boost/asio/detail/pipe_select_interrupter.hpp

   1 //
   2 // pipe_select_interrupter.hpp
   3 // ~~~~~~~~~~~~~~~~~~~~~~~~~~~
   4 //
   5 // Copyright (c) 2003-2008 Christopher M. Kohlhoff (chris at kohlhoff dot com)
   6 //
   7 // Distributed under the Boost Software License, Version 1.0. (See accompanying
   8 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
   9 //
  10
  11 #ifndef BOOST_ASIO_DETAIL_PIPE_SELECT_INTERRUPTER_HPP
  12 #define BOOST_ASIO_DETAIL_PIPE_SELECT_INTERRUPTER_HPP
  13
  14 #if defined(_MSC_VER) && (_MSC_VER >= 1200)
  15 # pragma once
  16 #endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
  17
  18 #include <boost/asio/detail/push_options.hpp>
  19
  20 #include <boost/asio/detail/push_options.hpp>
  21 #include <boost/config.hpp>
  22 #include <boost/throw_exception.hpp>
  23 #include <boost/system/system_error.hpp>
  24 #include <boost/asio/detail/pop_options.hpp>
  25
  26 #if !defined(BOOST_WINDOWS) && !defined(__CYGWIN__)
  27
  28 #include <boost/asio/detail/push_options.hpp>
  29 #include <fcntl.h>
  30 #include <boost/asio/detail/pop_options.hpp>
  31
  32 #include <boost/asio/error.hpp>
  33 #include <boost/asio/detail/socket_types.hpp>
  34
  35 namespace boost {
  36 namespace asio {
  37 namespace detail {
  38
  39 class pipe_select_interrupter
  40 {
  41 public:
  42   // Constructor.
  43   pipe_select_interrupter()
  44   {
  45     int pipe_fds[2];
  46     if (pipe(pipe_fds) == 0)
  47     {
  48       read_descriptor_ = pipe_fds[0];
  49       ::fcntl(read_descriptor_, F_SETFL, O_NONBLOCK);
  50       write_descriptor_ = pipe_fds[1];
  51       ::fcntl(write_descriptor_, F_SETFL, O_NONBLOCK);
  52     }
  53     else
  54     {
  55       boost::system::error_code ec(errno,
  56           boost::asio::error::get_system_category());
  57       boost::system::system_error e(ec, "pipe_select_interrupter");
  58       boost::throw_exception(e);
  59     }
  60   }
  61
  62   // Destructor.
  63   ~pipe_select_interrupter()
  64   {
  65     if (read_descriptor_ != -1)
  66       ::close(read_descriptor_);
  67     if (write_descriptor_ != -1)
  68       ::close(write_descriptor_);
  69   }
  70
  71   // Interrupt the select call.
  72   void interrupt()
  73   {
  74     char byte = 0;
  75     int result = ::write(write_descriptor_, &byte, 1);
  76     (void)result;
  77   }
  78
  79   // Reset the select interrupt. Returns true if the call was interrupted.
  80   bool reset()
  81   {
  82     char data[1024];
  83     int bytes_read = ::read(read_descriptor_, data, sizeof(data));
  84     bool was_interrupted = (bytes_read > 0);
  85     while (bytes_read == sizeof(data))
  86       bytes_read = ::read(read_descriptor_, data, sizeof(data));
  87     return was_interrupted;
  88   }
  89
  90   // Get the read descriptor to be passed to select.
  91   int read_descriptor() const
  92   {
  93     return read_descriptor_;
  94   }
  95
  96 private:
  97   // The read end of a connection used to interrupt the select call. This file
  98   // descriptor is passed to select such that when it is time to stop, a single
  99   // byte will be written on the other end of the connection and this
 100   // descriptor will become readable.
 101   int read_descriptor_;
 102
 103   // The write end of a connection used to interrupt the select call. A single
 104   // byte may be written to this to wake up the select which is waiting for the
 105   // other end to become readable.
 106   int write_descriptor_;
 107 };
 108
 109 } // namespace detail
 110 } // namespace asio
 111 } // namespace boost
 112
 113 #endif // !defined(BOOST_WINDOWS) && !defined(__CYGWIN__)
 114
 115 #include <boost/asio/detail/pop_options.hpp>
 116
 117 #endif // BOOST_ASIO_DETAIL_PIPE_SELECT_INTERRUPTER_HPP