asio/include/asio/detail/win_iocp_socket_service_base.hpp - third_party/asio - Git at Google

 //
 // detail/win_iocp_socket_service_base.hpp
 // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 //
 // Copyright (c) 2003-2015 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 ASIO_DETAIL_WIN_IOCP_SOCKET_SERVICE_BASE_HPP
 #define ASIO_DETAIL_WIN_IOCP_SOCKET_SERVICE_BASE_HPP

 #if defined(_MSC_VER) && (_MSC_VER >= 1200)
 # pragma once
 #endif // defined(_MSC_VER) && (_MSC_VER >= 1200)

 #include "asio/detail/config.hpp"

 #if defined(ASIO_HAS_IOCP)

 #include "asio/error.hpp"
 #include "asio/io_context.hpp"
 #include "asio/socket_base.hpp"
 #include "asio/detail/bind_handler.hpp"
 #include "asio/detail/buffer_sequence_adapter.hpp"
 #include "asio/detail/fenced_block.hpp"
 #include "asio/detail/handler_alloc_helpers.hpp"
 #include "asio/detail/handler_invoke_helpers.hpp"
 #include "asio/detail/memory.hpp"
 #include "asio/detail/mutex.hpp"
 #include "asio/detail/operation.hpp"
 #include "asio/detail/reactor_op.hpp"
 #include "asio/detail/select_reactor.hpp"
 #include "asio/detail/socket_holder.hpp"
 #include "asio/detail/socket_ops.hpp"
 #include "asio/detail/socket_types.hpp"
 #include "asio/detail/win_iocp_io_context.hpp"
 #include "asio/detail/win_iocp_null_buffers_op.hpp"
 #include "asio/detail/win_iocp_socket_connect_op.hpp"
 #include "asio/detail/win_iocp_socket_send_op.hpp"
 #include "asio/detail/win_iocp_socket_recv_op.hpp"
 #include "asio/detail/win_iocp_socket_recvmsg_op.hpp"
 #include "asio/detail/win_iocp_wait_op.hpp"

 #include "asio/detail/push_options.hpp"

 namespace asio {
 namespace detail {

 class win_iocp_socket_service_base
 {
 public:
   // 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_;

     // We use a shared pointer as a cancellation token here to work around the
     // broken Windows support for cancellation. MSDN says that when you call
     // closesocket any outstanding WSARecv or WSASend operations will complete
     // with the error ERROR_OPERATION_ABORTED. In practice they complete with
     // ERROR_NETNAME_DELETED, which means you can't tell the difference between
     // a local cancellation and the socket being hard-closed by the peer.
     socket_ops::shared_cancel_token_type cancel_token_;

     // Per-descriptor data used by the reactor.
     select_reactor::per_descriptor_data reactor_data_;

 #if defined(ASIO_ENABLE_CANCELIO)
     // The ID of the thread from which it is safe to cancel asynchronous
     // operations. 0 means no asynchronous operations have been started yet.
     // ~0 means asynchronous operations have been started from more than one
     // thread, and cancellation is not supported for the socket.
     DWORD safe_cancellation_thread_id_;
 #endif // defined(ASIO_ENABLE_CANCELIO)

     // Pointers to adjacent socket implementations in linked list.
     base_implementation_type* next_;
     base_implementation_type* prev_;
   };

   // Constructor.
   ASIO_DECL win_iocp_socket_service_base(
       asio::io_context& io_context);

   // Destroy all user-defined handler objects owned by the service.
   ASIO_DECL void shutdown();

   // Construct a new socket implementation.
   ASIO_DECL void construct(base_implementation_type& impl);

   // Move-construct a new socket implementation.
   ASIO_DECL void base_move_construct(base_implementation_type& impl,
       base_implementation_type& other_impl);

   // Move-assign from another socket implementation.
   ASIO_DECL void base_move_assign(base_implementation_type& impl,
       win_iocp_socket_service_base& other_service,
       base_implementation_type& other_impl);

   // Destroy a socket implementation.
   ASIO_DECL void destroy(base_implementation_type& impl);

   // Determine whether the socket is open.
   bool is_open(const base_implementation_type& impl) const
   {
     return impl.socket_ != invalid_socket;
   }

   // Destroy a socket implementation.
   ASIO_DECL asio::error_code close(
       base_implementation_type& impl, asio::error_code& ec);

   // Cancel all operations associated with the socket.
   ASIO_DECL asio::error_code cancel(
       base_implementation_type& impl, asio::error_code& ec);

   // Determine whether the socket is at the out-of-band data mark.
   bool at_mark(const base_implementation_type& impl,
       asio::error_code& ec) const
   {
     return socket_ops::sockatmark(impl.socket_, ec);
   }

   // Determine the number of bytes available for reading.
   std::size_t available(const base_implementation_type& impl,
       asio::error_code& ec) const
   {
     return socket_ops::available(impl.socket_, ec);
   }

   // Place the socket into the state where it will listen for new connections.
   asio::error_code listen(base_implementation_type& impl,
       int backlog, asio::error_code& ec)
   {
     socket_ops::listen(impl.socket_, backlog, ec);
     return ec;
   }

   // Perform an IO control command on the socket.
   template <typename IO_Control_Command>
   asio::error_code io_control(base_implementation_type& impl,
       IO_Control_Command& command, asio::error_code& ec)
   {
     socket_ops::ioctl(impl.socket_, impl.state_, command.name(),
         static_cast<ioctl_arg_type*>(command.data()), ec);
     return ec;
   }

   // Gets the non-blocking mode of the socket.
   bool non_blocking(const base_implementation_type& impl) const
   {
     return (impl.state_ & socket_ops::user_set_non_blocking) != 0;
   }

   // Sets the non-blocking mode of the socket.
   asio::error_code non_blocking(base_implementation_type& impl,
       bool mode, asio::error_code& ec)
   {
     socket_ops::set_user_non_blocking(impl.socket_, impl.state_, mode, ec);
     return ec;
   }

   // Gets the non-blocking mode of the native socket implementation.
   bool native_non_blocking(const base_implementation_type& impl) const
   {
     return (impl.state_ & socket_ops::internal_non_blocking) != 0;
   }

   // Sets the non-blocking mode of the native socket implementation.
   asio::error_code native_non_blocking(base_implementation_type& impl,
       bool mode, asio::error_code& ec)
   {
     socket_ops::set_internal_non_blocking(impl.socket_, impl.state_, mode, ec);
     return ec;
   }

   // Disable sends or receives on the socket.
   asio::error_code shutdown(base_implementation_type& impl,
       socket_base::shutdown_type what, asio::error_code& ec)
   {
     socket_ops::shutdown(impl.socket_, what, ec);
     return ec;
   }

   // Wait for the socket to become ready to read, ready to write, or to have
   // pending error conditions.
   asio::error_code wait(base_implementation_type& impl,
       socket_base::wait_type w, asio::error_code& ec)
   {
     switch (w)
     {
     case socket_base::wait_read:
       socket_ops::poll_read(impl.socket_, impl.state_, ec);
       break;
     case socket_base::wait_write:
       socket_ops::poll_write(impl.socket_, impl.state_, ec);
       break;
     case socket_base::wait_error:
       socket_ops::poll_error(impl.socket_, impl.state_, ec);
       break;
     default:
       ec = asio::error::invalid_argument;
       break;
     }

     return ec;
   }

   // Asynchronously wait for the socket to become ready to read, ready to
   // write, or to have pending error conditions.
   template <typename Handler>
   void async_wait(base_implementation_type& impl,
       socket_base::wait_type w, Handler& handler)
   {
     bool is_continuation =
       asio_handler_cont_helpers::is_continuation(handler);

     // Allocate and construct an operation to wrap the handler.
     typedef win_iocp_wait_op<Handler> op;
     typename op::ptr p = { asio::detail::addressof(handler),
       op::ptr::allocate(handler), 0 };
     p.p = new (p.v) op(impl.cancel_token_, handler);

     ASIO_HANDLER_CREATION((io_context_, *p.p, "socket",
           &impl, impl.socket_, "async_wait"));

     switch (w)
     {
       case socket_base::wait_read:
         start_null_buffers_receive_op(impl, 0, p.p);
         break;
       case socket_base::wait_write:
         start_reactor_op(impl, select_reactor::write_op, p.p);
         break;
       case socket_base::wait_error:
         start_reactor_op(impl, select_reactor::except_op, p.p);
         break;
       default:
         p.p->ec_ = asio::error::invalid_argument;
         iocp_service_.post_immediate_completion(p.p, is_continuation);
         break;
     }

     p.v = p.p = 0;
   }

   // Send the given data to the peer. Returns the number of bytes sent.
   template <typename ConstBufferSequence>
   size_t send(base_implementation_type& impl,
       const ConstBufferSequence& buffers,
       socket_base::message_flags flags, asio::error_code& ec)
   {
     buffer_sequence_adapter<asio::const_buffer,
         ConstBufferSequence> bufs(buffers);

     return socket_ops::sync_send(impl.socket_, impl.state_,
         bufs.buffers(), bufs.count(), flags, bufs.all_empty(), ec);
   }

   // Wait until data can be sent without blocking.
   size_t send(base_implementation_type& impl, const null_buffers&,
       socket_base::message_flags, asio::error_code& ec)
   {
     // Wait for socket to become ready.
     socket_ops::poll_write(impl.socket_, impl.state_, ec);

     return 0;
   }

   // Start an asynchronous send. The data being sent must be valid for the
   // lifetime of the asynchronous operation.
   template <typename ConstBufferSequence, typename Handler>
   void async_send(base_implementation_type& impl,
       const ConstBufferSequence& buffers,
       socket_base::message_flags flags, Handler& handler)
   {
     // Allocate and construct an operation to wrap the handler.
     typedef win_iocp_socket_send_op<ConstBufferSequence, Handler> op;
     typename op::ptr p = { asio::detail::addressof(handler),
       op::ptr::allocate(handler), 0 };
     p.p = new (p.v) op(impl.cancel_token_, buffers, handler);

     ASIO_HANDLER_CREATION((io_context_, *p.p, "socket",
           &impl, impl.socket_, "async_send"));

     buffer_sequence_adapter<asio::const_buffer,
         ConstBufferSequence> bufs(buffers);

     start_send_op(impl, bufs.buffers(), bufs.count(), flags,
         (impl.state_ & socket_ops::stream_oriented) != 0 && bufs.all_empty(),
         p.p);
     p.v = p.p = 0;
   }

   // Start an asynchronous wait until data can be sent without blocking.
   template <typename Handler>
   void async_send(base_implementation_type& impl, const null_buffers&,
       socket_base::message_flags, Handler& handler)
   {
     // Allocate and construct an operation to wrap the handler.
     typedef win_iocp_null_buffers_op<Handler> op;
     typename op::ptr p = { asio::detail::addressof(handler),
       op::ptr::allocate(handler), 0 };
     p.p = new (p.v) op(impl.cancel_token_, handler);

     ASIO_HANDLER_CREATION((io_context_, *p.p, "socket",
           &impl, impl.socket_, "async_send(null_buffers)"));

     start_reactor_op(impl, select_reactor::write_op, p.p);
     p.v = p.p = 0;
   }

   // Receive some data from the peer. Returns the number of bytes received.
   template <typename MutableBufferSequence>
   size_t receive(base_implementation_type& impl,
       const MutableBufferSequence& buffers,
       socket_base::message_flags flags, asio::error_code& ec)
   {
     buffer_sequence_adapter<asio::mutable_buffer,
         MutableBufferSequence> bufs(buffers);

     return socket_ops::sync_recv(impl.socket_, impl.state_,
         bufs.buffers(), bufs.count(), flags, bufs.all_empty(), ec);
   }

   // Wait until data can be received without blocking.
   size_t receive(base_implementation_type& impl, const null_buffers&,
       socket_base::message_flags, asio::error_code& ec)
   {
     // Wait for socket to become ready.
     socket_ops::poll_read(impl.socket_, impl.state_, ec);

     return 0;
   }

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

     ASIO_HANDLER_CREATION((io_context_, *p.p, "socket",
           &impl, impl.socket_, "async_receive"));

     buffer_sequence_adapter<asio::mutable_buffer,
         MutableBufferSequence> bufs(buffers);

     start_receive_op(impl, bufs.buffers(), bufs.count(), flags,
         (impl.state_ & socket_ops::stream_oriented) != 0 && bufs.all_empty(),
         p.p);
     p.v = p.p = 0;
   }

   // Wait until data can be received without blocking.
   template <typename Handler>
   void async_receive(base_implementation_type& impl, const null_buffers&,
       socket_base::message_flags flags, Handler& handler)
   {
     // Allocate and construct an operation to wrap the handler.
     typedef win_iocp_null_buffers_op<Handler> op;
     typename op::ptr p = { asio::detail::addressof(handler),
       op::ptr::allocate(handler), 0 };
     p.p = new (p.v) op(impl.cancel_token_, handler);

     ASIO_HANDLER_CREATION((io_context_, *p.p, "socket",
           &impl, impl.socket_, "async_receive(null_buffers)"));

     start_null_buffers_receive_op(impl, flags, p.p);
     p.v = p.p = 0;
   }

   // Receive some data with associated flags. Returns the number of bytes
   // received.
   template <typename MutableBufferSequence>
   size_t receive_with_flags(base_implementation_type& impl,
       const MutableBufferSequence& buffers,
       socket_base::message_flags in_flags,
       socket_base::message_flags& out_flags, asio::error_code& ec)
   {
     buffer_sequence_adapter<asio::mutable_buffer,
         MutableBufferSequence> bufs(buffers);

     return socket_ops::sync_recvmsg(impl.socket_, impl.state_,
         bufs.buffers(), bufs.count(), in_flags, out_flags, ec);
   }

   // Wait until data can be received without blocking.
   size_t receive_with_flags(base_implementation_type& impl,
       const null_buffers&, socket_base::message_flags,
       socket_base::message_flags& out_flags, asio::error_code& ec)
   {
     // Wait for socket to become ready.
     socket_ops::poll_read(impl.socket_, impl.state_, ec);

     // Clear out_flags, since we cannot give it any other sensible value when
     // performing a null_buffers operation.
     out_flags = 0;

     return 0;
   }

   // 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_with_flags(base_implementation_type& impl,
       const MutableBufferSequence& buffers, socket_base::message_flags in_flags,
       socket_base::message_flags& out_flags, Handler& handler)
   {
     // Allocate and construct an operation to wrap the handler.
     typedef win_iocp_socket_recvmsg_op<MutableBufferSequence, Handler> op;
     typename op::ptr p = { asio::detail::addressof(handler),
       op::ptr::allocate(handler), 0 };
     p.p = new (p.v) op(impl.cancel_token_, buffers, out_flags, handler);

     ASIO_HANDLER_CREATION((io_context_, *p.p, "socket",
           &impl, impl.socket_, "async_receive_with_flags"));

     buffer_sequence_adapter<asio::mutable_buffer,
         MutableBufferSequence> bufs(buffers);

     start_receive_op(impl, bufs.buffers(), bufs.count(), in_flags, false, p.p);
     p.v = p.p = 0;
   }

   // Wait until data can be received without blocking.
   template <typename Handler>
   void async_receive_with_flags(base_implementation_type& impl,
       const null_buffers&, socket_base::message_flags in_flags,
       socket_base::message_flags& out_flags, Handler& handler)
   {
     // Allocate and construct an operation to wrap the handler.
     typedef win_iocp_null_buffers_op<Handler> op;
     typename op::ptr p = { asio::detail::addressof(handler),
       op::ptr::allocate(handler), 0 };
     p.p = new (p.v) op(impl.cancel_token_, handler);

     ASIO_HANDLER_CREATION((io_context_, *p.p, "socket",
           &impl, impl.socket_, "async_receive_with_flags(null_buffers)"));

     // Reset out_flags since it can be given no sensible value at this time.
     out_flags = 0;

     start_null_buffers_receive_op(impl, in_flags, p.p);
     p.v = p.p = 0;
   }

   // Helper function to restart an asynchronous accept operation.
   ASIO_DECL void restart_accept_op(socket_type s,
       socket_holder& new_socket, int family, int type, int protocol,
       void* output_buffer, DWORD address_length, operation* op);

 protected:
   // Open a new socket implementation.
   ASIO_DECL asio::error_code do_open(
       base_implementation_type& impl, int family, int type,
       int protocol, asio::error_code& ec);

   // Assign a native socket to a socket implementation.
   ASIO_DECL asio::error_code do_assign(
       base_implementation_type& impl, int type,
       socket_type native_socket, asio::error_code& ec);

   // Helper function to start an asynchronous send operation.
   ASIO_DECL void start_send_op(base_implementation_type& impl,
       WSABUF* buffers, std::size_t buffer_count,
       socket_base::message_flags flags, bool noop, operation* op);

   // Helper function to start an asynchronous send_to operation.
   ASIO_DECL void start_send_to_op(base_implementation_type& impl,
       WSABUF* buffers, std::size_t buffer_count,
       const socket_addr_type* addr, int addrlen,
       socket_base::message_flags flags, operation* op);

   // Helper function to start an asynchronous receive operation.
   ASIO_DECL void start_receive_op(base_implementation_type& impl,
       WSABUF* buffers, std::size_t buffer_count,
       socket_base::message_flags flags, bool noop, operation* op);

   // Helper function to start an asynchronous null_buffers receive operation.
   ASIO_DECL void start_null_buffers_receive_op(
       base_implementation_type& impl,
       socket_base::message_flags flags, reactor_op* op);

   // Helper function to start an asynchronous receive_from operation.
   ASIO_DECL void start_receive_from_op(base_implementation_type& impl,
       WSABUF* buffers, std::size_t buffer_count, socket_addr_type* addr,
       socket_base::message_flags flags, int* addrlen, operation* op);

   // Helper function to start an asynchronous accept operation.
   ASIO_DECL void start_accept_op(base_implementation_type& impl,
       bool peer_is_open, socket_holder& new_socket, int family, int type,
       int protocol, void* output_buffer, DWORD address_length, operation* op);

   // Start an asynchronous read or write operation using the reactor.
   ASIO_DECL void start_reactor_op(base_implementation_type& impl,
       int op_type, reactor_op* op);

   // Start the asynchronous connect operation using the reactor.
   ASIO_DECL void start_connect_op(base_implementation_type& impl,
       int family, int type, const socket_addr_type* remote_addr,
       std::size_t remote_addrlen, win_iocp_socket_connect_op_base* op);

   // Helper function to close a socket when the associated object is being
   // destroyed.
   ASIO_DECL void close_for_destruction(base_implementation_type& impl);

   // Update the ID of the thread from which cancellation is safe.
   ASIO_DECL void update_cancellation_thread_id(
       base_implementation_type& impl);

   // Helper function to get the reactor. If no reactor has been created yet, a
   // new one is obtained from the io_context and a pointer to it is cached in
   // this service.
   ASIO_DECL select_reactor& get_reactor();

   // The type of a ConnectEx function pointer, as old SDKs may not provide it.
   typedef BOOL (PASCAL *connect_ex_fn)(SOCKET,
       const socket_addr_type*, int, void*, DWORD, DWORD*, OVERLAPPED*);

   // Helper function to get the ConnectEx pointer. If no ConnectEx pointer has
   // been obtained yet, one is obtained using WSAIoctl and the pointer is
   // cached. Returns a null pointer if ConnectEx is not available.
   ASIO_DECL connect_ex_fn get_connect_ex(
       base_implementation_type& impl, int type);

   // Helper function to emulate InterlockedCompareExchangePointer functionality
   // for:
   // - very old Platform SDKs; and
   // - platform SDKs where MSVC's /Wp64 option causes spurious warnings.
   ASIO_DECL void* interlocked_compare_exchange_pointer(
       void** dest, void* exch, void* cmp);

   // Helper function to emulate InterlockedExchangePointer functionality for:
   // - very old Platform SDKs; and
   // - platform SDKs where MSVC's /Wp64 option causes spurious warnings.
   ASIO_DECL void* interlocked_exchange_pointer(void** dest, void* val);

   // The io_context used to obtain the reactor, if required.
   asio::io_context& io_context_;

   // The IOCP service used for running asynchronous operations and dispatching
   // handlers.
   win_iocp_io_context& iocp_service_;

   // The reactor used for performing connect operations. This object is created
   // only if needed.
   select_reactor* reactor_;

   // Pointer to ConnectEx implementation.
   void* connect_ex_;

   // Mutex to protect access to the linked list of implementations.
   asio::detail::mutex mutex_;

   // The head of a linked list of all implementations.
   base_implementation_type* impl_list_;
 };

 } // namespace detail
 } // namespace asio

 #include "asio/detail/pop_options.hpp"

 #if defined(ASIO_HEADER_ONLY)
 # include "asio/detail/impl/win_iocp_socket_service_base.ipp"
 #endif // defined(ASIO_HEADER_ONLY)

 #endif // defined(ASIO_HAS_IOCP)

 #endif // ASIO_DETAIL_WIN_IOCP_SOCKET_SERVICE_BASE_HPP
	//
	// detail/win_iocp_socket_service_base.hpp
	// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
	//
	// Copyright (c) 2003-2015 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 ASIO_DETAIL_WIN_IOCP_SOCKET_SERVICE_BASE_HPP
	#define ASIO_DETAIL_WIN_IOCP_SOCKET_SERVICE_BASE_HPP

	#if defined(_MSC_VER) && (_MSC_VER >= 1200)
	# pragma once
	#endif // defined(_MSC_VER) && (_MSC_VER >= 1200)

	#include "asio/detail/config.hpp"

	#if defined(ASIO_HAS_IOCP)

	#include "asio/error.hpp"
	#include "asio/io_context.hpp"
	#include "asio/socket_base.hpp"
	#include "asio/detail/bind_handler.hpp"
	#include "asio/detail/buffer_sequence_adapter.hpp"
	#include "asio/detail/fenced_block.hpp"
	#include "asio/detail/handler_alloc_helpers.hpp"
	#include "asio/detail/handler_invoke_helpers.hpp"
	#include "asio/detail/memory.hpp"
	#include "asio/detail/mutex.hpp"
	#include "asio/detail/operation.hpp"
	#include "asio/detail/reactor_op.hpp"
	#include "asio/detail/select_reactor.hpp"
	#include "asio/detail/socket_holder.hpp"
	#include "asio/detail/socket_ops.hpp"
	#include "asio/detail/socket_types.hpp"
	#include "asio/detail/win_iocp_io_context.hpp"
	#include "asio/detail/win_iocp_null_buffers_op.hpp"
	#include "asio/detail/win_iocp_socket_connect_op.hpp"
	#include "asio/detail/win_iocp_socket_send_op.hpp"
	#include "asio/detail/win_iocp_socket_recv_op.hpp"
	#include "asio/detail/win_iocp_socket_recvmsg_op.hpp"
	#include "asio/detail/win_iocp_wait_op.hpp"

	#include "asio/detail/push_options.hpp"

	namespace asio {
	namespace detail {

	class win_iocp_socket_service_base
	{
	public:
	// 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_;

	// We use a shared pointer as a cancellation token here to work around the
	// broken Windows support for cancellation. MSDN says that when you call
	// closesocket any outstanding WSARecv or WSASend operations will complete
	// with the error ERROR_OPERATION_ABORTED. In practice they complete with
	// ERROR_NETNAME_DELETED, which means you can't tell the difference between
	// a local cancellation and the socket being hard-closed by the peer.
	socket_ops::shared_cancel_token_type cancel_token_;

	// Per-descriptor data used by the reactor.
	select_reactor::per_descriptor_data reactor_data_;

	#if defined(ASIO_ENABLE_CANCELIO)
	// The ID of the thread from which it is safe to cancel asynchronous
	// operations. 0 means no asynchronous operations have been started yet.
	// ~0 means asynchronous operations have been started from more than one
	// thread, and cancellation is not supported for the socket.
	DWORD safe_cancellation_thread_id_;
	#endif // defined(ASIO_ENABLE_CANCELIO)

	// Pointers to adjacent socket implementations in linked list.
	base_implementation_type* next_;
	base_implementation_type* prev_;
	};

	// Constructor.
	ASIO_DECL win_iocp_socket_service_base(
	asio::io_context& io_context);

	// Destroy all user-defined handler objects owned by the service.
	ASIO_DECL void shutdown();

	// Construct a new socket implementation.
	ASIO_DECL void construct(base_implementation_type& impl);

	// Move-construct a new socket implementation.
	ASIO_DECL void base_move_construct(base_implementation_type& impl,
	base_implementation_type& other_impl);

	// Move-assign from another socket implementation.
	ASIO_DECL void base_move_assign(base_implementation_type& impl,
	win_iocp_socket_service_base& other_service,
	base_implementation_type& other_impl);

	// Destroy a socket implementation.
	ASIO_DECL void destroy(base_implementation_type& impl);

	// Determine whether the socket is open.
	bool is_open(const base_implementation_type& impl) const
	{
	return impl.socket_ != invalid_socket;
	}

	// Destroy a socket implementation.
	ASIO_DECL asio::error_code close(
	base_implementation_type& impl, asio::error_code& ec);

	// Cancel all operations associated with the socket.
	ASIO_DECL asio::error_code cancel(
	base_implementation_type& impl, asio::error_code& ec);

	// Determine whether the socket is at the out-of-band data mark.
	bool at_mark(const base_implementation_type& impl,
	asio::error_code& ec) const
	{
	return socket_ops::sockatmark(impl.socket_, ec);
	}

	// Determine the number of bytes available for reading.
	std::size_t available(const base_implementation_type& impl,
	asio::error_code& ec) const
	{
	return socket_ops::available(impl.socket_, ec);
	}

	// Place the socket into the state where it will listen for new connections.
	asio::error_code listen(base_implementation_type& impl,
	int backlog, asio::error_code& ec)
	{
	socket_ops::listen(impl.socket_, backlog, ec);
	return ec;
	}

	// Perform an IO control command on the socket.
	template <typename IO_Control_Command>
	asio::error_code io_control(base_implementation_type& impl,
	IO_Control_Command& command, asio::error_code& ec)
	{
	socket_ops::ioctl(impl.socket_, impl.state_, command.name(),
	static_cast<ioctl_arg_type*>(command.data()), ec);
	return ec;
	}

	// Gets the non-blocking mode of the socket.
	bool non_blocking(const base_implementation_type& impl) const
	{
	return (impl.state_ & socket_ops::user_set_non_blocking) != 0;
	}

	// Sets the non-blocking mode of the socket.
	asio::error_code non_blocking(base_implementation_type& impl,
	bool mode, asio::error_code& ec)
	{
	socket_ops::set_user_non_blocking(impl.socket_, impl.state_, mode, ec);
	return ec;
	}

	// Gets the non-blocking mode of the native socket implementation.
	bool native_non_blocking(const base_implementation_type& impl) const
	{
	return (impl.state_ & socket_ops::internal_non_blocking) != 0;
	}

	// Sets the non-blocking mode of the native socket implementation.
	asio::error_code native_non_blocking(base_implementation_type& impl,
	bool mode, asio::error_code& ec)
	{
	socket_ops::set_internal_non_blocking(impl.socket_, impl.state_, mode, ec);
	return ec;
	}

	// Disable sends or receives on the socket.
	asio::error_code shutdown(base_implementation_type& impl,
	socket_base::shutdown_type what, asio::error_code& ec)
	{
	socket_ops::shutdown(impl.socket_, what, ec);
	return ec;
	}

	// Wait for the socket to become ready to read, ready to write, or to have
	// pending error conditions.
	asio::error_code wait(base_implementation_type& impl,
	socket_base::wait_type w, asio::error_code& ec)
	{
	switch (w)
	{
	case socket_base::wait_read:
	socket_ops::poll_read(impl.socket_, impl.state_, ec);
	break;
	case socket_base::wait_write:
	socket_ops::poll_write(impl.socket_, impl.state_, ec);
	break;
	case socket_base::wait_error:
	socket_ops::poll_error(impl.socket_, impl.state_, ec);
	break;
	default:
	ec = asio::error::invalid_argument;
	break;
	}

	return ec;
	}

	// Asynchronously wait for the socket to become ready to read, ready to
	// write, or to have pending error conditions.
	template <typename Handler>
	void async_wait(base_implementation_type& impl,
	socket_base::wait_type w, Handler& handler)
	{
	bool is_continuation =
	asio_handler_cont_helpers::is_continuation(handler);

	// Allocate and construct an operation to wrap the handler.
	typedef win_iocp_wait_op<Handler> op;
	typename op::ptr p = { asio::detail::addressof(handler),
	op::ptr::allocate(handler), 0 };
	p.p = new (p.v) op(impl.cancel_token_, handler);

	ASIO_HANDLER_CREATION((io_context_, *p.p, "socket",
	&impl, impl.socket_, "async_wait"));

	switch (w)
	{
	case socket_base::wait_read:
	start_null_buffers_receive_op(impl, 0, p.p);
	break;
	case socket_base::wait_write:
	start_reactor_op(impl, select_reactor::write_op, p.p);
	break;
	case socket_base::wait_error:
	start_reactor_op(impl, select_reactor::except_op, p.p);
	break;
	default:
	p.p->ec_ = asio::error::invalid_argument;
	iocp_service_.post_immediate_completion(p.p, is_continuation);
	break;
	}

	p.v = p.p = 0;
	}

	// Send the given data to the peer. Returns the number of bytes sent.
	template <typename ConstBufferSequence>
	size_t send(base_implementation_type& impl,
	const ConstBufferSequence& buffers,
	socket_base::message_flags flags, asio::error_code& ec)
	{
	buffer_sequence_adapter<asio::const_buffer,
	ConstBufferSequence> bufs(buffers);

	return socket_ops::sync_send(impl.socket_, impl.state_,
	bufs.buffers(), bufs.count(), flags, bufs.all_empty(), ec);
	}

	// Wait until data can be sent without blocking.
	size_t send(base_implementation_type& impl, const null_buffers&,
	socket_base::message_flags, asio::error_code& ec)
	{
	// Wait for socket to become ready.
	socket_ops::poll_write(impl.socket_, impl.state_, ec);

	return 0;
	}

	// Start an asynchronous send. The data being sent must be valid for the
	// lifetime of the asynchronous operation.
	template <typename ConstBufferSequence, typename Handler>
	void async_send(base_implementation_type& impl,
	const ConstBufferSequence& buffers,
	socket_base::message_flags flags, Handler& handler)
	{
	// Allocate and construct an operation to wrap the handler.
	typedef win_iocp_socket_send_op<ConstBufferSequence, Handler> op;
	typename op::ptr p = { asio::detail::addressof(handler),
	op::ptr::allocate(handler), 0 };
	p.p = new (p.v) op(impl.cancel_token_, buffers, handler);

	ASIO_HANDLER_CREATION((io_context_, *p.p, "socket",
	&impl, impl.socket_, "async_send"));

	buffer_sequence_adapter<asio::const_buffer,
	ConstBufferSequence> bufs(buffers);

	start_send_op(impl, bufs.buffers(), bufs.count(), flags,
	(impl.state_ & socket_ops::stream_oriented) != 0 && bufs.all_empty(),
	p.p);
	p.v = p.p = 0;
	}

	// Start an asynchronous wait until data can be sent without blocking.
	template <typename Handler>
	void async_send(base_implementation_type& impl, const null_buffers&,
	socket_base::message_flags, Handler& handler)
	{
	// Allocate and construct an operation to wrap the handler.
	typedef win_iocp_null_buffers_op<Handler> op;
	typename op::ptr p = { asio::detail::addressof(handler),
	op::ptr::allocate(handler), 0 };
	p.p = new (p.v) op(impl.cancel_token_, handler);

	ASIO_HANDLER_CREATION((io_context_, *p.p, "socket",
	&impl, impl.socket_, "async_send(null_buffers)"));

	start_reactor_op(impl, select_reactor::write_op, p.p);
	p.v = p.p = 0;
	}

	// Receive some data from the peer. Returns the number of bytes received.
	template <typename MutableBufferSequence>
	size_t receive(base_implementation_type& impl,
	const MutableBufferSequence& buffers,
	socket_base::message_flags flags, asio::error_code& ec)
	{
	buffer_sequence_adapter<asio::mutable_buffer,
	MutableBufferSequence> bufs(buffers);

	return socket_ops::sync_recv(impl.socket_, impl.state_,
	bufs.buffers(), bufs.count(), flags, bufs.all_empty(), ec);
	}

	// Wait until data can be received without blocking.
	size_t receive(base_implementation_type& impl, const null_buffers&,
	socket_base::message_flags, asio::error_code& ec)
	{
	// Wait for socket to become ready.
	socket_ops::poll_read(impl.socket_, impl.state_, ec);

	return 0;
	}

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

	ASIO_HANDLER_CREATION((io_context_, *p.p, "socket",
	&impl, impl.socket_, "async_receive"));

	buffer_sequence_adapter<asio::mutable_buffer,
	MutableBufferSequence> bufs(buffers);

	start_receive_op(impl, bufs.buffers(), bufs.count(), flags,
	(impl.state_ & socket_ops::stream_oriented) != 0 && bufs.all_empty(),
	p.p);
	p.v = p.p = 0;
	}

	// Wait until data can be received without blocking.
	template <typename Handler>
	void async_receive(base_implementation_type& impl, const null_buffers&,
	socket_base::message_flags flags, Handler& handler)
	{
	// Allocate and construct an operation to wrap the handler.
	typedef win_iocp_null_buffers_op<Handler> op;
	typename op::ptr p = { asio::detail::addressof(handler),
	op::ptr::allocate(handler), 0 };
	p.p = new (p.v) op(impl.cancel_token_, handler);

	ASIO_HANDLER_CREATION((io_context_, *p.p, "socket",
	&impl, impl.socket_, "async_receive(null_buffers)"));

	start_null_buffers_receive_op(impl, flags, p.p);
	p.v = p.p = 0;
	}

	// Receive some data with associated flags. Returns the number of bytes
	// received.
	template <typename MutableBufferSequence>
	size_t receive_with_flags(base_implementation_type& impl,
	const MutableBufferSequence& buffers,
	socket_base::message_flags in_flags,
	socket_base::message_flags& out_flags, asio::error_code& ec)
	{
	buffer_sequence_adapter<asio::mutable_buffer,
	MutableBufferSequence> bufs(buffers);

	return socket_ops::sync_recvmsg(impl.socket_, impl.state_,
	bufs.buffers(), bufs.count(), in_flags, out_flags, ec);
	}

	// Wait until data can be received without blocking.
	size_t receive_with_flags(base_implementation_type& impl,
	const null_buffers&, socket_base::message_flags,
	socket_base::message_flags& out_flags, asio::error_code& ec)
	{
	// Wait for socket to become ready.
	socket_ops::poll_read(impl.socket_, impl.state_, ec);

	// Clear out_flags, since we cannot give it any other sensible value when
	// performing a null_buffers operation.
	out_flags = 0;

	return 0;
	}

	// 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_with_flags(base_implementation_type& impl,
	const MutableBufferSequence& buffers, socket_base::message_flags in_flags,
	socket_base::message_flags& out_flags, Handler& handler)
	{
	// Allocate and construct an operation to wrap the handler.
	typedef win_iocp_socket_recvmsg_op<MutableBufferSequence, Handler> op;
	typename op::ptr p = { asio::detail::addressof(handler),
	op::ptr::allocate(handler), 0 };
	p.p = new (p.v) op(impl.cancel_token_, buffers, out_flags, handler);

	ASIO_HANDLER_CREATION((io_context_, *p.p, "socket",
	&impl, impl.socket_, "async_receive_with_flags"));

	buffer_sequence_adapter<asio::mutable_buffer,
	MutableBufferSequence> bufs(buffers);

	start_receive_op(impl, bufs.buffers(), bufs.count(), in_flags, false, p.p);
	p.v = p.p = 0;
	}

	// Wait until data can be received without blocking.
	template <typename Handler>
	void async_receive_with_flags(base_implementation_type& impl,
	const null_buffers&, socket_base::message_flags in_flags,
	socket_base::message_flags& out_flags, Handler& handler)
	{
	// Allocate and construct an operation to wrap the handler.
	typedef win_iocp_null_buffers_op<Handler> op;
	typename op::ptr p = { asio::detail::addressof(handler),
	op::ptr::allocate(handler), 0 };
	p.p = new (p.v) op(impl.cancel_token_, handler);

	ASIO_HANDLER_CREATION((io_context_, *p.p, "socket",
	&impl, impl.socket_, "async_receive_with_flags(null_buffers)"));

	// Reset out_flags since it can be given no sensible value at this time.
	out_flags = 0;

	start_null_buffers_receive_op(impl, in_flags, p.p);
	p.v = p.p = 0;
	}

	// Helper function to restart an asynchronous accept operation.
	ASIO_DECL void restart_accept_op(socket_type s,
	socket_holder& new_socket, int family, int type, int protocol,
	void* output_buffer, DWORD address_length, operation* op);

	protected:
	// Open a new socket implementation.
	ASIO_DECL asio::error_code do_open(
	base_implementation_type& impl, int family, int type,
	int protocol, asio::error_code& ec);

	// Assign a native socket to a socket implementation.
	ASIO_DECL asio::error_code do_assign(
	base_implementation_type& impl, int type,
	socket_type native_socket, asio::error_code& ec);

	// Helper function to start an asynchronous send operation.
	ASIO_DECL void start_send_op(base_implementation_type& impl,
	WSABUF* buffers, std::size_t buffer_count,
	socket_base::message_flags flags, bool noop, operation* op);

	// Helper function to start an asynchronous send_to operation.
	ASIO_DECL void start_send_to_op(base_implementation_type& impl,
	WSABUF* buffers, std::size_t buffer_count,
	const socket_addr_type* addr, int addrlen,
	socket_base::message_flags flags, operation* op);

	// Helper function to start an asynchronous receive operation.
	ASIO_DECL void start_receive_op(base_implementation_type& impl,
	WSABUF* buffers, std::size_t buffer_count,
	socket_base::message_flags flags, bool noop, operation* op);

	// Helper function to start an asynchronous null_buffers receive operation.
	ASIO_DECL void start_null_buffers_receive_op(
	base_implementation_type& impl,
	socket_base::message_flags flags, reactor_op* op);

	// Helper function to start an asynchronous receive_from operation.
	ASIO_DECL void start_receive_from_op(base_implementation_type& impl,
	WSABUF* buffers, std::size_t buffer_count, socket_addr_type* addr,
	socket_base::message_flags flags, int* addrlen, operation* op);

	// Helper function to start an asynchronous accept operation.
	ASIO_DECL void start_accept_op(base_implementation_type& impl,
	bool peer_is_open, socket_holder& new_socket, int family, int type,
	int protocol, void* output_buffer, DWORD address_length, operation* op);

	// Start an asynchronous read or write operation using the reactor.
	ASIO_DECL void start_reactor_op(base_implementation_type& impl,
	int op_type, reactor_op* op);

	// Start the asynchronous connect operation using the reactor.
	ASIO_DECL void start_connect_op(base_implementation_type& impl,
	int family, int type, const socket_addr_type* remote_addr,
	std::size_t remote_addrlen, win_iocp_socket_connect_op_base* op);

	// Helper function to close a socket when the associated object is being
	// destroyed.
	ASIO_DECL void close_for_destruction(base_implementation_type& impl);

	// Update the ID of the thread from which cancellation is safe.
	ASIO_DECL void update_cancellation_thread_id(
	base_implementation_type& impl);

	// Helper function to get the reactor. If no reactor has been created yet, a
	// new one is obtained from the io_context and a pointer to it is cached in
	// this service.
	ASIO_DECL select_reactor& get_reactor();

	// The type of a ConnectEx function pointer, as old SDKs may not provide it.
	typedef BOOL (PASCAL *connect_ex_fn)(SOCKET,
	const socket_addr_type, int, void, DWORD, DWORD, OVERLAPPED);

	// Helper function to get the ConnectEx pointer. If no ConnectEx pointer has
	// been obtained yet, one is obtained using WSAIoctl and the pointer is
	// cached. Returns a null pointer if ConnectEx is not available.
	ASIO_DECL connect_ex_fn get_connect_ex(
	base_implementation_type& impl, int type);

	// Helper function to emulate InterlockedCompareExchangePointer functionality
	// for:
	// - very old Platform SDKs; and
	// - platform SDKs where MSVC's /Wp64 option causes spurious warnings.
	ASIO_DECL void* interlocked_compare_exchange_pointer(
	void** dest, void* exch, void* cmp);

	// Helper function to emulate InterlockedExchangePointer functionality for:
	// - very old Platform SDKs; and
	// - platform SDKs where MSVC's /Wp64 option causes spurious warnings.
	ASIO_DECL void* interlocked_exchange_pointer(void** dest, void* val);

	// The io_context used to obtain the reactor, if required.
	asio::io_context& io_context_;

	// The IOCP service used for running asynchronous operations and dispatching
	// handlers.
	win_iocp_io_context& iocp_service_;

	// The reactor used for performing connect operations. This object is created
	// only if needed.
	select_reactor* reactor_;

	// Pointer to ConnectEx implementation.
	void* connect_ex_;

	// Mutex to protect access to the linked list of implementations.
	asio::detail::mutex mutex_;

	// The head of a linked list of all implementations.
	base_implementation_type* impl_list_;
	};

	} // namespace detail
	} // namespace asio

	#include "asio/detail/pop_options.hpp"

	#if defined(ASIO_HEADER_ONLY)
	# include "asio/detail/impl/win_iocp_socket_service_base.ipp"
	#endif // defined(ASIO_HEADER_ONLY)

	#endif // defined(ASIO_HAS_IOCP)

	#endif // ASIO_DETAIL_WIN_IOCP_SOCKET_SERVICE_BASE_HPP