Linux下Boost.Asio Proactor模式实现分析

namespace detail {
#if defined(BOOST_ASIO_HAS_IOCP)
  typedef class win_iocp_io_service io_service_impl;
  class win_iocp_overlapped_ptr;
#else
  typedef class task_io_service io_service_impl;
#endif
  class service_registry;
} // namespace detail

class io_service: private noncopyable
{
private:
  typedef detail::io_service_impl impl_type;
  ...
  // The service registry.
  boost::asio::detail::service_registry* service_registry_;

  // The implementation.
  impl_type& impl_;
public:
   ...
   // Run the io_service object's event processing loop.
   BOOST_ASIO_DECL std::size_t run();
   // Run the io_service object's event processing loop to execute ready handlers.
   BOOST_ASIO_DECL std::size_t poll();
 };

{
  boost::system::error_code ec;
  std::size_t s = impl_.run(ec);
  boost::asio::detail::throw_error(ec);
  return s;
}

class task_io_service : public boost::asio::detail::service_base<task_io_service>
{
public:
   ...
   typedef task_io_service_operation operation;
  // Run the event loop until interrupted or no more work.
  BOOST_ASIO_DECL std::size_t run(boost::system::error_code& ec);
private:
   ...
  // The task to be run by this service.
  reactor* task_;
  // The count of unfinished work.
  atomic_count outstanding_work_;
  // The queue of handlers that are ready to be delivered.
  op_queue<operation> op_queue_;
}

#if defined(BOOST_ASIO_WINDOWS_RUNTIME)
typedef class null_reactor reactor;
#elif defined(BOOST_ASIO_HAS_IOCP)
typedef class select_reactor reactor;
#elif defined(BOOST_ASIO_HAS_EPOLL)
typedef class epoll_reactor reactor;
#elif defined(BOOST_ASIO_HAS_KQUEUE)
typedef class kqueue_reactor reactor;
#elif defined(BOOST_ASIO_HAS_DEV_POLL)
typedef class dev_poll_reactor reactor;
#else
typedef class select_reactor reactor;
#endif

#include <iostream>
#include <string>
#include <boost/asio.hpp>
int main()
{
std::string output;
#if defined(BOOST_ASIO_HAS_IOCP)
  output = "iocp" ;
#elif defined(BOOST_ASIO_HAS_EPOLL)
  output = "epoll" ;
#elif defined(BOOST_ASIO_HAS_KQUEUE)
  output = "kqueue" ;
#elif defined(BOOST_ASIO_HAS_DEV_POLL)
  output = "/dev/poll" ;
#else
  output = "select" ;
#endif
    std::cout << output << std::endl;
}

#include <boost/asio.hpp>   
#include <boost/thread.hpp>   
#include <iostream>   

void handler1(const boost::system::error_code &ec)   
{   
    std::cout <<  boost::this_thread::get_id() << " handler1." << std::endl;
    //sleep(3);
}   

void handler2(const boost::system::error_code &ec)   
{   
    std::cout <<  boost::this_thread::get_id() << " handler2." << std::endl; 
    sleep(3);
}   

boost::asio::io_service io_service;   

void run()   
{   
    io_service.run();   
}   

int main()
{   
    boost::asio::deadline_timer timer1(io_service, boost::posix_time::seconds(2));   
    timer1.async_wait(handler1);   
    boost::asio::deadline_timer timer2(io_service, boost::posix_time::seconds(2));   
    timer2.async_wait(handler2);   
    boost::thread thread1(run);   
    boost::thread thread2(run);   
    thread1.join();   
    thread2.join();   
}

std::size_t task_io_service::run(boost::system::error_code& ec)
{
 ... 
    mutex::scoped_lock lock(mutex_); 
    std::size_t n = 0; 
    for (; do_run_one(lock, this_thread, ec); lock.lock()) 
    if (n != (std::numeric_limits<std::size_t>::max)())
        ++n; 
    return n;
}

std::size_t task_io_service::do_run_one(mutex::scoped_lock& lock,
    task_io_service::thread_info& this_thread,
    const boost::system::error_code& ec)
{
  while (!stopped_)
  {
    if (!op_queue_.empty())
    {
      // Prepare to execute first handler from queue.
      operation* o = op_queue_.front();
      op_queue_.pop();
      bool more_handlers = (!op_queue_.empty());

      if (o == &task_operation_)
      {
       ...
        task_->run(!more_handlers, this_thread.private_op_queue);
      }
      else
      {
     ...

        // Complete the operation. May throw an exception. Deletes the object.
        o->complete(*this, ec, task_result);
        return 1;
      }
    }
    else
    {
      // Nothing to run right now, so just wait for work to do.
      this_thread.next = first_idle_thread_;
      first_idle_thread_ = &this_thread;
      this_thread.wakeup_event->clear(lock);
      this_thread.wakeup_event->wait(lock);
    }
  }
  return 0;
}

void epoll_reactor::run(bool block, op_queue<operation>& ops)
{ 
    ... 
    // Block on the epoll descriptor. 
    epoll_event events[128]; 
    int num_events = epoll_wait(epoll_fd_, events, 128, timeout); 
    ...
   descriptor_state* descriptor_data = static_cast<descriptor_state*>(ptr); 
   descriptor_data->set_ready_events(events[i].events);  
   ops.push(descriptor_data);
}

class epoll_reactor : public boost::asio::detail::service_base<epoll_reactor>
{
  ...
private:
  ...
  BOOST_ASIO_DECL static int do_epoll_create();
  ...
  // The epoll file descriptor.
  int epoll_fd_;
  // The io_service implementation used to post completions.
  io_service_impl& io_service_;
  ...
 
 };

class tcp
{
public:
  /// The type of a TCP endpoint.
  typedef basic_endpoint<tcp> endpoint;

  /// Construct to represent the IPv4 TCP protocol.
  static tcp v4()
  {
    return tcp(BOOST_ASIO_OS_DEF(AF_INET));
  }
...
  /// The TCP socket type.
  typedef basic_stream_socket<tcp> socket;

  /// The TCP acceptor type.
  typedef basic_socket_acceptor<tcp> acceptor;

  /// The TCP resolver type.
  typedef basic_resolver<tcp> resolver;

#if !defined(BOOST_ASIO_NO_IOSTREAM)
  /// The TCP iostream type.
  typedef basic_socket_iostream<tcp> iostream;
#endif // !defined(BOOST_ASIO_NO_IOSTREAM)
...
private:
  // Construct with a specific family.
  explicit tcp(int protocol_family)
    : family_(protocol_family)
  {
  }

  int family_;
};

template <typename MutableBufferSequence, typename ReadHandler>
  BOOST_ASIO_INITFN_RESULT_TYPE(ReadHandler,
      void (boost::system::error_code, std::size_t))
  async_receive(const MutableBufferSequence& buffers,
      socket_base::message_flags flags,
      BOOST_ASIO_MOVE_ARG(ReadHandler) handler)
  {
    // If you get an error on the following line it means that your handler does
    // not meet the documented type requirements for a ReadHandler.
    BOOST_ASIO_READ_HANDLER_CHECK(ReadHandler, handler) type_check;

    return this->get_service().async_receive(this->get_implementation(),
        buffers, flags, BOOST_ASIO_MOVE_CAST(ReadHandler)(handler));
  }

class stream_socket_service
#if defined(GENERATING_DOCUMENTATION)
  : public boost::asio::io_service::service
#else
  : public boost::asio::detail::service_base<stream_socket_service<Protocol> >
#endif
{
public:
#if defined(GENERATING_DOCUMENTATION)
  /// The unique service identifier.
  static boost::asio::io_service::id id;
#endif

  /// The protocol type.
  typedef Protocol protocol_type;

  /// The endpoint type.
  typedef typename Protocol::endpoint endpoint_type;

private:
  // The type of the platform-specific implementation.
#if defined(BOOST_ASIO_WINDOWS_RUNTIME)
  typedef detail::winrt_ssocket_service<Protocol> service_impl_type;
#elif defined(BOOST_ASIO_HAS_IOCP)
  typedef detail::win_iocp_socket_service<Protocol> service_impl_type;
#else
  typedef detail::reactive_socket_service<Protocol> service_impl_type;
#endif

}

class reactive_socket_service_base
{
public:
  // The native type of a socket.
  typedef socket_type native_handle_type;

  // The implementation type of the socket.
  struct base_implementation_type
  {
    // The native socket representation.
    socket_type socket_;

    // The current state of the socket.
    socket_ops::state_type state_;

    // Per-descriptor data used by the reactor.
    reactor::per_descriptor_data reactor_data_;
  };
protected:
  // The selector that performs event demultiplexing for the service.
  reactor& reactor_;
}

// Start an asynchronous receive. The buffer for the data being received
  // must be valid for the lifetime of the asynchronous operation.
  template <typename MutableBufferSequence, typename Handler>
  void async_receive(base_implementation_type& impl,
      const MutableBufferSequence& buffers,
      socket_base::message_flags flags, Handler& handler)
  {
    bool is_continuation =
      boost_asio_handler_cont_helpers::is_continuation(handler);

    // Allocate and construct an operation to wrap the handler.
    typedef reactive_socket_recv_op<MutableBufferSequence, Handler> op;
    typename op::ptr p = { boost::asio::detail::addressof(handler),
      boost_asio_handler_alloc_helpers::allocate(
        sizeof(op), handler), 0 };
    p.p = new (p.v) op(impl.socket_, impl.state_, buffers, flags, handler);

    BOOST_ASIO_HANDLER_CREATION((p.p, "socket", &impl, "async_receive"));

    start_op(impl,
        (flags & socket_base::message_out_of_band)
          ? reactor::except_op : reactor::read_op,
        p.p, is_continuation,
        (flags & socket_base::message_out_of_band) == 0,
        ((impl.state_ & socket_ops::stream_oriented)
          && buffer_sequence_adapter<boost::asio::mutable_buffer,
            MutableBufferSequence>::all_empty(buffers)));
    p.v = p.p = 0;
  }