suyu/externals/vcpkg/packages/boost-asio_x64-windows/include/boost/asio/defer.hpp
2024-03-05 16:42:40 +08:00

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//
// defer.hpp
// ~~~~~~~~~
//
// Copyright (c) 2003-2022 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_DEFER_HPP
#define BOOST_ASIO_DEFER_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/async_result.hpp>
#include <boost/asio/detail/type_traits.hpp>
#include <boost/asio/execution_context.hpp>
#include <boost/asio/execution/executor.hpp>
#include <boost/asio/is_executor.hpp>
#include <boost/asio/detail/push_options.hpp>
namespace boost {
namespace asio {
/// Submits a completion token or function object for execution.
/**
* This function submits an object for execution using the object's associated
* executor. The function object is queued for execution, and is never called
* from the current thread prior to returning from <tt>defer()</tt>.
*
* The use of @c defer(), rather than @ref post(), indicates the caller's
* preference that the executor defer the queueing of the function object. This
* may allow the executor to optimise queueing for cases when the function
* object represents a continuation of the current call context.
*
* @param token The @ref completion_token that will be used to produce a
* completion handler. The function signature of the completion handler must be:
* @code void handler(); @endcode
*
* @returns This function returns <tt>async_initiate<NullaryToken,
* void()>(Init{}, token)</tt>, where @c Init is a function object type defined
* as:
*
* @code class Init
* {
* public:
* template <typename CompletionHandler>
* void operator()(CompletionHandler&& completion_handler) const;
* }; @endcode
*
* The function call operator of @c Init:
*
* @li Obtains the handler's associated executor object @c ex of type @c Ex by
* performing @code auto ex = get_associated_executor(handler); @endcode
*
* @li Obtains the handler's associated allocator object @c alloc by performing
* @code auto alloc = get_associated_allocator(handler); @endcode
*
* @li If <tt>execution::is_executor<Ex>::value</tt> is true, performs
* @code execution::execute(
* prefer(
* require(ex, execution::blocking.never),
* execution::relationship.continuation,
* execution::allocator(alloc)),
* std::forward<CompletionHandler>(completion_handler)); @endcode
*
* @li If <tt>execution::is_executor<Ex>::value</tt> is false, performs
* @code ex.defer(
* std::forward<CompletionHandler>(completion_handler),
* alloc); @endcode
*
* @par Completion Signature
* @code void() @endcode
*/
template <BOOST_ASIO_COMPLETION_TOKEN_FOR(void()) NullaryToken>
BOOST_ASIO_INITFN_AUTO_RESULT_TYPE(NullaryToken, void()) defer(
BOOST_ASIO_MOVE_ARG(NullaryToken) token);
/// Submits a completion token or function object for execution.
/**
* This function submits an object for execution using the specified executor.
* The function object is queued for execution, and is never called from the
* current thread prior to returning from <tt>defer()</tt>.
*
* The use of @c defer(), rather than @ref post(), indicates the caller's
* preference that the executor defer the queueing of the function object. This
* may allow the executor to optimise queueing for cases when the function
* object represents a continuation of the current call context.
*
* @param ex The target executor.
*
* @param token The @ref completion_token that will be used to produce a
* completion handler. The function signature of the completion handler must be:
* @code void handler(); @endcode
*
* @returns This function returns <tt>async_initiate<NullaryToken,
* void()>(Init{ex}, token)</tt>, where @c Init is a function object type
* defined as:
*
* @code class Init
* {
* public:
* using executor_type = Executor;
* explicit Init(const Executor& ex) : ex_(ex) {}
* executor_type get_executor() const noexcept { return ex_; }
* template <typename CompletionHandler>
* void operator()(CompletionHandler&& completion_handler) const;
* private:
* Executor ex_; // exposition only
* }; @endcode
*
* The function call operator of @c Init:
*
* @li Obtains the handler's associated executor object @c ex1 of type @c Ex1 by
* performing @code auto ex1 = get_associated_executor(handler, ex); @endcode
*
* @li Obtains the handler's associated allocator object @c alloc by performing
* @code auto alloc = get_associated_allocator(handler); @endcode
*
* @li If <tt>execution::is_executor<Ex1>::value</tt> is true, constructs a
* function object @c f with a member @c executor_ that is initialised with
* <tt>prefer(ex1, execution::outstanding_work.tracked)</tt>, a member @c
* handler_ that is a decay-copy of @c completion_handler, and a function call
* operator that performs:
* @code auto a = get_associated_allocator(handler_);
* execution::execute(
* prefer(executor_,
* execution::blocking.possibly,
* execution::allocator(a)),
* std::move(handler_)); @endcode
*
* @li If <tt>execution::is_executor<Ex1>::value</tt> is false, constructs a
* function object @c f with a member @c work_ that is initialised with
* <tt>make_work_guard(ex1)</tt>, a member @c handler_ that is a decay-copy of
* @c completion_handler, and a function call operator that performs:
* @code auto a = get_associated_allocator(handler_);
* work_.get_executor().dispatch(std::move(handler_), a);
* work_.reset(); @endcode
*
* @li If <tt>execution::is_executor<Ex>::value</tt> is true, performs
* @code execution::execute(
* prefer(
* require(ex, execution::blocking.never),
* execution::relationship.continuation,
* execution::allocator(alloc)),
* std::move(f)); @endcode
*
* @li If <tt>execution::is_executor<Ex>::value</tt> is false, performs
* @code ex.defer(std::move(f), alloc); @endcode
*
* @par Completion Signature
* @code void() @endcode
*/
template <typename Executor,
BOOST_ASIO_COMPLETION_TOKEN_FOR(void()) NullaryToken
BOOST_ASIO_DEFAULT_COMPLETION_TOKEN_TYPE(Executor)>
BOOST_ASIO_INITFN_AUTO_RESULT_TYPE(NullaryToken, void()) defer(
const Executor& ex,
BOOST_ASIO_MOVE_ARG(NullaryToken) token
BOOST_ASIO_DEFAULT_COMPLETION_TOKEN(Executor),
typename constraint<
execution::is_executor<Executor>::value || is_executor<Executor>::value
>::type = 0);
/// Submits a completion token or function object for execution.
/**
* @param ctx An execution context, from which the target executor is obtained.
*
* @param token The @ref completion_token that will be used to produce a
* completion handler. The function signature of the completion handler must be:
* @code void handler(); @endcode
*
* @returns <tt>defer(ctx.get_executor(), forward<NullaryToken>(token))</tt>.
*
* @par Completion Signature
* @code void() @endcode
*/
template <typename ExecutionContext,
BOOST_ASIO_COMPLETION_TOKEN_FOR(void()) NullaryToken
BOOST_ASIO_DEFAULT_COMPLETION_TOKEN_TYPE(
typename ExecutionContext::executor_type)>
BOOST_ASIO_INITFN_AUTO_RESULT_TYPE(NullaryToken, void()) defer(
ExecutionContext& ctx,
BOOST_ASIO_MOVE_ARG(NullaryToken) token
BOOST_ASIO_DEFAULT_COMPLETION_TOKEN(
typename ExecutionContext::executor_type),
typename constraint<is_convertible<
ExecutionContext&, execution_context&>::value>::type = 0);
} // namespace asio
} // namespace boost
#include <boost/asio/detail/pop_options.hpp>
#include <boost/asio/impl/defer.hpp>
#endif // BOOST_ASIO_DEFER_HPP