1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>basic_raw_socket::native_non_blocking (1 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_raw_socket::native_non_blocking"> 9<link rel="prev" href="../native_non_blocking.html" title="basic_raw_socket::native_non_blocking"> 10<link rel="next" href="overload2.html" title="basic_raw_socket::native_non_blocking (2 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="../native_non_blocking.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="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="boost_asio.reference.basic_raw_socket.native_non_blocking.overload1"></a><a class="link" href="overload1.html" title="basic_raw_socket::native_non_blocking (1 of 3 overloads)">basic_raw_socket::native_non_blocking 28 (1 of 3 overloads)</a> 29</h5></div></div></div> 30<p> 31 <span class="emphasis"><em>Inherited from basic_socket.</em></span> 32 </p> 33<p> 34 Gets the non-blocking mode of the native socket implementation. 35 </p> 36<pre class="programlisting">bool native_non_blocking() const; 37</pre> 38<p> 39 This function is used to retrieve the non-blocking mode of the underlying 40 native socket. This mode has no effect on the behaviour of the socket 41 object's synchronous operations. 42 </p> 43<h6> 44<a name="boost_asio.reference.basic_raw_socket.native_non_blocking.overload1.h0"></a> 45 <span class="phrase"><a name="boost_asio.reference.basic_raw_socket.native_non_blocking.overload1.return_value"></a></span><a class="link" href="overload1.html#boost_asio.reference.basic_raw_socket.native_non_blocking.overload1.return_value">Return 46 Value</a> 47 </h6> 48<p> 49 <code class="computeroutput">true</code> if the underlying socket is in non-blocking mode and 50 direct system calls may fail with <code class="computeroutput">boost::asio::error::would_block</code> 51 (or the equivalent system error). 52 </p> 53<h6> 54<a name="boost_asio.reference.basic_raw_socket.native_non_blocking.overload1.h1"></a> 55 <span class="phrase"><a name="boost_asio.reference.basic_raw_socket.native_non_blocking.overload1.remarks"></a></span><a class="link" href="overload1.html#boost_asio.reference.basic_raw_socket.native_non_blocking.overload1.remarks">Remarks</a> 56 </h6> 57<p> 58 The current non-blocking mode is cached by the socket object. Consequently, 59 the return value may be incorrect if the non-blocking mode was set directly 60 on the native socket. 61 </p> 62<h6> 63<a name="boost_asio.reference.basic_raw_socket.native_non_blocking.overload1.h2"></a> 64 <span class="phrase"><a name="boost_asio.reference.basic_raw_socket.native_non_blocking.overload1.example"></a></span><a class="link" href="overload1.html#boost_asio.reference.basic_raw_socket.native_non_blocking.overload1.example">Example</a> 65 </h6> 66<p> 67 This function is intended to allow the encapsulation of arbitrary non-blocking 68 system calls as asynchronous operations, in a way that is transparent 69 to the user of the socket object. The following example illustrates how 70 Linux's <code class="computeroutput">sendfile</code> system call might be encapsulated: 71 </p> 72<pre class="programlisting">template <typename Handler> 73struct sendfile_op 74{ 75 tcp::socket& sock_; 76 int fd_; 77 Handler handler_; 78 off_t offset_; 79 std::size_t total_bytes_transferred_; 80 81 // Function call operator meeting WriteHandler requirements. 82 // Used as the handler for the async_write_some operation. 83 void operator()(boost::system::error_code ec, std::size_t) 84 { 85 // Put the underlying socket into non-blocking mode. 86 if (!ec) 87 if (!sock_.native_non_blocking()) 88 sock_.native_non_blocking(true, ec); 89 90 if (!ec) 91 { 92 for (;;) 93 { 94 // Try the system call. 95 errno = 0; 96 int n = ::sendfile(sock_.native_handle(), fd_, &offset_, 65536); 97 ec = boost::system::error_code(n < 0 ? errno : 0, 98 boost::asio::error::get_system_category()); 99 total_bytes_transferred_ += ec ? 0 : n; 100 101 // Retry operation immediately if interrupted by signal. 102 if (ec == boost::asio::error::interrupted) 103 continue; 104 105 // Check if we need to run the operation again. 106 if (ec == boost::asio::error::would_block 107 || ec == boost::asio::error::try_again) 108 { 109 // We have to wait for the socket to become ready again. 110 sock_.async_wait(tcp::socket::wait_write, *this); 111 return; 112 } 113 114 if (ec || n == 0) 115 { 116 // An error occurred, or we have reached the end of the file. 117 // Either way we must exit the loop so we can call the handler. 118 break; 119 } 120 121 // Loop around to try calling sendfile again. 122 } 123 } 124 125 // Pass result back to user's handler. 126 handler_(ec, total_bytes_transferred_); 127 } 128}; 129 130template <typename Handler> 131void async_sendfile(tcp::socket& sock, int fd, Handler h) 132{ 133 sendfile_op<Handler> op = { sock, fd, h, 0, 0 }; 134 sock.async_wait(tcp::socket::wait_write, op); 135} 136</pre> 137</div> 138<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 139<td align="left"></td> 140<td align="right"><div class="copyright-footer">Copyright © 2003-2020 Christopher M. 141 Kohlhoff<p> 142 Distributed under the Boost Software License, Version 1.0. (See accompanying 143 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>) 144 </p> 145</div></td> 146</tr></table> 147<hr> 148<div class="spirit-nav"> 149<a accesskey="p" href="../native_non_blocking.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="overload2.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a> 150</div> 151</body> 152</html> 153
