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//
// eventfd_select_interrupter.hpp
// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
//
// Copyright (c) 2003-2010 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_EVENTFD_SELECT_INTERRUPTER_HPP
#define BOOST_ASIO_DETAIL_EVENTFD_SELECT_INTERRUPTER_HPP
#if defined(_MSC_VER) && (_MSC_VER >= 1200)
# pragma once
#endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
#include <boost/asio/detail/push_options.hpp>
#include <boost/asio/detail/push_options.hpp>
#include <boost/config.hpp>
#include <boost/throw_exception.hpp>
#include <boost/system/system_error.hpp>
#include <boost/asio/detail/pop_options.hpp>
#if defined(__linux__)
# if !defined(BOOST_ASIO_DISABLE_EVENTFD)
# include <linux/version.h>
# if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,22)
# define BOOST_ASIO_HAS_EVENTFD
# endif // LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,22)
# endif // !defined(BOOST_ASIO_DISABLE_EVENTFD)
#endif // defined(__linux__)
#if defined(BOOST_ASIO_HAS_EVENTFD)
#include <boost/asio/detail/push_options.hpp>
#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/pop_options.hpp>
#include <boost/asio/error.hpp>
#include <boost/asio/detail/socket_types.hpp>
namespace boost {
namespace asio {
namespace detail {
class eventfd_select_interrupter
{
public:
// Constructor.
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::system::system_error e(ec, "eventfd_select_interrupter");
boost::throw_exception(e);
}
}
}
// Destructor.
~eventfd_select_interrupter()
{
if (write_descriptor_ != -1 && write_descriptor_ != read_descriptor_)
::close(write_descriptor_);
if (read_descriptor_ != -1)
::close(read_descriptor_);
}
// Interrupt the select call.
void interrupt()
{
uint64_t counter(1UL);
int result = ::write(write_descriptor_, &counter, sizeof(uint64_t));
(void)result;
}
// Reset the select interrupt. Returns true if the call was interrupted.
bool 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;
}
}
}
// Get the read descriptor to be passed to select.
int read_descriptor() const
{
return read_descriptor_;
}
private:
// The read end of a connection used to interrupt the select call. This file
// descriptor is passed to select such that when it is time to stop, a single
// 64bit value will be written on the other end of the connection and this
// descriptor will become readable.
int read_descriptor_;
// The write end of a connection used to interrupt the select call. A single
// 64bit non-zero value may be written to this to wake up the select which is
// waiting for the other end to become readable. This descriptor will only
// differ from the read descriptor when a pipe is used.
int write_descriptor_;
};
} // namespace detail
} // namespace asio
} // namespace boost
#endif // defined(BOOST_ASIO_HAS_EVENTFD)
#include <boost/asio/detail/pop_options.hpp>
#endif // BOOST_ASIO_DETAIL_EVENTFD_SELECT_INTERRUPTER_HPP
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