boost/asio/detail/impl/eventfd_select_interrupter.ipp

   1 //
   2 // detail/impl/eventfd_select_interrupter.ipp
   3 // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   4 //
   5 // Copyright (c) 2003-2017 Christopher M. Kohlhoff (chris at kohlhoff dot com)
   6 // Copyright (c) 2008 Roelof Naude (roelof.naude at gmail dot com)
   7 //
   8 // Distributed under the Boost Software License, Version 1.0. (See accompanying
   9 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  10 //
  11
  12 #ifndef BOOST_ASIO_DETAIL_IMPL_EVENTFD_SELECT_INTERRUPTER_IPP
  13 #define BOOST_ASIO_DETAIL_IMPL_EVENTFD_SELECT_INTERRUPTER_IPP
  14
  15 #if defined(_MSC_VER) && (_MSC_VER >= 1200)
  16 # pragma once
  17 #endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
  18
  19 #include <boost/asio/detail/config.hpp>
  20
  21 #if defined(BOOST_ASIO_HAS_EVENTFD)
  22
  23 #include <sys/stat.h>
  24 #include <sys/types.h>
  25 #include <fcntl.h>
  26 #if __GLIBC__ == 2 && __GLIBC_MINOR__ < 8
  27 # include <asm/unistd.h>
  28 #else // __GLIBC__ == 2 && __GLIBC_MINOR__ < 8
  29 # include <sys/eventfd.h>
  30 #endif // __GLIBC__ == 2 && __GLIBC_MINOR__ < 8
  31 #include <boost/asio/detail/cstdint.hpp>
  32 #include <boost/asio/detail/eventfd_select_interrupter.hpp>
  33 #include <boost/asio/detail/throw_error.hpp>
  34 #include <boost/asio/error.hpp>
  35
  36 #include <boost/asio/detail/push_options.hpp>
  37
  38 namespace boost {
  39 namespace asio {
  40 namespace detail {
  41
  42 eventfd_select_interrupter::eventfd_select_interrupter()
  43 {
  44   open_descriptors();
  45 }
  46
  47 void eventfd_select_interrupter::open_descriptors()
  48 {
  49 #if __GLIBC__ == 2 && __GLIBC_MINOR__ < 8
  50   write_descriptor_ = read_descriptor_ = syscall(__NR_eventfd, 0);
  51   if (read_descriptor_ != -1)
  52   {
  53     ::fcntl(read_descriptor_, F_SETFL, O_NONBLOCK);
  54     ::fcntl(read_descriptor_, F_SETFD, FD_CLOEXEC);
  55   }
  56 #else // __GLIBC__ == 2 && __GLIBC_MINOR__ < 8
  57 # if defined(EFD_CLOEXEC) && defined(EFD_NONBLOCK)
  58   write_descriptor_ = read_descriptor_ =
  59     ::eventfd(0, EFD_CLOEXEC | EFD_NONBLOCK);
  60 # else // defined(EFD_CLOEXEC) && defined(EFD_NONBLOCK)
  61   errno = EINVAL;
  62   write_descriptor_ = read_descriptor_ = -1;
  63 # endif // defined(EFD_CLOEXEC) && defined(EFD_NONBLOCK)
  64   if (read_descriptor_ == -1 && errno == EINVAL)
  65   {
  66     write_descriptor_ = read_descriptor_ = ::eventfd(0, 0);
  67     if (read_descriptor_ != -1)
  68     {
  69       ::fcntl(read_descriptor_, F_SETFL, O_NONBLOCK);
  70       ::fcntl(read_descriptor_, F_SETFD, FD_CLOEXEC);
  71     }
  72   }
  73 #endif // __GLIBC__ == 2 && __GLIBC_MINOR__ < 8
  74
  75   if (read_descriptor_ == -1)
  76   {
  77     int pipe_fds[2];
  78     if (pipe(pipe_fds) == 0)
  79     {
  80       read_descriptor_ = pipe_fds[0];
  81       ::fcntl(read_descriptor_, F_SETFL, O_NONBLOCK);
  82       ::fcntl(read_descriptor_, F_SETFD, FD_CLOEXEC);
  83       write_descriptor_ = pipe_fds[1];
  84       ::fcntl(write_descriptor_, F_SETFL, O_NONBLOCK);
  85       ::fcntl(write_descriptor_, F_SETFD, FD_CLOEXEC);
  86     }
  87     else
  88     {
  89       boost::system::error_code ec(errno,
  90           boost::asio::error::get_system_category());
  91       boost::asio::detail::throw_error(ec, "eventfd_select_interrupter");
  92     }
  93   }
  94 }
  95
  96 eventfd_select_interrupter::~eventfd_select_interrupter()
  97 {
  98   close_descriptors();
  99 }
 100
 101 void eventfd_select_interrupter::close_descriptors()
 102 {
 103   if (write_descriptor_ != -1 && write_descriptor_ != read_descriptor_)
 104     ::close(write_descriptor_);
 105   if (read_descriptor_ != -1)
 106     ::close(read_descriptor_);
 107 }
 108
 109 void eventfd_select_interrupter::recreate()
 110 {
 111   close_descriptors();
 112
 113   write_descriptor_ = -1;
 114   read_descriptor_ = -1;
 115
 116   open_descriptors();
 117 }
 118
 119 void eventfd_select_interrupter::interrupt()
 120 {
 121   uint64_t counter(1UL);
 122   int result = ::write(write_descriptor_, &counter, sizeof(uint64_t));
 123   (void)result;
 124 }
 125
 126 bool eventfd_select_interrupter::reset()
 127 {
 128   if (write_descriptor_ == read_descriptor_)
 129   {
 130     for (;;)
 131     {
 132       // Only perform one read. The kernel maintains an atomic counter.
 133       uint64_t counter(0);
 134       errno = 0;
 135       int bytes_read = ::read(read_descriptor_, &counter, sizeof(uint64_t));
 136       if (bytes_read < 0 && errno == EINTR)
 137         continue;
 138       bool was_interrupted = (bytes_read > 0);
 139       return was_interrupted;
 140     }
 141   }
 142   else
 143   {
 144     for (;;)
 145     {
 146       // Clear all data from the pipe.
 147       char data[1024];
 148       int bytes_read = ::read(read_descriptor_, data, sizeof(data));
 149       if (bytes_read < 0 && errno == EINTR)
 150         continue;
 151       bool was_interrupted = (bytes_read > 0);
 152       while (bytes_read == sizeof(data))
 153         bytes_read = ::read(read_descriptor_, data, sizeof(data));
 154       return was_interrupted;
 155     }
 156   }
 157 }
 158
 159 } // namespace detail
 160 } // namespace asio
 161 } // namespace boost
 162
 163 #include <boost/asio/detail/pop_options.hpp>
 164
 165 #endif // defined(BOOST_ASIO_HAS_EVENTFD)
 166
 167 #endif // BOOST_ASIO_DETAIL_IMPL_EVENTFD_SELECT_INTERRUPTER_IPP