libs/capy/include/boost/capy/ex/run_on.hpp

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1		//
2		// Copyright (c) 2025 Vinnie Falco (vinnie dot falco at gmail dot com)
3		//
4		// Distributed under the Boost Software License, Version 1.0. (See accompanying
5		// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
6		//
7		// Official repository: https://github.com/cppalliance/capy
8		//
9
10		#ifndef BOOST_CAPY_RUN_ON_HPP
11		#define BOOST_CAPY_RUN_ON_HPP
12
13		#include <boost/capy/detail/config.hpp>
14		#include <boost/capy/concept/executor.hpp>
15		#include <boost/capy/concept/io_launchable_task.hpp>
16		#include <boost/capy/ex/executor_ref.hpp>
17
18		#include <stop_token>
19		#include <utility>
20
21		namespace boost {
22		namespace capy {
23		namespace detail {
24
25		/** Awaitable that binds an IoAwaitableTask to a specific executor.
26
27		Stores the executor and inner task by value. When co_awaited, the
28		co_await expression's lifetime extension keeps both alive for the
29		duration of the operation.
30
31		@tparam Task The IoAwaitableTask type
32		@tparam Ex The executor type
33		*/
34		template<IoLaunchableTask Task, Executor Ex>
35		struct [[nodiscard]]
36		run_on_awaitable
37		{
38		Ex ex_;
39		Task inner_;
40
41	2	run_on_awaitable(Ex ex, Task inner)
42	2	: ex_(std::move(ex))
43	2	, inner_(std::move(inner))
44		{
45	2	}
46
47	2	bool await_ready() const noexcept
48		{
49	2	return inner_.await_ready();
50		}
51
52	2	decltype(auto) await_resume()
53		{
54	2	return inner_.await_resume();
55		}
56
57		// IoAwaitable: receives caller's executor and stop_token for completion dispatch
58		template<typename Caller>
59	2	coro await_suspend(coro cont, Caller const& caller_ex, std::stop_token token)
60		{
61	2	auto h = inner_.handle();
62	2	auto& p = h.promise();
63	2	p.set_executor(ex_);
64	2	p.set_continuation(cont, caller_ex);
65	2	p.set_stop_token(token);
66	2	return h;
67		}
68
69		// Non-copyable
70		run_on_awaitable(run_on_awaitable const&) = delete;
71		run_on_awaitable& operator=(run_on_awaitable const&) = delete;
72
73		// Movable
74	2	run_on_awaitable(run_on_awaitable&& other) noexcept
75	2	: ex_(std::move(other.ex_))
76	2	, inner_(std::move(other.inner_))
77		{
78	2	}
79
80		run_on_awaitable& operator=(run_on_awaitable&& other) noexcept
81		{
82		if(this != &other)
83		{
84		ex_ = std::move(other.ex_);
85		inner_ = std::move(other.inner_);
86		}
87		return *this;
88		}
89		};
90
91		} // namespace detail
92
93		/** Binds a task to execute on a specific executor.
94
95		The executor is stored by value in the returned awaitable.
96		When co_awaited, the inner task receives this executor through
97		direct promise configuration.
98
99		@param ex The executor on which the task should run (copied by value).
100		@param t The IoAwaitableTask to bind to the executor.
101
102		@return An awaitable that runs t on the specified executor.
103		*/
104		template<Executor Ex, IoLaunchableTask Task>
105	2	[[nodiscard]] auto run_on(Ex ex, Task t)
106		{
107		return detail::run_on_awaitable<Task, Ex>{
108	2	std::move(ex), std::move(t)};
109		}
110
111		} // namespace capy
112		} // namespace boost
113
114		#endif
115