570 lines
17 KiB
C++
570 lines
17 KiB
C++
//
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// strand.hpp
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// ~~~~~~~~~~
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//
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// Copyright (c) 2003-2021 Christopher M. Kohlhoff (chris at kohlhoff dot com)
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//
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// Distributed under the Boost Software License, Version 1.0. (See accompanying
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// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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//
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#ifndef ASIO_STRAND_HPP
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#define ASIO_STRAND_HPP
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#if defined(_MSC_VER) && (_MSC_VER >= 1200)
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# pragma once
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#endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
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#include "asio/detail/config.hpp"
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#include "asio/detail/strand_executor_service.hpp"
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#include "asio/detail/type_traits.hpp"
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#include "asio/execution/blocking.hpp"
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#include "asio/execution/executor.hpp"
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#include "asio/is_executor.hpp"
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#include "asio/detail/push_options.hpp"
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namespace asio {
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/// Provides serialised function invocation for any executor type.
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template <typename Executor>
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class strand
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{
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public:
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/// The type of the underlying executor.
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typedef Executor inner_executor_type;
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/// Default constructor.
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/**
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* This constructor is only valid if the underlying executor type is default
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* constructible.
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*/
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strand()
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: executor_(),
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impl_(strand::create_implementation(executor_))
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{
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}
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/// Construct a strand for the specified executor.
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template <typename Executor1>
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explicit strand(const Executor1& e,
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typename constraint<
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conditional<
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!is_same<Executor1, strand>::value,
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is_convertible<Executor1, Executor>,
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false_type
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>::type::value
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>::type = 0)
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: executor_(e),
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impl_(strand::create_implementation(executor_))
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{
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}
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/// Copy constructor.
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strand(const strand& other) ASIO_NOEXCEPT
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: executor_(other.executor_),
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impl_(other.impl_)
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{
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}
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/// Converting constructor.
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/**
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* This constructor is only valid if the @c OtherExecutor type is convertible
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* to @c Executor.
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*/
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template <class OtherExecutor>
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strand(
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const strand<OtherExecutor>& other) ASIO_NOEXCEPT
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: executor_(other.executor_),
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impl_(other.impl_)
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{
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}
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/// Assignment operator.
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strand& operator=(const strand& other) ASIO_NOEXCEPT
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{
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executor_ = other.executor_;
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impl_ = other.impl_;
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return *this;
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}
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/// Converting assignment operator.
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/**
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* This assignment operator is only valid if the @c OtherExecutor type is
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* convertible to @c Executor.
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*/
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template <class OtherExecutor>
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strand& operator=(
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const strand<OtherExecutor>& other) ASIO_NOEXCEPT
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{
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executor_ = other.executor_;
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impl_ = other.impl_;
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return *this;
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}
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#if defined(ASIO_HAS_MOVE) || defined(GENERATING_DOCUMENTATION)
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/// Move constructor.
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strand(strand&& other) ASIO_NOEXCEPT
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: executor_(ASIO_MOVE_CAST(Executor)(other.executor_)),
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impl_(ASIO_MOVE_CAST(implementation_type)(other.impl_))
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{
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}
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/// Converting move constructor.
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/**
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* This constructor is only valid if the @c OtherExecutor type is convertible
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* to @c Executor.
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*/
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template <class OtherExecutor>
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strand(strand<OtherExecutor>&& other) ASIO_NOEXCEPT
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: executor_(ASIO_MOVE_CAST(OtherExecutor)(other.executor_)),
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impl_(ASIO_MOVE_CAST(implementation_type)(other.impl_))
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{
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}
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/// Move assignment operator.
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strand& operator=(strand&& other) ASIO_NOEXCEPT
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{
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executor_ = ASIO_MOVE_CAST(Executor)(other.executor_);
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impl_ = ASIO_MOVE_CAST(implementation_type)(other.impl_);
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return *this;
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}
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/// Converting move assignment operator.
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/**
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* This assignment operator is only valid if the @c OtherExecutor type is
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* convertible to @c Executor.
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*/
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template <class OtherExecutor>
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strand& operator=(strand<OtherExecutor>&& other) ASIO_NOEXCEPT
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{
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executor_ = ASIO_MOVE_CAST(OtherExecutor)(other.executor_);
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impl_ = ASIO_MOVE_CAST(implementation_type)(other.impl_);
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return *this;
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}
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#endif // defined(ASIO_HAS_MOVE) || defined(GENERATING_DOCUMENTATION)
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/// Destructor.
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~strand() ASIO_NOEXCEPT
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{
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}
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/// Obtain the underlying executor.
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inner_executor_type get_inner_executor() const ASIO_NOEXCEPT
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{
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return executor_;
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}
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/// Forward a query to the underlying executor.
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/**
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* Do not call this function directly. It is intended for use with the
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* asio::query customisation point.
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*
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* For example:
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* @code asio::strand<my_executor_type> ex = ...;
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* if (asio::query(ex, asio::execution::blocking)
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* == asio::execution::blocking.never)
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* ... @endcode
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*/
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template <typename Property>
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typename constraint<
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can_query<const Executor&, Property>::value,
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typename conditional<
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is_convertible<Property, execution::blocking_t>::value,
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execution::blocking_t,
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typename query_result<const Executor&, Property>::type
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>::type
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>::type query(const Property& p) const
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ASIO_NOEXCEPT_IF((
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is_nothrow_query<const Executor&, Property>::value))
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{
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return this->query_helper(
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is_convertible<Property, execution::blocking_t>(), p);
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}
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/// Forward a requirement to the underlying executor.
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/**
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* Do not call this function directly. It is intended for use with the
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* asio::require customisation point.
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*
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* For example:
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* @code asio::strand<my_executor_type> ex1 = ...;
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* auto ex2 = asio::require(ex1,
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* asio::execution::blocking.never); @endcode
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*/
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template <typename Property>
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typename constraint<
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can_require<const Executor&, Property>::value
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&& !is_convertible<Property, execution::blocking_t::always_t>::value,
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strand<typename decay<
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typename require_result<const Executor&, Property>::type
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>::type>
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>::type require(const Property& p) const
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ASIO_NOEXCEPT_IF((
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is_nothrow_require<const Executor&, Property>::value))
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{
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return strand<typename decay<
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typename require_result<const Executor&, Property>::type
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>::type>(asio::require(executor_, p), impl_);
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}
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/// Forward a preference to the underlying executor.
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/**
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* Do not call this function directly. It is intended for use with the
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* asio::prefer customisation point.
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*
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* For example:
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* @code asio::strand<my_executor_type> ex1 = ...;
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* auto ex2 = asio::prefer(ex1,
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* asio::execution::blocking.never); @endcode
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*/
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template <typename Property>
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typename constraint<
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can_prefer<const Executor&, Property>::value
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&& !is_convertible<Property, execution::blocking_t::always_t>::value,
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strand<typename decay<
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typename prefer_result<const Executor&, Property>::type
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>::type>
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>::type prefer(const Property& p) const
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ASIO_NOEXCEPT_IF((
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is_nothrow_prefer<const Executor&, Property>::value))
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{
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return strand<typename decay<
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typename prefer_result<const Executor&, Property>::type
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>::type>(asio::prefer(executor_, p), impl_);
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}
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#if !defined(ASIO_NO_TS_EXECUTORS)
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/// Obtain the underlying execution context.
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execution_context& context() const ASIO_NOEXCEPT
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{
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return executor_.context();
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}
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/// Inform the strand that it has some outstanding work to do.
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/**
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* The strand delegates this call to its underlying executor.
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*/
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void on_work_started() const ASIO_NOEXCEPT
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{
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executor_.on_work_started();
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}
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/// Inform the strand that some work is no longer outstanding.
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/**
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* The strand delegates this call to its underlying executor.
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*/
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void on_work_finished() const ASIO_NOEXCEPT
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{
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executor_.on_work_finished();
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}
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#endif // !defined(ASIO_NO_TS_EXECUTORS)
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/// Request the strand to invoke the given function object.
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/**
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* Do not call this function directly. It is intended for use with the
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* execution::execute customisation point.
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*
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* For example:
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* @code asio::strand<my_executor_type> ex = ...;
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* execution::execute(ex, my_function_object); @endcode
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*
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* This function is used to ask the strand to execute the given function
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* object on its underlying executor. The function object will be executed
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* according to the properties of the underlying executor.
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*
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* @param f The function object to be called. The executor will make
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* a copy of the handler object as required. The function signature of the
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* function object must be: @code void function(); @endcode
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*/
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template <typename Function>
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typename constraint<
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execution::can_execute<const Executor&, Function>::value,
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void
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>::type execute(ASIO_MOVE_ARG(Function) f) const
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{
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detail::strand_executor_service::execute(impl_,
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executor_, ASIO_MOVE_CAST(Function)(f));
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}
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#if !defined(ASIO_NO_TS_EXECUTORS)
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/// Request the strand to invoke the given function object.
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/**
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* This function is used to ask the strand to execute the given function
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* object on its underlying executor. The function object will be executed
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* inside this function if the strand is not otherwise busy and if the
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* underlying executor's @c dispatch() function is also able to execute the
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* function before returning.
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*
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* @param f The function object to be called. The executor will make
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* a copy of the handler object as required. The function signature of the
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* function object must be: @code void function(); @endcode
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*
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* @param a An allocator that may be used by the executor to allocate the
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* internal storage needed for function invocation.
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*/
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template <typename Function, typename Allocator>
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void dispatch(ASIO_MOVE_ARG(Function) f, const Allocator& a) const
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{
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detail::strand_executor_service::dispatch(impl_,
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executor_, ASIO_MOVE_CAST(Function)(f), a);
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}
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/// Request the strand to invoke the given function object.
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/**
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* This function is used to ask the executor to execute the given function
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* object. The function object will never be executed inside this function.
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* Instead, it will be scheduled by the underlying executor's defer function.
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*
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* @param f The function object to be called. The executor will make
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* a copy of the handler object as required. The function signature of the
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* function object must be: @code void function(); @endcode
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*
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* @param a An allocator that may be used by the executor to allocate the
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* internal storage needed for function invocation.
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*/
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template <typename Function, typename Allocator>
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void post(ASIO_MOVE_ARG(Function) f, const Allocator& a) const
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{
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detail::strand_executor_service::post(impl_,
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executor_, ASIO_MOVE_CAST(Function)(f), a);
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}
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/// Request the strand to invoke the given function object.
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/**
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* This function is used to ask the executor to execute the given function
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* object. The function object will never be executed inside this function.
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* Instead, it will be scheduled by the underlying executor's defer function.
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*
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* @param f The function object to be called. The executor will make
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* a copy of the handler object as required. The function signature of the
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* function object must be: @code void function(); @endcode
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*
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* @param a An allocator that may be used by the executor to allocate the
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* internal storage needed for function invocation.
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*/
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template <typename Function, typename Allocator>
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void defer(ASIO_MOVE_ARG(Function) f, const Allocator& a) const
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{
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detail::strand_executor_service::defer(impl_,
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executor_, ASIO_MOVE_CAST(Function)(f), a);
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}
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#endif // !defined(ASIO_NO_TS_EXECUTORS)
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/// Determine whether the strand is running in the current thread.
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/**
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* @return @c true if the current thread is executing a function that was
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* submitted to the strand using post(), dispatch() or defer(). Otherwise
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* returns @c false.
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*/
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bool running_in_this_thread() const ASIO_NOEXCEPT
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{
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return detail::strand_executor_service::running_in_this_thread(impl_);
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}
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/// Compare two strands for equality.
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/**
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* Two strands are equal if they refer to the same ordered, non-concurrent
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* state.
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*/
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friend bool operator==(const strand& a, const strand& b) ASIO_NOEXCEPT
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{
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return a.impl_ == b.impl_;
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}
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/// Compare two strands for inequality.
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/**
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* Two strands are equal if they refer to the same ordered, non-concurrent
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* state.
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*/
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friend bool operator!=(const strand& a, const strand& b) ASIO_NOEXCEPT
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{
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return a.impl_ != b.impl_;
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}
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#if defined(GENERATING_DOCUMENTATION)
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private:
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#endif // defined(GENERATING_DOCUMENTATION)
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typedef detail::strand_executor_service::implementation_type
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implementation_type;
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template <typename InnerExecutor>
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static implementation_type create_implementation(const InnerExecutor& ex,
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typename constraint<
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can_query<InnerExecutor, execution::context_t>::value
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>::type = 0)
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{
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return use_service<detail::strand_executor_service>(
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asio::query(ex, execution::context)).create_implementation();
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}
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template <typename InnerExecutor>
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static implementation_type create_implementation(const InnerExecutor& ex,
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typename constraint<
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!can_query<InnerExecutor, execution::context_t>::value
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>::type = 0)
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{
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return use_service<detail::strand_executor_service>(
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ex.context()).create_implementation();
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}
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strand(const Executor& ex, const implementation_type& impl)
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: executor_(ex),
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impl_(impl)
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{
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}
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template <typename Property>
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typename query_result<const Executor&, Property>::type query_helper(
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false_type, const Property& property) const
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{
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return asio::query(executor_, property);
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}
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template <typename Property>
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execution::blocking_t query_helper(true_type, const Property& property) const
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{
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execution::blocking_t result = asio::query(executor_, property);
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return result == execution::blocking.always
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? execution::blocking.possibly : result;
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}
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Executor executor_;
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implementation_type impl_;
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};
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/** @defgroup make_strand asio::make_strand
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*
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* @brief The asio::make_strand function creates a @ref strand object for
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* an executor or execution context.
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*/
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/*@{*/
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/// Create a @ref strand object for an executor.
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template <typename Executor>
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inline strand<Executor> make_strand(const Executor& ex,
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typename constraint<
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is_executor<Executor>::value || execution::is_executor<Executor>::value
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>::type = 0)
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{
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return strand<Executor>(ex);
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}
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/// Create a @ref strand object for an execution context.
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template <typename ExecutionContext>
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inline strand<typename ExecutionContext::executor_type>
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make_strand(ExecutionContext& ctx,
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typename constraint<
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is_convertible<ExecutionContext&, execution_context&>::value
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>::type = 0)
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{
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return strand<typename ExecutionContext::executor_type>(ctx.get_executor());
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}
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/*@}*/
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#if !defined(GENERATING_DOCUMENTATION)
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namespace traits {
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#if !defined(ASIO_HAS_DEDUCED_EQUALITY_COMPARABLE_TRAIT)
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template <typename Executor>
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struct equality_comparable<strand<Executor> >
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{
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ASIO_STATIC_CONSTEXPR(bool, is_valid = true);
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ASIO_STATIC_CONSTEXPR(bool, is_noexcept = true);
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};
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#endif // !defined(ASIO_HAS_DEDUCED_EQUALITY_COMPARABLE_TRAIT)
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#if !defined(ASIO_HAS_DEDUCED_EXECUTE_MEMBER_TRAIT)
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template <typename Executor, typename Function>
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struct execute_member<strand<Executor>, Function,
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typename enable_if<
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execution::can_execute<const Executor&, Function>::value
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>::type>
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{
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ASIO_STATIC_CONSTEXPR(bool, is_valid = true);
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ASIO_STATIC_CONSTEXPR(bool, is_noexcept = false);
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typedef void result_type;
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};
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#endif // !defined(ASIO_HAS_DEDUCED_EXECUTE_MEMBER_TRAIT)
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#if !defined(ASIO_HAS_DEDUCED_QUERY_MEMBER_TRAIT)
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template <typename Executor, typename Property>
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struct query_member<strand<Executor>, Property,
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typename enable_if<
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can_query<const Executor&, Property>::value
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>::type>
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{
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ASIO_STATIC_CONSTEXPR(bool, is_valid = true);
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ASIO_STATIC_CONSTEXPR(bool, is_noexcept =
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(is_nothrow_query<Executor, Property>::value));
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typedef typename conditional<
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is_convertible<Property, execution::blocking_t>::value,
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execution::blocking_t, typename query_result<Executor, Property>::type
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>::type result_type;
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};
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#endif // !defined(ASIO_HAS_DEDUCED_QUERY_MEMBER_TRAIT)
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#if !defined(ASIO_HAS_DEDUCED_REQUIRE_MEMBER_TRAIT)
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template <typename Executor, typename Property>
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struct require_member<strand<Executor>, Property,
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typename enable_if<
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can_require<const Executor&, Property>::value
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&& !is_convertible<Property, execution::blocking_t::always_t>::value
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>::type>
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{
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ASIO_STATIC_CONSTEXPR(bool, is_valid = true);
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ASIO_STATIC_CONSTEXPR(bool, is_noexcept =
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(is_nothrow_require<Executor, Property>::value));
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typedef strand<typename decay<
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typename require_result<Executor, Property>::type
|
|
>::type> result_type;
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|
};
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|
|
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#endif // !defined(ASIO_HAS_DEDUCED_REQUIRE_MEMBER_TRAIT)
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|
|
|
#if !defined(ASIO_HAS_DEDUCED_PREFER_MEMBER_TRAIT)
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|
|
|
template <typename Executor, typename Property>
|
|
struct prefer_member<strand<Executor>, Property,
|
|
typename enable_if<
|
|
can_prefer<const Executor&, Property>::value
|
|
&& !is_convertible<Property, execution::blocking_t::always_t>::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
|