text: //
  // posix/basic_descriptor.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_POSIX_BASIC_DESCRIPTOR_HPP
  #define ASIO_POSIX_BASIC_DESCRIPTOR_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_POSIX_STREAM_DESCRIPTOR) \
    || defined(GENERATING_DOCUMENTATION)
  
  #include "asio/basic_io_object.hpp"
  #include "asio/detail/throw_error.hpp"
  #include "asio/error.hpp"
  #include "asio/posix/descriptor_base.hpp"
  
  #include "asio/detail/push_options.hpp"
  
  namespace asio {
  namespace posix {
  
  /// Provides POSIX descriptor functionality.
  /**
   * The posix::basic_descriptor class template provides the ability to wrap a
   * POSIX descriptor.
   *
   * @par Thread Safety
   * @e Distinct @e objects: Safe.@n
   * @e Shared @e objects: Unsafe.
   */
  template <typename DescriptorService>
  class basic_descriptor
    : public basic_io_object<DescriptorService>,
      public descriptor_base
  {
  public:
    /// The native representation of a descriptor.
    typedef typename DescriptorService::native_handle_type native_handle_type;
  
    /// A basic_descriptor is always the lowest layer.
    typedef basic_descriptor<DescriptorService> lowest_layer_type;
  
    /// Construct a basic_descriptor without opening it.
    /**
     * This constructor creates a descriptor without opening it.
     *
     * @param io_service The io_service object that the descriptor will use to
     * dispatch handlers for any asynchronous operations performed on the
     * descriptor.
     */
    explicit basic_descriptor(asio::io_service& io_service)
      : basic_io_object<DescriptorService>(io_service)
    {
    }
  
    /// Construct a basic_descriptor on an existing native descriptor.
    /**
     * This constructor creates a descriptor object to hold an existing native
     * descriptor.
     *
     * @param io_service The io_service object that the descriptor will use to
     * dispatch handlers for any asynchronous operations performed on the
     * descriptor.
     *
     * @param native_descriptor A native descriptor.
     *
     * @throws asio::system_error Thrown on failure.
     */
    basic_descriptor(asio::io_service& io_service,
        const native_handle_type& native_descriptor)
      : basic_io_object<DescriptorService>(io_service)
    {
      asio::error_code ec;
      this->get_service().assign(this->get_implementation(),
          native_descriptor, ec);
      asio::detail::throw_error(ec, "assign");
    }
  
  #if defined(ASIO_HAS_MOVE) || defined(GENERATING_DOCUMENTATION)
    /// Move-construct a basic_descriptor from another.
    /**
     * This constructor moves a descriptor from one object to another.
     *
     * @param other The other basic_descriptor object from which the move will
     * occur.
     *
     * @note Following the move, the moved-from object is in the same state as if
     * constructed using the @c basic_descriptor(io_service&) constructor.
     */
    basic_descriptor(basic_descriptor&& other)
      : basic_io_object<DescriptorService>(
          ASIO_MOVE_CAST(basic_descriptor)(other))
    {
    }
  
    /// Move-assign a basic_descriptor from another.
    /**
     * This assignment operator moves a descriptor from one object to another.
     *
     * @param other The other basic_descriptor object from which the move will
     * occur.
     *
     * @note Following the move, the moved-from object is in the same state as if
     * constructed using the @c basic_descriptor(io_service&) constructor.
     */
    basic_descriptor& operator=(basic_descriptor&& other)
    {
      basic_io_object<DescriptorService>::operator=(
          ASIO_MOVE_CAST(basic_descriptor)(other));
      return *this;
    }
  #endif // defined(ASIO_HAS_MOVE) || defined(GENERATING_DOCUMENTATION)
  
    /// Get a reference to the lowest layer.
    /**
     * This function returns a reference to the lowest layer in a stack of
     * layers. Since a basic_descriptor cannot contain any further layers, it
     * simply returns a reference to itself.
     *
     * @return A reference to the lowest layer in the stack of layers. Ownership
     * is not transferred to the caller.
     */
    lowest_layer_type& lowest_layer()
    {
      return *this;
    }
  
    /// Get a const reference to the lowest layer.
    /**
     * This function returns a const reference to the lowest layer in a stack of
     * layers. Since a basic_descriptor cannot contain any further layers, it
     * simply returns a reference to itself.
     *
     * @return A const reference to the lowest layer in the stack of layers.
     * Ownership is not transferred to the caller.
     */
    const lowest_layer_type& lowest_layer() const
    {
      return *this;
    }
  
    /// Assign an existing native descriptor to the descriptor.
    /*
     * This function opens the descriptor to hold an existing native descriptor.
     *
     * @param native_descriptor A native descriptor.
     *
     * @throws asio::system_error Thrown on failure.
     */
    void assign(const native_handle_type& native_descriptor)
    {
      asio::error_code ec;
      this->get_service().assign(this->get_implementation(),
          native_descriptor, ec);
      asio::detail::throw_error(ec, "assign");
    }
  
    /// Assign an existing native descriptor to the descriptor.
    /*
     * This function opens the descriptor to hold an existing native descriptor.
     *
     * @param native_descriptor A native descriptor.
     *
     * @param ec Set to indicate what error occurred, if any.
     */
    asio::error_code assign(const native_handle_type& native_descriptor,
        asio::error_code& ec)
    {
      return this->get_service().assign(
          this->get_implementation(), native_descriptor, ec);
    }
  
    /// Determine whether the descriptor is open.
    bool is_open() const
    {
      return this->get_service().is_open(this->get_implementation());
    }
  
    /// Close the descriptor.
    /**
     * This function is used to close the descriptor. Any asynchronous read or
     * write operations will be cancelled immediately, and will complete with the
     * asio::error::operation_aborted error.
     *
     * @throws asio::system_error Thrown on failure. Note that, even if
     * the function indicates an error, the underlying descriptor is closed.
     */
    void close()
    {
      asio::error_code ec;
      this->get_service().close(this->get_implementation(), ec);
      asio::detail::throw_error(ec, "close");
    }
  
    /// Close the descriptor.
    /**
     * This function is used to close the descriptor. Any asynchronous read or
     * write operations will be cancelled immediately, and will complete with the
     * asio::error::operation_aborted error.
     *
     * @param ec Set to indicate what error occurred, if any. Note that, even if
     * the function indicates an error, the underlying descriptor is closed.
     */
    asio::error_code close(asio::error_code& ec)
    {
      return this->get_service().close(this->get_implementation(), ec);
    }
  
    /// Get the native descriptor representation.
    /**
     * This function may be used to obtain the underlying representation of the
     * descriptor. This is intended to allow access to native descriptor
     * functionality that is not otherwise provided.
     */
    native_handle_type native_handle()
    {
      return this->get_service().native_handle(this->get_implementation());
    }
  
    /// Release ownership of the native descriptor implementation.
    /**
     * This function may be used to obtain the underlying representation of the
     * descriptor. After calling this function, @c is_open() returns false. The
     * caller is responsible for closing the descriptor.
     *
     * All outstanding asynchronous read or write operations will finish
     * immediately, and the handlers for cancelled operations will be passed the
     * asio::error::operation_aborted error.
     */
    native_handle_type release()
    {
      return this->get_service().release(this->get_implementation());
    }
  
    /// Cancel all asynchronous operations associated with the descriptor.
    /**
     * This function causes all outstanding asynchronous read or write operations
     * to finish immediately, and the handlers for cancelled operations will be
     * passed the asio::error::operation_aborted error.
     *
     * @throws asio::system_error Thrown on failure.
     */
    void cancel()
    {
      asio::error_code ec;
      this->get_service().cancel(this->get_implementation(), ec);
      asio::detail::throw_error(ec, "cancel");
    }
  
    /// Cancel all asynchronous operations associated with the descriptor.
    /**
     * This function causes all outstanding asynchronous read or write operations
     * to finish immediately, and the handlers for cancelled operations will be
     * passed the asio::error::operation_aborted error.
     *
     * @param ec Set to indicate what error occurred, if any.
     */
    asio::error_code cancel(asio::error_code& ec)
    {
      return this->get_service().cancel(this->get_implementation(), ec);
    }
  
    /// Perform an IO control command on the descriptor.
    /**
     * This function is used to execute an IO control command on the descriptor.
     *
     * @param command The IO control command to be performed on the descriptor.
     *
     * @throws asio::system_error Thrown on failure.
     *
     * @sa IoControlCommand @n
     * asio::posix::descriptor_base::bytes_readable @n
     * asio::posix::descriptor_base::non_blocking_io
     *
     * @par Example
     * Getting the number of bytes ready to read:
     * @code
     * asio::posix::stream_descriptor descriptor(io_service);
     * ...
     * asio::posix::stream_descriptor::bytes_readable command;
     * descriptor.io_control(command);
     * std::size_t bytes_readable = command.get();
     * @endcode
     */
    template <typename IoControlCommand>
    void io_control(IoControlCommand& command)
    {
      asio::error_code ec;
      this->get_service().io_control(this->get_implementation(), command, ec);
      asio::detail::throw_error(ec, "io_control");
    }
  
    /// Perform an IO control command on the descriptor.
    /**
     * This function is used to execute an IO control command on the descriptor.
     *
     * @param command The IO control command to be performed on the descriptor.
     *
     * @param ec Set to indicate what error occurred, if any.
     *
     * @sa IoControlCommand @n
     * asio::posix::descriptor_base::bytes_readable @n
     * asio::posix::descriptor_base::non_blocking_io
     *
     * @par Example
     * Getting the number of bytes ready to read:
     * @code
     * asio::posix::stream_descriptor descriptor(io_service);
     * ...
     * asio::posix::stream_descriptor::bytes_readable command;
     * asio::error_code ec;
     * descriptor.io_control(command, ec);
     * if (ec)
     * {
     *   // An error occurred.
     * }
     * std::size_t bytes_readable = command.get();
     * @endcode
     */
    template <typename IoControlCommand>
    asio::error_code io_control(IoControlCommand& command,
        asio::error_code& ec)
    {
      return this->get_service().io_control(
          this->get_implementation(), command, ec);
    }
  
    /// Gets the non-blocking mode of the descriptor.
    /**
     * @returns @c true if the descriptor's synchronous operations will fail with
     * asio::error::would_block if they are unable to perform the requested
     * operation immediately. If @c false, synchronous operations will block
     * until complete.
     *
     * @note The non-blocking mode has no effect on the behaviour of asynchronous
     * operations. Asynchronous operations will never fail with the error
     * asio::error::would_block.
     */
    bool non_blocking() const
    {
      return this->get_service().non_blocking(this->get_implementation());
    }
  
    /// Sets the non-blocking mode of the descriptor.
    /**
     * @param mode If @c true, the descriptor's synchronous operations will fail
     * with asio::error::would_block if they are unable to perform the
     * requested operation immediately. If @c false, synchronous operations will
     * block until complete.
     *
     * @throws asio::system_error Thrown on failure.
     *
     * @note The non-blocking mode has no effect on the behaviour of asynchronous
     * operations. Asynchronous operations will never fail with the error
     * asio::error::would_block.
     */
    void non_blocking(bool mode)
    {
      asio::error_code ec;
      this->get_service().non_blocking(this->get_implementation(), mode, ec);
      asio::detail::throw_error(ec, "non_blocking");
    }
  
    /// Sets the non-blocking mode of the descriptor.
    /**
     * @param mode If @c true, the descriptor's synchronous operations will fail
     * with asio::error::would_block if they are unable to perform the
     * requested operation immediately. If @c false, synchronous operations will
     * block until complete.
     *
     * @param ec Set to indicate what error occurred, if any.
     *
     * @note The non-blocking mode has no effect on the behaviour of asynchronous
     * operations. Asynchronous operations will never fail with the error
     * asio::error::would_block.
     */
    asio::error_code non_blocking(
        bool mode, asio::error_code& ec)
    {
      return this->get_service().non_blocking(
          this->get_implementation(), mode, ec);
    }
  
    /// Gets the non-blocking mode of the native descriptor implementation.
    /**
     * This function is used to retrieve the non-blocking mode of the underlying
     * native descriptor. This mode has no effect on the behaviour of the
     * descriptor object's synchronous operations.
     *
     * @returns @c true if the underlying descriptor is in non-blocking mode and
     * direct system calls may fail with asio::error::would_block (or the
     * equivalent system error).
     *
     * @note The current non-blocking mode is cached by the descriptor object.
     * Consequently, the return value may be incorrect if the non-blocking mode
     * was set directly on the native descriptor.
     */
    bool native_non_blocking() const
    {
      return this->get_service().native_non_blocking(
          this->get_implementation());
    }
  
    /// Sets the non-blocking mode of the native descriptor implementation.
    /**
     * This function is used to modify the non-blocking mode of the underlying
     * native descriptor. It has no effect on the behaviour of the descriptor
     * object's synchronous operations.
     *
     * @param mode If @c true, the underlying descriptor is put into non-blocking
     * mode and direct system calls may fail with asio::error::would_block
     * (or the equivalent system error).
     *
     * @throws asio::system_error Thrown on failure. If the @c mode is
     * @c false, but the current value of @c non_blocking() is @c true, this
     * function fails with asio::error::invalid_argument, as the
     * combination does not make sense.
     */
    void native_non_blocking(bool mode)
    {
      asio::error_code ec;
      this->get_service().native_non_blocking(
          this->get_implementation(), mode, ec);
      asio::detail::throw_error(ec, "native_non_blocking");
    }
  
    /// Sets the non-blocking mode of the native descriptor implementation.
    /**
     * This function is used to modify the non-blocking mode of the underlying
     * native descriptor. It has no effect on the behaviour of the descriptor
     * object's synchronous operations.
     *
     * @param mode If @c true, the underlying descriptor is put into non-blocking
     * mode and direct system calls may fail with asio::error::would_block
     * (or the equivalent system error).
     *
     * @param ec Set to indicate what error occurred, if any. If the @c mode is
     * @c false, but the current value of @c non_blocking() is @c true, this
     * function fails with asio::error::invalid_argument, as the
     * combination does not make sense.
     */
    asio::error_code native_non_blocking(
        bool mode, asio::error_code& ec)
    {
      return this->get_service().native_non_blocking(
          this->get_implementation(), mode, ec);
    }
  
    /// Wait for the descriptor to become ready to read, ready to write, or to
    /// have pending error conditions.
    /**
     * This function is used to perform a blocking wait for a descriptor to enter
     * a ready to read, write or error condition state.
     *
     * @param w Specifies the desired descriptor state.
     *
     * @par Example
     * Waiting for a descriptor to become readable.
     * @code
     * asio::posix::stream_descriptor descriptor(io_service);
     * ...
     * descriptor.wait(asio::posix::stream_descriptor::wait_read);
     * @endcode
     */
    void wait(wait_type w)
    {
      asio::error_code ec;
      this->get_service().wait(this->get_implementation(), w, ec);
      asio::detail::throw_error(ec, "wait");
    }
  
    /// Wait for the descriptor to become ready to read, ready to write, or to
    /// have pending error conditions.
    /**
     * This function is used to perform a blocking wait for a descriptor to enter
     * a ready to read, write or error condition state.
     *
     * @param w Specifies the desired descriptor state.
     *
     * @param ec Set to indicate what error occurred, if any.
     *
     * @par Example
     * Waiting for a descriptor to become readable.
     * @code
     * asio::posix::stream_descriptor descriptor(io_service);
     * ...
     * asio::error_code ec;
     * descriptor.wait(asio::posix::stream_descriptor::wait_read, ec);
     * @endcode
     */
    asio::error_code wait(wait_type w, asio::error_code& ec)
    {
      return this->get_service().wait(this->get_implementation(), w, ec);
    }
  
    /// Asynchronously wait for the descriptor to become ready to read, ready to
    /// write, or to have pending error conditions.
    /**
     * This function is used to perform an asynchronous wait for a descriptor to
     * enter a ready to read, write or error condition state.
     *
     * @param w Specifies the desired descriptor state.
     *
     * @param handler The handler to be called when the wait 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().
     *
     * @par Example
     * @code
     * void wait_handler(const asio::error_code& error)
     * {
     *   if (!error)
     *   {
     *     // Wait succeeded.
     *   }
     * }
     *
     * ...
     *
     * asio::posix::stream_descriptor descriptor(io_service);
     * ...
     * descriptor.async_wait(
     *     asio::posix::stream_descriptor::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));
    }
  
  protected:
    /// Protected destructor to prevent deletion through this type.
    ~basic_descriptor()
    {
    }
  };
  
  } // namespace posix
  } // namespace asio
  
  #include "asio/detail/pop_options.hpp"
  
  #endif // defined(ASIO_HAS_POSIX_STREAM_DESCRIPTOR)
         //   || defined(GENERATING_DOCUMENTATION)
  
  #endif // ASIO_POSIX_BASIC_DESCRIPTOR_HPP
  