//
// epoll_reactor.hpp
// ~~~~~~~~~~~~~~~~~
//
// Copyright (c) 2003-2006 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_EPOLL_REACTOR_HPP
#define BOOST_ASIO_DETAIL_EPOLL_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/epoll_reactor_fwd.hpp>

#if defined(BOOST_ASIO_HAS_EPOLL)

#include <boost/asio/detail/push_options.hpp>
#include <cstddef>
#include <vector>
#include <sys/epoll.h>
#include <boost/config.hpp>
#include <boost/date_time/posix_time/posix_time_types.hpp>
#include <boost/throw_exception.hpp>
#include <boost/asio/detail/pop_options.hpp>

#include <boost/asio/io_service.hpp>
#include <boost/asio/system_exception.hpp>
#include <boost/asio/detail/bind_handler.hpp>
#include <boost/asio/detail/hash_map.hpp>
#include <boost/asio/detail/mutex.hpp>
#include <boost/asio/detail/task_io_service.hpp>
#include <boost/asio/detail/thread.hpp>
#include <boost/asio/detail/reactor_op_queue.hpp>
#include <boost/asio/detail/reactor_timer_queue.hpp>
#include <boost/asio/detail/select_interrupter.hpp>
#include <boost/asio/detail/signal_blocker.hpp>
#include <boost/asio/detail/socket_types.hpp>

namespace boost {
namespace asio {
namespace detail {

template <bool Own_Thread>
class epoll_reactor
  : public boost::asio::io_service::service
{
public:
  // Constructor.
  epoll_reactor(boost::asio::io_service& io_service)
    : boost::asio::io_service::service(io_service),
      mutex_(),
      epoll_fd_(do_epoll_create()),
      wait_in_progress_(false),
      interrupter_(),
      read_op_queue_(),
      write_op_queue_(),
      except_op_queue_(),
      pending_cancellations_(),
      stop_thread_(false),
      thread_(0),
      shutdown_(false)
  {
    // Start the reactor's internal thread only if needed.
    if (Own_Thread)
    {
      boost::asio::detail::signal_blocker sb;
      thread_ = new boost::asio::detail::thread(
          bind_handler(&epoll_reactor::call_run_thread, this));
    }

    // Add the interrupter's descriptor to epoll.
    epoll_event ev = { 0, { 0 } };
    ev.events = EPOLLIN | EPOLLERR;
    ev.data.fd = interrupter_.read_descriptor();
    epoll_ctl(epoll_fd_, EPOLL_CTL_ADD, interrupter_.read_descriptor(), &ev);
  }

  // Destructor.
  ~epoll_reactor()
  {
    shutdown_service();
    close(epoll_fd_);
  }

  // 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();
    timer_queue_.destroy_timers();
  }

  // Register a socket with the reactor. Returns 0 on success, system error
  // code on failure.
  int register_descriptor(socket_type descriptor)
  {
    // No need to lock according to epoll documentation.

    epoll_event ev = { 0, { 0 } };
    ev.events = 0;
    ev.data.fd = descriptor;
    int result = epoll_ctl(epoll_fd_, EPOLL_CTL_ADD, descriptor, &ev);
    if (result != 0)
      return errno;
    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, Handler handler)
  {
    boost::asio::detail::mutex::scoped_lock lock(mutex_);

    if (shutdown_)
      return;

    if (!read_op_queue_.has_operation(descriptor))
      if (handler(0))
        return;

    if (read_op_queue_.enqueue_operation(descriptor, handler))
    {
      epoll_event ev = { 0, { 0 } };
      ev.events = EPOLLIN | EPOLLERR | EPOLLHUP;
      if (write_op_queue_.has_operation(descriptor))
        ev.events |= EPOLLOUT;
      if (except_op_queue_.has_operation(descriptor))
        ev.events |= EPOLLPRI;
      ev.data.fd = descriptor;

      int result = epoll_ctl(epoll_fd_, EPOLL_CTL_MOD, descriptor, &ev);
      if (result != 0)
      {
        int error = errno;
        read_op_queue_.dispatch_all_operations(descriptor, error);
      }
    }
  }

  // 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, Handler handler)
  {
    boost::asio::detail::mutex::scoped_lock lock(mutex_);

    if (shutdown_)
      return;

    if (!write_op_queue_.has_operation(descriptor))
      if (handler(0))
        return;

    if (write_op_queue_.enqueue_operation(descriptor, handler))
    {
      epoll_event ev = { 0, { 0 } };
      ev.events = EPOLLOUT | EPOLLERR | EPOLLHUP;
      if (read_op_queue_.has_operation(descriptor))
        ev.events |= EPOLLIN;
      if (except_op_queue_.has_operation(descriptor))
        ev.events |= EPOLLPRI;
      ev.data.fd = descriptor;

      int result = epoll_ctl(epoll_fd_, EPOLL_CTL_MOD, descriptor, &ev);
      if (result != 0)
      {
        int error = errno;
        write_op_queue_.dispatch_all_operations(descriptor, error);
      }
    }
  }

  // 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, Handler handler)
  {
    boost::asio::detail::mutex::scoped_lock lock(mutex_);

    if (shutdown_)
      return;

    if (except_op_queue_.enqueue_operation(descriptor, handler))
    {
      epoll_event ev = { 0, { 0 } };
      ev.events = EPOLLPRI | EPOLLERR | EPOLLHUP;
      if (read_op_queue_.has_operation(descriptor))
        ev.events |= EPOLLIN;
      if (write_op_queue_.has_operation(descriptor))
        ev.events |= EPOLLOUT;
      ev.data.fd = descriptor;

      int result = epoll_ctl(epoll_fd_, EPOLL_CTL_MOD, descriptor, &ev);
      if (result != 0)
      {
        int error = errno;
        except_op_queue_.dispatch_all_operations(descriptor, error);
      }
    }
  }

  // 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.
  template <typename Handler>
  void start_write_and_except_ops(socket_type descriptor, Handler handler)
  {
    boost::asio::detail::mutex::scoped_lock lock(mutex_);

    if (shutdown_)
      return;

    bool need_mod = write_op_queue_.enqueue_operation(descriptor, handler);
    need_mod = except_op_queue_.enqueue_operation(descriptor, handler)
      && need_mod;
    if (need_mod)
    {
      epoll_event ev = { 0, { 0 } };
      ev.events = EPOLLOUT | EPOLLPRI | EPOLLERR | EPOLLHUP;
      if (read_op_queue_.has_operation(descriptor))
        ev.events |= EPOLLIN;
      ev.data.fd = descriptor;

      int result = epoll_ctl(epoll_fd_, EPOLL_CTL_MOD, descriptor, &ev);
      if (result != 0)
      {
        int error = errno;
        write_op_queue_.dispatch_all_operations(descriptor, error);
        except_op_queue_.dispatch_all_operations(descriptor, error);
      }
    }
  }

  // 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)
  {
    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
  // epoll_reactor's mutex, and so should only be used from within a reactor
  // handler.
  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)
  {
    boost::asio::detail::mutex::scoped_lock lock(mutex_);

    // Remove the descriptor from epoll.
    epoll_event ev = { 0, { 0 } };
    epoll_ctl(epoll_fd_, EPOLL_CTL_DEL, descriptor, &ev);

    // Cancel any outstanding operations associated with the descriptor.
    cancel_ops_unlocked(descriptor);
  }

  // Schedule a timer to expire at the specified absolute time. The handler
  // object will be invoked when the timer expires.
  template <typename Handler>
  void schedule_timer(const boost::posix_time::ptime& 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.
  std::size_t cancel_timer(void* token)
  {
    boost::asio::detail::mutex::scoped_lock lock(mutex_);
    return timer_queue_.cancel_timer(token);
  }

private:
  friend class task_io_service<epoll_reactor<Own_Thread> >;

  // Run epoll 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_.dispatch_cancellations();
    write_op_queue_.dispatch_cancellations();
    except_op_queue_.dispatch_cancellations();

    // Check if the thread is supposed to stop.
    if (stop_thread_)
    {
      // Clean up operations. We must not hold the lock since the operations may
      // make calls back into this reactor.
      lock.unlock();
      read_op_queue_.cleanup_operations();
      write_op_queue_.cleanup_operations();
      except_op_queue_.cleanup_operations();
      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() && timer_queue_.empty())
    {
      // Clean up operations. We must not hold the lock since the operations may
      // make calls back into this reactor.
      lock.unlock();
      read_op_queue_.cleanup_operations();
      write_op_queue_.cleanup_operations();
      except_op_queue_.cleanup_operations();
      return;
    }

    int timeout = block ? get_timeout() : 0;
    wait_in_progress_ = true;
    lock.unlock();

    // Block on the epoll descriptor.
    epoll_event events[128];
    int num_events = epoll_wait(epoll_fd_, events, 128, timeout);

    lock.lock();
    wait_in_progress_ = false;

    // Block signals while dispatching operations.
    boost::asio::detail::signal_blocker sb;

    // Dispatch the waiting events.
    for (int i = 0; i < num_events; ++i)
    {
      int descriptor = events[i].data.fd;
      if (descriptor == interrupter_.read_descriptor())
      {
        interrupter_.reset();
      }
      else
      {
        if (events[i].events & (EPOLLERR | EPOLLHUP))
        {
          except_op_queue_.dispatch_all_operations(descriptor, 0);
          read_op_queue_.dispatch_all_operations(descriptor, 0);
          write_op_queue_.dispatch_all_operations(descriptor, 0);

          epoll_event ev = { 0, { 0 } };
          ev.events = 0;
          ev.data.fd = descriptor;
          epoll_ctl(epoll_fd_, EPOLL_CTL_MOD, descriptor, &ev);
        }
        else
        {
          bool more_reads = false;
          bool more_writes = false;
          bool more_except = false;

          // Exception operations must be processed first to ensure that any
          // out-of-band data is read before normal data.
          if (events[i].events & EPOLLPRI)
            more_except = except_op_queue_.dispatch_operation(descriptor, 0);
          else
            more_except = except_op_queue_.has_operation(descriptor);

          if (events[i].events & EPOLLIN)
            more_reads = read_op_queue_.dispatch_operation(descriptor, 0);
          else
            more_reads = read_op_queue_.has_operation(descriptor);

          if (events[i].events & EPOLLOUT)
            more_writes = write_op_queue_.dispatch_operation(descriptor, 0);
          else
            more_writes = write_op_queue_.has_operation(descriptor);

          epoll_event ev = { 0, { 0 } };
          ev.events = EPOLLERR | EPOLLHUP;
          if (more_reads)
            ev.events |= EPOLLIN;
          if (more_writes)
            ev.events |= EPOLLOUT;
          if (more_except)
            ev.events |= EPOLLPRI;
          ev.data.fd = descriptor;
          int result = epoll_ctl(epoll_fd_, EPOLL_CTL_MOD, descriptor, &ev);
          if (result != 0)
          {
            int error = errno;
            read_op_queue_.dispatch_all_operations(descriptor, error);
            write_op_queue_.dispatch_all_operations(descriptor, error);
            except_op_queue_.dispatch_all_operations(descriptor, error);
          }
        }
      }
    }
    read_op_queue_.dispatch_cancellations();
    write_op_queue_.dispatch_cancellations();
    except_op_queue_.dispatch_cancellations();
    timer_queue_.dispatch_timers(
        boost::posix_time::microsec_clock::universal_time());

    // Issue any pending cancellations.
    for (size_t i = 0; i < pending_cancellations_.size(); ++i)
      cancel_ops_unlocked(pending_cancellations_[i]);
    pending_cancellations_.clear();

    // Clean up operations. We must not hold the lock since the operations may
    // make calls back into this reactor.
    lock.unlock();
    read_op_queue_.cleanup_operations();
    write_op_queue_.cleanup_operations();
    except_op_queue_.cleanup_operations();
  }

  // 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(epoll_reactor* reactor)
  {
    reactor->run_thread();
  }

  // Interrupt the select loop.
  void interrupt()
  {
    interrupter_.interrupt();
  }

  // The hint to pass to epoll_create to size its data structures.
  enum { epoll_size = 20000 };

  // Create the epoll file descriptor. Throws an exception if the descriptor
  // cannot be created.
  static int do_epoll_create()
  {
    int fd = epoll_create(epoll_size);
    if (fd == -1)
    {
      system_exception e("epoll", errno);
      boost::throw_exception(e);
    }
    return fd;
  }

  // Get the timeout value for the epoll_wait call. The timeout value is
  // returned as a number of milliseconds. A return value of -1 indicates
  // that epoll_wait should block indefinitely.
  int get_timeout()
  {
    if (timer_queue_.empty())
      return -1;

    boost::posix_time::ptime now
      = boost::posix_time::microsec_clock::universal_time();
    boost::posix_time::ptime earliest_timer;
    timer_queue_.get_earliest_time(earliest_timer);
    if (now < earliest_timer)
    {
      boost::posix_time::time_duration timeout = earliest_timer - now;
      const int max_timeout_in_seconds = INT_MAX / 1000;
      if (max_timeout_in_seconds < timeout.total_seconds())
        return max_timeout_in_seconds * 1000;
      else
        return timeout.total_milliseconds();
    }
    else
    {
      return 0;
    }
  }

  // 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 epoll_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();
  }

  // Mutex to protect access to internal data.
  boost::asio::detail::mutex mutex_;

  // The epoll file descriptor.
  int epoll_fd_;

  // Whether the epoll_wait call is currently in progress
  bool wait_in_progress_;

  // The interrupter is used to break a blocking epoll_wait 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 except operations.
  reactor_op_queue<socket_type> except_op_queue_;

  // The queue of timers.
  reactor_timer_queue<boost::posix_time::ptime> timer_queue_;

  // 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

#endif // defined(BOOST_ASIO_HAS_EPOLL)

#include <boost/asio/detail/pop_options.hpp>

#endif // BOOST_ASIO_DETAIL_EPOLL_REACTOR_HPP