| // |
| // strand.hpp |
| // ~~~~~~~~~~ |
| // |
| // Copyright (c) 2003-2021 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_STRAND_HPP |
| #define ASIO_STRAND_HPP |
| |
| #if defined(_MSC_VER) && (_MSC_VER >= 1200) |
| # pragma once |
| #endif // defined(_MSC_VER) && (_MSC_VER >= 1200) |
| |
| #include "asio/detail/config.hpp" |
| #include "asio/detail/strand_executor_service.hpp" |
| #include "asio/detail/type_traits.hpp" |
| #include "asio/execution/executor.hpp" |
| #include "asio/is_executor.hpp" |
| |
| #include "asio/detail/push_options.hpp" |
| |
| 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_(strand::create_implementation(executor_)) |
| { |
| } |
| |
| /// Construct a strand for the specified executor. |
| template <typename Executor1> |
| explicit strand(const Executor1& e, |
| typename enable_if< |
| conditional< |
| !is_same<Executor1, strand>::value, |
| is_convertible<Executor1, Executor>, |
| false_type |
| >::type::value |
| >::type* = 0) |
| : executor_(e), |
| impl_(strand::create_implementation(executor_)) |
| { |
| } |
| |
| /// Copy constructor. |
| strand(const strand& other) 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) ASIO_NOEXCEPT |
| : executor_(other.executor_), |
| impl_(other.impl_) |
| { |
| } |
| |
| /// Assignment operator. |
| strand& operator=(const strand& other) 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) ASIO_NOEXCEPT |
| { |
| executor_ = other.executor_; |
| impl_ = other.impl_; |
| return *this; |
| } |
| |
| #if defined(ASIO_HAS_MOVE) || defined(GENERATING_DOCUMENTATION) |
| /// Move constructor. |
| strand(strand&& other) ASIO_NOEXCEPT |
| : executor_(ASIO_MOVE_CAST(Executor)(other.executor_)), |
| impl_(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) ASIO_NOEXCEPT |
| : executor_(ASIO_MOVE_CAST(OtherExecutor)(other.executor_)), |
| impl_(ASIO_MOVE_CAST(implementation_type)(other.impl_)) |
| { |
| } |
| |
| /// Move assignment operator. |
| strand& operator=(strand&& other) ASIO_NOEXCEPT |
| { |
| executor_ = ASIO_MOVE_CAST(Executor)(other.executor_); |
| impl_ = 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=(strand<OtherExecutor>&& other) ASIO_NOEXCEPT |
| { |
| executor_ = ASIO_MOVE_CAST(OtherExecutor)(other.executor_); |
| impl_ = ASIO_MOVE_CAST(implementation_type)(other.impl_); |
| return *this; |
| } |
| #endif // defined(ASIO_HAS_MOVE) || defined(GENERATING_DOCUMENTATION) |
| |
| /// Destructor. |
| ~strand() ASIO_NOEXCEPT |
| { |
| } |
| |
| /// Obtain the underlying executor. |
| inner_executor_type get_inner_executor() const ASIO_NOEXCEPT |
| { |
| return executor_; |
| } |
| |
| /// Forward a query to the underlying executor. |
| /** |
| * Do not call this function directly. It is intended for use with the |
| * execution::execute customisation point. |
| * |
| * For example: |
| * @code asio::strand<my_executor_type> ex = ...; |
| * if (asio::query(ex, asio::execution::blocking) |
| * == asio::execution::blocking.never) |
| * ... @endcode |
| */ |
| template <typename Property> |
| typename enable_if< |
| can_query<const Executor&, Property>::value, |
| typename query_result<const Executor&, Property>::type |
| >::type query(const Property& p) const |
| ASIO_NOEXCEPT_IF(( |
| is_nothrow_query<const Executor&, Property>::value)) |
| { |
| return asio::query(executor_, p); |
| } |
| |
| /// Forward a requirement to the underlying executor. |
| /** |
| * Do not call this function directly. It is intended for use with the |
| * asio::require customisation point. |
| * |
| * For example: |
| * @code asio::strand<my_executor_type> ex1 = ...; |
| * auto ex2 = asio::require(ex1, |
| * asio::execution::blocking.never); @endcode |
| */ |
| template <typename Property> |
| typename enable_if< |
| can_require<const Executor&, Property>::value, |
| strand<typename decay< |
| typename require_result<const Executor&, Property>::type |
| >::type> |
| >::type require(const Property& p) const |
| ASIO_NOEXCEPT_IF(( |
| is_nothrow_require<const Executor&, Property>::value)) |
| { |
| return strand<typename decay< |
| typename require_result<const Executor&, Property>::type |
| >::type>(asio::require(executor_, p), impl_); |
| } |
| |
| /// Forward a preference to the underlying executor. |
| /** |
| * Do not call this function directly. It is intended for use with the |
| * asio::prefer customisation point. |
| * |
| * For example: |
| * @code asio::strand<my_executor_type> ex1 = ...; |
| * auto ex2 = asio::prefer(ex1, |
| * asio::execution::blocking.never); @endcode |
| */ |
| template <typename Property> |
| typename enable_if< |
| can_prefer<const Executor&, Property>::value, |
| strand<typename decay< |
| typename prefer_result<const Executor&, Property>::type |
| >::type> |
| >::type prefer(const Property& p) const |
| ASIO_NOEXCEPT_IF(( |
| is_nothrow_prefer<const Executor&, Property>::value)) |
| { |
| return strand<typename decay< |
| typename prefer_result<const Executor&, Property>::type |
| >::type>(asio::prefer(executor_, p), impl_); |
| } |
| |
| #if !defined(ASIO_NO_TS_EXECUTORS) |
| /// Obtain the underlying execution context. |
| execution_context& context() const 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 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 ASIO_NOEXCEPT |
| { |
| executor_.on_work_finished(); |
| } |
| #endif // !defined(ASIO_NO_TS_EXECUTORS) |
| |
| /// Request the strand to invoke the given function object. |
| /** |
| * Do not call this function directly. It is intended for use with the |
| * execution::execute customisation point. |
| * |
| * For example: |
| * @code asio::strand<my_executor_type> ex = ...; |
| * execution::execute(ex, my_function_object); @endcode |
| * |
| * This function is used to ask the strand to execute the given function |
| * object on its underlying executor. The function object will be executed |
| * according to the properties of the underlying executor. |
| * |
| * @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 |
| */ |
| template <typename Function> |
| typename enable_if< |
| execution::can_execute<const Executor&, Function>::value |
| >::type execute(ASIO_MOVE_ARG(Function) f) const |
| { |
| detail::strand_executor_service::execute(impl_, |
| executor_, ASIO_MOVE_CAST(Function)(f)); |
| } |
| |
| #if !defined(ASIO_NO_TS_EXECUTORS) |
| /// 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(ASIO_MOVE_ARG(Function) f, const Allocator& a) const |
| { |
| detail::strand_executor_service::dispatch(impl_, |
| executor_, 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(ASIO_MOVE_ARG(Function) f, const Allocator& a) const |
| { |
| detail::strand_executor_service::post(impl_, |
| executor_, 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(ASIO_MOVE_ARG(Function) f, const Allocator& a) const |
| { |
| detail::strand_executor_service::defer(impl_, |
| executor_, ASIO_MOVE_CAST(Function)(f), a); |
| } |
| #endif // !defined(ASIO_NO_TS_EXECUTORS) |
| |
| /// 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 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) 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) ASIO_NOEXCEPT |
| { |
| return a.impl_ != b.impl_; |
| } |
| |
| #if defined(GENERATING_DOCUMENTATION) |
| private: |
| #endif // defined(GENERATING_DOCUMENTATION) |
| typedef detail::strand_executor_service::implementation_type |
| implementation_type; |
| |
| template <typename InnerExecutor> |
| static implementation_type create_implementation(const InnerExecutor& ex, |
| typename enable_if< |
| can_query<InnerExecutor, execution::context_t>::value |
| >::type* = 0) |
| { |
| return use_service<detail::strand_executor_service>( |
| asio::query(ex, execution::context)).create_implementation(); |
| } |
| |
| template <typename InnerExecutor> |
| static implementation_type create_implementation(const InnerExecutor& ex, |
| typename enable_if< |
| !can_query<InnerExecutor, execution::context_t>::value |
| >::type* = 0) |
| { |
| return use_service<detail::strand_executor_service>( |
| ex.context()).create_implementation(); |
| } |
| |
| strand(const Executor& ex, const implementation_type& impl) |
| : executor_(ex), |
| impl_(impl) |
| { |
| } |
| |
| Executor executor_; |
| implementation_type impl_; |
| }; |
| |
| /** @defgroup make_strand asio::make_strand |
| * |
| * @brief The 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 || execution::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()); |
| } |
| |
| /*@}*/ |
| |
| #if !defined(GENERATING_DOCUMENTATION) |
| |
| namespace traits { |
| |
| #if !defined(ASIO_HAS_DEDUCED_EQUALITY_COMPARABLE_TRAIT) |
| |
| template <typename Executor> |
| struct equality_comparable<strand<Executor> > |
| { |
| ASIO_STATIC_CONSTEXPR(bool, is_valid = true); |
| ASIO_STATIC_CONSTEXPR(bool, is_noexcept = true); |
| }; |
| |
| #endif // !defined(ASIO_HAS_DEDUCED_EQUALITY_COMPARABLE_TRAIT) |
| |
| #if !defined(ASIO_HAS_DEDUCED_EXECUTE_MEMBER_TRAIT) |
| |
| template <typename Executor, typename Function> |
| struct execute_member<strand<Executor>, Function, |
| typename enable_if< |
| execution::can_execute<const Executor&, Function>::value |
| >::type> |
| { |
| ASIO_STATIC_CONSTEXPR(bool, is_valid = true); |
| ASIO_STATIC_CONSTEXPR(bool, is_noexcept = false); |
| typedef void result_type; |
| }; |
| |
| #endif // !defined(ASIO_HAS_DEDUCED_EXECUTE_MEMBER_TRAIT) |
| |
| #if !defined(ASIO_HAS_DEDUCED_QUERY_MEMBER_TRAIT) |
| |
| template <typename Executor, typename Property> |
| struct query_member<strand<Executor>, Property, |
| typename enable_if< |
| can_query<const Executor&, Property>::value |
| >::type> |
| { |
| ASIO_STATIC_CONSTEXPR(bool, is_valid = true); |
| ASIO_STATIC_CONSTEXPR(bool, is_noexcept = |
| (is_nothrow_query<Executor, Property>::value)); |
| typedef typename query_result<Executor, Property>::type result_type; |
| }; |
| |
| #endif // !defined(ASIO_HAS_DEDUCED_QUERY_MEMBER_TRAIT) |
| |
| #if !defined(ASIO_HAS_DEDUCED_REQUIRE_MEMBER_TRAIT) |
| |
| template <typename Executor, typename Property> |
| struct require_member<strand<Executor>, Property, |
| typename enable_if< |
| can_require<const Executor&, Property>::value |
| >::type> |
| { |
| ASIO_STATIC_CONSTEXPR(bool, is_valid = true); |
| ASIO_STATIC_CONSTEXPR(bool, is_noexcept = |
| (is_nothrow_require<Executor, Property>::value)); |
| typedef strand<typename decay< |
| typename require_result<Executor, Property>::type |
| >::type> result_type; |
| }; |
| |
| #endif // !defined(ASIO_HAS_DEDUCED_REQUIRE_MEMBER_TRAIT) |
| |
| #if !defined(ASIO_HAS_DEDUCED_PREFER_MEMBER_TRAIT) |
| |
| template <typename Executor, typename Property> |
| struct prefer_member<strand<Executor>, Property, |
| typename enable_if< |
| can_prefer<const Executor&, Property>::value |
| >::type> |
| { |
| ASIO_STATIC_CONSTEXPR(bool, is_valid = true); |
| ASIO_STATIC_CONSTEXPR(bool, is_noexcept = |
| (is_nothrow_prefer<Executor, Property>::value)); |
| typedef strand<typename decay< |
| typename prefer_result<Executor, Property>::type |
| >::type> result_type; |
| }; |
| |
| #endif // !defined(ASIO_HAS_DEDUCED_PREFER_MEMBER_TRAIT) |
| |
| } // namespace traits |
| |
| #endif // !defined(GENERATING_DOCUMENTATION) |
| |
| } // namespace asio |
| |
| #include "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(ASIO_NO_EXTENSIONS) |
| # if defined(ASIO_IO_CONTEXT_HPP) |
| # include "asio/io_context_strand.hpp" |
| # endif // defined(ASIO_IO_CONTEXT_HPP) |
| #endif // !defined(ASIO_NO_EXTENSIONS) |
| |
| #endif // ASIO_STRAND_HPP |