text: //
  // detail/impl/eventfd_select_interrupter.ipp
  // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  //
  // Copyright (c) 2003-2011 Christopher M. Kohlhoff (chris at kohlhoff dot com)
  // Copyright (c) 2008 Roelof Naude (roelof.naude at gmail dot com)
  //
  // Distributed under the Boost Software License, Version 1.0. (See accompanying
  // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  //
  
  #ifndef BOOST_ASIO_DETAIL_IMPL_EVENTFD_SELECT_INTERRUPTER_IPP
  #define BOOST_ASIO_DETAIL_IMPL_EVENTFD_SELECT_INTERRUPTER_IPP
  
  #if defined(_MSC_VER) && (_MSC_VER >= 1200)
  # pragma once
  #endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
  
  #include <boost/asio/detail/config.hpp>
  
  #if defined(BOOST_ASIO_HAS_EVENTFD)
  
  #include <sys/stat.h>
  #include <sys/types.h>
  #include <fcntl.h>
  #if __GLIBC__ == 2 && __GLIBC_MINOR__ < 8
  # include <asm/unistd.h>
  #else // __GLIBC__ == 2 && __GLIBC_MINOR__ < 8
  # include <sys/eventfd.h>
  #endif // __GLIBC__ == 2 && __GLIBC_MINOR__ < 8
  #include <boost/asio/detail/eventfd_select_interrupter.hpp>
  #include <boost/asio/detail/throw_error.hpp>
  #include <boost/asio/error.hpp>
  
  #include <boost/asio/detail/push_options.hpp>
  
  namespace boost {
  namespace asio {
  namespace detail {
  
  eventfd_select_interrupter::eventfd_select_interrupter()
  {
  #if __GLIBC__ == 2 && __GLIBC_MINOR__ < 8
    write_descriptor_ = read_descriptor_ = syscall(__NR_eventfd, 0);
  #else // __GLIBC__ == 2 && __GLIBC_MINOR__ < 8
    write_descriptor_ = read_descriptor_ = ::eventfd(0, 0);
  #endif // __GLIBC__ == 2 && __GLIBC_MINOR__ < 8
    if (read_descriptor_ != -1)
    {
      ::fcntl(read_descriptor_, F_SETFL, O_NONBLOCK);
    }
    else
    {
      int pipe_fds[2];
      if (pipe(pipe_fds) == 0)
      {
        read_descriptor_ = pipe_fds[0];
        ::fcntl(read_descriptor_, F_SETFL, O_NONBLOCK);
        write_descriptor_ = pipe_fds[1];
        ::fcntl(write_descriptor_, F_SETFL, O_NONBLOCK);
      }
      else
      {
        boost::system::error_code ec(errno,
            boost::asio::error::get_system_category());
        boost::asio::detail::throw_error(ec, "eventfd_select_interrupter");
      }
    }
  }
  
  eventfd_select_interrupter::~eventfd_select_interrupter()
  {
    if (write_descriptor_ != -1 && write_descriptor_ != read_descriptor_)
      ::close(write_descriptor_);
    if (read_descriptor_ != -1)
      ::close(read_descriptor_);
  }
  
  void eventfd_select_interrupter::interrupt()
  {
    uint64_t counter(1UL);
    int result = ::write(write_descriptor_, &counter, sizeof(uint64_t));
    (void)result;
  }
  
  bool eventfd_select_interrupter::reset()
  {
    if (write_descriptor_ == read_descriptor_)
    {
      for (;;)
      {
        // Only perform one read. The kernel maintains an atomic counter.
        uint64_t counter(0);
        errno = 0;
        int bytes_read = ::read(read_descriptor_, &counter, sizeof(uint64_t));
        if (bytes_read < 0 && errno == EINTR)
          continue;
        bool was_interrupted = (bytes_read > 0);
        return was_interrupted;
      }
    }
    else
    {
      for (;;)
      {
        // Clear all data from the pipe.
        char data[1024];
        int bytes_read = ::read(read_descriptor_, data, sizeof(data));
        if (bytes_read < 0 && errno == EINTR)
          continue;
        bool was_interrupted = (bytes_read > 0);
        while (bytes_read == sizeof(data))
          bytes_read = ::read(read_descriptor_, data, sizeof(data));
        return was_interrupted;
      }
    }
  }
  
  } // namespace detail
  } // namespace asio
  } // namespace boost
  
  #include <boost/asio/detail/pop_options.hpp>
  
  #endif // defined(BOOST_ASIO_HAS_EVENTFD)
  
  #endif // BOOST_ASIO_DETAIL_IMPL_EVENTFD_SELECT_INTERRUPTER_IPP
  