345 lines
11 KiB
C++
345 lines
11 KiB
C++
//
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// spawn.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_SPAWN_HPP
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#define ASIO_SPAWN_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 <boost/coroutine/all.hpp>
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#include "asio/any_io_executor.hpp"
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#include "asio/bind_executor.hpp"
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#include "asio/detail/memory.hpp"
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#include "asio/detail/type_traits.hpp"
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#include "asio/detail/wrapped_handler.hpp"
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#include "asio/io_context.hpp"
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#include "asio/is_executor.hpp"
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#include "asio/strand.hpp"
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#include "asio/detail/push_options.hpp"
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namespace asio {
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/// Context object the represents the currently executing coroutine.
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/**
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* The basic_yield_context class is used to represent the currently executing
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* stackful coroutine. A basic_yield_context may be passed as a handler to an
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* asynchronous operation. For example:
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*
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* @code template <typename Handler>
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* void my_coroutine(basic_yield_context<Handler> yield)
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* {
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* ...
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* std::size_t n = my_socket.async_read_some(buffer, yield);
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* ...
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* } @endcode
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*
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* The initiating function (async_read_some in the above example) suspends the
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* current coroutine. The coroutine is resumed when the asynchronous operation
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* completes, and the result of the operation is returned.
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*/
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template <typename Handler>
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class basic_yield_context
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{
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public:
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/// The coroutine callee type, used by the implementation.
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/**
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* When using Boost.Coroutine v1, this type is:
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* @code typename coroutine<void()> @endcode
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* When using Boost.Coroutine v2 (unidirectional coroutines), this type is:
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* @code push_coroutine<void> @endcode
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*/
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#if defined(GENERATING_DOCUMENTATION)
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typedef implementation_defined callee_type;
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#elif defined(BOOST_COROUTINES_UNIDIRECT) || defined(BOOST_COROUTINES_V2)
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typedef boost::coroutines::push_coroutine<void> callee_type;
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#else
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typedef boost::coroutines::coroutine<void()> callee_type;
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#endif
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/// The coroutine caller type, used by the implementation.
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/**
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* When using Boost.Coroutine v1, this type is:
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* @code typename coroutine<void()>::caller_type @endcode
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* When using Boost.Coroutine v2 (unidirectional coroutines), this type is:
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* @code pull_coroutine<void> @endcode
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*/
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#if defined(GENERATING_DOCUMENTATION)
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typedef implementation_defined caller_type;
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#elif defined(BOOST_COROUTINES_UNIDIRECT) || defined(BOOST_COROUTINES_V2)
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typedef boost::coroutines::pull_coroutine<void> caller_type;
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#else
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typedef boost::coroutines::coroutine<void()>::caller_type caller_type;
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#endif
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/// Construct a yield context to represent the specified coroutine.
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/**
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* Most applications do not need to use this constructor. Instead, the
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* spawn() function passes a yield context as an argument to the coroutine
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* function.
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*/
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basic_yield_context(
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const detail::weak_ptr<callee_type>& coro,
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caller_type& ca, Handler& handler)
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: coro_(coro),
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ca_(ca),
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handler_(handler),
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ec_(0)
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{
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}
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/// Construct a yield context from another yield context type.
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/**
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* Requires that OtherHandler be convertible to Handler.
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*/
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template <typename OtherHandler>
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basic_yield_context(const basic_yield_context<OtherHandler>& other)
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: coro_(other.coro_),
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ca_(other.ca_),
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handler_(other.handler_),
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ec_(other.ec_)
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{
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}
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/// Return a yield context that sets the specified error_code.
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/**
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* By default, when a yield context is used with an asynchronous operation, a
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* non-success error_code is converted to system_error and thrown. This
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* operator may be used to specify an error_code object that should instead be
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* set with the asynchronous operation's result. For example:
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*
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* @code template <typename Handler>
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* void my_coroutine(basic_yield_context<Handler> yield)
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* {
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* ...
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* std::size_t n = my_socket.async_read_some(buffer, yield[ec]);
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* if (ec)
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* {
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* // An error occurred.
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* }
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* ...
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* } @endcode
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*/
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basic_yield_context operator[](asio::error_code& ec) const
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{
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basic_yield_context tmp(*this);
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tmp.ec_ = &ec;
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return tmp;
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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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detail::weak_ptr<callee_type> coro_;
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caller_type& ca_;
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Handler handler_;
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asio::error_code* ec_;
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};
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#if defined(GENERATING_DOCUMENTATION)
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/// Context object that represents the currently executing coroutine.
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typedef basic_yield_context<unspecified> yield_context;
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#else // defined(GENERATING_DOCUMENTATION)
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typedef basic_yield_context<
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executor_binder<void(*)(), any_io_executor> > yield_context;
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#endif // defined(GENERATING_DOCUMENTATION)
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/**
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* @defgroup spawn asio::spawn
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*
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* @brief Start a new stackful coroutine.
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*
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* The spawn() function is a high-level wrapper over the Boost.Coroutine
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* library. This function enables programs to implement asynchronous logic in a
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* synchronous manner, as illustrated by the following example:
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*
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* @code asio::spawn(my_strand, do_echo);
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*
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* // ...
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*
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* void do_echo(asio::yield_context yield)
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* {
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* try
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* {
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* char data[128];
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* for (;;)
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* {
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* std::size_t length =
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* my_socket.async_read_some(
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* asio::buffer(data), yield);
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*
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* asio::async_write(my_socket,
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* asio::buffer(data, length), yield);
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* }
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* }
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* catch (std::exception& e)
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* {
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* // ...
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* }
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* } @endcode
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*/
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/*@{*/
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/// Start a new stackful coroutine, calling the specified handler when it
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/// completes.
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/**
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* This function is used to launch a new coroutine.
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*
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* @param function The coroutine function. The function must have the signature:
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* @code void function(basic_yield_context<Handler> yield); @endcode
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*
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* @param attributes Boost.Coroutine attributes used to customise the coroutine.
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*/
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template <typename Function>
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void spawn(ASIO_MOVE_ARG(Function) function,
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const boost::coroutines::attributes& attributes
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= boost::coroutines::attributes());
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/// Start a new stackful coroutine, calling the specified handler when it
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/// completes.
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/**
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* This function is used to launch a new coroutine.
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*
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* @param handler A handler to be called when the coroutine exits. More
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* importantly, the handler provides an execution context (via the the handler
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* invocation hook) for the coroutine. The handler must have the signature:
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* @code void handler(); @endcode
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*
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* @param function The coroutine function. The function must have the signature:
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* @code void function(basic_yield_context<Handler> yield); @endcode
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*
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* @param attributes Boost.Coroutine attributes used to customise the coroutine.
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*/
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template <typename Handler, typename Function>
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void spawn(ASIO_MOVE_ARG(Handler) handler,
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ASIO_MOVE_ARG(Function) function,
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const boost::coroutines::attributes& attributes
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= boost::coroutines::attributes(),
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typename constraint<
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!is_executor<typename decay<Handler>::type>::value &&
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!execution::is_executor<typename decay<Handler>::type>::value &&
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!is_convertible<Handler&, execution_context&>::value>::type = 0);
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/// Start a new stackful coroutine, inheriting the execution context of another.
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/**
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* This function is used to launch a new coroutine.
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*
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* @param ctx Identifies the current coroutine as a parent of the new
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* coroutine. This specifies that the new coroutine should inherit the
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* execution context of the parent. For example, if the parent coroutine is
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* executing in a particular strand, then the new coroutine will execute in the
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* same strand.
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*
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* @param function The coroutine function. The function must have the signature:
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* @code void function(basic_yield_context<Handler> yield); @endcode
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*
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* @param attributes Boost.Coroutine attributes used to customise the coroutine.
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*/
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template <typename Handler, typename Function>
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void spawn(basic_yield_context<Handler> ctx,
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ASIO_MOVE_ARG(Function) function,
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const boost::coroutines::attributes& attributes
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= boost::coroutines::attributes());
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/// Start a new stackful coroutine that executes on a given executor.
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/**
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* This function is used to launch a new coroutine.
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*
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* @param ex Identifies the executor that will run the coroutine. The new
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* coroutine is implicitly given its own strand within this executor.
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*
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* @param function The coroutine function. The function must have the signature:
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* @code void function(yield_context yield); @endcode
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*
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* @param attributes Boost.Coroutine attributes used to customise the coroutine.
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*/
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template <typename Function, typename Executor>
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void spawn(const Executor& ex,
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ASIO_MOVE_ARG(Function) function,
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const boost::coroutines::attributes& attributes
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= boost::coroutines::attributes(),
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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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/// Start a new stackful coroutine that executes on a given strand.
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/**
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* This function is used to launch a new coroutine.
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*
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* @param ex Identifies the strand that will run the coroutine.
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*
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* @param function The coroutine function. The function must have the signature:
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* @code void function(yield_context yield); @endcode
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*
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* @param attributes Boost.Coroutine attributes used to customise the coroutine.
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*/
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template <typename Function, typename Executor>
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void spawn(const strand<Executor>& ex,
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ASIO_MOVE_ARG(Function) function,
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const boost::coroutines::attributes& attributes
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= boost::coroutines::attributes());
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#if !defined(ASIO_NO_TS_EXECUTORS)
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/// Start a new stackful coroutine that executes in the context of a strand.
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/**
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* This function is used to launch a new coroutine.
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*
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* @param s Identifies a strand. By starting multiple coroutines on the same
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* strand, the implementation ensures that none of those coroutines can execute
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* simultaneously.
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*
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* @param function The coroutine function. The function must have the signature:
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* @code void function(yield_context yield); @endcode
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*
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* @param attributes Boost.Coroutine attributes used to customise the coroutine.
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*/
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template <typename Function>
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void spawn(const asio::io_context::strand& s,
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ASIO_MOVE_ARG(Function) function,
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const boost::coroutines::attributes& attributes
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= boost::coroutines::attributes());
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#endif // !defined(ASIO_NO_TS_EXECUTORS)
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/// Start a new stackful coroutine that executes on a given execution context.
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/**
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* This function is used to launch a new coroutine.
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*
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* @param ctx Identifies the execution context that will run the coroutine. The
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* new coroutine is implicitly given its own strand within this execution
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* context.
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*
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* @param function The coroutine function. The function must have the signature:
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* @code void function(yield_context yield); @endcode
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*
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* @param attributes Boost.Coroutine attributes used to customise the coroutine.
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*/
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template <typename Function, typename ExecutionContext>
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void spawn(ExecutionContext& ctx,
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ASIO_MOVE_ARG(Function) function,
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const boost::coroutines::attributes& attributes
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= boost::coroutines::attributes(),
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typename constraint<is_convertible<
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ExecutionContext&, execution_context&>::value>::type = 0);
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/*@}*/
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} // namespace asio
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#include "asio/detail/pop_options.hpp"
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#include "asio/impl/spawn.hpp"
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#endif // ASIO_SPAWN_HPP
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