overload11.html
9.36 KB
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>async_read_until (11 of 12 overloads)</title>
<link rel="stylesheet" href="../../../boostbook.css" type="text/css">
<meta name="generator" content="DocBook XSL Stylesheets V1.75.2">
<link rel="home" href="../../../index.html" title="Asio">
<link rel="up" href="../async_read_until.html" title="async_read_until">
<link rel="prev" href="overload10.html" title="async_read_until (10 of 12 overloads)">
<link rel="next" href="overload12.html" title="async_read_until (12 of 12 overloads)">
</head>
<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
<table cellpadding="2" width="100%"><tr><td valign="top"><img alt="asio C++ library" width="250" height="60" src="../../../asio.png"></td></tr></table>
<hr>
<div class="spirit-nav">
<a accesskey="p" href="overload10.html"><img src="../../../prev.png" alt="Prev"></a><a accesskey="u" href="../async_read_until.html"><img src="../../../up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../home.png" alt="Home"></a><a accesskey="n" href="overload12.html"><img src="../../../next.png" alt="Next"></a>
</div>
<div class="section">
<div class="titlepage"><div><div><h4 class="title">
<a name="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<
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#asio.reference.asynchronous_operations.default_completion_tokens"><span class="emphasis"><em>DEFAULT</em></span></a>>
<a class="link" href="../asynchronous_operations.html#asio.reference.asynchronous_operations.automatic_deduction_of_initiating_function_return_type"><span class="emphasis"><em>DEDUCED</em></span></a> async_read_until(
AsyncReadStream & s,
DynamicBuffer_v2 buffers,
const boost::regex & expr,
ReadHandler && handler = <a class="link" href="../asynchronous_operations.html#asio.reference.asynchronous_operations.default_completion_tokens"><span class="emphasis"><em>DEFAULT</em></span></a>,
typename enable_if< is_dynamic_buffer_v2< DynamicBuffer_v2 >::value >::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" 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="asio.reference.async_read_until.overload11.h0"></a>
<span><a name="asio.reference.async_read_until.overload11.parameters"></a></span><a class="link" href="overload11.html#asio.reference.async_read_until.overload11.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">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 asio::error_code& 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="asio.reference.async_read_until.overload11.h1"></a>
<span><a name="asio.reference.async_read_until.overload11.remarks"></a></span><a class="link" href="overload11.html#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="asio.reference.async_read_until.overload11.h2"></a>
<span><a name="asio.reference.async_read_until.overload11.example"></a></span><a class="link" href="overload11.html#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 asio::error_code& e, std::size_t size)
{
if (!e)
{
std::string line = data.substr(0, n);
data.erase(0, n);
...
}
}
...
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 © 2003-2020 Christopher M.
Kohlhoff<p>
Distributed under the Boost Software License, Version 1.0. (See accompanying
file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
</p>
</div></td>
</tr></table>
<hr>
<div class="spirit-nav">
<a accesskey="p" href="overload10.html"><img src="../../../prev.png" alt="Prev"></a><a accesskey="u" href="../async_read_until.html"><img src="../../../up.png" alt="Up"></a><a accesskey="h" href="../../../index.html"><img src="../../../home.png" alt="Home"></a><a accesskey="n" href="overload12.html"><img src="../../../next.png" alt="Next"></a>
</div>
</body>
</html>