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