async_accept(basic_socket<Protocol1, SocketService>& peer,
      ASIO_MOVE_ARG(AcceptHandler) handler,
      typename enable_if<is_convertible<Protocol, Protocol1>::value>::type* = 0)
  {
    // If you get an error on the following line it means that your handler does
    // not meet the documented type requirements for a AcceptHandler.
    ASIO_ACCEPT_HANDLER_CHECK(AcceptHandler, handler) type_check;

    return this->get_service().async_accept(this->get_implementation(),
        peer, static_cast<endpoint_type*>(0),
        ASIO_MOVE_CAST(AcceptHandler)(handler));
  }

     * @code void handler(
     *   const asio::error_code& error, // Result of operation.
     *
     *   std::size_t bytes_transferred           // Number of bytes written from the
     *                                           // buffers. If an error occurred,
     *                                           // this will be less than the sum
     *                                           // of the buffer sizes.
     * ); @endcode
     * Regardless of whether the asynchronous operation completes immediately or
     * not, the handler will not be invoked from within this function. Invocation of
     * the handler will be performed in a manner equivalent to using
     * asio::io_service::post().
     */
    template <typename AsyncWriteStream, typename Allocator, typename WriteHandler>
    ASIO_INITFN_RESULT_TYPE( WriteHandler, void( asio::error_code, std::size_t ) )
    async_write( AsyncWriteStream& s, basic_streambuf<Allocator>& b, ASIO_MOVE_ARG( WriteHandler ) handler );

    /// Start an asynchronous operation to write a certain amount of data to a
    /// stream.
    /**
     * This function is used to asynchronously write a certain number of bytes of
     * data to a stream. The function call always returns immediately. The
     * asynchronous operation will continue until one of the following conditions
     * is true:
     *
     * @li All of the data in the supplied basic_streambuf has been written.
     *
     * @li The completion_condition function object returns 0.
     *
     * This operation is implemented in terms of zero or more calls to the stream's
     * async_write_some function, and is known as a <em>composed operation</em>. The

  /**
   * This function is used to ask the strand to execute the given function
   * object on its underlying executor. The function object will be executed
   * inside this function if the strand is not otherwise busy and if the
   * underlying executor's @c dispatch() function is also able to execute the
   * function before returning.
   *
   * @param f The function object to be called. The executor will make
   * a copy of the handler object as required. The function signature of the
   * function object must be: @code void function(); @endcode
   *
   * @param a An allocator that may be used by the executor to allocate the
   * internal storage needed for function invocation.
   */
  template <typename Function, typename Allocator>
  void dispatch(ASIO_MOVE_ARG(Function) f, const Allocator& a)
  {
    detail::strand_executor_service::dispatch(impl_,
        executor_, ASIO_MOVE_CAST(Function)(f), a);
  }

  /// Request the strand to invoke the given function object.
  /**
   * This function is used to ask the executor to execute the given function
   * object. The function object will never be executed inside this function.
   * Instead, it will be scheduled by the underlying executor's defer function.
   *
   * @param f The function object to be called. The executor will make
   * a copy of the handler object as required. The function signature of the
   * function object must be: @code void function(); @endcode
   *

 * Regardless of whether the asynchronous operation completes immediately or
 * not, the handler will not be invoked from within this function. Invocation of
 * the handler will be performed in a manner equivalent to using
 * clmdep_asio::io_service::post().
 *
 * @note This overload is equivalent to calling:
 * @code clmdep_asio::async_read(
 *     s, b,
 *     clmdep_asio::transfer_all(),
 *     handler); @endcode
 */
template <typename AsyncReadStream, typename Allocator, typename ReadHandler>
ASIO_INITFN_RESULT_TYPE(ReadHandler,
    void (clmdep_asio::error_code, std::size_t))
async_read(AsyncReadStream& s, basic_streambuf<Allocator>& b,
    ASIO_MOVE_ARG(ReadHandler) handler);

/// Start an asynchronous operation to read a certain amount of data from a
/// stream.
/**
 * This function is used to asynchronously read a certain number of bytes of
 * data from a stream. The function call always returns immediately. The
 * asynchronous operation will continue until one of the following conditions is
 * true:
 *
 * @li The supplied buffer is full (that is, it has reached maximum size).
 *
 * @li The completion_condition function object returns 0.
 *
 * This operation is implemented in terms of zero or more calls to the stream's
 * async_read_some function, and is known as a <em>composed operation</em>. The

  /// Flush all data from the buffer to the next layer. Returns the number of
  /// bytes written to the next layer on the last write operation. Throws an
  /// exception on failure.
  std::size_t flush();

  /// Flush all data from the buffer to the next layer. Returns the number of
  /// bytes written to the next layer on the last write operation, or 0 if an
  /// error occurred.
  std::size_t flush(asio::error_code& ec);

  /// Start an asynchronous flush.
  template <typename WriteHandler>
  ASIO_INITFN_RESULT_TYPE(WriteHandler,
      void (asio::error_code, std::size_t))
  async_flush(ASIO_MOVE_ARG(WriteHandler) handler);

  /// Write the given data to the stream. Returns the number of bytes written.
  /// Throws an exception on failure.
  template <typename ConstBufferSequence>
  std::size_t write_some(const ConstBufferSequence& buffers);

  /// Write the given data to the stream. Returns the number of bytes written,
  /// or 0 if an error occurred and the error handler did not throw.
  template <typename ConstBufferSequence>
  std::size_t write_some(const ConstBufferSequence& buffers,
      asio::error_code& ec);

  /// Start an asynchronous write. The data being written must be valid for the
  /// lifetime of the asynchronous operation.
  template <typename ConstBufferSequence, typename WriteHandler>

inline std::size_t write(SyncWriteStream& s, const ConstBufferSequence& buffers,
    CompletionCondition completion_condition,
    typename enable_if<
      is_const_buffer_sequence<ConstBufferSequence>::value
    >::type*)
{
  asio::error_code ec;
  std::size_t bytes_transferred = write(s, buffers, completion_condition, ec);
  asio::detail::throw_error(ec, "write");
  return bytes_transferred;
}

template <typename SyncWriteStream, typename DynamicBufferSequence,
    typename CompletionCondition>
std::size_t write(SyncWriteStream& s,
    ASIO_MOVE_ARG(DynamicBufferSequence) buffers,
    CompletionCondition completion_condition, asio::error_code& ec,
    typename enable_if<
      is_dynamic_buffer_sequence<DynamicBufferSequence>::value
    >::type*)
{
  typename decay<DynamicBufferSequence>::type b(
      ASIO_MOVE_CAST(DynamicBufferSequence)(buffers));

  std::size_t bytes_transferred = write(s, b.data(), completion_condition, ec);
  b.consume(bytes_transferred);
  return bytes_transferred;
}

template <typename SyncWriteStream, typename DynamicBufferSequence>
inline std::size_t write(SyncWriteStream& s,

 * @li Constructs an object @c result of type <tt>async_result<Handler></tt>,
 * initializing the object as <tt>result(handler)</tt>.
 *
 * @li Obtains the handler's associated executor object @c ex by performing
 * <tt>get_associated_executor(handler)</tt>.
 *
 * @li Obtains the handler's associated allocator object @c alloc by performing
 * <tt>get_associated_allocator(handler)</tt>.
 *
 * @li Performs <tt>ex.post(std::move(handler), alloc)</tt>.
 *
 * @li Returns <tt>result.get()</tt>.
 */
template <typename CompletionToken>
ASIO_INITFN_RESULT_TYPE(CompletionToken, void()) post(
    ASIO_MOVE_ARG(CompletionToken) token);

/// Submits a completion token or function object for execution.
/**
 * This function submits an object for execution using the specified executor.
 * The function object is queued for execution, and is never called from the
 * current thread prior to returning from <tt>post()</tt>.
 *
 * This function has the following effects:
 *
 * @li Constructs a function object handler of type @c Handler, initialized
 * with <tt>handler(forward<CompletionToken>(token))</tt>.
 *
 * @li Constructs an object @c result of type <tt>async_result<Handler></tt>,
 * initializing the object as <tt>result(handler)</tt>.
 *

#include "asio/detail/recycling_allocator.hpp"
#include "asio/detail/type_traits.hpp"
#include "asio/execution_context.hpp"

#include "asio/detail/push_options.hpp"

namespace asio {

inline execution_context& system_executor::context() const ASIO_NOEXCEPT
{
  return detail::global<context_impl>();
}

template <typename Function, typename Allocator>
void system_executor::dispatch(
    ASIO_MOVE_ARG(Function) f, const Allocator&) const
{
  typename decay<Function>::type tmp(ASIO_MOVE_CAST(Function)(f));
  asio_handler_invoke_helpers::invoke(tmp, tmp);
}

template <typename Function, typename Allocator>
void system_executor::post(
    ASIO_MOVE_ARG(Function) f, const Allocator& a) const
{
  context_impl& ctx = detail::global<context_impl>();

  // Make a local, non-const copy of the function.
  typedef typename decay<Function>::type function_type;
  function_type tmp(ASIO_MOVE_CAST(Function)(f));

 *
 * // ...
 *
 * void connect_handler(
 *     const asio::error_code& ec,
 *     tcp::resolver::iterator i)
 * {
 *   // ...
 * } @endcode
 */
template <typename Protocol, typename SocketService,
    typename Iterator, typename ComposedConnectHandler>
ASIO_INITFN_RESULT_TYPE(ComposedConnectHandler,
    void (asio::error_code, Iterator))
async_connect(basic_socket<Protocol, SocketService>& s,
    Iterator begin, ASIO_MOVE_ARG(ComposedConnectHandler) handler);

/// Asynchronously establishes a socket connection by trying each endpoint in a
/// sequence.
/**
 * This function attempts to connect a socket to one of a sequence of
 * endpoints. It does this by repeated calls to the socket's @c async_connect
 * member function, once for each endpoint in the sequence, until a connection
 * is successfully established.
 *
 * @param s The socket to be connected. If the socket is already open, it will
 * be closed.
 *
 * @param begin An iterator pointing to the start of a sequence of endpoints.
 *
 * @param end An iterator pointing to the end of a sequence of endpoints.

};

// Helper to:
// - Apply the empty base optimisation to the executor.
// - Perform uses_executor construction of the target type, if required.

template <typename T, typename Executor, bool UsesExecutor>
class executor_binder_base;

template <typename T, typename Executor>
class executor_binder_base<T, Executor, true>
  : protected Executor
{
protected:
  template <typename E, typename U>
  executor_binder_base(ASIO_MOVE_ARG(E) e, ASIO_MOVE_ARG(U) u)
    : executor_(ASIO_MOVE_CAST(E)(e)),
      target_(executor_arg_t(), executor_, ASIO_MOVE_CAST(U)(u))
  {
  }

  Executor executor_;
  T target_;
};

template <typename T, typename Executor>
class executor_binder_base<T, Executor, false>
{
protected:
  template <typename E, typename U>
  executor_binder_base(ASIO_MOVE_ARG(E) e, ASIO_MOVE_ARG(U) u)

   *   }
   * }
   *
   * ...
   *
   * asio::ip::tcp::acceptor acceptor(io_service);
   * ...
   * acceptor.async_wait(
   *     asio::ip::tcp::acceptor::wait_read,
   *     wait_handler);
   * @endcode
   */
  template <typename WaitHandler>
  ASIO_INITFN_RESULT_TYPE(WaitHandler,
      void (asio::error_code))
  async_wait(wait_type w, ASIO_MOVE_ARG(WaitHandler) handler)
  {
    // If you get an error on the following line it means that your handler does
    // not meet the documented type requirements for a WaitHandler.
    ASIO_WAIT_HANDLER_CHECK(WaitHandler, handler) type_check;

    return this->get_service().async_wait(this->get_implementation(),
        w, ASIO_MOVE_CAST(WaitHandler)(handler));
  }

  /// Accept a new connection.
  /**
   * This function is used to accept a new connection from a peer into the
   * given socket. The function call will block until a new connection has been
   * accepted successfully or an error occurs.
   *

  /// Request the executor to invoke the given function object.
  /**
   * This function is used to ask the executor to execute the given function
   * object. The function object is executed according to the rules of the
   * target executor object.
   *
   * @param f The function object to be called. The executor will make a copy
   * of the handler object as required. The function signature of the function
   * object must be: @code void function(); @endcode
   *
   * @param a An allocator that may be used by the executor to allocate the
   * internal storage needed for function invocation.
   */
  template <typename Function, typename Allocator>
  void dispatch(ASIO_MOVE_ARG(Function) f, const Allocator& a) const;

  /// Request the executor to invoke the given function object.
  /**
   * This function is used to ask the executor to execute the given function
   * object. The function object is executed according to the rules of the
   * target executor object.
   *
   * @param f The function object to be called. The executor will make
   * a copy of the handler object as required. The function signature of the
   * function object must be: @code void function(); @endcode
   *
   * @param a An allocator that may be used by the executor to allocate the
   * internal storage needed for function invocation.
   */
  template <typename Function, typename Allocator>

 * not, the handler will not be invoked from within this function. Invocation of
 * the handler will be performed in a manner equivalent to using
 * asio::io_context::post().
 *
 * @note This overload is equivalent to calling:
 * @code asio::async_read_at(
 *     d, 42, b,
 *     asio::transfer_all(),
 *     handler); @endcode
 */
template <typename AsyncRandomAccessReadDevice, typename Allocator,
    typename ReadHandler>
ASIO_INITFN_RESULT_TYPE(ReadHandler,
    void (asio::error_code, std::size_t))
async_read_at(AsyncRandomAccessReadDevice& d, uint64_t offset,
    basic_streambuf<Allocator>& b, ASIO_MOVE_ARG(ReadHandler) handler);

/// Start an asynchronous operation to read a certain amount of data at the
/// specified offset.
/**
 * This function is used to asynchronously read a certain number of bytes of
 * data from a random access device at the specified offset. The function call
 * always returns immediately. The asynchronous operation will continue until
 * one of the following conditions is true:
 *
 * @li The completion_condition function object returns 0.
 *
 * This operation is implemented in terms of zero or more calls to the device's
 * async_read_some_at function.
 *
 * @param d The device from which the data is to be read. The type must support

// Wraps a handler to create an OVERLAPPED object for use with overlapped I/O.
class win_iocp_overlapped_ptr
  : private noncopyable
{
public:
  // Construct an empty win_iocp_overlapped_ptr.
  win_iocp_overlapped_ptr()
    : ptr_(0),
      iocp_service_(0)
  {
  }

  // Construct an win_iocp_overlapped_ptr to contain the specified handler.
  template <typename Handler>
  explicit win_iocp_overlapped_ptr(
      asio::io_service& io_service, ASIO_MOVE_ARG(Handler) handler)
    : ptr_(0),
      iocp_service_(0)
  {
    this->reset(io_service, ASIO_MOVE_CAST(Handler)(handler));
  }

  // Destructor automatically frees the OVERLAPPED object unless released.
  ~win_iocp_overlapped_ptr()
  {
    reset();
  }

  // Reset to empty.
  void reset()
  {

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

#include "asio/detail/config.hpp"
#include "asio/associated_allocator.hpp"
#include "asio/associated_executor.hpp"
#include "asio/detail/work_dispatcher.hpp"

#include "asio/detail/push_options.hpp"

namespace asio {

template <typename CompletionToken>
ASIO_INITFN_RESULT_TYPE(CompletionToken, void()) post(
    ASIO_MOVE_ARG(CompletionToken) token)
{
  typedef ASIO_HANDLER_TYPE(CompletionToken, void()) handler;

  async_completion<CompletionToken, void()> init(token);

  typename associated_executor<handler>::type ex(
      (get_associated_executor)(init.completion_handler));

  typename associated_allocator<handler>::type alloc(
      (get_associated_allocator)(init.completion_handler));

  ex.post(ASIO_MOVE_CAST(handler)(init.completion_handler), alloc);

  return init.result.get();
}

//.........这里部分代码省略.........
 * @par Example
 * @code tcp::resolver r(io_service);
 * tcp::resolver::query q("host", "service");
 * tcp::socket s(io_service);
 *
 * // ...
 *
 * r.async_resolve(q, resolve_handler);
 *
 * // ...
 *
 * void resolve_handler(
 *     const asio::error_code& ec,
 *     tcp::resolver::iterator i)
 * {
 *   if (!ec)
 *   {
 *     asio::async_connect(s, i, connect_handler);
 *   }
 * }
 *
 * // ...
 *
 * void connect_handler(
 *     const asio::error_code& ec,
 *     tcp::resolver::iterator i)
 * {
 *   // ...
 * } @endcode
 */
template <typename Protocol, typename SocketService,
    typename Iterator, typename ComposedConnectHandler>
void async_connect(basic_socket<Protocol, SocketService>& s,
    Iterator begin, ASIO_MOVE_ARG(ComposedConnectHandler) handler);

/// Asynchronously establishes a socket connection by trying each endpoint in a
/// sequence.
/**
 * This function attempts to connect a socket to one of a sequence of
 * endpoints. It does this by repeated calls to the socket's @c async_connect
 * member function, once for each endpoint in the sequence, until a connection
 * is successfully established.
 *
 * @param s The socket to be connected. If the socket is already open, it will
 * be closed.
 *
 * @param begin An iterator pointing to the start of a sequence of endpoints.
 *
 * @param end An iterator pointing to the end of a sequence of endpoints.
 *
 * @param handler The handler to be called when the connect operation
 * completes. Copies will be made of the handler as required. The function
 * signature of the handler must be:
 * @code void handler(
 *   // Result of operation. if the sequence is empty, set to
 *   // asio::error::not_found. Otherwise, contains the
 *   // error from the last connection attempt.
 *   const asio::error_code& error,
 *
 *   // On success, an iterator denoting the successfully
 *   // connected endpoint. Otherwise, the end iterator.
 *   Iterator iterator
 * ); @endcode
 * Regardless of whether the asynchronous operation completes immediately or
 * not, the handler will not be invoked from within this function. Invocation
 * of the handler will be performed in a manner equivalent to using

/// completes.
/**
 * This function is used to launch a new coroutine.
 *
 * @param handler A handler to be called when the coroutine exits. More
 * importantly, the handler provides an execution context (via the the handler
 * invocation hook) for the coroutine. The handler must have the signature:
 * @code void handler(); @endcode
 *
 * @param function The coroutine function. The function must have the signature:
 * @code void function(basic_yield_context<Handler> yield); @endcode
 *
 * @param attributes Boost.Coroutine attributes used to customise the coroutine.
 */
template <typename Handler, typename Function>
void spawn(ASIO_MOVE_ARG(Handler) handler,
    ASIO_MOVE_ARG(Function) function,
    const boost::coroutines::attributes& attributes
      = boost::coroutines::attributes());

/// Start a new stackful coroutine, inheriting the execution context of another.
/**
 * This function is used to launch a new coroutine.
 *
 * @param ctx Identifies the current coroutine as a parent of the new
 * coroutine. This specifies that the new coroutine should inherit the
 * execution context of the parent. For example, if the parent coroutine is
 * executing in a particular strand, then the new coroutine will execute in the
 * same strand.
 *
 * @param function The coroutine function. The function must have the signature:

 *
 * @param buffers The dynamic buffer sequence from which data will be written.
 * Successfully written data is automatically consumed from the buffers.
 *
 * @returns The number of bytes transferred.
 *
 * @throws asio::system_error Thrown on failure.
 *
 * @note This overload is equivalent to calling:
 * @code asio::write(
 *     s, buffers,
 *     asio::transfer_all()); @endcode
 */
template <typename SyncWriteStream, typename DynamicBuffer>
std::size_t write(SyncWriteStream& s,
    ASIO_MOVE_ARG(DynamicBuffer) buffers,
    typename enable_if<
      is_dynamic_buffer<DynamicBuffer>::value
    >::type* = 0);

/// Write all of the supplied data to a stream before returning.
/**
 * This function is used to write a certain number of bytes of data to a stream.
 * The call will block until one of the following conditions is true:
 *
 * @li All of the data in the supplied dynamic buffer sequence has been written.
 *
 * @li An error occurred.
 *
 * This operation is implemented in terms of zero or more calls to the stream's
 * write_some function.

   * @param handler The handler to be called when the accept operation
   * completes. Copies will be made of the handler as required. The function
   * signature of the handler must be:
   * @code void handler(
   *   const asio::error_code& error // Result of operation.
   * ); @endcode
   * Regardless of whether the asynchronous operation completes immediately or
   * not, the handler will not be invoked from within this function. Invocation
   * of the handler will be performed in a manner equivalent to using
   * asio::io_service::post().
   */
  template <typename SocketService, typename AcceptHandler>
  ASIO_INITFN_RESULT_TYPE(AcceptHandler,
      void (asio::error_code))
  async_accept(basic_socket<protocol_type, SocketService>& peer,
      endpoint_type& peer_endpoint, ASIO_MOVE_ARG(AcceptHandler) handler)
  {
    // If you get an error on the following line it means that your handler does
    // not meet the documented type requirements for a AcceptHandler.
    ASIO_ACCEPT_HANDLER_CHECK(AcceptHandler, handler) type_check;

    return this->get_service().async_accept(this->get_implementation(), peer,
        &peer_endpoint, ASIO_MOVE_CAST(AcceptHandler)(handler));
  }
};

} // namespace asio

#include "asio/detail/pop_options.hpp"

#endif // ASIO_BASIC_SOCKET_ACCEPTOR_HPP

inline io_service::executor_type
io_service::get_executor() ASIO_NOEXCEPT
{
    return executor_type(*this);
}

#if !defined(ASIO_NO_DEPRECATED)

inline void io_service::reset()
{
    restart();
}

template <typename CompletionHandler>
ASIO_INITFN_RESULT_TYPE(CompletionHandler, void ())
io_service::dispatch(ASIO_MOVE_ARG(CompletionHandler) handler)
{
    // If you get an error on the following line it means that your handler does
    // not meet the documented type requirements for a CompletionHandler.
    ASIO_COMPLETION_HANDLER_CHECK(CompletionHandler, handler) type_check;

    async_completion<CompletionHandler, void ()> init(handler);

    if (impl_.can_dispatch())
    {
        detail::fenced_block b(detail::fenced_block::full);
        asio_handler_invoke_helpers::invoke(init.handler, init.handler);
    }
    else
    {
        // Allocate and construct an operation to wrap the handler.