1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>basic_socket::native_non_blocking (2 of 3 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="../../../../boost_asio.html" title="Boost.Asio"> 8<link rel="up" href="../native_non_blocking.html" title="basic_socket::native_non_blocking"> 9<link rel="prev" href="overload1.html" title="basic_socket::native_non_blocking (1 of 3 overloads)"> 10<link rel="next" href="overload3.html" title="basic_socket::native_non_blocking (3 of 3 overloads)"> 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="../native_non_blocking.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../../boost_asio.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="overload3.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="boost_asio.reference.basic_socket.native_non_blocking.overload2"></a><a class="link" href="overload2.html" title="basic_socket::native_non_blocking (2 of 3 overloads)">basic_socket::native_non_blocking 28 (2 of 3 overloads)</a> 29</h5></div></div></div> 30<p> 31 Sets the non-blocking mode of the native socket implementation. 32 </p> 33<pre class="programlisting">void native_non_blocking( 34 bool mode); 35</pre> 36<p> 37 This function is used to modify the non-blocking mode of the underlying 38 native socket. It has no effect on the behaviour of the socket object's 39 synchronous operations. 40 </p> 41<h6> 42<a name="boost_asio.reference.basic_socket.native_non_blocking.overload2.h0"></a> 43 <span class="phrase"><a name="boost_asio.reference.basic_socket.native_non_blocking.overload2.parameters"></a></span><a class="link" href="overload2.html#boost_asio.reference.basic_socket.native_non_blocking.overload2.parameters">Parameters</a> 44 </h6> 45<div class="variablelist"> 46<p class="title"><b></b></p> 47<dl class="variablelist"> 48<dt><span class="term">mode</span></dt> 49<dd><p> 50 If <code class="computeroutput">true</code>, the underlying socket is put into non-blocking 51 mode and direct system calls may fail with <code class="computeroutput">boost::asio::error::would_block</code> 52 (or the equivalent system error). 53 </p></dd> 54</dl> 55</div> 56<h6> 57<a name="boost_asio.reference.basic_socket.native_non_blocking.overload2.h1"></a> 58 <span class="phrase"><a name="boost_asio.reference.basic_socket.native_non_blocking.overload2.exceptions"></a></span><a class="link" href="overload2.html#boost_asio.reference.basic_socket.native_non_blocking.overload2.exceptions">Exceptions</a> 59 </h6> 60<div class="variablelist"> 61<p class="title"><b></b></p> 62<dl class="variablelist"> 63<dt><span class="term">boost::system::system_error</span></dt> 64<dd><p> 65 Thrown on failure. If the <code class="computeroutput">mode</code> is <code class="computeroutput">false</code>, 66 but the current value of <code class="computeroutput">non_blocking()</code> is <code class="computeroutput">true</code>, 67 this function fails with <code class="computeroutput">boost::asio::error::invalid_argument</code>, 68 as the combination does not make sense. 69 </p></dd> 70</dl> 71</div> 72<h6> 73<a name="boost_asio.reference.basic_socket.native_non_blocking.overload2.h2"></a> 74 <span class="phrase"><a name="boost_asio.reference.basic_socket.native_non_blocking.overload2.example"></a></span><a class="link" href="overload2.html#boost_asio.reference.basic_socket.native_non_blocking.overload2.example">Example</a> 75 </h6> 76<p> 77 This function is intended to allow the encapsulation of arbitrary non-blocking 78 system calls as asynchronous operations, in a way that is transparent 79 to the user of the socket object. The following example illustrates how 80 Linux's <code class="computeroutput">sendfile</code> system call might be encapsulated: 81 </p> 82<pre class="programlisting">template <typename Handler> 83struct sendfile_op 84{ 85 tcp::socket& sock_; 86 int fd_; 87 Handler handler_; 88 off_t offset_; 89 std::size_t total_bytes_transferred_; 90 91 // Function call operator meeting WriteHandler requirements. 92 // Used as the handler for the async_write_some operation. 93 void operator()(boost::system::error_code ec, std::size_t) 94 { 95 // Put the underlying socket into non-blocking mode. 96 if (!ec) 97 if (!sock_.native_non_blocking()) 98 sock_.native_non_blocking(true, ec); 99 100 if (!ec) 101 { 102 for (;;) 103 { 104 // Try the system call. 105 errno = 0; 106 int n = ::sendfile(sock_.native_handle(), fd_, &offset_, 65536); 107 ec = boost::system::error_code(n < 0 ? errno : 0, 108 boost::asio::error::get_system_category()); 109 total_bytes_transferred_ += ec ? 0 : n; 110 111 // Retry operation immediately if interrupted by signal. 112 if (ec == boost::asio::error::interrupted) 113 continue; 114 115 // Check if we need to run the operation again. 116 if (ec == boost::asio::error::would_block 117 || ec == boost::asio::error::try_again) 118 { 119 // We have to wait for the socket to become ready again. 120 sock_.async_wait(tcp::socket::wait_write, *this); 121 return; 122 } 123 124 if (ec || n == 0) 125 { 126 // An error occurred, or we have reached the end of the file. 127 // Either way we must exit the loop so we can call the handler. 128 break; 129 } 130 131 // Loop around to try calling sendfile again. 132 } 133 } 134 135 // Pass result back to user's handler. 136 handler_(ec, total_bytes_transferred_); 137 } 138}; 139 140template <typename Handler> 141void async_sendfile(tcp::socket& sock, int fd, Handler h) 142{ 143 sendfile_op<Handler> op = { sock, fd, h, 0, 0 }; 144 sock.async_wait(tcp::socket::wait_write, op); 145} 146</pre> 147</div> 148<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 149<td align="left"></td> 150<td align="right"><div class="copyright-footer">Copyright © 2003-2020 Christopher M. 151 Kohlhoff<p> 152 Distributed under the Boost Software License, Version 1.0. (See accompanying 153 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>) 154 </p> 155</div></td> 156</tr></table> 157<hr> 158<div class="spirit-nav"> 159<a accesskey="p" href="overload1.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../native_non_blocking.html"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../../boost_asio.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="overload3.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a> 160</div> 161</body> 162</html> 163
