text: //
  // detail/reactive_descriptor_service.hpp
  // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  //
  // Copyright (c) 2003-2020 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_REACTIVE_DESCRIPTOR_SERVICE_HPP
  #define ASIO_DETAIL_REACTIVE_DESCRIPTOR_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_WINDOWS) \
    && !defined(ASIO_WINDOWS_RUNTIME) \
    && !defined(__CYGWIN__)
  
  #include "asio/buffer.hpp"
  #include "asio/execution_context.hpp"
  #include "asio/detail/bind_handler.hpp"
  #include "asio/detail/buffer_sequence_adapter.hpp"
  #include "asio/detail/descriptor_ops.hpp"
  #include "asio/detail/descriptor_read_op.hpp"
  #include "asio/detail/descriptor_write_op.hpp"
  #include "asio/detail/fenced_block.hpp"
  #include "asio/detail/memory.hpp"
  #include "asio/detail/noncopyable.hpp"
  #include "asio/detail/reactive_null_buffers_op.hpp"
  #include "asio/detail/reactive_wait_op.hpp"
  #include "asio/detail/reactor.hpp"
  #include "asio/posix/descriptor_base.hpp"
  
  #include "asio/detail/push_options.hpp"
  
  namespace asio {
  namespace detail {
  
  class reactive_descriptor_service :
    public execution_context_service_base<reactive_descriptor_service>
  {
  public:
    // The native type of a descriptor.
    typedef int native_handle_type;
  
    // The implementation type of the descriptor.
    class implementation_type
      : private asio::detail::noncopyable
    {
    public:
      // Default constructor.
      implementation_type()
        : descriptor_(-1),
          state_(0)
      {
      }
  
    private:
      // Only this service will have access to the internal values.
      friend class reactive_descriptor_service;
  
      // The native descriptor representation.
      int descriptor_;
  
      // The current state of the descriptor.
      descriptor_ops::state_type state_;
  
      // Per-descriptor data used by the reactor.
      reactor::per_descriptor_data reactor_data_;
    };
  
    // Constructor.
    ASIO_DECL reactive_descriptor_service(execution_context& context);
  
    // Destroy all user-defined handler objects owned by the service.
    ASIO_DECL void shutdown();
  
    // Construct a new descriptor implementation.
    ASIO_DECL void construct(implementation_type& impl);
  
    // Move-construct a new descriptor implementation.
    ASIO_DECL void move_construct(implementation_type& impl,
        implementation_type& other_impl) ASIO_NOEXCEPT;
  
    // Move-assign from another descriptor implementation.
    ASIO_DECL void move_assign(implementation_type& impl,
        reactive_descriptor_service& other_service,
        implementation_type& other_impl);
  
    // Destroy a descriptor implementation.
    ASIO_DECL void destroy(implementation_type& impl);
  
    // Assign a native descriptor to a descriptor implementation.
    ASIO_DECL asio::error_code assign(implementation_type& impl,
        const native_handle_type& native_descriptor,
        asio::error_code& ec);
  
    // Determine whether the descriptor is open.
    bool is_open(const implementation_type& impl) const
    {
      return impl.descriptor_ != -1;
    }
  
    // Destroy a descriptor implementation.
    ASIO_DECL asio::error_code close(implementation_type& impl,
        asio::error_code& ec);
  
    // Get the native descriptor representation.
    native_handle_type native_handle(const implementation_type& impl) const
    {
      return impl.descriptor_;
    }
  
    // Release ownership of the native descriptor representation.
    ASIO_DECL native_handle_type release(implementation_type& impl);
  
    // Cancel all operations associated with the descriptor.
    ASIO_DECL asio::error_code cancel(implementation_type& impl,
        asio::error_code& ec);
  
    // Perform an IO control command on the descriptor.
    template <typename IO_Control_Command>
    asio::error_code io_control(implementation_type& impl,
        IO_Control_Command& command, asio::error_code& ec)
    {
      descriptor_ops::ioctl(impl.descriptor_, impl.state_,
          command.name(), static_cast<ioctl_arg_type*>(command.data()), ec);
      return ec;
    }
  
    // Gets the non-blocking mode of the descriptor.
    bool non_blocking(const implementation_type& impl) const
    {
      return (impl.state_ & descriptor_ops::user_set_non_blocking) != 0;
    }
  
    // Sets the non-blocking mode of the descriptor.
    asio::error_code non_blocking(implementation_type& impl,
        bool mode, asio::error_code& ec)
    {
      descriptor_ops::set_user_non_blocking(
          impl.descriptor_, impl.state_, mode, ec);
      return ec;
    }
  
    // Gets the non-blocking mode of the native descriptor implementation.
    bool native_non_blocking(const implementation_type& impl) const
    {
      return (impl.state_ & descriptor_ops::internal_non_blocking) != 0;
    }
  
    // Sets the non-blocking mode of the native descriptor implementation.
    asio::error_code native_non_blocking(implementation_type& impl,
        bool mode, asio::error_code& ec)
    {
      descriptor_ops::set_internal_non_blocking(
          impl.descriptor_, impl.state_, mode, ec);
      return ec;
    }
  
    // Wait for the descriptor to become ready to read, ready to write, or to have
    // pending error conditions.
    asio::error_code wait(implementation_type& impl,
        posix::descriptor_base::wait_type w, asio::error_code& ec)
    {
      switch (w)
      {
      case posix::descriptor_base::wait_read:
        descriptor_ops::poll_read(impl.descriptor_, impl.state_, ec);
        break;
      case posix::descriptor_base::wait_write:
        descriptor_ops::poll_write(impl.descriptor_, impl.state_, ec);
        break;
      case posix::descriptor_base::wait_error:
        descriptor_ops::poll_error(impl.descriptor_, impl.state_, ec);
        break;
      default:
        ec = asio::error::invalid_argument;
        break;
      }
  
      return ec;
    }
  
    // Asynchronously wait for the descriptor to become ready to read, ready to
    // write, or to have pending error conditions.
    template <typename Handler, typename IoExecutor>
    void async_wait(implementation_type& impl,
        posix::descriptor_base::wait_type w,
        Handler& handler, const IoExecutor& io_ex)
    {
      bool is_continuation =
        asio_handler_cont_helpers::is_continuation(handler);
  
      // Allocate and construct an operation to wrap the handler.
      typedef reactive_wait_op<Handler, IoExecutor> op;
      typename op::ptr p = { asio::detail::addressof(handler),
        op::ptr::allocate(handler), 0 };
      p.p = new (p.v) op(handler, io_ex);
  
      ASIO_HANDLER_CREATION((reactor_.context(), *p.p, "descriptor",
            &impl, impl.descriptor_, "async_wait"));
  
      int op_type;
      switch (w)
      {
      case posix::descriptor_base::wait_read:
          op_type = reactor::read_op;
          break;
      case posix::descriptor_base::wait_write:
          op_type = reactor::write_op;
          break;
      case posix::descriptor_base::wait_error:
          op_type = reactor::except_op;
          break;
        default:
          p.p->ec_ = asio::error::invalid_argument;
          reactor_.post_immediate_completion(p.p, is_continuation);
          p.v = p.p = 0;
          return;
      }
  
      start_op(impl, op_type, p.p, is_continuation, false, false);
      p.v = p.p = 0;
    }
  
    // Write some data to the descriptor.
    template <typename ConstBufferSequence>
    size_t write_some(implementation_type& impl,
        const ConstBufferSequence& buffers, asio::error_code& ec)
    {
      buffer_sequence_adapter<asio::const_buffer,
          ConstBufferSequence> bufs(buffers);
  
      return descriptor_ops::sync_write(impl.descriptor_, impl.state_,
          bufs.buffers(), bufs.count(), bufs.all_empty(), ec);
    }
  
    // Wait until data can be written without blocking.
    size_t write_some(implementation_type& impl,
        const null_buffers&, asio::error_code& ec)
    {
      // Wait for descriptor to become ready.
      descriptor_ops::poll_write(impl.descriptor_, impl.state_, ec);
  
      return 0;
    }
  
    // Start an asynchronous write. The data being sent 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)
    {
      bool is_continuation =
        asio_handler_cont_helpers::is_continuation(handler);
  
      // Allocate and construct an operation to wrap the handler.
      typedef descriptor_write_op<ConstBufferSequence, Handler, IoExecutor> op;
      typename op::ptr p = { asio::detail::addressof(handler),
        op::ptr::allocate(handler), 0 };
      p.p = new (p.v) op(impl.descriptor_, buffers, handler, io_ex);
  
      ASIO_HANDLER_CREATION((reactor_.context(), *p.p, "descriptor",
            &impl, impl.descriptor_, "async_write_some"));
  
      start_op(impl, reactor::write_op, p.p, is_continuation, true,
          buffer_sequence_adapter<asio::const_buffer,
            ConstBufferSequence>::all_empty(buffers));
      p.v = p.p = 0;
    }
  
    // Start an asynchronous wait until data can be written without blocking.
    template <typename Handler, typename IoExecutor>
    void async_write_some(implementation_type& impl,
        const null_buffers&, Handler& handler, const IoExecutor& io_ex)
    {
      bool is_continuation =
        asio_handler_cont_helpers::is_continuation(handler);
  
      // Allocate and construct an operation to wrap the handler.
      typedef reactive_null_buffers_op<Handler, IoExecutor> op;
      typename op::ptr p = { asio::detail::addressof(handler),
        op::ptr::allocate(handler), 0 };
      p.p = new (p.v) op(handler, io_ex);
  
      ASIO_HANDLER_CREATION((reactor_.context(), *p.p, "descriptor",
            &impl, impl.descriptor_, "async_write_some(null_buffers)"));
  
      start_op(impl, reactor::write_op, p.p, is_continuation, false, false);
      p.v = p.p = 0;
    }
  
    // Read some data from the stream. Returns the number of bytes read.
    template <typename MutableBufferSequence>
    size_t read_some(implementation_type& impl,
        const MutableBufferSequence& buffers, asio::error_code& ec)
    {
      buffer_sequence_adapter<asio::mutable_buffer,
          MutableBufferSequence> bufs(buffers);
  
      return descriptor_ops::sync_read(impl.descriptor_, impl.state_,
          bufs.buffers(), bufs.count(), bufs.all_empty(), ec);
    }
  
    // Wait until data can be read without blocking.
    size_t read_some(implementation_type& impl,
        const null_buffers&, asio::error_code& ec)
    {
      // Wait for descriptor to become ready.
      descriptor_ops::poll_read(impl.descriptor_, impl.state_, ec);
  
      return 0;
    }
  
    // Start an asynchronous read. The buffer for the data being read 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)
    {
      bool is_continuation =
        asio_handler_cont_helpers::is_continuation(handler);
  
      // Allocate and construct an operation to wrap the handler.
      typedef descriptor_read_op<MutableBufferSequence, Handler, IoExecutor> op;
      typename op::ptr p = { asio::detail::addressof(handler),
        op::ptr::allocate(handler), 0 };
      p.p = new (p.v) op(impl.descriptor_, buffers, handler, io_ex);
  
      ASIO_HANDLER_CREATION((reactor_.context(), *p.p, "descriptor",
            &impl, impl.descriptor_, "async_read_some"));
  
      start_op(impl, reactor::read_op, p.p, is_continuation, true,
          buffer_sequence_adapter<asio::mutable_buffer,
            MutableBufferSequence>::all_empty(buffers));
      p.v = p.p = 0;
    }
  
    // Wait until data can be read without blocking.
    template <typename Handler, typename IoExecutor>
    void async_read_some(implementation_type& impl,
        const null_buffers&, Handler& handler, const IoExecutor& io_ex)
    {
      bool is_continuation =
        asio_handler_cont_helpers::is_continuation(handler);
  
      // Allocate and construct an operation to wrap the handler.
      typedef reactive_null_buffers_op<Handler, IoExecutor> op;
      typename op::ptr p = { asio::detail::addressof(handler),
        op::ptr::allocate(handler), 0 };
      p.p = new (p.v) op(handler, io_ex);
  
      ASIO_HANDLER_CREATION((reactor_.context(), *p.p, "descriptor",
            &impl, impl.descriptor_, "async_read_some(null_buffers)"));
  
      start_op(impl, reactor::read_op, p.p, is_continuation, false, false);
      p.v = p.p = 0;
    }
  
  private:
    // Start the asynchronous operation.
    ASIO_DECL void start_op(implementation_type& impl, int op_type,
        reactor_op* op, bool is_continuation, bool is_non_blocking, bool noop);
  
    // The selector that performs event demultiplexing for the service.
    reactor& reactor_;
  };
  
  } // namespace detail
  } // namespace asio
  
  #include "asio/detail/pop_options.hpp"
  
  #if defined(ASIO_HEADER_ONLY)
  # include "asio/detail/impl/reactive_descriptor_service.ipp"
  #endif // defined(ASIO_HEADER_ONLY)
  
  #endif // !defined(ASIO_WINDOWS)
         //   && !defined(ASIO_WINDOWS_RUNTIME)
         //   && !defined(__CYGWIN__)
  
  #endif // ASIO_DETAIL_REACTIVE_DESCRIPTOR_SERVICE_HPP
  