text: //
  // detail/win_iocp_handle_service.hpp
  // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  //
  // Copyright (c) 2003-2020 Christopher M. Kohlhoff (chris at kohlhoff dot com)
  // Copyright (c) 2008 Rep Invariant Systems, Inc. (info@repinvariant.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_HANDLE_SERVICE_HPP
  #define ASIO_DETAIL_WIN_IOCP_HANDLE_SERVICE_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/execution_context.hpp"
  #include "asio/detail/buffer_sequence_adapter.hpp"
  #include "asio/detail/cstdint.hpp"
  #include "asio/detail/handler_alloc_helpers.hpp"
  #include "asio/detail/memory.hpp"
  #include "asio/detail/mutex.hpp"
  #include "asio/detail/operation.hpp"
  #include "asio/detail/win_iocp_handle_read_op.hpp"
  #include "asio/detail/win_iocp_handle_write_op.hpp"
  #include "asio/detail/win_iocp_io_context.hpp"
  
  #include "asio/detail/push_options.hpp"
  
  
  namespace clmdep_asio {
  namespace detail {
  
  class win_iocp_handle_service :
    public execution_context_service_base<win_iocp_handle_service>
  {
  public:
    // The native type of a stream handle.
    typedef HANDLE native_handle_type;
  
    // The implementation type of the stream handle.
    class implementation_type
    {
    public:
      // Default constructor.
      implementation_type()
        : handle_(INVALID_HANDLE_VALUE),
          safe_cancellation_thread_id_(0),
          next_(0),
          prev_(0)
      {
      }
  
    private:
      // Only this service will have access to the internal values.
      friend class win_iocp_handle_service;
  
      // The native stream handle representation.
      native_handle_type handle_;
  
      // 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 handle.
      DWORD safe_cancellation_thread_id_;
  
      // Pointers to adjacent handle implementations in linked list.
      implementation_type* next_;
      implementation_type* prev_;
    };
  
    ASIO_DECL win_iocp_handle_service(execution_context& context);
  
    // Destroy all user-defined handler objects owned by the service.
    ASIO_DECL void shutdown();
  
    // Construct a new handle implementation.
    ASIO_DECL void construct(implementation_type& impl);
  
    // Move-construct a new handle implementation.
    ASIO_DECL void move_construct(implementation_type& impl,
        implementation_type& other_impl);
  
    // Move-assign from another handle implementation.
    ASIO_DECL void move_assign(implementation_type& impl,
        win_iocp_handle_service& other_service,
        implementation_type& other_impl);
  
    // Destroy a handle implementation.
    ASIO_DECL void destroy(implementation_type& impl);
  
    // Assign a native handle to a handle implementation.
    ASIO_DECL clmdep_asio::error_code assign(implementation_type& impl,
        const native_handle_type& handle, clmdep_asio::error_code& ec);
  
    // Determine whether the handle is open.
    bool is_open(const implementation_type& impl) const
    {
      return impl.handle_ != INVALID_HANDLE_VALUE;
    }
  
    // Destroy a handle implementation.
    ASIO_DECL clmdep_asio::error_code close(implementation_type& impl,
        clmdep_asio::error_code& ec);
  
    // Get the native handle representation.
    native_handle_type native_handle(const implementation_type& impl) const
    {
      return impl.handle_;
    }
  
    // Cancel all operations associated with the handle.
    ASIO_DECL clmdep_asio::error_code cancel(implementation_type& impl,
        clmdep_asio::error_code& ec);
  
    // Write the given data. Returns the number of bytes written.
    template <typename ConstBufferSequence>
    size_t write_some(implementation_type& impl,
        const ConstBufferSequence& buffers, clmdep_asio::error_code& ec)
    {
      return write_some_at(impl, 0, buffers, ec);
    }
  
    // Write the given data at the specified offset. Returns the number of bytes
    // written.
    template <typename ConstBufferSequence>
    size_t write_some_at(implementation_type& impl, uint64_t offset,
        const ConstBufferSequence& buffers, clmdep_asio::error_code& ec)
    {
      clmdep_asio::const_buffer buffer =
        buffer_sequence_adapter<clmdep_asio::const_buffer,
          ConstBufferSequence>::first(buffers);
  
      return do_write(impl, offset, buffer, ec);
    }
  
    // Start an asynchronous write. The data being written must be valid for the
    // lifetime of the asynchronous operation.
    template <typename ConstBufferSequence, typename Handler, typename IoExecutor>
    void async_write_some(implementation_type& impl,
        const ConstBufferSequence& buffers,
        Handler& handler, const IoExecutor& io_ex)
    {
      // Allocate and construct an operation to wrap the handler.
      typedef win_iocp_handle_write_op<
          ConstBufferSequence, Handler, IoExecutor> op;
      typename op::ptr p = { clmdep_asio::detail::addressof(handler),
        op::ptr::allocate(handler), 0 };
      p.p = new (p.v) op(buffers, handler, io_ex);
  
      ASIO_HANDLER_CREATION((iocp_service_.context(), *p.p, "handle", &impl,
            reinterpret_cast<uintmax_t>(impl.handle_), "async_write_some"));
  
      start_write_op(impl, 0,
          buffer_sequence_adapter<clmdep_asio::const_buffer,
            ConstBufferSequence>::first(buffers), p.p);
      p.v = p.p = 0;
    }
  
    // Start an asynchronous write at a specified offset. The data being written
    // must be valid for the lifetime of the asynchronous operation.
    template <typename ConstBufferSequence, typename Handler, typename IoExecutor>
    void async_write_some_at(implementation_type& impl,
        uint64_t offset, const ConstBufferSequence& buffers,
        Handler& handler, const IoExecutor& io_ex)
    {
      // Allocate and construct an operation to wrap the handler.
      typedef win_iocp_handle_write_op<
          ConstBufferSequence, Handler, IoExecutor> op;
      typename op::ptr p = { clmdep_asio::detail::addressof(handler),
        op::ptr::allocate(handler), 0 };
      p.p = new (p.v) op(buffers, handler, io_ex);
  
      ASIO_HANDLER_CREATION((iocp_service_.context(), *p.p, "handle", &impl,
            reinterpret_cast<uintmax_t>(impl.handle_), "async_write_some_at"));
  
      start_write_op(impl, offset,
          buffer_sequence_adapter<clmdep_asio::const_buffer,
            ConstBufferSequence>::first(buffers), p.p);
      p.v = p.p = 0;
    }
  
    // Read some data. Returns the number of bytes received.
    template <typename MutableBufferSequence>
    size_t read_some(implementation_type& impl,
        const MutableBufferSequence& buffers, clmdep_asio::error_code& ec)
    {
      return read_some_at(impl, 0, buffers, ec);
    }
  
    // Read some data at a specified offset. Returns the number of bytes received.
    template <typename MutableBufferSequence>
    size_t read_some_at(implementation_type& impl, uint64_t offset,
        const MutableBufferSequence& buffers, clmdep_asio::error_code& ec)
    {
      clmdep_asio::mutable_buffer buffer =
        buffer_sequence_adapter<clmdep_asio::mutable_buffer,
          MutableBufferSequence>::first(buffers);
  
      return do_read(impl, offset, buffer, ec);
    }
  
    // Start an asynchronous read. The buffer for the data being received must be
    // valid for the lifetime of the asynchronous operation.
    template <typename MutableBufferSequence,
        typename Handler, typename IoExecutor>
    void async_read_some(implementation_type& impl,
        const MutableBufferSequence& buffers,
        Handler& handler, const IoExecutor& io_ex)
    {
      // Allocate and construct an operation to wrap the handler.
      typedef win_iocp_handle_read_op<
          MutableBufferSequence, Handler, IoExecutor> op;
      typename op::ptr p = { clmdep_asio::detail::addressof(handler),
        op::ptr::allocate(handler), 0 };
      p.p = new (p.v) op(buffers, handler, io_ex);
  
      ASIO_HANDLER_CREATION((iocp_service_.context(), *p.p, "handle", &impl,
            reinterpret_cast<uintmax_t>(impl.handle_), "async_read_some"));
  
      start_read_op(impl, 0,
          buffer_sequence_adapter<clmdep_asio::mutable_buffer,
            MutableBufferSequence>::first(buffers), p.p);
      p.v = p.p = 0;
    }
  
    // Start an asynchronous read at a specified offset. The buffer for the data
    // being received must be valid for the lifetime of the asynchronous
    // operation.
    template <typename MutableBufferSequence,
        typename Handler, typename IoExecutor>
    void async_read_some_at(implementation_type& impl,
        uint64_t offset, const MutableBufferSequence& buffers,
        Handler& handler, const IoExecutor& io_ex)
    {
      // Allocate and construct an operation to wrap the handler.
      typedef win_iocp_handle_read_op<
          MutableBufferSequence, Handler, IoExecutor> op;
      typename op::ptr p = { clmdep_asio::detail::addressof(handler),
        op::ptr::allocate(handler), 0 };
      p.p = new (p.v) op(buffers, handler, io_ex);
  
      ASIO_HANDLER_CREATION((iocp_service_.context(), *p.p, "handle", &impl,
            reinterpret_cast<uintmax_t>(impl.handle_), "async_read_some_at"));
  
      start_read_op(impl, offset,
          buffer_sequence_adapter<clmdep_asio::mutable_buffer,
            MutableBufferSequence>::first(buffers), p.p);
      p.v = p.p = 0;
    }
  
  private:
    // Prevent the use of the null_buffers type with this service.
    size_t write_some(implementation_type& impl,
        const null_buffers& buffers, clmdep_asio::error_code& ec);
    size_t write_some_at(implementation_type& impl, uint64_t offset,
        const null_buffers& buffers, clmdep_asio::error_code& ec);
    template <typename Handler, typename IoExecutor>
    void async_write_some(implementation_type& impl,
        const null_buffers& buffers, Handler& handler,
        const IoExecutor& io_ex);
    template <typename Handler, typename IoExecutor>
    void async_write_some_at(implementation_type& impl, uint64_t offset,
        const null_buffers& buffers, Handler& handler, const IoExecutor& io_ex);
    size_t read_some(implementation_type& impl,
        const null_buffers& buffers, clmdep_asio::error_code& ec);
    size_t read_some_at(implementation_type& impl, uint64_t offset,
        const null_buffers& buffers, clmdep_asio::error_code& ec);
    template <typename Handler, typename IoExecutor>
    void async_read_some(implementation_type& impl,
        const null_buffers& buffers, Handler& handler,
        const IoExecutor& io_ex);
    template <typename Handler, typename IoExecutor>
    void async_read_some_at(implementation_type& impl, uint64_t offset,
        const null_buffers& buffers, Handler& handler, const IoExecutor& io_ex);
  
    // Helper class for waiting for synchronous operations to complete.
    class overlapped_wrapper;
  
    // Helper function to perform a synchronous write operation.
    ASIO_DECL size_t do_write(implementation_type& impl,
        uint64_t offset, const clmdep_asio::const_buffer& buffer,
        clmdep_asio::error_code& ec);
  
    // Helper function to start a write operation.
    ASIO_DECL void start_write_op(implementation_type& impl,
        uint64_t offset, const clmdep_asio::const_buffer& buffer,
        operation* op);
  
    // Helper function to perform a synchronous write operation.
    ASIO_DECL size_t do_read(implementation_type& impl,
        uint64_t offset, const clmdep_asio::mutable_buffer& buffer,
        clmdep_asio::error_code& ec);
  
    // Helper function to start a read operation.
    ASIO_DECL void start_read_op(implementation_type& impl,
        uint64_t offset, const clmdep_asio::mutable_buffer& buffer,
        operation* op);
  
    // Update the ID of the thread from which cancellation is safe.
    ASIO_DECL void update_cancellation_thread_id(implementation_type& impl);
  
    // Helper function to close a handle when the associated object is being
    // destroyed.
    ASIO_DECL void close_for_destruction(implementation_type& impl);
  
    // The IOCP service used for running asynchronous operations and dispatching
    // handlers.
    win_iocp_io_context& iocp_service_;
  
    // Mutex to protect access to the linked list of implementations.
    mutex mutex_;
  
    // The head of a linked list of all implementations.
    implementation_type* impl_list_;
  };
  
  } // namespace detail
  } // namespace clmdep_asio
  
  
  #include "asio/detail/pop_options.hpp"
  
  #if defined(ASIO_HEADER_ONLY)
  # include "asio/detail/impl/win_iocp_handle_service.ipp"
  #endif // defined(ASIO_HEADER_ONLY)
  
  #endif // defined(ASIO_HAS_IOCP)
  
  #endif // ASIO_DETAIL_WIN_IOCP_HANDLE_SERVICE_HPP
  