1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>http::async_read (1 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. 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23<a accesskey="p" href="../boost__beast__http__async_read.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="overload2.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.overload1"></a><a class="link" href="overload1.html" title="http::async_read (1 of 2 overloads)">http::async_read 28 (1 of 2 overloads)</a> 29</h5></div></div></div> 30<p> 31 Read a complete message asynchronously from a stream using a parser. 32 </p> 33<h6> 34<a name="beast.ref.boost__beast__http__async_read.overload1.h0"></a> 35 <span class="phrase"><a name="beast.ref.boost__beast__http__async_read.overload1.synopsis"></a></span><a class="link" href="overload1.html#beast.ref.boost__beast__http__async_read.overload1.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 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> 45<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> 46<span class="identifier">async_read</span><span class="special">(</span> 47 <span class="identifier">AsyncReadStream</span><span class="special">&</span> <span class="identifier">stream</span><span class="special">,</span> 48 <span class="identifier">DynamicBuffer</span><span class="special">&</span> <span class="identifier">buffer</span><span class="special">,</span> 49 <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> 50 <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> 51</pre> 52<h6> 53<a name="beast.ref.boost__beast__http__async_read.overload1.h1"></a> 54 <span class="phrase"><a name="beast.ref.boost__beast__http__async_read.overload1.description"></a></span><a class="link" href="overload1.html#beast.ref.boost__beast__http__async_read.overload1.description">Description</a> 55 </h6> 56<p> 57 This function is used to asynchronously read a complete message from a 58 stream 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 59 always returns immediately. The asynchronous operation will continue until 60 one of the following conditions is true: 61 </p> 62<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> 63<li class="listitem"> 64 <a class="link" href="../boost__beast__http__basic_parser/is_done.html" title="http::basic_parser::is_done"><code class="computeroutput"><span class="identifier">basic_parser</span><span class="special">::</span><span class="identifier">is_done</span></code></a> returns <code class="computeroutput"><span class="keyword">true</span></code> 65 </li> 66<li class="listitem"> 67 An error occurs. 68 </li> 69</ul></div> 70<p> 71 This operation is implemented in terms of zero or more calls to the next 72 layer's <code class="computeroutput"><span class="identifier">async_read_some</span></code> 73 function, and is known as a <span class="emphasis"><em>composed operation</em></span>. The 74 program must ensure that the stream performs no other reads until this 75 operation completes. The implementation may read additional bytes from 76 the stream that lie past the end of the message being read. These additional 77 bytes are stored in the dynamic buffer, which must be preserved for subsequent 78 reads. If the end of file error is received while reading from the stream, 79 then the error returned from this function will be: 80 </p> 81<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "> 82<li class="listitem"> 83 <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> 84 if no bytes were parsed, or 85 </li> 86<li class="listitem"> 87 <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> 88 if any bytes were parsed but the message was incomplete, otherwise: 89 </li> 90<li class="listitem"> 91 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> 92 </li> 93</ul></div> 94<h6> 95<a name="beast.ref.boost__beast__http__async_read.overload1.h2"></a> 96 <span class="phrase"><a name="beast.ref.boost__beast__http__async_read.overload1.parameters"></a></span><a class="link" href="overload1.html#beast.ref.boost__beast__http__async_read.overload1.parameters">Parameters</a> 97 </h6> 98<div class="informaltable"><table class="table"> 99<colgroup> 100<col> 101<col> 102</colgroup> 103<thead><tr> 104<th> 105 <p> 106 Name 107 </p> 108 </th> 109<th> 110 <p> 111 Description 112 </p> 113 </th> 114</tr></thead> 115<tbody> 116<tr> 117<td> 118 <p> 119 <code class="computeroutput"><span class="identifier">stream</span></code> 120 </p> 121 </td> 122<td> 123 <p> 124 The stream from which the data is to be read. The type must meet 125 the <span class="emphasis"><em>AsyncReadStream</em></span> requirements. 126 </p> 127 </td> 128</tr> 129<tr> 130<td> 131 <p> 132 <code class="computeroutput"><span class="identifier">buffer</span></code> 133 </p> 134 </td> 135<td> 136 <p> 137 Storage for additional bytes read by the implementation from 138 the stream. This is both an input and an output parameter; on 139 entry, the parser will be presented with any remaining data in 140 the dynamic buffer's readable bytes sequence first. The type 141 must meet the <span class="emphasis"><em>DynamicBuffer</em></span> requirements. 142 The object must remain valid at least until the handler is called; 143 ownership is not transferred. 144 </p> 145 </td> 146</tr> 147<tr> 148<td> 149 <p> 150 <code class="computeroutput"><span class="identifier">parser</span></code> 151 </p> 152 </td> 153<td> 154 <p> 155 The parser to use. The object must remain valid at least until 156 the handler is called; ownership is not transferred. 157 </p> 158 </td> 159</tr> 160<tr> 161<td> 162 <p> 163 <code class="computeroutput"><span class="identifier">handler</span></code> 164 </p> 165 </td> 166<td> 167 <p> 168 The completion handler to invoke when the operation completes. 169 The implementation takes ownership of the handler by performing 170 a decay-copy. The equivalent function signature of the handler 171 must be: 172 </p> 173<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> 174 <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> 175 <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> 176<span class="special">);</span> 177</pre> 178 <p> 179 Regardless of whether the asynchronous operation completes immediately 180 or not, the handler will not be invoked from within this function. 181 Invocation of the handler will be performed in a manner equivalent 182 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>. 183 </p> 184 </td> 185</tr> 186</tbody> 187</table></div> 188<h6> 189<a name="beast.ref.boost__beast__http__async_read.overload1.h3"></a> 190 <span class="phrase"><a name="beast.ref.boost__beast__http__async_read.overload1.remarks"></a></span><a class="link" href="overload1.html#beast.ref.boost__beast__http__async_read.overload1.remarks">Remarks</a> 191 </h6> 192<p> 193 The completion handler will receive as a parameter the total number of 194 bytes transferred from the stream. This may be zero for the case where 195 there is sufficient pre-existing message data in the dynamic buffer. The 196 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. 197 </p> 198</div> 199<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 200<td align="left"></td> 201<td align="right"><div class="copyright-footer">Copyright © 2016-2019 Vinnie 202 Falco<p> 203 Distributed under the Boost Software License, Version 1.0. (See accompanying 204 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>) 205 </p> 206</div></td> 207</tr></table> 208<hr> 209<div class="spirit-nav"> 210<a accesskey="p" href="../boost__beast__http__async_read.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="overload2.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a> 211</div> 212</body> 213</html> 214
