ext-boost/boost/asio/strand.hpp

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//
// strand.hpp
// ~~~~~~~~~~
//
// Copyright (c) 2003-2019 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 BOOST_ASIO_STRAND_HPP
#define BOOST_ASIO_STRAND_HPP
#if defined(_MSC_VER) && (_MSC_VER >= 1200)
# pragma once
#endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
#include <boost/asio/detail/config.hpp>
#include <boost/asio/detail/strand_executor_service.hpp>
#include <boost/asio/detail/type_traits.hpp>
#include <boost/asio/detail/push_options.hpp>
namespace boost {
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) BOOST_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) BOOST_ASIO_NOEXCEPT
: executor_(other.executor_),
impl_(other.impl_)
{
}
/// Assignment operator.
strand& operator=(const strand& other) BOOST_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) BOOST_ASIO_NOEXCEPT
{
executor_ = other.executor_;
impl_ = other.impl_;
return *this;
}
#if defined(BOOST_ASIO_HAS_MOVE) || defined(GENERATING_DOCUMENTATION)
/// Move constructor.
strand(strand&& other) BOOST_ASIO_NOEXCEPT
: executor_(BOOST_ASIO_MOVE_CAST(Executor)(other.executor_)),
impl_(BOOST_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) BOOST_ASIO_NOEXCEPT
: executor_(BOOST_ASIO_MOVE_CAST(OtherExecutor)(other)),
impl_(BOOST_ASIO_MOVE_CAST(implementation_type)(other.impl_))
{
}
/// Move assignment operator.
strand& operator=(strand&& other) BOOST_ASIO_NOEXCEPT
{
executor_ = BOOST_ASIO_MOVE_CAST(Executor)(other);
impl_ = BOOST_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) BOOST_ASIO_NOEXCEPT
{
executor_ = BOOST_ASIO_MOVE_CAST(OtherExecutor)(other);
impl_ = BOOST_ASIO_MOVE_CAST(implementation_type)(other.impl_);
return *this;
}
#endif // defined(BOOST_ASIO_HAS_MOVE) || defined(GENERATING_DOCUMENTATION)
/// Destructor.
~strand()
{
}
/// Obtain the underlying executor.
inner_executor_type get_inner_executor() const BOOST_ASIO_NOEXCEPT
{
return executor_;
}
/// Obtain the underlying execution context.
execution_context& context() const BOOST_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 BOOST_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 BOOST_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(BOOST_ASIO_MOVE_ARG(Function) f, const Allocator& a) const
{
detail::strand_executor_service::dispatch(impl_,
executor_, BOOST_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(BOOST_ASIO_MOVE_ARG(Function) f, const Allocator& a) const
{
detail::strand_executor_service::post(impl_,
executor_, BOOST_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(BOOST_ASIO_MOVE_ARG(Function) f, const Allocator& a) const
{
detail::strand_executor_service::defer(impl_,
executor_, BOOST_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 BOOST_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) BOOST_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) BOOST_ASIO_NOEXCEPT
{
return a.impl_ != b.impl_;
}
private:
Executor executor_;
typedef detail::strand_executor_service::implementation_type
implementation_type;
implementation_type impl_;
};
/** @defgroup make_strand boost::asio::make_strand
*
* @brief The boost::asio::make_strand function creates a @ref strand object for
* an executor or execution context.
*/
/*@{*/
/// Create a @ref strand object for an executor.
template <typename Executor>
inline strand<Executor> make_strand(const Executor& ex,
typename enable_if<is_executor<Executor>::value>::type* = 0)
{
return strand<Executor>(ex);
}
/// Create a @ref strand object for an execution context.
template <typename ExecutionContext>
inline strand<typename ExecutionContext::executor_type>
make_strand(ExecutionContext& ctx,
typename enable_if<
is_convertible<ExecutionContext&, execution_context&>::value>::type* = 0)
{
return strand<typename ExecutionContext::executor_type>(ctx.get_executor());
}
/*@}*/
} // namespace asio
} // namespace boost
#include <boost/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(BOOST_ASIO_NO_EXTENSIONS)
# if defined(BOOST_ASIO_IO_CONTEXT_HPP)
# include <boost/asio/io_context_strand.hpp>
# endif // defined(BOOST_ASIO_IO_CONTEXT_HPP)
#endif // !defined(BOOST_ASIO_NO_EXTENSIONS)
#endif // BOOST_ASIO_STRAND_HPP