text: //
  // strand.hpp
  // ~~~~~~~~~~
  //
  // Copyright (c) 2003-2018 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 EGT_ASIO_STRAND_HPP
  #define EGT_ASIO_STRAND_HPP
  
  #if defined(_MSC_VER) && (_MSC_VER >= 1200)
  # pragma once
  #endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
  
  #include <egt/asio/detail/config.hpp>
  #include <egt/asio/detail/strand_executor_service.hpp>
  #include <egt/asio/detail/type_traits.hpp>
  
  #include <egt/asio/detail/push_options.hpp>
  
  namespace egt {
  namespace asio {
  
  /// Provides serialised function invocation for any executor type.
  template <typename Executor>
  class strand
  {
  public:
    /// The type of the underlying executor.
    typedef Executor inner_executor_type;
  
    /// Default constructor.
    /**
     * This constructor is only valid if the underlying executor type is default
     * constructible.
     */
    strand()
      : executor_(),
        impl_(use_service<detail::strand_executor_service>(
              executor_.context()).create_implementation())
    {
    }
  
    /// Construct a strand for the specified executor.
    explicit strand(const Executor& e)
      : executor_(e),
        impl_(use_service<detail::strand_executor_service>(
              executor_.context()).create_implementation())
    {
    }
  
    /// Copy constructor.
    strand(const strand& other) EGT_ASIO_NOEXCEPT
      : executor_(other.executor_),
        impl_(other.impl_)
    {
    }
  
    /// Converting constructor.
    /**
     * This constructor is only valid if the @c OtherExecutor type is convertible
     * to @c Executor.
     */
    template <class OtherExecutor>
    strand(
        const strand<OtherExecutor>& other) EGT_ASIO_NOEXCEPT
      : executor_(other.executor_),
        impl_(other.impl_)
    {
    }
  
    /// Assignment operator.
    strand& operator=(const strand& other) EGT_ASIO_NOEXCEPT
    {
      executor_ = other.executor_;
      impl_ = other.impl_;
      return *this;
    }
  
    /// Converting assignment operator.
    /**
     * This assignment operator is only valid if the @c OtherExecutor type is
     * convertible to @c Executor.
     */
    template <class OtherExecutor>
    strand& operator=(
        const strand<OtherExecutor>& other) EGT_ASIO_NOEXCEPT
    {
      executor_ = other.executor_;
      impl_ = other.impl_;
      return *this;
    }
  
  #if defined(EGT_ASIO_HAS_MOVE) || defined(GENERATING_DOCUMENTATION)
    /// Move constructor.
    strand(strand&& other) EGT_ASIO_NOEXCEPT
      : executor_(EGT_ASIO_MOVE_CAST(Executor)(other.executor_)),
        impl_(EGT_ASIO_MOVE_CAST(implementation_type)(other.impl_))
    {
    }
  
    /// Converting move constructor.
    /**
     * This constructor is only valid if the @c OtherExecutor type is convertible
     * to @c Executor.
     */
    template <class OtherExecutor>
    strand(strand<OtherExecutor>&& other) EGT_ASIO_NOEXCEPT
      : executor_(EGT_ASIO_MOVE_CAST(OtherExecutor)(other)),
        impl_(EGT_ASIO_MOVE_CAST(implementation_type)(other.impl_))
    {
    }
  
    /// Move assignment operator.
    strand& operator=(strand&& other) EGT_ASIO_NOEXCEPT
    {
      executor_ = EGT_ASIO_MOVE_CAST(Executor)(other);
      impl_ = EGT_ASIO_MOVE_CAST(implementation_type)(other.impl_);
      return *this;
    }
  
    /// Converting move assignment operator.
    /**
     * This assignment operator is only valid if the @c OtherExecutor type is
     * convertible to @c Executor.
     */
    template <class OtherExecutor>
    strand& operator=(
        const strand<OtherExecutor>&& other) EGT_ASIO_NOEXCEPT
    {
      executor_ = EGT_ASIO_MOVE_CAST(OtherExecutor)(other);
      impl_ = EGT_ASIO_MOVE_CAST(implementation_type)(other.impl_);
      return *this;
    }
  #endif // defined(EGT_ASIO_HAS_MOVE) || defined(GENERATING_DOCUMENTATION)
  
    /// Destructor.
    ~strand()
    {
    }
  
    /// Obtain the underlying executor.
    inner_executor_type get_inner_executor() const EGT_ASIO_NOEXCEPT
    {
      return executor_;
    }
  
    /// Obtain the underlying execution context.
    execution_context& context() const EGT_ASIO_NOEXCEPT
    {
      return executor_.context();
    }
  
    /// Inform the strand that it has some outstanding work to do.
    /**
     * The strand delegates this call to its underlying executor.
     */
    void on_work_started() const EGT_ASIO_NOEXCEPT
    {
      executor_.on_work_started();
    }
  
    /// Inform the strand that some work is no longer outstanding.
    /**
     * The strand delegates this call to its underlying executor.
     */
    void on_work_finished() const EGT_ASIO_NOEXCEPT
    {
      executor_.on_work_finished();
    }
  
    /// Request the strand to invoke the given function object.
    /**
     * 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(EGT_ASIO_MOVE_ARG(Function) f, const Allocator& a) const
    {
      detail::strand_executor_service::dispatch(impl_,
          executor_, EGT_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
     *
     * @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 post(EGT_ASIO_MOVE_ARG(Function) f, const Allocator& a) const
    {
      detail::strand_executor_service::post(impl_,
          executor_, EGT_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
     *
     * @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 defer(EGT_ASIO_MOVE_ARG(Function) f, const Allocator& a) const
    {
      detail::strand_executor_service::defer(impl_,
          executor_, EGT_ASIO_MOVE_CAST(Function)(f), a);
    }
  
    /// Determine whether the strand is running in the current thread.
    /**
     * @return @c true if the current thread is executing a function that was
     * submitted to the strand using post(), dispatch() or defer(). Otherwise
     * returns @c false.
     */
    bool running_in_this_thread() const EGT_ASIO_NOEXCEPT
    {
      return detail::strand_executor_service::running_in_this_thread(impl_);
    }
  
    /// Compare two strands for equality.
    /**
     * Two strands are equal if they refer to the same ordered, non-concurrent
     * state.
     */
    friend bool operator==(const strand& a, const strand& b) EGT_ASIO_NOEXCEPT
    {
      return a.impl_ == b.impl_;
    }
  
    /// Compare two strands for inequality.
    /**
     * Two strands are equal if they refer to the same ordered, non-concurrent
     * state.
     */
    friend bool operator!=(const strand& a, const strand& b) EGT_ASIO_NOEXCEPT
    {
      return a.impl_ != b.impl_;
    }
  
  private:
    Executor executor_;
    typedef detail::strand_executor_service::implementation_type
      implementation_type;
    implementation_type impl_;
  };
  
  } // namespace asio
  } // namespace egt
  
  #include <egt/asio/detail/pop_options.hpp>
  
  // If both io_context.hpp and strand.hpp have been included, automatically
  // include the header file needed for the io_context::strand class.
  #if !defined(EGT_ASIO_NO_EXTENSIONS)
  # if defined(EGT_ASIO_IO_CONTEXT_HPP)
  #  include <egt/asio/io_context_strand.hpp>
  # endif // defined(EGT_ASIO_IO_CONTEXT_HPP)
  #endif // !defined(EGT_ASIO_NO_EXTENSIONS)
  
  #endif // EGT_ASIO_STRAND_HPP
  