131 lines
4.8 KiB
C++
131 lines
4.8 KiB
C++
//
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// defer.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_DEFER_HPP
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#define ASIO_DEFER_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/async_result.hpp"
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#include "asio/detail/type_traits.hpp"
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#include "asio/execution_context.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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/// Submits a completion token or function object for execution.
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/**
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* This function submits an object for execution using the object's associated
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* executor. The function object is queued for execution, and is never called
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* from the current thread prior to returning from <tt>defer()</tt>.
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*
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* The use of @c defer(), rather than @ref post(), indicates the caller's
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* preference that the executor defer the queueing of the function object. This
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* may allow the executor to optimise queueing for cases when the function
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* object represents a continuation of the current call context.
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*
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* This function has the following effects:
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*
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* @li Constructs a function object handler of type @c Handler, initialized
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* with <tt>handler(forward<CompletionToken>(token))</tt>.
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*
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* @li Constructs an object @c result of type <tt>async_result<Handler></tt>,
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* initializing the object as <tt>result(handler)</tt>.
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*
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* @li Obtains the handler's associated executor object @c ex by performing
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* <tt>get_associated_executor(handler)</tt>.
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*
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* @li Obtains the handler's associated allocator object @c alloc by performing
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* <tt>get_associated_allocator(handler)</tt>.
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*
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* @li Performs <tt>ex.defer(std::move(handler), alloc)</tt>.
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*
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* @li Returns <tt>result.get()</tt>.
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*/
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template <ASIO_COMPLETION_TOKEN_FOR(void()) CompletionToken>
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ASIO_INITFN_AUTO_RESULT_TYPE(CompletionToken, void()) defer(
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ASIO_MOVE_ARG(CompletionToken) token);
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/// Submits a completion token or function object for execution.
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/**
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* This function submits an object for execution using the specified executor.
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* The function object is queued for execution, and is never called from the
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* current thread prior to returning from <tt>defer()</tt>.
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*
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* The use of @c defer(), rather than @ref post(), indicates the caller's
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* preference that the executor defer the queueing of the function object. This
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* may allow the executor to optimise queueing for cases when the function
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* object represents a continuation of the current call context.
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*
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* This function has the following effects:
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*
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* @li Constructs a function object handler of type @c Handler, initialized
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* with <tt>handler(forward<CompletionToken>(token))</tt>.
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*
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* @li Constructs an object @c result of type <tt>async_result<Handler></tt>,
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* initializing the object as <tt>result(handler)</tt>.
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*
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* @li Obtains the handler's associated executor object @c ex1 by performing
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* <tt>get_associated_executor(handler)</tt>.
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*
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* @li Creates a work object @c w by performing <tt>make_work(ex1)</tt>.
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*
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* @li Obtains the handler's associated allocator object @c alloc by performing
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* <tt>get_associated_allocator(handler)</tt>.
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*
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* @li Constructs a function object @c f with a function call operator that
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* performs <tt>ex1.dispatch(std::move(handler), alloc)</tt> followed by
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* <tt>w.reset()</tt>.
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*
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* @li Performs <tt>Executor(ex).defer(std::move(f), alloc)</tt>.
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*
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* @li Returns <tt>result.get()</tt>.
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*/
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template <typename Executor,
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ASIO_COMPLETION_TOKEN_FOR(void()) CompletionToken
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ASIO_DEFAULT_COMPLETION_TOKEN_TYPE(Executor)>
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ASIO_INITFN_AUTO_RESULT_TYPE(CompletionToken, void()) defer(
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const Executor& ex,
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ASIO_MOVE_ARG(CompletionToken) token
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ASIO_DEFAULT_COMPLETION_TOKEN(Executor),
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typename constraint<
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execution::is_executor<Executor>::value || is_executor<Executor>::value
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>::type = 0);
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/// Submits a completion token or function object for execution.
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/**
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* @returns <tt>defer(ctx.get_executor(), forward<CompletionToken>(token))</tt>.
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*/
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template <typename ExecutionContext,
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ASIO_COMPLETION_TOKEN_FOR(void()) CompletionToken
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ASIO_DEFAULT_COMPLETION_TOKEN_TYPE(
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typename ExecutionContext::executor_type)>
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ASIO_INITFN_AUTO_RESULT_TYPE(CompletionToken, void()) defer(
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ExecutionContext& ctx,
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ASIO_MOVE_ARG(CompletionToken) token
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ASIO_DEFAULT_COMPLETION_TOKEN(
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typename ExecutionContext::executor_type),
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typename constraint<is_convertible<
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ExecutionContext&, execution_context&>::value>::type = 0);
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} // namespace asio
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#include "asio/detail/pop_options.hpp"
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#include "asio/impl/defer.hpp"
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#endif // ASIO_DEFER_HPP
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