boost/asio/detail/select_reactor.hpp
//
// select_reactor.hpp
// ~~~~~~~~~~~~~~~~~~
//
// Copyright (c) 2003-2008 Christopher M. Kohlhoff (chris at kohlhoff 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_SELECT_REACTOR_HPP
#define BOOST_ASIO_DETAIL_SELECT_REACTOR_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/socket_types.hpp> // Must come before posix_time.
#include <boost/asio/detail/push_options.hpp>
#include <cstddef>
#include <boost/config.hpp>
#include <boost/date_time/posix_time/posix_time_types.hpp>
#include <boost/shared_ptr.hpp>
#include <vector>
#include <boost/asio/detail/pop_options.hpp>
#include <boost/asio/io_service.hpp>
#include <boost/asio/detail/bind_handler.hpp>
#include <boost/asio/detail/fd_set_adapter.hpp>
#include <boost/asio/detail/mutex.hpp>
#include <boost/asio/detail/noncopyable.hpp>
#include <boost/asio/detail/reactor_op_queue.hpp>
#include <boost/asio/detail/select_interrupter.hpp>
#include <boost/asio/detail/select_reactor_fwd.hpp>
#include <boost/asio/detail/service_base.hpp>
#include <boost/asio/detail/signal_blocker.hpp>
#include <boost/asio/detail/socket_ops.hpp>
#include <boost/asio/detail/socket_types.hpp>
#include <boost/asio/detail/task_io_service.hpp>
#include <boost/asio/detail/thread.hpp>
#include <boost/asio/detail/timer_queue.hpp>
namespace boost {
namespace asio {
namespace detail {
template <bool Own_Thread>
class select_reactor
: public boost::asio::detail::service_base<select_reactor<Own_Thread> >
{
public:
// Per-descriptor data.
struct per_descriptor_data
{
};
// Constructor.
select_reactor(boost::asio::io_service& io_service)
: boost::asio::detail::service_base<
select_reactor<Own_Thread> >(io_service),
mutex_(),
select_in_progress_(false),
interrupter_(),
read_op_queue_(),
write_op_queue_(),
except_op_queue_(),
pending_cancellations_(),
stop_thread_(false),
thread_(0),
shutdown_(false)
{
if (Own_Thread)
{
boost::asio::detail::signal_blocker sb;
thread_ = new boost::asio::detail::thread(
bind_handler(&select_reactor::call_run_thread, this));
}
}
// Destructor.
~select_reactor()
{
shutdown_service();
}
// Destroy all user-defined handler objects owned by the service.
void shutdown_service()
{
boost::asio::detail::mutex::scoped_lock lock(mutex_);
shutdown_ = true;
stop_thread_ = true;
lock.unlock();
if (thread_)
{
interrupter_.interrupt();
thread_->join();
delete thread_;
thread_ = 0;
}
read_op_queue_.destroy_operations();
write_op_queue_.destroy_operations();
except_op_queue_.destroy_operations();
for (std::size_t i = 0; i < timer_queues_.size(); ++i)
timer_queues_[i]->destroy_timers();
timer_queues_.clear();
}
// Initialise the task, but only if the reactor is not in its own thread.
void init_task()
{
if (!Own_Thread)
{
typedef task_io_service<select_reactor<Own_Thread> > task_io_service_type;
use_service<task_io_service_type>(this->get_io_service()).init_task();
}
}
// Register a socket with the reactor. Returns 0 on success, system error
// code on failure.
int register_descriptor(socket_type, per_descriptor_data&)
{
return 0;
}
// Start a new read operation. The handler object will be invoked when the
// given descriptor is ready to be read, or an error has occurred.
template <typename Handler>
void start_read_op(socket_type descriptor, per_descriptor_data&,
Handler handler, bool /*allow_speculative_read*/ = true)
{
boost::asio::detail::mutex::scoped_lock lock(mutex_);
if (!shutdown_)
if (read_op_queue_.enqueue_operation(descriptor, handler))
interrupter_.interrupt();
}
// Start a new write operation. The handler object will be invoked when the
// given descriptor is ready to be written, or an error has occurred.
template <typename Handler>
void start_write_op(socket_type descriptor, per_descriptor_data&,
Handler handler, bool /*allow_speculative_write*/ = true)
{
boost::asio::detail::mutex::scoped_lock lock(mutex_);
if (!shutdown_)
if (write_op_queue_.enqueue_operation(descriptor, handler))
interrupter_.interrupt();
}
// Start a new exception operation. The handler object will be invoked when
// the given descriptor has exception information, or an error has occurred.
template <typename Handler>
void start_except_op(socket_type descriptor,
per_descriptor_data&, Handler handler)
{
boost::asio::detail::mutex::scoped_lock lock(mutex_);
if (!shutdown_)
if (except_op_queue_.enqueue_operation(descriptor, handler))
interrupter_.interrupt();
}
// Wrapper for connect handlers to enable the handler object to be placed
// in both the write and the except operation queues, but ensure that only
// one of the handlers is called.
template <typename Handler>
class connect_handler_wrapper
{
public:
connect_handler_wrapper(socket_type descriptor,
boost::shared_ptr<bool> completed,
select_reactor<Own_Thread>& reactor, Handler handler)
: descriptor_(descriptor),
completed_(completed),
reactor_(reactor),
handler_(handler)
{
}
bool perform(boost::system::error_code& ec,
std::size_t& bytes_transferred)
{
// Check whether one of the handlers has already been called. If it has,
// then we don't want to do anything in this handler.
if (*completed_)
{
completed_.reset(); // Indicate that this handler should not complete.
return true;
}
// Cancel the other reactor operation for the connection.
*completed_ = true;
reactor_.enqueue_cancel_ops_unlocked(descriptor_);
// Call the contained handler.
return handler_.perform(ec, bytes_transferred);
}
void complete(const boost::system::error_code& ec,
std::size_t bytes_transferred)
{
if (completed_.get())
handler_.complete(ec, bytes_transferred);
}
private:
socket_type descriptor_;
boost::shared_ptr<bool> completed_;
select_reactor<Own_Thread>& reactor_;
Handler handler_;
};
// Start new write and exception operations. The handler object will be
// invoked when the given descriptor is ready for writing or has exception
// information available, or an error has occurred. The handler will be called
// only once.
template <typename Handler>
void start_connect_op(socket_type descriptor,
per_descriptor_data&, Handler handler)
{
boost::asio::detail::mutex::scoped_lock lock(mutex_);
if (!shutdown_)
{
boost::shared_ptr<bool> completed(new bool(false));
connect_handler_wrapper<Handler> wrapped_handler(
descriptor, completed, *this, handler);
bool interrupt = write_op_queue_.enqueue_operation(
descriptor, wrapped_handler);
interrupt = except_op_queue_.enqueue_operation(
descriptor, wrapped_handler) || interrupt;
if (interrupt)
interrupter_.interrupt();
}
}
// Cancel all operations associated with the given descriptor. The
// handlers associated with the descriptor will be invoked with the
// operation_aborted error.
void cancel_ops(socket_type descriptor, per_descriptor_data&)
{
boost::asio::detail::mutex::scoped_lock lock(mutex_);
cancel_ops_unlocked(descriptor);
}
// Enqueue cancellation of all operations associated with the given
// descriptor. The handlers associated with the descriptor will be invoked
// with the operation_aborted error. This function does not acquire the
// select_reactor's mutex, and so should only be used when the reactor lock is
// already held.
void enqueue_cancel_ops_unlocked(socket_type descriptor)
{
pending_cancellations_.push_back(descriptor);
}
// Cancel any operations that are running against the descriptor and remove
// its registration from the reactor.
void close_descriptor(socket_type descriptor, per_descriptor_data&)
{
boost::asio::detail::mutex::scoped_lock lock(mutex_);
cancel_ops_unlocked(descriptor);
}
// Add a new timer queue to the reactor.
template <typename Time_Traits>
void add_timer_queue(timer_queue<Time_Traits>& timer_queue)
{
boost::asio::detail::mutex::scoped_lock lock(mutex_);
timer_queues_.push_back(&timer_queue);
}
// Remove a timer queue from the reactor.
template <typename Time_Traits>
void remove_timer_queue(timer_queue<Time_Traits>& timer_queue)
{
boost::asio::detail::mutex::scoped_lock lock(mutex_);
for (std::size_t i = 0; i < timer_queues_.size(); ++i)
{
if (timer_queues_[i] == &timer_queue)
{
timer_queues_.erase(timer_queues_.begin() + i);
return;
}
}
}
// Schedule a timer in the given timer queue to expire at the specified
// absolute time. The handler object will be invoked when the timer expires.
template <typename Time_Traits, typename Handler>
void schedule_timer(timer_queue<Time_Traits>& timer_queue,
const typename Time_Traits::time_type& time, Handler handler, void* token)
{
boost::asio::detail::mutex::scoped_lock lock(mutex_);
if (!shutdown_)
if (timer_queue.enqueue_timer(time, handler, token))
interrupter_.interrupt();
}
// Cancel the timer associated with the given token. Returns the number of
// handlers that have been posted or dispatched.
template <typename Time_Traits>
std::size_t cancel_timer(timer_queue<Time_Traits>& timer_queue, void* token)
{
boost::asio::detail::mutex::scoped_lock lock(mutex_);
std::size_t n = timer_queue.cancel_timer(token);
if (n > 0)
interrupter_.interrupt();
return n;
}
private:
friend class task_io_service<select_reactor<Own_Thread> >;
// Run select once until interrupted or events are ready to be dispatched.
void run(bool block)
{
boost::asio::detail::mutex::scoped_lock lock(mutex_);
// Dispatch any operation cancellations that were made while the select
// loop was not running.
read_op_queue_.perform_cancellations();
write_op_queue_.perform_cancellations();
except_op_queue_.perform_cancellations();
for (std::size_t i = 0; i < timer_queues_.size(); ++i)
timer_queues_[i]->dispatch_cancellations();
// Check if the thread is supposed to stop.
if (stop_thread_)
{
complete_operations_and_timers(lock);
return;
}
// We can return immediately if there's no work to do and the reactor is
// not supposed to block.
if (!block && read_op_queue_.empty() && write_op_queue_.empty()
&& except_op_queue_.empty() && all_timer_queues_are_empty())
{
complete_operations_and_timers(lock);
return;
}
// Set up the descriptor sets.
fd_set_adapter read_fds;
read_fds.set(interrupter_.read_descriptor());
read_op_queue_.get_descriptors(read_fds);
fd_set_adapter write_fds;
write_op_queue_.get_descriptors(write_fds);
fd_set_adapter except_fds;
except_op_queue_.get_descriptors(except_fds);
socket_type max_fd = read_fds.max_descriptor();
if (write_fds.max_descriptor() > max_fd)
max_fd = write_fds.max_descriptor();
if (except_fds.max_descriptor() > max_fd)
max_fd = except_fds.max_descriptor();
// Block on the select call without holding the lock so that new
// operations can be started while the call is executing.
timeval tv_buf = { 0, 0 };
timeval* tv = block ? get_timeout(tv_buf) : &tv_buf;
select_in_progress_ = true;
lock.unlock();
boost::system::error_code ec;
int retval = socket_ops::select(static_cast<int>(max_fd + 1),
read_fds, write_fds, except_fds, tv, ec);
lock.lock();
select_in_progress_ = false;
// Block signals while dispatching operations.
boost::asio::detail::signal_blocker sb;
// Reset the interrupter.
if (retval > 0 && read_fds.is_set(interrupter_.read_descriptor()))
interrupter_.reset();
// Dispatch all ready operations.
if (retval > 0)
{
// Exception operations must be processed first to ensure that any
// out-of-band data is read before normal data.
except_op_queue_.perform_operations_for_descriptors(
except_fds, boost::system::error_code());
read_op_queue_.perform_operations_for_descriptors(
read_fds, boost::system::error_code());
write_op_queue_.perform_operations_for_descriptors(
write_fds, boost::system::error_code());
except_op_queue_.perform_cancellations();
read_op_queue_.perform_cancellations();
write_op_queue_.perform_cancellations();
}
for (std::size_t i = 0; i < timer_queues_.size(); ++i)
{
timer_queues_[i]->dispatch_timers();
timer_queues_[i]->dispatch_cancellations();
}
// Issue any pending cancellations.
for (size_t i = 0; i < pending_cancellations_.size(); ++i)
cancel_ops_unlocked(pending_cancellations_[i]);
pending_cancellations_.clear();
complete_operations_and_timers(lock);
}
// Run the select loop in the thread.
void run_thread()
{
boost::asio::detail::mutex::scoped_lock lock(mutex_);
while (!stop_thread_)
{
lock.unlock();
run(true);
lock.lock();
}
}
// Entry point for the select loop thread.
static void call_run_thread(select_reactor* reactor)
{
reactor->run_thread();
}
// Interrupt the select loop.
void interrupt()
{
interrupter_.interrupt();
}
// Check if all timer queues are empty.
bool all_timer_queues_are_empty() const
{
for (std::size_t i = 0; i < timer_queues_.size(); ++i)
if (!timer_queues_[i]->empty())
return false;
return true;
}
// Get the timeout value for the select call.
timeval* get_timeout(timeval& tv)
{
if (all_timer_queues_are_empty())
return 0;
// By default we will wait no longer than 5 minutes. This will ensure that
// any changes to the system clock are detected after no longer than this.
boost::posix_time::time_duration minimum_wait_duration
= boost::posix_time::minutes(5);
for (std::size_t i = 0; i < timer_queues_.size(); ++i)
{
boost::posix_time::time_duration wait_duration
= timer_queues_[i]->wait_duration();
if (wait_duration < minimum_wait_duration)
minimum_wait_duration = wait_duration;
}
if (minimum_wait_duration > boost::posix_time::time_duration())
{
tv.tv_sec = minimum_wait_duration.total_seconds();
tv.tv_usec = minimum_wait_duration.total_microseconds() % 1000000;
}
else
{
tv.tv_sec = 0;
tv.tv_usec = 0;
}
return &tv;
}
// Cancel all operations associated with the given descriptor. The do_cancel
// function of the handler objects will be invoked. This function does not
// acquire the select_reactor's mutex.
void cancel_ops_unlocked(socket_type descriptor)
{
bool interrupt = read_op_queue_.cancel_operations(descriptor);
interrupt = write_op_queue_.cancel_operations(descriptor) || interrupt;
interrupt = except_op_queue_.cancel_operations(descriptor) || interrupt;
if (interrupt)
interrupter_.interrupt();
}
// Clean up operations and timers. We must not hold the lock since the
// destructors may make calls back into this reactor. We make a copy of the
// vector of timer queues since the original may be modified while the lock
// is not held.
void complete_operations_and_timers(
boost::asio::detail::mutex::scoped_lock& lock)
{
timer_queues_for_cleanup_ = timer_queues_;
lock.unlock();
read_op_queue_.complete_operations();
write_op_queue_.complete_operations();
except_op_queue_.complete_operations();
for (std::size_t i = 0; i < timer_queues_for_cleanup_.size(); ++i)
timer_queues_for_cleanup_[i]->complete_timers();
}
// Mutex to protect access to internal data.
boost::asio::detail::mutex mutex_;
// Whether the select loop is currently running or not.
bool select_in_progress_;
// The interrupter is used to break a blocking select call.
select_interrupter interrupter_;
// The queue of read operations.
reactor_op_queue<socket_type> read_op_queue_;
// The queue of write operations.
reactor_op_queue<socket_type> write_op_queue_;
// The queue of exception operations.
reactor_op_queue<socket_type> except_op_queue_;
// The timer queues.
std::vector<timer_queue_base*> timer_queues_;
// A copy of the timer queues, used when cleaning up timers. The copy is
// stored as a class data member to avoid unnecessary memory allocation.
std::vector<timer_queue_base*> timer_queues_for_cleanup_;
// The descriptors that are pending cancellation.
std::vector<socket_type> pending_cancellations_;
// Does the reactor loop thread need to stop.
bool stop_thread_;
// The thread that is running the reactor loop.
boost::asio::detail::thread* thread_;
// Whether the service has been shut down.
bool shutdown_;
};
} // namespace detail
} // namespace asio
} // namespace boost
#include <boost/asio/detail/pop_options.hpp>
#endif // BOOST_ASIO_DETAIL_SELECT_REACTOR_HPP