1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>http::async_read_some</title> 5<link rel="stylesheet" href="../../../../../../doc/src/boostbook.css" type="text/css"> 6<meta name="generator" content="DocBook XSL Stylesheets V1.79.1"> 7<link rel="home" href="../../index.html" title="Chapter 1. Boost.Beast"> 8<link rel="up" href="../ref.html" title="This Page Intentionally Left Blank 2/2"> 9<link rel="prev" href="boost__beast__http__read_some/overload2.html" title="http::read_some (2 of 2 overloads)"> 10<link rel="next" href="boost__beast__http__read_header.html" title="http::read_header"> 11</head> 12<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> 13<table cellpadding="2" width="100%"><tr> 14<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../boost.png"></td> 15<td align="center"><a href="../../../../../../index.html">Home</a></td> 16<td align="center"><a href="../../../../../../libs/libraries.htm">Libraries</a></td> 17<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td> 18<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td> 19<td align="center"><a href="../../../../../../more/index.htm">More</a></td> 20</tr></table> 21<hr> 22<div class="spirit-nav"> 23<a accesskey="p" href="boost__beast__http__read_some/overload2.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../ref.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="boost__beast__http__read_header.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a> 24</div> 25<div class="section"> 26<div class="titlepage"><div><div><h4 class="title"> 27<a name="beast.ref.boost__beast__http__async_read_some"></a><a class="link" href="boost__beast__http__async_read_some.html" title="http::async_read_some">http::async_read_some</a> 28</h4></div></div></div> 29<p> 30 <a class="indexterm" name="idm46057506503792"></a> 31 </p> 32<p> 33 Read part of a message asynchronously from a stream using a parser. 34 </p> 35<h5> 36<a name="beast.ref.boost__beast__http__async_read_some.h0"></a> 37 <span class="phrase"><a name="beast.ref.boost__beast__http__async_read_some.synopsis"></a></span><a class="link" href="boost__beast__http__async_read_some.html#beast.ref.boost__beast__http__async_read_some.synopsis">Synopsis</a> 38 </h5> 39<p> 40 Defined in header <code class="literal"><<a href="../../../../../../boost/beast/http/read.hpp" target="_top">boost/beast/http/read.hpp</a>></code> 41 </p> 42<pre class="programlisting"><span class="keyword">template</span><span class="special"><</span> 43 <span class="keyword">class</span> <a href="../../../../../../doc/html/boost_asio/reference/AsyncReadStream.html" target="_top"><span class="emphasis"><em>AsyncReadStream</em></span></a><span class="special">,</span> 44 <span class="keyword">class</span> <a class="link" href="../concepts/DynamicBuffer.html" title="DynamicBuffer"><span class="emphasis"><em>DynamicBuffer</em></span></a><span class="special">,</span> 45 <span class="keyword">bool</span> <span class="identifier">isRequest</span><span class="special">,</span> 46 <span class="keyword">class</span> <a href="../../../../../../doc/html/boost_asio/reference/ReadHandler.html" target="_top"><span class="emphasis"><em>ReadHandler</em></span></a> <span class="special">=</span> <span class="identifier">net</span><span class="special">::</span><span class="identifier">default_completion_token_t</span><span class="special"><</span> <span class="identifier">executor_type</span><span class="special"><</span><span class="identifier">AsyncReadStream</span><span class="special">>>></span> 47<a href="../../../../../../doc/html/boost_asio/reference/asynchronous_operations.html#boost_asio.reference.asynchronous_operations.automatic_deduction_of_initiating_function_return_type" target="_top"><span class="emphasis"><em>DEDUCED</em></span></a> 48<span class="identifier">async_read_some</span><span class="special">(</span> 49 <span class="identifier">AsyncReadStream</span><span class="special">&</span> <span class="identifier">stream</span><span class="special">,</span> 50 <span class="identifier">DynamicBuffer</span><span class="special">&</span> <span class="identifier">buffer</span><span class="special">,</span> 51 <span class="identifier">basic_parser</span><span class="special"><</span> <span class="identifier">isRequest</span> <span class="special">>&</span> <span class="identifier">parser</span><span class="special">,</span> 52 <span class="identifier">ReadHandler</span><span class="special">&&</span> <span class="identifier">handler</span> <span class="special">=</span> <span class="identifier">net</span><span class="special">::</span><span class="identifier">default_completion_token_t</span><span class="special"><</span> <a class="link" href="boost__beast__executor_type.html" title="executor_type">executor_type</a><span class="special"><</span> <span class="identifier">AsyncReadStream</span> <span class="special">>>{});</span> 53</pre> 54<h5> 55<a name="beast.ref.boost__beast__http__async_read_some.h1"></a> 56 <span class="phrase"><a name="beast.ref.boost__beast__http__async_read_some.description"></a></span><a class="link" href="boost__beast__http__async_read_some.html#beast.ref.boost__beast__http__async_read_some.description">Description</a> 57 </h5> 58<p> 59 This function is used to asynchronously read part of a message from a stream 60 into an instance of <a class="link" href="boost__beast__http__basic_parser.html" title="http::basic_parser"><code class="computeroutput"><span class="identifier">basic_parser</span></code></a>. The function call 61 always returns immediately. The asynchronous operation will continue until 62 one of the following conditions is true: 63 </p> 64<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> 65<li class="listitem"> 66 A call to <a class="link" href="boost__beast__http__basic_parser/put.html" title="http::basic_parser::put"><code class="computeroutput"><span class="identifier">basic_parser</span><span class="special">::</span><span class="identifier">put</span></code></a> with a non-empty buffer 67 sequence is successful. 68 </li> 69<li class="listitem"> 70 An error occurs. 71 </li> 72</ul></div> 73<p> 74 This operation is implemented in terms of zero or more calls to the next 75 layer's <code class="computeroutput"><span class="identifier">async_read_some</span></code> function, 76 and is known as a <span class="emphasis"><em>composed operation</em></span>. The program must 77 ensure that the stream performs no other reads until this operation completes. 78 The implementation may read additional bytes from the stream that lie past 79 the end of the message being read. These additional bytes are stored in the 80 dynamic buffer, which must be preserved for subsequent reads. If the end 81 of file error is received while reading from the stream, then the error returned 82 from this function will be: 83 </p> 84<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> 85<li class="listitem"> 86 <a class="link" href="boost__beast__http__error.html" title="http::error"><code class="computeroutput"><span class="identifier">error</span><span class="special">::</span><span class="identifier">end_of_stream</span></code></a> 87 if no bytes were parsed, or 88 </li> 89<li class="listitem"> 90 <a class="link" href="boost__beast__http__error.html" title="http::error"><code class="computeroutput"><span class="identifier">error</span><span class="special">::</span><span class="identifier">partial_message</span></code></a> 91 if any bytes were parsed but the message was incomplete, otherwise: 92 </li> 93<li class="listitem"> 94 A successful result. The next attempt to read will return <a class="link" href="boost__beast__http__error.html" title="http::error"><code class="computeroutput"><span class="identifier">error</span><span class="special">::</span><span class="identifier">end_of_stream</span></code></a> 95 </li> 96</ul></div> 97<h5> 98<a name="beast.ref.boost__beast__http__async_read_some.h2"></a> 99 <span class="phrase"><a name="beast.ref.boost__beast__http__async_read_some.parameters"></a></span><a class="link" href="boost__beast__http__async_read_some.html#beast.ref.boost__beast__http__async_read_some.parameters">Parameters</a> 100 </h5> 101<div class="informaltable"><table class="table"> 102<colgroup> 103<col> 104<col> 105</colgroup> 106<thead><tr> 107<th> 108 <p> 109 Name 110 </p> 111 </th> 112<th> 113 <p> 114 Description 115 </p> 116 </th> 117</tr></thead> 118<tbody> 119<tr> 120<td> 121 <p> 122 <code class="computeroutput"><span class="identifier">stream</span></code> 123 </p> 124 </td> 125<td> 126 <p> 127 The stream from which the data is to be read. The type must meet 128 the <span class="emphasis"><em>AsyncReadStream</em></span> requirements. 129 </p> 130 </td> 131</tr> 132<tr> 133<td> 134 <p> 135 <code class="computeroutput"><span class="identifier">buffer</span></code> 136 </p> 137 </td> 138<td> 139 <p> 140 Storage for additional bytes read by the implementation from the 141 stream. This is both an input and an output parameter; on entry, 142 the parser will be presented with any remaining data in the dynamic 143 buffer's readable bytes sequence first. The type must meet the 144 <span class="emphasis"><em>DynamicBuffer</em></span> requirements. The object must 145 remain valid at least until the handler is called; ownership is 146 not transferred. 147 </p> 148 </td> 149</tr> 150<tr> 151<td> 152 <p> 153 <code class="computeroutput"><span class="identifier">parser</span></code> 154 </p> 155 </td> 156<td> 157 <p> 158 The parser to use. The object must remain valid at least until 159 the handler is called; ownership is not transferred. 160 </p> 161 </td> 162</tr> 163<tr> 164<td> 165 <p> 166 <code class="computeroutput"><span class="identifier">handler</span></code> 167 </p> 168 </td> 169<td> 170 <p> 171 The completion handler to invoke when the operation completes. 172 The implementation takes ownership of the handler by performing 173 a decay-copy. The equivalent function signature of the handler 174 must be: 175 </p> 176<pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="keyword">void</span> <span class="identifier">handler</span><span class="special">(</span> 177 <span class="identifier">error_code</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">error</span><span class="special">,</span> <span class="comment">// result of operation</span> 178 <span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span> <span class="identifier">bytes_transferred</span> <span class="comment">// the total number of bytes transferred from the stream</span> 179<span class="special">);</span> 180</pre> 181 <p> 182 Regardless of whether the asynchronous operation completes immediately 183 or not, the handler will not be invoked from within this function. 184 Invocation of the handler will be performed in a manner equivalent 185 to using <a class="link" href="boost__beast__http__verb.html" title="http::verb"><code class="computeroutput"><span class="identifier">net</span><span class="special">::</span><span class="identifier">post</span></code></a>. 186 </p> 187 </td> 188</tr> 189</tbody> 190</table></div> 191<h5> 192<a name="beast.ref.boost__beast__http__async_read_some.h3"></a> 193 <span class="phrase"><a name="beast.ref.boost__beast__http__async_read_some.remarks"></a></span><a class="link" href="boost__beast__http__async_read_some.html#beast.ref.boost__beast__http__async_read_some.remarks">Remarks</a> 194 </h5> 195<p> 196 The completion handler will receive as a parameter the total number of bytes 197 transferred from the stream. This may be zero for the case where there is 198 sufficient pre-existing message data in the dynamic buffer. 199 </p> 200</div> 201<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 202<td align="left"></td> 203<td align="right"><div class="copyright-footer">Copyright © 2016-2019 Vinnie 204 Falco<p> 205 Distributed under the Boost Software License, Version 1.0. (See accompanying 206 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>) 207 </p> 208</div></td> 209</tr></table> 210<hr> 211<div class="spirit-nav"> 212<a accesskey="p" href="boost__beast__http__read_some/overload2.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../ref.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="boost__beast__http__read_header.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a> 213</div> 214</body> 215</html> 216
