until(s, data, '\n', handler);
</pre>
<p>
After the <code class="computeroutput">async_read_until</code> operation completes successfully,
the buffer <code class="computeroutput">data</code> contains the delimiter:
</p>
<pre class="programlisting">{ 'a', 'b', ..., 'c', '\n', 'd', 'e', ... }
</pre>
<p>
The call to <code class="computeroutput">substr</code> then extracts the data up to and including
the delimiter, so that the string <code class="computeroutput">line</code> contains:
</p>
<pre class="programlisting">{ 'a', 'b', ..., 'c', '\n' }
</pre>
<p>
After the call to <code class="computeroutput">erase</code>, the remaining data is left in the
buffer <code class="computeroutput">data</code> as follows:
</p>
<pre class="programlisting">{ 'd', 'e', ... }
</pre>
<p>
This data may be the start of a new line, to be extracted by a subsequent
<code class="computeroutput">async_read_until</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 © 2003-2021 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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<div class="section">
<div class="titlepage"><div><div><h4 class="title">
<a name="boost_asio.reference.async_read_until.overload10"></a><a class="link" href="overload10.html" title="async_read_until (10 of 12 overloads)">async_read_until
(10 of 12 overloads)</a>
</h4></div></div></div>
<p>
Start an asynchronous operation to read data into a dynamic buffer sequence
until it contains a specified delimiter.
</p>
<pre class="programlisting">template&lt;
typename <a class="link" href="../AsyncReadStream.html" title="Buffer-oriented asynchronous read stream requirements">AsyncReadStream</a>,
typename <a class="link" href="../DynamicBuffer_v2.html" title="Dynamic buffer requirements (version 2)">DynamicBuffer_v2</a>,
typename <a class="link" href="../ReadHandler.html" title="Read handler requirements">ReadHandler</a> = <a class="link" href="../asynchronous_operations.html#boost_asio.reference.asynchronous_operations.default_completion_tokens"><span class="emphasis"><em>DEFAULT</em></span></a>&gt;
<a class="link" href="../asynchronous_operations.html#boost_asio.reference.asynchronous_operations.automatic_deduction_of_initiating_function_return_type"><span class="emphasis"><em>DEDUCED</em></span></a> async_read_until(
AsyncReadStream &amp; s,
DynamicBuffer_v2 buffers,
string_view delim,
ReadHandler &amp;&amp; handler = <a class="link" href="../asynchronous_operations.html#boost_asio.reference.asynchronous_operations.default_completion_tokens"><span class="emphasis"><em>DEFAULT</em></span></a>,
typename constraint&lt; is_dynamic_buffer_v2&lt; DynamicBuffer_v2 &gt;::value &gt;::type = 0);
</pre>
<p>
This function is used to asynchronously read data into the specified dynamic
buffer sequence until the dynamic buffer sequence's get area contains the
specified delimiter. 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" style="list-style-type: disc; ">
<li class="listitem">
The get area of the dynamic buffer sequence contains the specified
delimiter.
</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="emphasis"><em>composed operation</em></span>.
If the dynamic buffer sequence's get area already contains the delimiter,
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>
<h6>
<a name="boost_asio.reference.async_read_until.overload10.h0"></a>
<span class="phrase"><a name="boost_asio.reference.async_read_until.overload10.parameters"></a></span><a class="link" href="overload10.html#boost_asio.reference.async_read_until.overload10.parameters">Parameters</a>
</h6>
<div class="variablelist">
<p class="title"><b></b></p>
<dl class="variablelist">
<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">buffers</span></dt>
<dd><p>
The dynamic buffer sequence into which the data will be read. Although
the buffers object may be copied as necessary, ownership of the underlying
memory blocks is retained by the caller, which must guarantee that
they remain valid until the handler is called.
</p></dd>
<dt><span class="term">delim</span></dt>
<dd><p>
The delimiter string.
</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">void handler(
// Result of operation.
const boost::system::error_code&amp; error,
// The number of bytes in the dynamic buffer sequence's
// get area up to and including the delimiter.
// 0 if an error occurred.
std::size_t bytes_transferred
);
</pre>
<p>
Regardless of whether the asynchronous operation completes immediately
or not, the handler will not be invoked from within this function.
On immediate completion, invocation of the handler will be performed
in a manner equivalent to using <a class="link" href="../post.html" title="post"><code class="computeroutput">post</code></a>.
</p>
</dd>
</dl>
</div>
<h6>
<a name="boost_asio.reference.async_read_until.overload10.h1"></a>
<span class="phrase"><a name="boost_asio.reference.async_read_until.overload10.remarks"></a></span><a class="link" href="overload10.html#boost_asio.reference.async_read_until.overload10.remarks">Remarks</a>
</h6>
<p>
After a successful async_read_until operation, the dynamic buffer sequence
may contain additional data beyond the delimiter. An application will typically
leave that data in the dynamic buffer sequence for a subsequent async_read_until
operation to examine.
</p>
<h6>
<a name="boost_asio.reference.async_read_until.overload10.h2"></a>
<span class="phrase"><a name="boost_asio.reference.async_read_until.overload10.example"></a></span><a class="link" href="overload10.html#boost_asio.reference.async_read_until.overload10.example">Example</a>
</h6>
<p>
To asynchronously read data into a <code class="computeroutput">std::string</code> until a CR-LF
sequence is encountered:
</p>
<pre class="programlisting">std::string data;
...
void handler(const boost::system::error_code&amp; e, std::size_t size)
{
if (!e)
{
std::string line = data.substr(0, n);
data.erase(0, n);
...
}
}
...
boost::asio::async_read_until(s, data, "\r\n", handler);
</pre>
<p>
After the <code class="computeroutput">async_read_until</code> operation completes successfully,
the string <code class="computeroutput">data</code> contains the delimiter:
</p>
<pre class="programlisting">{ 'a', 'b', ..., 'c', '\r', '\n', 'd', 'e', ... }
</pre>
<p>
The call to <code class="computeroutput">substr</code> then extracts the data up to and including
the delimiter, so that the string <code class="computeroutput">line</code> contains:
</p>
<pre class="programlisting">{ 'a', 'b', ..., 'c', '\r', '\n' }
</pre>
<p>
After the call to <code class="computeroutput">erase</code>, the remaining data is left in the
string <code class="computeroutput">data</code> as follows:
</p>
<pre class="programlisting">{ 'd', 'e', ... }
</pre>
<p>
This data may be the start of a new line, to be extracted by a subsequent
<code class="computeroutput">async_read_until</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 © 2003-2021 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>
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<div class="section">
<div class="titlepage"><div><div><h4 class="title">
<a name="boost_asio.reference.async_read_until.overload11"></a><a class="link" href="overload11.html" title="async_read_until (11 of 12 overloads)">async_read_until
(11 of 12 overloads)</a>
</h4></div></div></div>
<p>
Start an asynchronous operation to read data into a dynamic buffer sequence
until some part of its data matches a regular expression.
</p>
<pre class="programlisting">template&lt;
typename <a class="link" href="../AsyncReadStream.html" title="Buffer-oriented asynchronous read stream requirements">AsyncReadStream</a>,
typename <a class="link" href="../DynamicBuffer_v2.html" title="Dynamic buffer requirements (version 2)">DynamicBuffer_v2</a>,
typename <a class="link" href="../ReadHandler.html" title="Read handler requirements">ReadHandler</a> = <a class="link" href="../asynchronous_operations.html#boost_asio.reference.asynchronous_operations.default_completion_tokens"><span class="emphasis"><em>DEFAULT</em></span></a>&gt;
<a class="link" href="../asynchronous_operations.html#boost_asio.reference.asynchronous_operations.automatic_deduction_of_initiating_function_return_type"><span class="emphasis"><em>DEDUCED</em></span></a> async_read_until(
AsyncReadStream &amp; s,
DynamicBuffer_v2 buffers,
const boost::regex &amp; expr,
ReadHandler &amp;&amp; handler = <a class="link" href="../asynchronous_operations.html#boost_asio.reference.asynchronous_operations.default_completion_tokens"><span class="emphasis"><em>DEFAULT</em></span></a>,
typename constraint&lt; is_dynamic_buffer_v2&lt; DynamicBuffer_v2 &gt;::value &gt;::type = 0);
</pre>
<p>
This function is used to asynchronously read data into the specified dynamic
buffer sequence until the dynamic buffer sequence'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" style="list-style-type: disc; ">
<li class="listitem">
A substring of the dynamic buffer sequence'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="emphasis"><em>composed operation</em></span>.
If the dynamic buffer sequence'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>
<h6>
<a name="boost_asio.reference.async_read_until.overload11.h0"></a>
<span class="phrase"><a name="boost_asio.reference.async_read_until.overload11.parameters"></a></span><a class="link" href="overload11.html#boost_asio.reference.async_read_until.overload11.parameters">Parameters</a>
</h6>
<div class="variablelist">
<p class="title"><b></b></p>
<dl class="variablelist">
<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">buffers</span></dt>
<dd><p>
The dynamic buffer sequence into which the data will be read. Although
the buffers object may be copied as necessary, ownership of the underlying
memory blocks is retained by the caller, which must guarantee that
they remain 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">void handler(
// Result of operation.
const boost::system::error_code&amp; error,
// The number of bytes in the dynamic buffer
// sequence's get area up to and including the
// substring that matches the regular expression.
// 0 if an error occurred.
std::size_t bytes_transferred
);
</pre>
<p>
Regardless of whether the asynchronous operation completes immediately
or not, the handler will not be invoked from within this function.
On immediate completion, invocation of the handler will be performed
in a manner equivalent to using <a class="link" href="../post.html" title="post"><code class="computeroutput">post</code></a>.
</p>
</dd>
</dl>
</div>
<h6>
<a name="boost_asio.reference.async_read_until.overload11.h1"></a>
<span class="phrase"><a name="boost_asio.reference.async_read_until.overload11.remarks"></a></span><a class="link" href="overload11.html#boost_asio.reference.async_read_until.overload11.remarks">Remarks</a>
</h6>
<p>
After a successful async_read_until operation, the dynamic buffer sequence
may contain additional data beyond that which matched the regular expression.
An application will typically leave that data in the dynamic buffer sequence
for a subsequent async_read_until operation to examine.
</p>
<h6>
<a name="boost_asio.reference.async_read_until.overload11.h2"></a>
<span class="phrase"><a name="boost_asio.reference.async_read_until.overload11.example"></a></span><a class="link" href="overload11.html#boost_asio.reference.async_read_until.overload11.example">Example</a>
</h6>
<p>
To asynchronously read data into a <code class="computeroutput">std::string</code> until a CR-LF
sequence is encountered:
</p>
<pre class="programlisting">std::string data;
...
void handler(const boost::system::error_code&amp; e, std::size_t size)
{
if (!e)
{
std::string line = data.substr(0, n);
data.erase(0, n);
...
}
}
...
boost::asio::async_read_until(s, data,
boost::regex("\r\n"), handler);
</pre>
<p>
After the <code class="computeroutput">async_read_until</code> operation completes successfully,
the string <code class="computeroutput">data</code> contains the data which matched the regular
expression:
</p>
<pre class="programlisting">{ 'a', 'b', ..., 'c', '\r', '\n', 'd', 'e', ... }
</pre>
<p>
The call to <code class="computeroutput">substr</code> then extracts the data up to and including
the match, so that the string <code class="computeroutput">line</code> contains:
</p>
<pre class="programlisting">{ 'a', 'b', ..., 'c', '\r', '\n' }
</pre>
<p>
After the call to <code class="computeroutput">erase</code>, the remaining data is left in the
string <code class="computeroutput">data</code> as follows:
</p>
<pre class="programlisting">{ 'd', 'e', ... }
</pre>
<p>
This data may be the start of a new line, to be extracted by a subsequent
<code class="computeroutput">async_read_until</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 © 2003-2021 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>
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<div class="section">
<div class="titlepage"><div><div><h4 class="title">
<a name="boost_asio.reference.async_read_until.overload12"></a><a class="link" href="overload12.html" title="async_read_until (12 of 12 overloads)">async_read_until
(12 of 12 overloads)</a>
</h4></div></div></div>
<p>
Start an asynchronous operation to read data into a dynamic buffer sequence
until a function object indicates a match.
</p>
<pre class="programlisting">template&lt;
typename <a class="link" href="../AsyncReadStream.html" title="Buffer-oriented asynchronous read stream requirements">AsyncReadStream</a>,
typename <a class="link" href="../DynamicBuffer_v2.html" title="Dynamic buffer requirements (version 2)">DynamicBuffer_v2</a>,
typename MatchCondition,
typename <a class="link" href="../ReadHandler.html" title="Read handler requirements">ReadHandler</a> = <a class="link" href="../asynchronous_operations.html#boost_asio.reference.asynchronous_operations.default_completion_tokens"><span class="emphasis"><em>DEFAULT</em></span></a>&gt;
<a class="link" href="../asynchronous_operations.html#boost_asio.reference.asynchronous_operations.automatic_deduction_of_initiating_function_return_type"><span class="emphasis"><em>DEDUCED</em></span></a> async_read_until(
AsyncReadStream &amp; s,
DynamicBuffer_v2 buffers,
MatchCondition match_condition,
ReadHandler &amp;&amp; handler = <a class="link" href="../asynchronous_operations.html#boost_asio.reference.asynchronous_operations.default_completion_tokens"><span class="emphasis"><em>DEFAULT</em></span></a>,
typename constraint&lt; is_match_condition&lt; MatchCondition &gt;::value &gt;::type = 0,
typename constraint&lt; is_dynamic_buffer_v2&lt; DynamicBuffer_v2 &gt;::value &gt;::type = 0);
</pre>
<p>
This function is used to asynchronously read data into the specified dynamic
buffer sequence until a user-defined match condition function object, when
applied to the data contained in the dynamic buffer sequence, indicates
a successful match. 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" style="list-style-type: disc; ">
<li class="listitem">
The match condition function object returns a std::pair where the second
element evaluates to true.
</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="emphasis"><em>composed operation</em></span>.
If the match condition function object already indicates a match, 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>
<h6>
<a name="boost_asio.reference.async_read_until.overload12.h0"></a>
<span class="phrase"><a name="boost_asio.reference.async_read_until.overload12.parameters"></a></span><a class="link" href="overload12.html#boost_asio.reference.async_read_until.overload12.parameters">Parameters</a>
</h6>
<div class="variablelist">
<p class="title"><b></b></p>
<dl class="variablelist">
<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">buffers</span></dt>
<dd><p>
The dynamic buffer sequence into which the data will be read. Although
the buffers object may be copied as necessary, ownership of the underlying
memory blocks is retained by the caller, which must guarantee that
they remain valid until the handler is called.
</p></dd>
<dt><span class="term">match_condition</span></dt>
<dd>
<p>
The function object to be called to determine whether a match exists.
The signature of the function object must be:
</p>
<pre class="programlisting">pair&lt;iterator, bool&gt; match_condition(iterator begin, iterator end);
</pre>
<p>
where <code class="computeroutput">iterator</code> represents the type:
</p>
<pre class="programlisting">buffers_iterator&lt;typename DynamicBuffer_v2::const_buffers_type&gt;
</pre>
<p>
The iterator parameters <code class="computeroutput">begin</code> and <code class="computeroutput">end</code> define
the range of bytes to be scanned to determine whether there is a
match. The <code class="computeroutput">first</code> member of the return value is an iterator
marking one-past-the-end of the bytes that have been consumed by
the match function. This iterator is used to calculate the <code class="computeroutput">begin</code>
parameter for any subsequent invocation of the match condition. The
<code class="computeroutput">second</code> member of the return value is true if a match
has been found, false otherwise.
</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">void handler(
// Result of operation.
const boost::system::error_code&amp; error,
// The number of bytes in the dynamic buffer sequence's
// get area that have been fully consumed by the match
// function. O if an error occurred.
std::size_t bytes_transferred
);
</pre>
<p>
Regardless of whether the asynchronous operation completes immediately
or not, the handler will not be invoked from within this function.
On immediate completion, invocation of the handler will be performed
in a manner equivalent to using <a class="link" href="../post.html" title="post"><code class="computeroutput">post</code></a>.
</p>
</dd>
</dl>
</div>
<h6>
<a name="boost_asio.reference.async_read_until.overload12.h1"></a>
<span class="phrase"><a name="boost_asio.reference.async_read_until.overload12.remarks"></a></span><a class="link" href="overload12.html#boost_asio.reference.async_read_until.overload12.remarks">Remarks</a>
</h6>
<p>
After a successful async_read_until operation, the dynamic buffer sequence
may contain additional data beyond that which matched the function object.
An application will typically leave that data in the dynamic buffer sequence
for a subsequent async_read_until operation to examine.
</p>
<p>
The default implementation of the <code class="computeroutput">is_match_condition</code> type
trait evaluates to true for function pointers and function objects with
a <code class="computeroutput">result_type</code> typedef. It must be specialised for other user-defined
function objects.
</p>
<h6>
<a name="boost_asio.reference.async_read_until.overload12.h2"></a>
<span class="phrase"><a name="boost_asio.reference.async_read_until.overload12.examples"></a></span><a class="link" href="overload12.html#boost_asio.reference.async_read_until.overload12.examples">Examples</a>
</h6>
<p>
To asynchronously read data into a <code class="computeroutput">std::string</code> until whitespace
is encountered:
</p>
<pre class="programlisting">typedef boost::asio::buffers_iterator&lt;
boost::asio::const_buffers_1&gt; iterator;
std::pair&lt;iterator, bool&gt;
match_whitespace(iterator begin, iterator end)
{
iterator i = begin;
while (i != end)
if (std::isspace(*i++))
return std::make_pair(i, true);
return std::make_pair(i, false);
}
...
void handler(const boost::system::error_code&amp; e, std::size_t size);
...
std::string data;
boost::asio::async_read_until(s, data, match_whitespace, handler);
</pre>
<p>
To asynchronously read data into a <code class="computeroutput">std::string</code> until a matching
character is found:
</p>
<pre class="programlisting">class match_char
{
public:
explicit match_char(char c) : c_(c) {}
template &lt;typename Iterator&gt;
std::pair&lt;Iterator, bool&gt; operator()(
Iterator begin, Iterator end) const
{
Iterator i = begin;
while (i != end)
if (c_ == *i++)
return std::make_pair(i, true);
return std::make_pair(i, false);
}
private:
char c_;
};
namespace asio {
template &lt;&gt; struct is_match_condition&lt;match_char&gt;
: public boost::true_type {};
} // namespace asio
...
void handler(const boost::system::error_code&amp; e, std::size_t size);
...
std::string data;
boost::asio::async_read_until(s, data, match_char('a'), handler);
</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 © 2003-2021 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>
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<div class="section">
<div class="titlepage"><div><div><h4 class="title">
<a name="boost_asio.reference.async_read_until.overload2"></a><a class="link" href="overload2.html" title="async_read_until (2 of 12 overloads)">async_read_until
(2 of 12 overloads)</a>
</h4></div></div></div>
<p>
Start an asynchronous operation to read data into a dynamic buffer sequence
until it contains a specified delimiter.
</p>
<pre class="programlisting">template&lt;
typename <a class="link" href="../AsyncReadStream.html" title="Buffer-oriented asynchronous read stream requirements">AsyncReadStream</a>,
typename <a class="link" href="../DynamicBuffer_v1.html" title="Dynamic buffer requirements (version 1)">DynamicBuffer_v1</a>,
typename <a class="link" href="../ReadHandler.html" title="Read handler requirements">ReadHandler</a> = <a class="link" href="../asynchronous_operations.html#boost_asio.reference.asynchronous_operations.default_completion_tokens"><span class="emphasis"><em>DEFAULT</em></span></a>&gt;
<a class="link" href="../asynchronous_operations.html#boost_asio.reference.asynchronous_operations.automatic_deduction_of_initiating_function_return_type"><span class="emphasis"><em>DEDUCED</em></span></a> async_read_until(
AsyncReadStream &amp; s,
DynamicBuffer_v1 &amp;&amp; buffers,
string_view delim,
ReadHandler &amp;&amp; handler = <a class="link" href="../asynchronous_operations.html#boost_asio.reference.asynchronous_operations.default_completion_tokens"><span class="emphasis"><em>DEFAULT</em></span></a>,
typename constraint&lt; is_dynamic_buffer_v1&lt; typename decay&lt; DynamicBuffer_v1 &gt;::type &gt;::value &gt;::type = 0,
typename constraint&lt; !is_dynamic_buffer_v2&lt; typename decay&lt; DynamicBuffer_v1 &gt;::type &gt;::value &gt;::type = 0);
</pre>
<p>
This function is used to asynchronously read data into the specified dynamic
buffer sequence until the dynamic buffer sequence's get area contains the
specified delimiter. 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" style="list-style-type: disc; ">
<li class="listitem">
The get area of the dynamic buffer sequence contains the specified
delimiter.
</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="emphasis"><em>composed operation</em></span>.
If the dynamic buffer sequence's get area already contains the delimiter,
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>
<h6>
<a name="boost_asio.reference.async_read_until.overload2.h0"></a>
<span class="phrase"><a name="boost_asio.reference.async_read_until.overload2.parameters"></a></span><a class="link" href="overload2.html#boost_asio.reference.async_read_until.overload2.parameters">Parameters</a>
</h6>
<div class="variablelist">
<p class="title"><b></b></p>
<dl class="variablelist">
<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">buffers</span></dt>
<dd><p>
The dynamic buffer sequence into which the data will be read. Although
the buffers object may be copied as necessary, ownership of the underlying
memory blocks is retained by the caller, which must guarantee that
they remain valid until the handler is called.
</p></dd>
<dt><span class="term">delim</span></dt>
<dd><p>
The delimiter string.
</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">void handler(
// Result of operation.
const boost::system::error_code&amp; error,
// The number of bytes in the dynamic buffer sequence's
// get area up to and including the delimiter.
// 0 if an error occurred.
std::size_t bytes_transferred
);
</pre>
<p>
Regardless of whether the asynchronous operation completes immediately
or not, the handler will not be invoked from within this function.
On immediate completion, invocation of the handler will be performed
in a manner equivalent to using <a class="link" href="../post.html" title="post"><code class="computeroutput">post</code></a>.
</p>
</dd>
</dl>
</div>
<h6>
<a name="boost_asio.reference.async_read_until.overload2.h1"></a>
<span class="phrase"><a name="boost_asio.reference.async_read_until.overload2.remarks"></a></span><a class="link" href="overload2.html#boost_asio.reference.async_read_until.overload2.remarks">Remarks</a>
</h6>
<p>
After a successful async_read_until operation, the dynamic buffer sequence
may contain additional data beyond the delimiter. An application will typically
leave that data in the dynamic buffer sequence for a subsequent async_read_until
operation to examine.
</p>
<h6>
<a name="boost_asio.reference.async_read_until.overload2.h2"></a>
<span class="phrase"><a name="boost_asio.reference.async_read_until.overload2.example"></a></span><a class="link" href="overload2.html#boost_asio.reference.async_read_until.overload2.example">Example</a>
</h6>
<p>
To asynchronously read data into a <code class="computeroutput">std::string</code> until a CR-LF
sequence is encountered:
</p>
<pre class="programlisting">std::string data;
...
void handler(const boost::system::error_code&amp; e, std::size_t size)
{
if (!e)
{
std::string line = data.substr(0, n);
data.erase(0, n);
...
}
}
...
boost::asio::async_read_until(s, data, "\r\n", handler);
</pre>
<p>
After the <code class="computeroutput">async_read_until</code> operation completes successfully,
the string <code class="computeroutput">data</code> contains the delimiter:
</p>
<pre class="programlisting">{ 'a', 'b', ..., 'c', '\r', '\n', 'd', 'e', ... }
</pre>
<p>
The call to <code class="computeroutput">substr</code> then extracts the data up to and including
the delimiter, so that the string <code class="computeroutput">line</code> contains:
</p>
<pre class="programlisting">{ 'a', 'b', ..., 'c', '\r', '\n' }
</pre>
<p>
After the call to <code class="computeroutput">erase</code>, the remaining data is left in the
string <code class="computeroutput">data</code> as follows:
</p>
<pre class="programlisting">{ 'd', 'e', ... }
</pre>
<p>
This data may be the start of a new line, to be extracted by a subsequent
<code class="computeroutput">async_read_until</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 © 2003-2021 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>
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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 12 overloads)">async_read_until
(3 of 12 overloads)</a>
</h4></div></div></div>
<p>
Start an asynchronous operation to read data into a dynamic buffer sequence
until some part of its data matches a regular expression.
</p>
<pre class="programlisting">template&lt;
typename <a class="link" href="../AsyncReadStream.html" title="Buffer-oriented asynchronous read stream requirements">AsyncReadStream</a>,
typename <a class="link" href="../DynamicBuffer_v1.html" title="Dynamic buffer requirements (version 1)">DynamicBuffer_v1</a>,
typename <a class="link" href="../ReadHandler.html" title="Read handler requirements">ReadHandler</a> = <a class="link" href="../asynchronous_operations.html#boost_asio.reference.asynchronous_operations.default_completion_tokens"><span class="emphasis"><em>DEFAULT</em></span></a>&gt;
<a class="link" href="../asynchronous_operations.html#boost_asio.reference.asynchronous_operations.automatic_deduction_of_initiating_function_return_type"><span class="emphasis"><em>DEDUCED</em></span></a> async_read_until(
AsyncReadStream &amp; s,
DynamicBuffer_v1 &amp;&amp; buffers,
const boost::regex &amp; expr,
ReadHandler &amp;&amp; handler = <a class="link" href="../asynchronous_operations.html#boost_asio.reference.asynchronous_operations.default_completion_tokens"><span class="emphasis"><em>DEFAULT</em></span></a>,
typename constraint&lt; is_dynamic_buffer_v1&lt; typename decay&lt; DynamicBuffer_v1 &gt;::type &gt;::value &gt;::type = 0,
typename constraint&lt; !is_dynamic_buffer_v2&lt; typename decay&lt; DynamicBuffer_v1 &gt;::type &gt;::value &gt;::type = 0);
</pre>
<p>
This function is used to asynchronously read data into the specified dynamic
buffer sequence until the dynamic buffer sequence'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" style="list-style-type: disc; ">
<li class="listitem">
A substring of the dynamic buffer sequence'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="emphasis"><em>composed operation</em></span>.
If the dynamic buffer sequence'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>
<h6>
<a name="boost_asio.reference.async_read_until.overload3.h0"></a>
<span class="phrase"><a name="boost_asio.reference.async_read_until.overload3.parameters"></a></span><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 class="variablelist">
<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">buffers</span></dt>
<dd><p>
The dynamic buffer sequence into which the data will be read. Although
the buffers object may be copied as necessary, ownership of the underlying
memory blocks is retained by the caller, which must guarantee that
they remain 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">void handler(
// Result of operation.
const boost::system::error_code&amp; error,
// The number of bytes in the dynamic buffer
// sequence's get area up to and including the
// substring that matches the regular expression.
// 0 if an error occurred.
std::size_t bytes_transferred
);
</pre>
<p>
Regardless of whether the asynchronous operation completes immediately
or not, the handler will not be invoked from within this function.
On immediate completion, invocation of the handler will be performed
in a manner equivalent to using <a class="link" href="../post.html" title="post"><code class="computeroutput">post</code></a>.
</p>
</dd>
</dl>
</div>
<h6>
<a name="boost_asio.reference.async_read_until.overload3.h1"></a>
<span class="phrase"><a name="boost_asio.reference.async_read_until.overload3.remarks"></a></span><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 dynamic buffer sequence
may contain additional data beyond that which matched the regular expression.
An application will typically leave that data in the dynamic buffer sequence
for a subsequent async_read_until operation to examine.
</p>
<h6>
<a name="boost_asio.reference.async_read_until.overload3.h2"></a>
<span class="phrase"><a name="boost_asio.reference.async_read_until.overload3.example"></a></span><a class="link" href="overload3.html#boost_asio.reference.async_read_until.overload3.example">Example</a>
</h6>
<p>
To asynchronously read data into a <code class="computeroutput">std::string</code> until a CR-LF
sequence is encountered:
</p>
<pre class="programlisting">std::string data;
...
void handler(const boost::system::error_code&amp; e, std::size_t size)
{
if (!e)
{
std::string line = data.substr(0, n);
data.erase(0, n);
...
}
}
...
boost::asio::async_read_until(s, data,
boost::regex("\r\n"), handler);
</pre>
<p>
After the <code class="computeroutput">async_read_until</code> operation completes successfully,
the string <code class="computeroutput">data</code> contains the data which matched the regular
expression:
</p>
<pre class="programlisting">{ 'a', 'b', ..., 'c', '\r', '\n', 'd', 'e', ... }
</pre>
<p>
The call to <code class="computeroutput">substr</code> then extracts the data up to and including
the match, so that the string <code class="computeroutput">line</code> contains:
</p>
<pre class="programlisting">{ 'a', 'b', ..., 'c', '\r', '\n' }
</pre>
<p>
After the call to <code class="computeroutput">erase</code>, the remaining data is left in the
string <code class="computeroutput">data</code> as follows:
</p>
<pre class="programlisting">{ 'd', 'e', ... }
</pre>
<p>
This data may be the start of a new line, to be extracted by a subsequent
<code class="computeroutput">async_read_until</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 © 2003-2021 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>
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<div class="section">
<div class="titlepage"><div><div><h4 class="title">
<a name="boost_asio.reference.async_read_until.overload4"></a><a class="link" href="overload4.html" title="async_read_until (4 of 12 overloads)">async_read_until
(4 of 12 overloads)</a>
</h4></div></div></div>
<p>
Start an asynchronous operation to read data into a dynamic buffer sequence
until a function object indicates a match.
</p>
<pre class="programlisting">template&lt;
typename <a class="link" href="../AsyncReadStream.html" title="Buffer-oriented asynchronous read stream requirements">AsyncReadStream</a>,
typename <a class="link" href="../DynamicBuffer_v1.html" title="Dynamic buffer requirements (version 1)">DynamicBuffer_v1</a>,
typename MatchCondition,
typename <a class="link" href="../ReadHandler.html" title="Read handler requirements">ReadHandler</a> = <a class="link" href="../asynchronous_operations.html#boost_asio.reference.asynchronous_operations.default_completion_tokens"><span class="emphasis"><em>DEFAULT</em></span></a>&gt;
<a class="link" href="../asynchronous_operations.html#boost_asio.reference.asynchronous_operations.automatic_deduction_of_initiating_function_return_type"><span class="emphasis"><em>DEDUCED</em></span></a> async_read_until(
AsyncReadStream &amp; s,
DynamicBuffer_v1 &amp;&amp; buffers,
MatchCondition match_condition,
ReadHandler &amp;&amp; handler = <a class="link" href="../asynchronous_operations.html#boost_asio.reference.asynchronous_operations.default_completion_tokens"><span class="emphasis"><em>DEFAULT</em></span></a>,
typename constraint&lt; is_match_condition&lt; MatchCondition &gt;::value &gt;::type = 0,
typename constraint&lt; is_dynamic_buffer_v1&lt; typename decay&lt; DynamicBuffer_v1 &gt;::type &gt;::value &gt;::type = 0,
typename constraint&lt; !is_dynamic_buffer_v2&lt; typename decay&lt; DynamicBuffer_v1 &gt;::type &gt;::value &gt;::type = 0);
</pre>
<p>
This function is used to asynchronously read data into the specified dynamic
buffer sequence until a user-defined match condition function object, when
applied to the data contained in the dynamic buffer sequence, indicates
a successful match. 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" style="list-style-type: disc; ">
<li class="listitem">
The match condition function object returns a std::pair where the second
element evaluates to true.
</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="emphasis"><em>composed operation</em></span>.
If the match condition function object already indicates a match, 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>
<h6>
<a name="boost_asio.reference.async_read_until.overload4.h0"></a>
<span class="phrase"><a name="boost_asio.reference.async_read_until.overload4.parameters"></a></span><a class="link" href="overload4.html#boost_asio.reference.async_read_until.overload4.parameters">Parameters</a>
</h6>
<div class="variablelist">
<p class="title"><b></b></p>
<dl class="variablelist">
<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">buffers</span></dt>
<dd><p>
The dynamic buffer sequence into which the data will be read. Although
the buffers object may be copied as necessary, ownership of the underlying
memory blocks is retained by the caller, which must guarantee that
they remain valid until the handler is called.
</p></dd>
<dt><span class="term">match_condition</span></dt>
<dd>
<p>
The function object to be called to determine whether a match exists.
The signature of the function object must be:
</p>
<pre class="programlisting">pair&lt;iterator, bool&gt; match_condition(iterator begin, iterator end);
</pre>
<p>
where <code class="computeroutput">iterator</code> represents the type:
</p>
<pre class="programlisting">buffers_iterator&lt;typename DynamicBuffer_v1::const_buffers_type&gt;
</pre>
<p>
The iterator parameters <code class="computeroutput">begin</code> and <code class="computeroutput">end</code> define
the range of bytes to be scanned to determine whether there is a
match. The <code class="computeroutput">first</code> member of the return value is an iterator
marking one-past-the-end of the bytes that have been consumed by
the match function. This iterator is used to calculate the <code class="computeroutput">begin</code>
parameter for any subsequent invocation of the match condition. The
<code class="computeroutput">second</code> member of the return value is true if a match
has been found, false otherwise.
</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">void handler(
// Result of operation.
const boost::system::error_code&amp; error,
// The number of bytes in the dynamic buffer sequence's
// get area that have been fully consumed by the match
// function. O if an error occurred.
std::size_t bytes_transferred
);
</pre>
<p>
Regardless of whether the asynchronous operation completes immediately
or not, the handler will not be invoked from within this function.
On immediate completion, invocation of the handler will be performed
in a manner equivalent to using <a class="link" href="../post.html" title="post"><code class="computeroutput">post</code></a>.
</p>
</dd>
</dl>
</div>
<h6>
<a name="boost_asio.reference.async_read_until.overload4.h1"></a>
<span class="phrase"><a name="boost_asio.reference.async_read_until.overload4.remarks"></a></span><a class="link" href="overload4.html#boost_asio.reference.async_read_until.overload4.remarks">Remarks</a>
</h6>
<p>
After a successful async_read_until operation, the dynamic buffer sequence
may contain additional data beyond that which matched the function object.
An application will typically leave that data in the dynamic buffer sequence
for a subsequent async_read_until operation to examine.
</p>
<p>
The default implementation of the <code class="computeroutput">is_match_condition</code> type
trait evaluates to true for function pointers and function objects with
a <code class="computeroutput">result_type</code> typedef. It must be specialised for other user-defined
function objects.
</p>
<h6>
<a name="boost_asio.reference.async_read_until.overload4.h2"></a>
<span class="phrase"><a name="boost_asio.reference.async_read_until.overload4.examples"></a></span><a class="link" href="overload4.html#boost_asio.reference.async_read_until.overload4.examples">Examples</a>
</h6>
<p>
To asynchronously read data into a <code class="computeroutput">std::string</code> until whitespace
is encountered:
</p>
<pre class="programlisting">typedef boost::asio::buffers_iterator&lt;
boost::asio::const_buffers_1&gt; iterator;
std::pair&lt;iterator, bool&gt;
match_whitespace(iterator begin, iterator end)
{
iterator i = begin;
while (i != end)
if (std::isspace(*i++))
return std::make_pair(i, true);
return std::make_pair(i, false);
}
...
void handler(const boost::system::error_code&amp; e, std::size_t size);
...
std::string data;
boost::asio::async_read_until(s, data, match_whitespace, handler);
</pre>
<p>
To asynchronously read data into a <code class="computeroutput">std::string</code> until a matching
character is found:
</p>
<pre class="programlisting">class match_char
{
public:
explicit match_char(char c) : c_(c) {}
template &lt;typename Iterator&gt;
std::pair&lt;Iterator, bool&gt; operator()(
Iterator begin, Iterator end) const
{
Iterator i = begin;
while (i != end)
if (c_ == *i++)
return std::make_pair(i, true);
return std::make_pair(i, false);
}
private:
char c_;
};
namespace asio {
template &lt;&gt; struct is_match_condition&lt;match_char&gt;
: public boost::true_type {};
} // namespace asio
...
void handler(const boost::system::error_code&amp; e, std::size_t size);
...
std::string data;
boost::asio::async_read_until(s, data, match_char('a'), handler);
</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 © 2003-2021 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>
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<a name="boost_asio.reference.async_read_until.overload5"></a><a class="link" href="overload5.html" title="async_read_until (5 of 12 overloads)">async_read_until
(5 of 12 overloads)</a>
</h4></div></div></div>
<p>
Start an asynchronous operation to read data into a streambuf until it
contains a specified delimiter.
</p>
<pre class="programlisting">template&lt;
typename <a class="link" href="../AsyncReadStream.html" title="Buffer-oriented asynchronous read stream requirements">AsyncReadStream</a>,
typename Allocator,
typename <a class="link" href="../ReadHandler.html" title="Read handler requirements">ReadHandler</a> = <a class="link" href="../asynchronous_operations.html#boost_asio.reference.asynchronous_operations.default_completion_tokens"><span class="emphasis"><em>DEFAULT</em></span></a>&gt;
<a class="link" href="../asynchronous_operations.html#boost_asio.reference.asynchronous_operations.automatic_deduction_of_initiating_function_return_type"><span class="emphasis"><em>DEDUCED</em></span></a> async_read_until(
AsyncReadStream &amp; s,
boost::asio::basic_streambuf&lt; Allocator &gt; &amp; b,
char delim,
ReadHandler &amp;&amp; handler = <a class="link" href="../asynchronous_operations.html#boost_asio.reference.asynchronous_operations.default_completion_tokens"><span class="emphasis"><em>DEFAULT</em></span></a>);
</pre>
<p>
This function is used to asynchronously read data into the specified streambuf
until the streambuf's get area contains the specified delimiter. 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" style="list-style-type: disc; ">
<li class="listitem">
The get area of the streambuf contains the specified delimiter.
</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="emphasis"><em>composed operation</em></span>.
If the streambuf's get area already contains the delimiter, 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>
<h6>
<a name="boost_asio.reference.async_read_until.overload5.h0"></a>
<span class="phrase"><a name="boost_asio.reference.async_read_until.overload5.parameters"></a></span><a class="link" href="overload5.html#boost_asio.reference.async_read_until.overload5.parameters">Parameters</a>
</h6>
<div class="variablelist">
<p class="title"><b></b></p>
<dl class="variablelist">
<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">delim</span></dt>
<dd><p>
The delimiter character.
</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">void handler(
// Result of operation.
const boost::system::error_code&amp; error,
// The number of bytes in the streambuf's get
// area up to and including the delimiter.
// 0 if an error occurred.
std::size_t bytes_transferred
);
</pre>
<p>
Regardless of whether the asynchronous operation completes immediately
or not, the handler will not be invoked from within this function.
On immediate completion, invocation of the handler will be performed
in a manner equivalent to using <a class="link" href="../post.html" title="post"><code class="computeroutput">post</code></a>.
</p>
</dd>
</dl>
</div>
<h6>
<a name="boost_asio.reference.async_read_until.overload5.h1"></a>
<span class="phrase"><a name="boost_asio.reference.async_read_until.overload5.remarks"></a></span><a class="link" href="overload5.html#boost_asio.reference.async_read_until.overload5.remarks">Remarks</a>
</h6>
<p>
After a successful async_read_until operation, the streambuf may contain
additional data beyond the delimiter. An application will typically leave
that data in the streambuf for a subsequent async_read_until operation
to examine.
</p>
<h6>
<a name="boost_asio.reference.async_read_until.overload5.h2"></a>
<span class="phrase"><a name="boost_asio.reference.async_read_until.overload5.example"></a></span><a class="link" href="overload5.html#boost_asio.reference.async_read_until.overload5.example">Example</a>
</h6>
<p>
To asynchronously read data into a streambuf until a newline is encountered:
</p>
<pre class="programlisting">boost::asio::streambuf b;
...
void handler(const boost::system::error_code&amp; e, std::size_t size)
{
if (!e)
{
std::istream is(&amp;b);
std::string line;
std::getline(is, line);
...
}
}
...
boost::asio::async_read_until(s, b, '\n', handler);
</pre>
<p>
After the <code class="computeroutput">async_read_until</code> operation completes successfully,
the buffer <code class="computeroutput">b</code> contains the delimiter:
</p>
<pre class="programlisting">{ 'a', 'b', ..., 'c', '\n', 'd', 'e', ... }
</pre>
<p>
The call to <code class="computeroutput">std::getline</code> then extracts the data up to and
including the newline (which is discarded), so that the string <code class="computeroutput">line</code>
contains:
</p>
<pre class="programlisting">{ 'a', 'b', ..., 'c' }
</pre>
<p>
The remaining data is left in the buffer <code class="computeroutput">b</code> as follows:
</p>
<pre class="programlisting">{ 'd', 'e', ... }
</pre>
<p>
This data may be the start of a new line, to be extracted by a subsequent
<code class="computeroutput">async_read_until</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 © 2003-2021 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>
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<div class="section">
<div class="titlepage"><div><div><h4 class="title">
<a name="boost_asio.reference.async_read_until.overload6"></a><a class="link" href="overload6.html" title="async_read_until (6 of 12 overloads)">async_read_until
(6 of 12 overloads)</a>
</h4></div></div></div>
<p>
Start an asynchronous operation to read data into a streambuf until it
contains a specified delimiter.
</p>
<pre class="programlisting">template&lt;
typename <a class="link" href="../AsyncReadStream.html" title="Buffer-oriented asynchronous read stream requirements">AsyncReadStream</a>,
typename Allocator,
typename <a class="link" href="../ReadHandler.html" title="Read handler requirements">ReadHandler</a> = <a class="link" href="../asynchronous_operations.html#boost_asio.reference.asynchronous_operations.default_completion_tokens"><span class="emphasis"><em>DEFAULT</em></span></a>&gt;
<a class="link" href="../asynchronous_operations.html#boost_asio.reference.asynchronous_operations.automatic_deduction_of_initiating_function_return_type"><span class="emphasis"><em>DEDUCED</em></span></a> async_read_until(
AsyncReadStream &amp; s,
boost::asio::basic_streambuf&lt; Allocator &gt; &amp; b,
string_view delim,
ReadHandler &amp;&amp; handler = <a class="link" href="../asynchronous_operations.html#boost_asio.reference.asynchronous_operations.default_completion_tokens"><span class="emphasis"><em>DEFAULT</em></span></a>);
</pre>
<p>
This function is used to asynchronously read data into the specified streambuf
until the streambuf's get area contains the specified delimiter. 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" style="list-style-type: disc; ">
<li class="listitem">
The get area of the streambuf contains the specified delimiter.
</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="emphasis"><em>composed operation</em></span>.
If the streambuf's get area already contains the delimiter, 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>
<h6>
<a name="boost_asio.reference.async_read_until.overload6.h0"></a>
<span class="phrase"><a name="boost_asio.reference.async_read_until.overload6.parameters"></a></span><a class="link" href="overload6.html#boost_asio.reference.async_read_until.overload6.parameters">Parameters</a>
</h6>
<div class="variablelist">
<p class="title"><b></b></p>
<dl class="variablelist">
<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">delim</span></dt>
<dd><p>
The delimiter string.
</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">void handler(
// Result of operation.
const boost::system::error_code&amp; error,
// The number of bytes in the streambuf's get
// area up to and including the delimiter.
// 0 if an error occurred.
std::size_t bytes_transferred
);
</pre>
<p>
Regardless of whether the asynchronous operation completes immediately
or not, the handler will not be invoked from within this function.
On immediate completion, invocation of the handler will be performed
in a manner equivalent to using <a class="link" href="../post.html" title="post"><code class="computeroutput">post</code></a>.
</p>
</dd>
</dl>
</div>
<h6>
<a name="boost_asio.reference.async_read_until.overload6.h1"></a>
<span class="phrase"><a name="boost_asio.reference.async_read_until.overload6.remarks"></a></span><a class="link" href="overload6.html#boost_asio.reference.async_read_until.overload6.remarks">Remarks</a>
</h6>
<p>
After a successful async_read_until operation, the streambuf may contain
additional data beyond the delimiter. An application will typically leave
that data in the streambuf for a subsequent async_read_until operation
to examine.
</p>
<h6>
<a name="boost_asio.reference.async_read_until.overload6.h2"></a>
<span class="phrase"><a name="boost_asio.reference.async_read_until.overload6.example"></a></span><a class="link" href="overload6.html#boost_asio.reference.async_read_until.overload6.example">Example</a>
</h6>
<p>
To asynchronously read data into a streambuf until a newline is encountered:
</p>
<pre class="programlisting">boost::asio::streambuf b;
...
void handler(const boost::system::error_code&amp; e, std::size_t size)
{
if (!e)
{
std::istream is(&amp;b);
std::string line;
std::getline(is, line);
...
}
}
...
boost::asio::async_read_until(s, b, "\r\n", handler);
</pre>
<p>
After the <code class="computeroutput">async_read_until</code> operation completes successfully,
the buffer <code class="computeroutput">b</code> contains the delimiter:
</p>
<pre class="programlisting">{ 'a', 'b', ..., 'c', '\r', '\n', 'd', 'e', ... }
</pre>
<p>
The call to <code class="computeroutput">std::getline</code> then extracts the data up to and
including the newline (which is discarded), so that the string <code class="computeroutput">line</code>
contains:
</p>
<pre class="programlisting">{ 'a', 'b', ..., 'c', '\r' }
</pre>
<p>
The remaining data is left in the buffer <code class="computeroutput">b</code> as follows:
</p>
<pre class="programlisting">{ 'd', 'e', ... }
</pre>
<p>
This data may be the start of a new line, to be extracted by a subsequent
<code class="computeroutput">async_read_until</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 © 2003-2021 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>
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<div class="section">
<div class="titlepage"><div><div><h4 class="title">
<a name="boost_asio.reference.async_read_until.overload7"></a><a class="link" href="overload7.html" title="async_read_until (7 of 12 overloads)">async_read_until
(7 of 12 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">template&lt;
typename <a class="link" href="../AsyncReadStream.html" title="Buffer-oriented asynchronous read stream requirements">AsyncReadStream</a>,
typename Allocator,
typename <a class="link" href="../ReadHandler.html" title="Read handler requirements">ReadHandler</a> = <a class="link" href="../asynchronous_operations.html#boost_asio.reference.asynchronous_operations.default_completion_tokens"><span class="emphasis"><em>DEFAULT</em></span></a>&gt;
<a class="link" href="../asynchronous_operations.html#boost_asio.reference.asynchronous_operations.automatic_deduction_of_initiating_function_return_type"><span class="emphasis"><em>DEDUCED</em></span></a> async_read_until(
AsyncReadStream &amp; s,
boost::asio::basic_streambuf&lt; Allocator &gt; &amp; b,
const boost::regex &amp; expr,
ReadHandler &amp;&amp; handler = <a class="link" href="../asynchronous_operations.html#boost_asio.reference.asynchronous_operations.default_completion_tokens"><span class="emphasis"><em>DEFAULT</em></span></a>);
</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" style="list-style-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="emphasis"><em>composed operation</em></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>
<h6>
<a name="boost_asio.reference.async_read_until.overload7.h0"></a>
<span class="phrase"><a name="boost_asio.reference.async_read_until.overload7.parameters"></a></span><a class="link" href="overload7.html#boost_asio.reference.async_read_until.overload7.parameters">Parameters</a>
</h6>
<div class="variablelist">
<p class="title"><b></b></p>
<dl class="variablelist">
<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">void handler(
// Result of operation.
const boost::system::error_code&amp; error,
// The number of bytes in the streambuf's get
// area up to and including the substring
// that matches the regular. expression.
// 0 if an error occurred.
std::size_t bytes_transferred
);
</pre>
<p>
Regardless of whether the asynchronous operation completes immediately
or not, the handler will not be invoked from within this function.
On immediate completion, invocation of the handler will be performed
in a manner equivalent to using <a class="link" href="../post.html" title="post"><code class="computeroutput">post</code></a>.
</p>
</dd>
</dl>
</div>
<h6>
<a name="boost_asio.reference.async_read_until.overload7.h1"></a>
<span class="phrase"><a name="boost_asio.reference.async_read_until.overload7.remarks"></a></span><a class="link" href="overload7.html#boost_asio.reference.async_read_until.overload7.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>
<h6>
<a name="boost_asio.reference.async_read_until.overload7.h2"></a>
<span class="phrase"><a name="boost_asio.reference.async_read_until.overload7.example"></a></span><a class="link" href="overload7.html#boost_asio.reference.async_read_until.overload7.example">Example</a>
</h6>
<p>
To asynchronously read data into a streambuf until a CR-LF sequence is
encountered:
</p>
<pre class="programlisting">boost::asio::streambuf b;
...
void handler(const boost::system::error_code&amp; e, std::size_t size)
{
if (!e)
{
std::istream is(&amp;b);
std::string line;
std::getline(is, line);
...
}
}
...
boost::asio::async_read_until(s, b, boost::regex("\r\n"), handler);
</pre>
<p>
After the <code class="computeroutput">async_read_until</code> operation completes successfully,
the buffer <code class="computeroutput">b</code> contains the data which matched the regular expression:
</p>
<pre class="programlisting">{ 'a', 'b', ..., 'c', '\r', '\n', 'd', 'e', ... }
</pre>
<p>
The call to <code class="computeroutput">std::getline</code> then extracts the data up to and
including the newline (which is discarded), so that the string <code class="computeroutput">line</code>
contains:
</p>
<pre class="programlisting">{ 'a', 'b', ..., 'c', '\r' }
</pre>
<p>
The remaining data is left in the buffer <code class="computeroutput">b</code> as follows:
</p>
<pre class="programlisting">{ 'd', 'e', ... }
</pre>
<p>
This data may be the start of a new line, to be extracted by a subsequent
<code class="computeroutput">async_read_until</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 © 2003-2021 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>
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<div class="section">
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<a name="boost_asio.reference.async_read_until.overload8"></a><a class="link" href="overload8.html" title="async_read_until (8 of 12 overloads)">async_read_until
(8 of 12 overloads)</a>
</h4></div></div></div>
<p>
Start an asynchronous operation to read data into a streambuf until a function
object indicates a match.
</p>
<pre class="programlisting">template&lt;
typename <a class="link" href="../AsyncReadStream.html" title="Buffer-oriented asynchronous read stream requirements">AsyncReadStream</a>,
typename Allocator,
typename MatchCondition,
typename <a class="link" href="../ReadHandler.html" title="Read handler requirements">ReadHandler</a> = <a class="link" href="../asynchronous_operations.html#boost_asio.reference.asynchronous_operations.default_completion_tokens"><span class="emphasis"><em>DEFAULT</em></span></a>&gt;
<a class="link" href="../asynchronous_operations.html#boost_asio.reference.asynchronous_operations.automatic_deduction_of_initiating_function_return_type"><span class="emphasis"><em>DEDUCED</em></span></a> async_read_until(
AsyncReadStream &amp; s,
boost::asio::basic_streambuf&lt; Allocator &gt; &amp; b,
MatchCondition match_condition,
ReadHandler &amp;&amp; handler = <a class="link" href="../asynchronous_operations.html#boost_asio.reference.asynchronous_operations.default_completion_tokens"><span class="emphasis"><em>DEFAULT</em></span></a>,
typename constraint&lt; is_match_condition&lt; MatchCondition &gt;::value &gt;::type = 0);
</pre>
<p>
This function is used to asynchronously read data into the specified streambuf
until a user-defined match condition function object, when applied to the
data contained in the streambuf, indicates a successful match. 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" style="list-style-type: disc; ">
<li class="listitem">
The match condition function object returns a std::pair where the second
element evaluates to true.
</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="emphasis"><em>composed operation</em></span>.
If the match condition function object already indicates a match, 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>
<h6>
<a name="boost_asio.reference.async_read_until.overload8.h0"></a>
<span class="phrase"><a name="boost_asio.reference.async_read_until.overload8.parameters"></a></span><a class="link" href="overload8.html#boost_asio.reference.async_read_until.overload8.parameters">Parameters</a>
</h6>
<div class="variablelist">
<p class="title"><b></b></p>
<dl class="variablelist">
<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.
</p></dd>
<dt><span class="term">match_condition</span></dt>
<dd>
<p>
The function object to be called to determine whether a match exists.
The signature of the function object must be:
</p>
<pre class="programlisting">pair&lt;iterator, bool&gt; match_condition(iterator begin, iterator end);
</pre>
<p>
where <code class="computeroutput">iterator</code> represents the type:
</p>
<pre class="programlisting">buffers_iterator&lt;basic_streambuf&lt;Allocator&gt;::const_buffers_type&gt;
</pre>
<p>
The iterator parameters <code class="computeroutput">begin</code> and <code class="computeroutput">end</code> define
the range of bytes to be scanned to determine whether there is a
match. The <code class="computeroutput">first</code> member of the return value is an iterator
marking one-past-the-end of the bytes that have been consumed by
the match function. This iterator is used to calculate the <code class="computeroutput">begin</code>
parameter for any subsequent invocation of the match condition. The
<code class="computeroutput">second</code> member of the return value is true if a match
has been found, false otherwise.
</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">void handler(
// Result of operation.
const boost::system::error_code&amp; error,
// The number of bytes in the streambuf's get
// area that have been fully consumed by the
// match function. O if an error occurred.
std::size_t bytes_transferred
);
</pre>
<p>
Regardless of whether the asynchronous operation completes immediately
or not, the handler will not be invoked from within this function.
On immediate completion, invocation of the handler will be performed
in a manner equivalent to using <a class="link" href="../post.html" title="post"><code class="computeroutput">post</code></a>.
</p>
</dd>
</dl>
</div>
<h6>
<a name="boost_asio.reference.async_read_until.overload8.h1"></a>
<span class="phrase"><a name="boost_asio.reference.async_read_until.overload8.remarks"></a></span><a class="link" href="overload8.html#boost_asio.reference.async_read_until.overload8.remarks">Remarks</a>
</h6>
<p>
After a successful async_read_until operation, the streambuf may contain
additional data beyond that which matched the function object. An application
will typically leave that data in the streambuf for a subsequent async_read_until
operation to examine.
</p>
<p>
The default implementation of the <code class="computeroutput">is_match_condition</code> type
trait evaluates to true for function pointers and function objects with
a <code class="computeroutput">result_type</code> typedef. It must be specialised for other user-defined
function objects.
</p>
<h6>
<a name="boost_asio.reference.async_read_until.overload8.h2"></a>
<span class="phrase"><a name="boost_asio.reference.async_read_until.overload8.examples"></a></span><a class="link" href="overload8.html#boost_asio.reference.async_read_until.overload8.examples">Examples</a>
</h6>
<p>
To asynchronously read data into a streambuf until whitespace is encountered:
</p>
<pre class="programlisting">typedef boost::asio::buffers_iterator&lt;
boost::asio::streambuf::const_buffers_type&gt; iterator;
std::pair&lt;iterator, bool&gt;
match_whitespace(iterator begin, iterator end)
{
iterator i = begin;
while (i != end)
if (std::isspace(*i++))
return std::make_pair(i, true);
return std::make_pair(i, false);
}
...
void handler(const boost::system::error_code&amp; e, std::size_t size);
...
boost::asio::streambuf b;
boost::asio::async_read_until(s, b, match_whitespace, handler);
</pre>
<p>
To asynchronously read data into a streambuf until a matching character
is found:
</p>
<pre class="programlisting">class match_char
{
public:
explicit match_char(char c) : c_(c) {}
template &lt;typename Iterator&gt;
std::pair&lt;Iterator, bool&gt; operator()(
Iterator begin, Iterator end) const
{
Iterator i = begin;
while (i != end)
if (c_ == *i++)
return std::make_pair(i, true);
return std::make_pair(i, false);
}
private:
char c_;
};
namespace asio {
template &lt;&gt; struct is_match_condition&lt;match_char&gt;
: public boost::true_type {};
} // namespace asio
...
void handler(const boost::system::error_code&amp; e, std::size_t size);
...
boost::asio::streambuf b;
boost::asio::async_read_until(s, b, match_char('a'), handler);
</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 © 2003-2021 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>
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<div class="section">
<div class="titlepage"><div><div><h4 class="title">
<a name="boost_asio.reference.async_read_until.overload9"></a><a class="link" href="overload9.html" title="async_read_until (9 of 12 overloads)">async_read_until
(9 of 12 overloads)</a>
</h4></div></div></div>
<p>
Start an asynchronous operation to read data into a dynamic buffer sequence
until it contains a specified delimiter.
</p>
<pre class="programlisting">template&lt;
typename <a class="link" href="../AsyncReadStream.html" title="Buffer-oriented asynchronous read stream requirements">AsyncReadStream</a>,
typename <a class="link" href="../DynamicBuffer_v2.html" title="Dynamic buffer requirements (version 2)">DynamicBuffer_v2</a>,
typename <a class="link" href="../ReadHandler.html" title="Read handler requirements">ReadHandler</a> = <a class="link" href="../asynchronous_operations.html#boost_asio.reference.asynchronous_operations.default_completion_tokens"><span class="emphasis"><em>DEFAULT</em></span></a>&gt;
<a class="link" href="../asynchronous_operations.html#boost_asio.reference.asynchronous_operations.automatic_deduction_of_initiating_function_return_type"><span class="emphasis"><em>DEDUCED</em></span></a> async_read_until(
AsyncReadStream &amp; s,
DynamicBuffer_v2 buffers,
char delim,
ReadHandler &amp;&amp; handler = <a class="link" href="../asynchronous_operations.html#boost_asio.reference.asynchronous_operations.default_completion_tokens"><span class="emphasis"><em>DEFAULT</em></span></a>,
typename constraint&lt; is_dynamic_buffer_v2&lt; DynamicBuffer_v2 &gt;::value &gt;::type = 0);
</pre>
<p>
This function is used to asynchronously read data into the specified dynamic
buffer sequence until the dynamic buffer sequence's get area contains the
specified delimiter. 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" style="list-style-type: disc; ">
<li class="listitem">
The get area of the dynamic buffer sequence contains the specified
delimiter.
</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="emphasis"><em>composed operation</em></span>.
If the dynamic buffer sequence's get area already contains the delimiter,
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>
<h6>
<a name="boost_asio.reference.async_read_until.overload9.h0"></a>
<span class="phrase"><a name="boost_asio.reference.async_read_until.overload9.parameters"></a></span><a class="link" href="overload9.html#boost_asio.reference.async_read_until.overload9.parameters">Parameters</a>
</h6>
<div class="variablelist">
<p class="title"><b></b></p>
<dl class="variablelist">
<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">buffers</span></dt>
<dd><p>
The dynamic buffer sequence into which the data will be read. Although
the buffers object may be copied as necessary, ownership of the underlying
memory blocks is retained by the caller, which must guarantee that
they remain valid until the handler is called.
</p></dd>
<dt><span class="term">delim</span></dt>
<dd><p>
The delimiter character.
</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">void handler(
// Result of operation.
const boost::system::error_code&amp; error,
// The number of bytes in the dynamic buffer sequence's
// get area up to and including the delimiter.
// 0 if an error occurred.
std::size_t bytes_transferred
);
</pre>
<p>
Regardless of whether the asynchronous operation completes immediately
or not, the handler will not be invoked from within this function.
On immediate completion, invocation of the handler will be performed
in a manner equivalent to using <a class="link" href="../post.html" title="post"><code class="computeroutput">post</code></a>.
</p>
</dd>
</dl>
</div>
<h6>
<a name="boost_asio.reference.async_read_until.overload9.h1"></a>
<span class="phrase"><a name="boost_asio.reference.async_read_until.overload9.remarks"></a></span><a class="link" href="overload9.html#boost_asio.reference.async_read_until.overload9.remarks">Remarks</a>
</h6>
<p>
After a successful async_read_until operation, the dynamic buffer sequence
may contain additional data beyond the delimiter. An application will typically
leave that data in the dynamic buffer sequence for a subsequent async_read_until
operation to examine.
</p>
<h6>
<a name="boost_asio.reference.async_read_until.overload9.h2"></a>
<span class="phrase"><a name="boost_asio.reference.async_read_until.overload9.example"></a></span><a class="link" href="overload9.html#boost_asio.reference.async_read_until.overload9.example">Example</a>
</h6>
<p>
To asynchronously read data into a <code class="computeroutput">std::string</code> until a newline
is encountered:
</p>
<pre class="programlisting">std::string data;
...
void handler(const boost::system::error_code&amp; e, std::size_t size)
{
if (!e)
{
std::string line = data.substr(0, n);
data.erase(0, n);
...
}
}
...
boost::asio::async_read_until(s, data, '\n', handler);
</pre>
<p>
After the <code class="computeroutput">async_read_until</code> operation completes successfully,
the buffer <code class="computeroutput">data</code> contains the delimiter:
</p>
<pre class="programlisting">{ 'a', 'b', ..., 'c', '\n', 'd', 'e', ... }
</pre>
<p>
The call to <code class="computeroutput">substr</code> then extracts the data up to and including
the delimiter, so that the string <code class="computeroutput">line</code> contains:
</p>
<pre class="programlisting">{ 'a', 'b', ..., 'c', '\n' }
</pre>
<p>
After the call to <code class="computeroutput">erase</code>, the remaining data is left in the
buffer <code class="computeroutput">data</code> as follows:
</p>
<pre class="programlisting">{ 'd', 'e', ... }
</pre>
<p>
This data may be the start of a new line, to be extracted by a subsequent
<code class="computeroutput">async_read_until</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 © 2003-2021 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>
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