1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>http::async_read (2 of 2 overloads)</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="../boost__beast__http__async_read.html" title="http::async_read"> 9<link rel="prev" href="overload1.html" title="http::async_read (1 of 2 overloads)"> 10<link rel="next" href="../boost__beast__http__validate_list.html" title="http::validate_list"> 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="overload1.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../boost__beast__http__async_read.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__validate_list.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a> 24</div> 25<div class="section"> 26<div class="titlepage"><div><div><h5 class="title"> 27<a name="beast.ref.boost__beast__http__async_read.overload2"></a><a class="link" href="overload2.html" title="http::async_read (2 of 2 overloads)">http::async_read 28 (2 of 2 overloads)</a> 29</h5></div></div></div> 30<p> 31 Read a complete message asynchronously from a stream. 32 </p> 33<h6> 34<a name="beast.ref.boost__beast__http__async_read.overload2.h0"></a> 35 <span class="phrase"><a name="beast.ref.boost__beast__http__async_read.overload2.synopsis"></a></span><a class="link" href="overload2.html#beast.ref.boost__beast__http__async_read.overload2.synopsis">Synopsis</a> 36 </h6> 37<p> 38 Defined in header <code class="literal"><<a href="../../../../../../../boost/beast/http/read.hpp" target="_top">boost/beast/http/read.hpp</a>></code> 39 </p> 40<pre class="programlisting"><span class="keyword">template</span><span class="special"><</span> 41 <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> 42 <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> 43 <span class="keyword">bool</span> <span class="identifier">isRequest</span><span class="special">,</span> 44 <span class="keyword">class</span> <a class="link" href="../../concepts/Body.html" title="Body"><span class="emphasis"><em>Body</em></span></a><span class="special">,</span> 45 <span class="keyword">class</span> <a href="https://en.cppreference.com/w/cpp/named_req/Allocator" target="_top"><span class="emphasis"><em>Allocator</em></span></a><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</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">message</span><span class="special"><</span> <span class="identifier">isRequest</span><span class="special">,</span> <span class="identifier">Body</span><span class="special">,</span> <span class="identifier">basic_fields</span><span class="special"><</span> <span class="identifier">Allocator</span> <span class="special">>>&</span> <span class="identifier">msg</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<h6> 55<a name="beast.ref.boost__beast__http__async_read.overload2.h1"></a> 56 <span class="phrase"><a name="beast.ref.boost__beast__http__async_read.overload2.description"></a></span><a class="link" href="overload2.html#beast.ref.boost__beast__http__async_read.overload2.description">Description</a> 57 </h6> 58<p> 59 This function is used to asynchronously read a complete message from a 60 stream into an instance of <a class="link" href="../boost__beast__http__message.html" title="http::message"><code class="computeroutput"><span class="identifier">message</span></code></a>. The function call always 61 returns immediately. The asynchronous operation will continue until one 62 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 The entire message is read in. 67 </li> 68<li class="listitem"> 69 An error occurs. 70 </li> 71</ul></div> 72<p> 73 This operation is implemented in terms of zero or more calls to the next 74 layer's <code class="computeroutput"><span class="identifier">async_read_some</span></code> 75 function, and is known as a <span class="emphasis"><em>composed operation</em></span>. The 76 program must ensure that the stream performs no other reads until this 77 operation completes. The implementation may read additional bytes from 78 the stream that lie past the end of the message being read. These additional 79 bytes are stored in the dynamic buffer, which must be preserved for subsequent 80 reads. If the end of file error is received while reading from the stream, 81 then the error returned from this function will be: 82 </p> 83<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> 84<li class="listitem"> 85 <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> 86 if no bytes were parsed, or 87 </li> 88<li class="listitem"> 89 <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> 90 if any bytes were parsed but the message was incomplete, otherwise: 91 </li> 92<li class="listitem"> 93 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> 94 </li> 95</ul></div> 96<h6> 97<a name="beast.ref.boost__beast__http__async_read.overload2.h2"></a> 98 <span class="phrase"><a name="beast.ref.boost__beast__http__async_read.overload2.parameters"></a></span><a class="link" href="overload2.html#beast.ref.boost__beast__http__async_read.overload2.parameters">Parameters</a> 99 </h6> 100<div class="informaltable"><table class="table"> 101<colgroup> 102<col> 103<col> 104</colgroup> 105<thead><tr> 106<th> 107 <p> 108 Name 109 </p> 110 </th> 111<th> 112 <p> 113 Description 114 </p> 115 </th> 116</tr></thead> 117<tbody> 118<tr> 119<td> 120 <p> 121 <code class="computeroutput"><span class="identifier">stream</span></code> 122 </p> 123 </td> 124<td> 125 <p> 126 The stream from which the data is to be read. The type must meet 127 the <span class="emphasis"><em>AsyncReadStream</em></span> requirements. 128 </p> 129 </td> 130</tr> 131<tr> 132<td> 133 <p> 134 <code class="computeroutput"><span class="identifier">buffer</span></code> 135 </p> 136 </td> 137<td> 138 <p> 139 Storage for additional bytes read by the implementation from 140 the stream. This is both an input and an output parameter; on 141 entry, the parser will be presented with any remaining data in 142 the dynamic buffer's readable bytes sequence first. The type 143 must meet the <span class="emphasis"><em>DynamicBuffer</em></span> requirements. 144 The object must remain valid at least until the handler is called; 145 ownership is not transferred. 146 </p> 147 </td> 148</tr> 149<tr> 150<td> 151 <p> 152 <code class="computeroutput"><span class="identifier">msg</span></code> 153 </p> 154 </td> 155<td> 156 <p> 157 The container in which to store the message contents. This message 158 container should not have previous contents, otherwise the behavior 159 is undefined. The type must be meet the <span class="emphasis"><em>MoveAssignable</em></span> 160 and <span class="emphasis"><em>MoveConstructible</em></span> requirements. The 161 object must remain valid at least until the handler is called; 162 ownership is not transferred. 163 </p> 164 </td> 165</tr> 166<tr> 167<td> 168 <p> 169 <code class="computeroutput"><span class="identifier">handler</span></code> 170 </p> 171 </td> 172<td> 173 <p> 174 The completion handler to invoke when the operation completes. 175 The implementation takes ownership of the handler by performing 176 a decay-copy. The equivalent function signature of the handler 177 must be: 178 </p> 179<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> 180 <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> 181 <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> 182<span class="special">);</span> 183</pre> 184 <p> 185 Regardless of whether the asynchronous operation completes immediately 186 or not, the handler will not be invoked from within this function. 187 Invocation of the handler will be performed in a manner equivalent 188 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>. 189 </p> 190 </td> 191</tr> 192</tbody> 193</table></div> 194<h6> 195<a name="beast.ref.boost__beast__http__async_read.overload2.h3"></a> 196 <span class="phrase"><a name="beast.ref.boost__beast__http__async_read.overload2.remarks"></a></span><a class="link" href="overload2.html#beast.ref.boost__beast__http__async_read.overload2.remarks">Remarks</a> 197 </h6> 198<p> 199 The completion handler will receive as a parameter the total number of 200 bytes transferred from the stream. This may be zero for the case where 201 there is sufficient pre-existing message data in the dynamic buffer. The 202 implementation will call <a class="link" href="../boost__beast__http__basic_parser/eager/overload1.html" title="http::basic_parser::eager (1 of 2 overloads)"><code class="computeroutput"><span class="identifier">basic_parser</span><span class="special">::</span><span class="identifier">eager</span></code></a> with the value <code class="computeroutput"><span class="keyword">true</span></code> on the parser passed in. 203 </p> 204</div> 205<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 206<td align="left"></td> 207<td align="right"><div class="copyright-footer">Copyright © 2016-2019 Vinnie 208 Falco<p> 209 Distributed under the Boost Software License, Version 1.0. (See accompanying 210 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>) 211 </p> 212</div></td> 213</tr></table> 214<hr> 215<div class="spirit-nav"> 216<a accesskey="p" href="overload1.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../boost__beast__http__async_read.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__validate_list.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a> 217</div> 218</body> 219</html> 220
