include/boost/corosio/detail/op_base.hpp

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op_base.hpp

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1			//
2			// Copyright (c) 2026 Michael Vandeberg
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/corosio
8			//
9
10			#ifndef BOOST_COROSIO_DETAIL_OP_BASE_HPP
11			#define BOOST_COROSIO_DETAIL_OP_BASE_HPP
12
13			#include <boost/capy/error.hpp>
14			#include <boost/capy/continuation.hpp>
15			#include <boost/capy/results.hpp>
16			#include <boost/capy/ex/executor_ref.hpp>
17			#include <boost/capy/ex/await_context.hpp>
18
19			#include <coroutine>
20			#include <cstddef>
21			#include <stop_token>
22			#include <system_error>
23
24			namespace boost::corosio::detail {
25
26			/* CRTP base for awaitables that return results<std::size_t>.
27
28			Derived classes must provide:
29
30			std::coroutine_handle<> dispatch(
31			capy::continuation& cont,
32			capy::executor_ref ex) const;
33
34			which forwards to the backend implementation method, passing
35			token_, &ec_, and &bytes_ as the cancellation/output parameters.
36			*/
37			template<class Derived>
38			class bytes_op_base
39			{
40			friend Derived;
41		423021x	bytes_op_base() = default;
42
43			public:
44			std::stop_token token_;
45			mutable std::error_code ec_;
46			mutable std::size_t bytes_ = 0;
47			// Lives in the awaiting frame until resumption, so a completion
48			// posted through an executor never shares the object's state.
49			mutable capy::continuation cont_;
50
51		423021x	bool await_ready() const noexcept
52			{
53			// A pre-set ec_ means the initiator failed before dispatch
54			// (e.g. a closed object); complete immediately with that error.
55		423021x	return static_cast<bool>(ec_);
56			}
57
58		422793x	[[nodiscard]] capy::results<std::size_t> await_resume() const noexcept
59			{
60		422793x	return {ec_, bytes_};
61			}
62
63		423011x	auto await_suspend(std::coroutine_handle<> h, capy::await_context const* env)
64			-> std::coroutine_handle<>
65			{
66		423011x	token_ = env->stop_token;
67			// A pre-stopped token short-circuits before dispatch so no I/O
68			// is performed. A stop landing after dispatch is decoded by the
69			// backend, and a completed transfer is reported verbatim: the
70			// stream contracts forbid discarding the byte count.
71	2/2 ✓ Branch 4 → 5 taken 31 times. ✓ Branch 4 → 7 taken 422980 times.	423011x	if (token_.stop_requested())
72			{
73		31x	ec_ = capy::error::canceled;
74		31x	return h;
75			}
76		422980x	cont_.h = h;
77		422980x	cont_.owner = env->owner;
78		422980x	return static_cast<Derived const*>(this)->dispatch(
79		422980x	cont_, env->executor);
80			}
81			};
82
83			/* CRTP base for awaitables that return results<Value> for a
84			moved-out result object (e.g. the resolver's result lists).
85
86			Derived classes must provide:
87
88			std::coroutine_handle<> dispatch(
89			capy::continuation& cont,
90			capy::executor_ref ex) const;
91
92			which forwards to the backend implementation method, passing
93			token_, &ec_, and &value_ as the cancellation/output parameters.
94			*/
95			template<class Derived, class Value>
96			class value_op_base
97			{
98			friend Derived;
99		102437x	value_op_base() = default;
100
101			public:
102			std::stop_token token_;
103			mutable std::error_code ec_;
104			mutable Value value_{};
105			// See bytes_op_base::cont_.
106			mutable capy::continuation cont_;
107
108		102437x	bool await_ready() const noexcept
109			{
110			// A pre-set ec_ means the initiator failed before dispatch;
111			// complete immediately with that error.
112		102437x	return static_cast<bool>(ec_);
113			}
114
115		100817x	[[nodiscard]] capy::results<Value> await_resume() const noexcept
116			{
117		100817x	return {ec_, std::move(value_)};
118			}
119
120		102437x	auto await_suspend(std::coroutine_handle<> h, capy::await_context const* env)
121			-> std::coroutine_handle<>
122			{
123		102437x	token_ = env->stop_token;
124			// A pre-stopped token short-circuits before dispatch; a stop
125			// landing after dispatch leaves the completed result intact.
126	2/2 ✓ Branch 4 → 5 taken 22 times. ✓ Branch 4 → 7 taken 102415 times.	102437x	if (token_.stop_requested())
127			{
128		22x	ec_ = capy::error::canceled;
129		22x	return h;
130			}
131		102415x	cont_.h = h;
132		102415x	cont_.owner = env->owner;
133		102415x	return static_cast<Derived const*>(this)->dispatch(
134		102415x	cont_, env->executor);
135			}
136			};
137
138			/* CRTP base for awaitables that return results<>.
139
140			Derived classes must provide:
141
142			std::coroutine_handle<> dispatch(
143			capy::continuation& cont,
144			capy::executor_ref ex) const;
145
146			which forwards to the backend implementation method, passing
147			token_ and &ec_ as the cancellation/output parameters.
148			*/
149			template<class Derived>
150			class void_op_base
151			{
152			friend Derived;
153		10201x	void_op_base() = default;
154
155			public:
156			std::stop_token token_;
157			mutable std::error_code ec_;
158			// See bytes_op_base::cont_.
159			mutable capy::continuation cont_;
160
161		10201x	bool await_ready() const noexcept
162			{
163			// A pre-set ec_ means the initiator failed before dispatch
164			// (e.g. auto-open); complete immediately with that error.
165		10201x	return static_cast<bool>(ec_);
166			}
167
168		6842x	[[nodiscard]] capy::results<> await_resume() const noexcept
169			{
170		6842x	return {ec_};
171			}
172
173		10188x	auto await_suspend(std::coroutine_handle<> h, capy::await_context const* env)
174			-> std::coroutine_handle<>
175			{
176		10188x	token_ = env->stop_token;
177			// A pre-stopped token short-circuits before dispatch; a stop
178			// landing after dispatch leaves the completed result intact.
179	2/2 ✓ Branch 4 → 5 taken 510 times. ✓ Branch 4 → 7 taken 9678 times.	10188x	if (token_.stop_requested())
180			{
181		510x	ec_ = capy::error::canceled;
182		510x	return h;
183			}
184		9678x	cont_.h = h;
185		9678x	cont_.owner = env->owner;
186		9678x	return static_cast<Derived const*>(this)->dispatch(
187		9678x	cont_, env->executor);
188			}
189			};
190
191			} // namespace boost::corosio::detail
192
193			#endif // BOOST_COROSIO_DETAIL_OP_BASE_HPP
194