Boost C++ Libraries

boost/asio/basic_serial_port.hpp

//
// basic_serial_port.hpp
// ~~~~~~~~~~~~~~~~~~~~~
//
// Copyright (c) 2003-2024 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 BOOST_ASIO_BASIC_SERIAL_PORT_HPP
#define BOOST_ASIO_BASIC_SERIAL_PORT_HPP

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

#include <boost/asio/detail/config.hpp>

#if defined(BOOST_ASIO_HAS_SERIAL_PORT) \
  || defined(GENERATING_DOCUMENTATION)

#include <string>
#include <utility>
#include <boost/asio/any_io_executor.hpp>
#include <boost/asio/async_result.hpp>
#include <boost/asio/detail/handler_type_requirements.hpp>
#include <boost/asio/detail/io_object_impl.hpp>
#include <boost/asio/detail/non_const_lvalue.hpp>
#include <boost/asio/detail/throw_error.hpp>
#include <boost/asio/detail/type_traits.hpp>
#include <boost/asio/error.hpp>
#include <boost/asio/execution_context.hpp>
#include <boost/asio/serial_port_base.hpp>
#if defined(BOOST_ASIO_HAS_IOCP)
# include <boost/asio/detail/win_iocp_serial_port_service.hpp>
#else
# include <boost/asio/detail/posix_serial_port_service.hpp>
#endif

#include <boost/asio/detail/push_options.hpp>

namespace boost {
namespace asio {

/// Provides serial port functionality.
/**
 * The basic_serial_port class provides a wrapper over serial port
 * functionality.
 *
 * @par Thread Safety
 * @e Distinct @e objects: Safe.@n
 * @e Shared @e objects: Unsafe.
 */
template <typename Executor = any_io_executor>
class basic_serial_port
  : public serial_port_base
{
private:
  class initiate_async_write_some;
  class initiate_async_read_some;

public:
  /// The type of the executor associated with the object.
  typedef Executor executor_type;

  /// Rebinds the serial port type to another executor.
  template <typename Executor1>
  struct rebind_executor
  {
    /// The serial port type when rebound to the specified executor.
    typedef basic_serial_port<Executor1> other;
  };

  /// The native representation of a serial port.
#if defined(GENERATING_DOCUMENTATION)
  typedef implementation_defined native_handle_type;
#elif defined(BOOST_ASIO_HAS_IOCP)
  typedef detail::win_iocp_serial_port_service::native_handle_type
    native_handle_type;
#else
  typedef detail::posix_serial_port_service::native_handle_type
    native_handle_type;
#endif

  /// A basic_basic_serial_port is always the lowest layer.
  typedef basic_serial_port lowest_layer_type;

  /// Construct a basic_serial_port without opening it.
  /**
   * This constructor creates a serial port without opening it.
   *
   * @param ex The I/O executor that the serial port will use, by default, to
   * dispatch handlers for any asynchronous operations performed on the
   * serial port.
   */
  explicit basic_serial_port(const executor_type& ex)
    : impl_(0, ex)
  {
  }

  /// Construct a basic_serial_port without opening it.
  /**
   * This constructor creates a serial port without opening it.
   *
   * @param context An execution context which provides the I/O executor that
   * the serial port will use, by default, to dispatch handlers for any
   * asynchronous operations performed on the serial port.
   */
  template <typename ExecutionContext>
  explicit basic_serial_port(ExecutionContext& context,
      constraint_t<
        is_convertible<ExecutionContext&, execution_context&>::value,
        defaulted_constraint
      > = defaulted_constraint())
    : impl_(0, 0, context)
  {
  }

  /// Construct and open a basic_serial_port.
  /**
   * This constructor creates and opens a serial port for the specified device
   * name.
   *
   * @param ex The I/O executor that the serial port will use, by default, to
   * dispatch handlers for any asynchronous operations performed on the
   * serial port.
   *
   * @param device The platform-specific device name for this serial
   * port.
   */
  basic_serial_port(const executor_type& ex, const char* device)
    : impl_(0, ex)
  {
    boost::system::error_code ec;
    impl_.get_service().open(impl_.get_implementation(), device, ec);
    boost::asio::detail::throw_error(ec, "open");
  }

  /// Construct and open a basic_serial_port.
  /**
   * This constructor creates and opens a serial port for the specified device
   * name.
   *
   * @param context An execution context which provides the I/O executor that
   * the serial port will use, by default, to dispatch handlers for any
   * asynchronous operations performed on the serial port.
   *
   * @param device The platform-specific device name for this serial
   * port.
   */
  template <typename ExecutionContext>
  basic_serial_port(ExecutionContext& context, const char* device,
      constraint_t<
        is_convertible<ExecutionContext&, execution_context&>::value
      > = 0)
    : impl_(0, 0, context)
  {
    boost::system::error_code ec;
    impl_.get_service().open(impl_.get_implementation(), device, ec);
    boost::asio::detail::throw_error(ec, "open");
  }

  /// Construct and open a basic_serial_port.
  /**
   * This constructor creates and opens a serial port for the specified device
   * name.
   *
   * @param ex The I/O executor that the serial port will use, by default, to
   * dispatch handlers for any asynchronous operations performed on the
   * serial port.
   *
   * @param device The platform-specific device name for this serial
   * port.
   */
  basic_serial_port(const executor_type& ex, const std::string& device)
    : impl_(0, ex)
  {
    boost::system::error_code ec;
    impl_.get_service().open(impl_.get_implementation(), device, ec);
    boost::asio::detail::throw_error(ec, "open");
  }

  /// Construct and open a basic_serial_port.
  /**
   * This constructor creates and opens a serial port for the specified device
   * name.
   *
   * @param context An execution context which provides the I/O executor that
   * the serial port will use, by default, to dispatch handlers for any
   * asynchronous operations performed on the serial port.
   *
   * @param device The platform-specific device name for this serial
   * port.
   */
  template <typename ExecutionContext>
  basic_serial_port(ExecutionContext& context, const std::string& device,
      constraint_t<
        is_convertible<ExecutionContext&, execution_context&>::value
      > = 0)
    : impl_(0, 0, context)
  {
    boost::system::error_code ec;
    impl_.get_service().open(impl_.get_implementation(), device, ec);
    boost::asio::detail::throw_error(ec, "open");
  }

  /// Construct a basic_serial_port on an existing native serial port.
  /**
   * This constructor creates a serial port object to hold an existing native
   * serial port.
   *
   * @param ex The I/O executor that the serial port will use, by default, to
   * dispatch handlers for any asynchronous operations performed on the
   * serial port.
   *
   * @param native_serial_port A native serial port.
   *
   * @throws boost::system::system_error Thrown on failure.
   */
  basic_serial_port(const executor_type& ex,
      const native_handle_type& native_serial_port)
    : impl_(0, ex)
  {
    boost::system::error_code ec;
    impl_.get_service().assign(impl_.get_implementation(),
        native_serial_port, ec);
    boost::asio::detail::throw_error(ec, "assign");
  }

  /// Construct a basic_serial_port on an existing native serial port.
  /**
   * This constructor creates a serial port object to hold an existing native
   * serial port.
   *
   * @param context An execution context which provides the I/O executor that
   * the serial port will use, by default, to dispatch handlers for any
   * asynchronous operations performed on the serial port.
   *
   * @param native_serial_port A native serial port.
   *
   * @throws boost::system::system_error Thrown on failure.
   */
  template <typename ExecutionContext>
  basic_serial_port(ExecutionContext& context,
      const native_handle_type& native_serial_port,
      constraint_t<
        is_convertible<ExecutionContext&, execution_context&>::value
      > = 0)
    : impl_(0, 0, context)
  {
    boost::system::error_code ec;
    impl_.get_service().assign(impl_.get_implementation(),
        native_serial_port, ec);
    boost::asio::detail::throw_error(ec, "assign");
  }

  /// Move-construct a basic_serial_port from another.
  /**
   * This constructor moves a serial port from one object to another.
   *
   * @param other The other basic_serial_port 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_serial_port(const executor_type&)
   * constructor.
   */
  basic_serial_port(basic_serial_port&& other)
    : impl_(std::move(other.impl_))
  {
  }

  /// Move-assign a basic_serial_port from another.
  /**
   * This assignment operator moves a serial port from one object to another.
   *
   * @param other The other basic_serial_port 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_serial_port(const executor_type&)
   * constructor.
   */
  basic_serial_port& operator=(basic_serial_port&& other)
  {
    impl_ = std::move(other.impl_);
    return *this;
  }

  // All serial ports have access to each other's implementations.
  template <typename Executor1>
  friend class basic_serial_port;

  /// Move-construct a basic_serial_port from a serial port of another executor
  /// type.
  /**
   * This constructor moves a serial port from one object to another.
   *
   * @param other The other basic_serial_port 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_serial_port(const executor_type&)
   * constructor.
   */
  template <typename Executor1>
  basic_serial_port(basic_serial_port<Executor1>&& other,
      constraint_t<
        is_convertible<Executor1, Executor>::value,
        defaulted_constraint
      > = defaulted_constraint())
    : impl_(std::move(other.impl_))
  {
  }

  /// Move-assign a basic_serial_port from a serial port of another executor
  /// type.
  /**
   * This assignment operator moves a serial port from one object to another.
   *
   * @param other The other basic_serial_port 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_serial_port(const executor_type&)
   * constructor.
   */
  template <typename Executor1>
  constraint_t<
    is_convertible<Executor1, Executor>::value,
    basic_serial_port&
  > operator=(basic_serial_port<Executor1>&& other)
  {
    basic_serial_port tmp(std::move(other));
    impl_ = std::move(tmp.impl_);
    return *this;
  }

  /// Destroys the serial port.
  /**
   * This function destroys the serial port, cancelling any outstanding
   * asynchronous wait operations associated with the serial port as if by
   * calling @c cancel.
   */
  ~basic_serial_port()
  {
  }

  /// Get the executor associated with the object.
  const executor_type& get_executor() noexcept
  {
    return impl_.get_executor();
  }

  /// Get a reference to the lowest layer.
  /**
   * This function returns a reference to the lowest layer in a stack of
   * layers. Since a basic_serial_port 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_serial_port 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;
  }

  /// Open the serial port using the specified device name.
  /**
   * This function opens the serial port for the specified device name.
   *
   * @param device The platform-specific device name.
   *
   * @throws boost::system::system_error Thrown on failure.
   */
  void open(const std::string& device)
  {
    boost::system::error_code ec;
    impl_.get_service().open(impl_.get_implementation(), device, ec);
    boost::asio::detail::throw_error(ec, "open");
  }

  /// Open the serial port using the specified device name.
  /**
   * This function opens the serial port using the given platform-specific
   * device name.
   *
   * @param device The platform-specific device name.
   *
   * @param ec Set the indicate what error occurred, if any.
   */
  BOOST_ASIO_SYNC_OP_VOID open(const std::string& device,
      boost::system::error_code& ec)
  {
    impl_.get_service().open(impl_.get_implementation(), device, ec);
    BOOST_ASIO_SYNC_OP_VOID_RETURN(ec);
  }

  /// Assign an existing native serial port to the serial port.
  /*
   * This function opens the serial port to hold an existing native serial port.
   *
   * @param native_serial_port A native serial port.
   *
   * @throws boost::system::system_error Thrown on failure.
   */
  void assign(const native_handle_type& native_serial_port)
  {
    boost::system::error_code ec;
    impl_.get_service().assign(impl_.get_implementation(),
        native_serial_port, ec);
    boost::asio::detail::throw_error(ec, "assign");
  }

  /// Assign an existing native serial port to the serial port.
  /*
   * This function opens the serial port to hold an existing native serial port.
   *
   * @param native_serial_port A native serial port.
   *
   * @param ec Set to indicate what error occurred, if any.
   */
  BOOST_ASIO_SYNC_OP_VOID assign(const native_handle_type& native_serial_port,
      boost::system::error_code& ec)
  {
    impl_.get_service().assign(impl_.get_implementation(),
        native_serial_port, ec);
    BOOST_ASIO_SYNC_OP_VOID_RETURN(ec);
  }

  /// Determine whether the serial port is open.
  bool is_open() const
  {
    return impl_.get_service().is_open(impl_.get_implementation());
  }

  /// Close the serial port.
  /**
   * This function is used to close the serial port. Any asynchronous read or
   * write operations will be cancelled immediately, and will complete with the
   * boost::asio::error::operation_aborted error.
   *
   * @throws boost::system::system_error Thrown on failure.
   */
  void close()
  {
    boost::system::error_code ec;
    impl_.get_service().close(impl_.get_implementation(), ec);
    boost::asio::detail::throw_error(ec, "close");
  }

  /// Close the serial port.
  /**
   * This function is used to close the serial port. Any asynchronous read or
   * write operations will be cancelled immediately, and will complete with the
   * boost::asio::error::operation_aborted error.
   *
   * @param ec Set to indicate what error occurred, if any.
   */
  BOOST_ASIO_SYNC_OP_VOID close(boost::system::error_code& ec)
  {
    impl_.get_service().close(impl_.get_implementation(), ec);
    BOOST_ASIO_SYNC_OP_VOID_RETURN(ec);
  }

  /// Get the native serial port representation.
  /**
   * This function may be used to obtain the underlying representation of the
   * serial port. This is intended to allow access to native serial port
   * functionality that is not otherwise provided.
   */
  native_handle_type native_handle()
  {
    return impl_.get_service().native_handle(impl_.get_implementation());
  }

  /// Cancel all asynchronous operations associated with the serial port.
  /**
   * This function causes all outstanding asynchronous read or write operations
   * to finish immediately, and the handlers for cancelled operations will be
   * passed the boost::asio::error::operation_aborted error.
   *
   * @throws boost::system::system_error Thrown on failure.
   */
  void cancel()
  {
    boost::system::error_code ec;
    impl_.get_service().cancel(impl_.get_implementation(), ec);
    boost::asio::detail::throw_error(ec, "cancel");
  }

  /// Cancel all asynchronous operations associated with the serial port.
  /**
   * This function causes all outstanding asynchronous read or write operations
   * to finish immediately, and the handlers for cancelled operations will be
   * passed the boost::asio::error::operation_aborted error.
   *
   * @param ec Set to indicate what error occurred, if any.
   */
  BOOST_ASIO_SYNC_OP_VOID cancel(boost::system::error_code& ec)
  {
    impl_.get_service().cancel(impl_.get_implementation(), ec);
    BOOST_ASIO_SYNC_OP_VOID_RETURN(ec);
  }

  /// Send a break sequence to the serial port.
  /**
   * This function causes a break sequence of platform-specific duration to be
   * sent out the serial port.
   *
   * @throws boost::system::system_error Thrown on failure.
   */
  void send_break()
  {
    boost::system::error_code ec;
    impl_.get_service().send_break(impl_.get_implementation(), ec);
    boost::asio::detail::throw_error(ec, "send_break");
  }

  /// Send a break sequence to the serial port.
  /**
   * This function causes a break sequence of platform-specific duration to be
   * sent out the serial port.
   *
   * @param ec Set to indicate what error occurred, if any.
   */
  BOOST_ASIO_SYNC_OP_VOID send_break(boost::system::error_code& ec)
  {
    impl_.get_service().send_break(impl_.get_implementation(), ec);
    BOOST_ASIO_SYNC_OP_VOID_RETURN(ec);
  }

  /// Set an option on the serial port.
  /**
   * This function is used to set an option on the serial port.
   *
   * @param option The option value to be set on the serial port.
   *
   * @throws boost::system::system_error Thrown on failure.
   *
   * @sa SettableSerialPortOption @n
   * boost::asio::serial_port_base::baud_rate @n
   * boost::asio::serial_port_base::flow_control @n
   * boost::asio::serial_port_base::parity @n
   * boost::asio::serial_port_base::stop_bits @n
   * boost::asio::serial_port_base::character_size
   */
  template <typename SettableSerialPortOption>
  void set_option(const SettableSerialPortOption& option)
  {
    boost::system::error_code ec;
    impl_.get_service().set_option(impl_.get_implementation(), option, ec);
    boost::asio::detail::throw_error(ec, "set_option");
  }

  /// Set an option on the serial port.
  /**
   * This function is used to set an option on the serial port.
   *
   * @param option The option value to be set on the serial port.
   *
   * @param ec Set to indicate what error occurred, if any.
   *
   * @sa SettableSerialPortOption @n
   * boost::asio::serial_port_base::baud_rate @n
   * boost::asio::serial_port_base::flow_control @n
   * boost::asio::serial_port_base::parity @n
   * boost::asio::serial_port_base::stop_bits @n
   * boost::asio::serial_port_base::character_size
   */
  template <typename SettableSerialPortOption>
  BOOST_ASIO_SYNC_OP_VOID set_option(const SettableSerialPortOption& option,
      boost::system::error_code& ec)
  {
    impl_.get_service().set_option(impl_.get_implementation(), option, ec);
    BOOST_ASIO_SYNC_OP_VOID_RETURN(ec);
  }

  /// Get an option from the serial port.
  /**
   * This function is used to get the current value of an option on the serial
   * port.
   *
   * @param option The option value to be obtained from the serial port.
   *
   * @throws boost::system::system_error Thrown on failure.
   *
   * @sa GettableSerialPortOption @n
   * boost::asio::serial_port_base::baud_rate @n
   * boost::asio::serial_port_base::flow_control @n
   * boost::asio::serial_port_base::parity @n
   * boost::asio::serial_port_base::stop_bits @n
   * boost::asio::serial_port_base::character_size
   */
  template <typename GettableSerialPortOption>
  void get_option(GettableSerialPortOption& option) const
  {
    boost::system::error_code ec;
    impl_.get_service().get_option(impl_.get_implementation(), option, ec);
    boost::asio::detail::throw_error(ec, "get_option");
  }

  /// Get an option from the serial port.
  /**
   * This function is used to get the current value of an option on the serial
   * port.
   *
   * @param option The option value to be obtained from the serial port.
   *
   * @param ec Set to indicate what error occurred, if any.
   *
   * @sa GettableSerialPortOption @n
   * boost::asio::serial_port_base::baud_rate @n
   * boost::asio::serial_port_base::flow_control @n
   * boost::asio::serial_port_base::parity @n
   * boost::asio::serial_port_base::stop_bits @n
   * boost::asio::serial_port_base::character_size
   */
  template <typename GettableSerialPortOption>
  BOOST_ASIO_SYNC_OP_VOID get_option(GettableSerialPortOption& option,
      boost::system::error_code& ec) const
  {
    impl_.get_service().get_option(impl_.get_implementation(), option, ec);
    BOOST_ASIO_SYNC_OP_VOID_RETURN(ec);
  }

  /// Write some data to the serial port.
  /**
   * This function is used to write data to the serial port. The function call
   * will block until one or more bytes of the data has been written
   * successfully, or until an error occurs.
   *
   * @param buffers One or more data buffers to be written to the serial port.
   *
   * @returns The number of bytes written.
   *
   * @throws boost::system::system_error Thrown on failure. An error code of
   * boost::asio::error::eof indicates that the connection was closed by the
   * peer.
   *
   * @note The write_some operation may not transmit all of the data to the
   * peer. Consider using the @ref write function if you need to ensure that
   * all data is written before the blocking operation completes.
   *
   * @par Example
   * To write a single data buffer use the @ref buffer function as follows:
   * @code
   * basic_serial_port.write_some(boost::asio::buffer(data, size));
   * @endcode
   * See the @ref buffer documentation for information on writing multiple
   * buffers in one go, and how to use it with arrays, boost::array or
   * std::vector.
   */
  template <typename ConstBufferSequence>
  std::size_t write_some(const ConstBufferSequence& buffers)
  {
    boost::system::error_code ec;
    std::size_t s = impl_.get_service().write_some(
        impl_.get_implementation(), buffers, ec);
    boost::asio::detail::throw_error(ec, "write_some");
    return s;
  }

  /// Write some data to the serial port.
  /**
   * This function is used to write data to the serial port. The function call
   * will block until one or more bytes of the data has been written
   * successfully, or until an error occurs.
   *
   * @param buffers One or more data buffers to be written to the serial port.
   *
   * @param ec Set to indicate what error occurred, if any.
   *
   * @returns The number of bytes written. Returns 0 if an error occurred.
   *
   * @note The write_some operation may not transmit all of the data to the
   * peer. Consider using the @ref write function if you need to ensure that
   * all data is written before the blocking operation completes.
   */
  template <typename ConstBufferSequence>
  std::size_t write_some(const ConstBufferSequence& buffers,
      boost::system::error_code& ec)
  {
    return impl_.get_service().write_some(
        impl_.get_implementation(), buffers, ec);
  }

  /// Start an asynchronous write.
  /**
   * This function is used to asynchronously write data to the serial port.
   * It is an initiating function for an @ref asynchronous_operation, and always
   * returns immediately.
   *
   * @param buffers One or more data buffers to be written to the serial port.
   * Although the buffers object may be copied as necessary, ownership of the
   * underlying memory blocks is retained by the caller, which must guarantee
   * that they remain valid until the completion handler is called.
   *
   * @param token The @ref completion_token that will be used to produce a
   * completion handler, which will be called when the write completes.
   * Potential completion tokens include @ref use_future, @ref use_awaitable,
   * @ref yield_context, or a function object with the correct completion
   * signature. The function signature of the completion handler must be:
   * @code void handler(
   *   const boost::system::error_code& error, // Result of operation.
   *   std::size_t bytes_transferred // Number of bytes written.
   * ); @endcode
   * Regardless of whether the asynchronous operation completes immediately or
   * not, the completion handler will not be invoked from within this function.
   * On immediate completion, invocation of the handler will be performed in a
   * manner equivalent to using boost::asio::post().
   *
   * @par Completion Signature
   * @code void(boost::system::error_code, std::size_t) @endcode
   *
   * @note The write operation may not transmit all of the data to the peer.
   * Consider using the @ref async_write function if you need to ensure that all
   * data is written before the asynchronous operation completes.
   *
   * @par Example
   * To write a single data buffer use the @ref buffer function as follows:
   * @code
   * basic_serial_port.async_write_some(
   *     boost::asio::buffer(data, size), handler);
   * @endcode
   * See the @ref buffer documentation for information on writing multiple
   * buffers in one go, and how to use it with arrays, boost::array or
   * std::vector.
   *
   * @par Per-Operation Cancellation
   * On POSIX or Windows operating systems, this asynchronous operation supports
   * cancellation for the following boost::asio::cancellation_type values:
   *
   * @li @c cancellation_type::terminal
   *
   * @li @c cancellation_type::partial
   *
   * @li @c cancellation_type::total
   */
  template <typename ConstBufferSequence,
      BOOST_ASIO_COMPLETION_TOKEN_FOR(void (boost::system::error_code,
        std::size_t)) WriteToken = default_completion_token_t<executor_type>>
  auto async_write_some(const ConstBufferSequence& buffers,
      WriteToken&& token = default_completion_token_t<executor_type>())
    -> decltype(
      async_initiate<WriteToken,
        void (boost::system::error_code, std::size_t)>(
          declval<initiate_async_write_some>(), token, buffers))
  {
    return async_initiate<WriteToken,
      void (boost::system::error_code, std::size_t)>(
        initiate_async_write_some(this), token, buffers);
  }

  /// Read some data from the serial port.
  /**
   * This function is used to read data from the serial port. The function
   * call will block until one or more bytes of data has been read successfully,
   * or until an error occurs.
   *
   * @param buffers One or more buffers into which the data will be read.
   *
   * @returns The number of bytes read.
   *
   * @throws boost::system::system_error Thrown on failure. An error code of
   * boost::asio::error::eof indicates that the connection was closed by the
   * peer.
   *
   * @note The read_some operation may not read all of the requested number of
   * bytes. Consider using the @ref read function if you need to ensure that
   * the requested amount of data is read before the blocking operation
   * completes.
   *
   * @par Example
   * To read into a single data buffer use the @ref buffer function as follows:
   * @code
   * basic_serial_port.read_some(boost::asio::buffer(data, size));
   * @endcode
   * See the @ref buffer documentation for information on reading into multiple
   * buffers in one go, and how to use it with arrays, boost::array or
   * std::vector.
   */
  template <typename MutableBufferSequence>
  std::size_t read_some(const MutableBufferSequence& buffers)
  {
    boost::system::error_code ec;
    std::size_t s = impl_.get_service().read_some(
        impl_.get_implementation(), buffers, ec);
    boost::asio::detail::throw_error(ec, "read_some");
    return s;
  }

  /// Read some data from the serial port.
  /**
   * This function is used to read data from the serial port. The function
   * call will block until one or more bytes of data has been read successfully,
   * or until an error occurs.
   *
   * @param buffers One or more buffers into which the data will be read.
   *
   * @param ec Set to indicate what error occurred, if any.
   *
   * @returns The number of bytes read. Returns 0 if an error occurred.
   *
   * @note The read_some operation may not read all of the requested number of
   * bytes. Consider using the @ref read function if you need to ensure that
   * the requested amount of data is read before the blocking operation
   * completes.
   */
  template <typename MutableBufferSequence>
  std::size_t read_some(const MutableBufferSequence& buffers,
      boost::system::error_code& ec)
  {
    return impl_.get_service().read_some(
        impl_.get_implementation(), buffers, ec);
  }

  /// Start an asynchronous read.
  /**
   * This function is used to asynchronously read data from the serial port.
   * It is an initiating function for an @ref asynchronous_operation, and always
   * returns immediately.
   *
   * @param buffers One or more buffers into which the data will be read.
   * Although the buffers object may be copied as necessary, ownership of the
   * underlying memory blocks is retained by the caller, which must guarantee
   * that they remain valid until the completion handler is called.
   *
   * @param token The @ref completion_token that will be used to produce a
   * completion handler, which will be called when the read completes.
   * Potential completion tokens include @ref use_future, @ref use_awaitable,
   * @ref yield_context, or a function object with the correct completion
   * signature. The function signature of the completion handler must be:
   * @code void handler(
   *   const boost::system::error_code& error, // Result of operation.
   *   std::size_t bytes_transferred // Number of bytes read.
   * ); @endcode
   * Regardless of whether the asynchronous operation completes immediately or
   * not, the completion handler will not be invoked from within this function.
   * On immediate completion, invocation of the handler will be performed in a
   * manner equivalent to using boost::asio::post().
   *
   * @par Completion Signature
   * @code void(boost::system::error_code, std::size_t) @endcode
   *
   * @note The read operation may not read all of the requested number of bytes.
   * Consider using the @ref async_read function if you need to ensure that the
   * requested amount of data is read before the asynchronous operation
   * completes.
   *
   * @par Example
   * To read into a single data buffer use the @ref buffer function as follows:
   * @code
   * basic_serial_port.async_read_some(
   *     boost::asio::buffer(data, size), handler);
   * @endcode
   * See the @ref buffer documentation for information on reading into multiple
   * buffers in one go, and how to use it with arrays, boost::array or
   * std::vector.
   *
   * @par Per-Operation Cancellation
   * On POSIX or Windows operating systems, this asynchronous operation supports
   * cancellation for the following boost::asio::cancellation_type values:
   *
   * @li @c cancellation_type::terminal
   *
   * @li @c cancellation_type::partial
   *
   * @li @c cancellation_type::total
   */
  template <typename MutableBufferSequence,
      BOOST_ASIO_COMPLETION_TOKEN_FOR(void (boost::system::error_code,
        std::size_t)) ReadToken = default_completion_token_t<executor_type>>
  auto async_read_some(const MutableBufferSequence& buffers,
      ReadToken&& token = default_completion_token_t<executor_type>())
    -> decltype(
      async_initiate<ReadToken,
        void (boost::system::error_code, std::size_t)>(
          declval<initiate_async_read_some>(), token, buffers))
  {
    return async_initiate<ReadToken,
      void (boost::system::error_code, std::size_t)>(
        initiate_async_read_some(this), token, buffers);
  }

private:
  // Disallow copying and assignment.
  basic_serial_port(const basic_serial_port&) = delete;
  basic_serial_port& operator=(const basic_serial_port&) = delete;

  class initiate_async_write_some
  {
  public:
    typedef Executor executor_type;

    explicit initiate_async_write_some(basic_serial_port* self)
      : self_(self)
    {
    }

    const executor_type& get_executor() const noexcept
    {
      return self_->get_executor();
    }

    template <typename WriteHandler, typename ConstBufferSequence>
    void operator()(WriteHandler&& handler,
        const ConstBufferSequence& buffers) const
    {
      // If you get an error on the following line it means that your handler
      // does not meet the documented type requirements for a WriteHandler.
      BOOST_ASIO_WRITE_HANDLER_CHECK(WriteHandler, handler) type_check;

      detail::non_const_lvalue<WriteHandler> handler2(handler);
      self_->impl_.get_service().async_write_some(
          self_->impl_.get_implementation(), buffers,
          handler2.value, self_->impl_.get_executor());
    }

  private:
    basic_serial_port* self_;
  };

  class initiate_async_read_some
  {
  public:
    typedef Executor executor_type;

    explicit initiate_async_read_some(basic_serial_port* self)
      : self_(self)
    {
    }

    const executor_type& get_executor() const noexcept
    {
      return self_->get_executor();
    }

    template <typename ReadHandler, typename MutableBufferSequence>
    void operator()(ReadHandler&& handler,
        const MutableBufferSequence& buffers) const
    {
      // If you get an error on the following line it means that your handler
      // does not meet the documented type requirements for a ReadHandler.
      BOOST_ASIO_READ_HANDLER_CHECK(ReadHandler, handler) type_check;

      detail::non_const_lvalue<ReadHandler> handler2(handler);
      self_->impl_.get_service().async_read_some(
          self_->impl_.get_implementation(), buffers,
          handler2.value, self_->impl_.get_executor());
    }

  private:
    basic_serial_port* self_;
  };

#if defined(BOOST_ASIO_HAS_IOCP)
  detail::io_object_impl<detail::win_iocp_serial_port_service, Executor> impl_;
#else
  detail::io_object_impl<detail::posix_serial_port_service, Executor> impl_;
#endif
};

} // namespace asio
} // namespace boost

#include <boost/asio/detail/pop_options.hpp>

#endif // defined(BOOST_ASIO_HAS_SERIAL_PORT)
       //   || defined(GENERATING_DOCUMENTATION)

#endif // BOOST_ASIO_BASIC_SERIAL_PORT_HPP