include/boost/corosio/io/io_write_stream.hpp

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io_write_stream.hpp

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1			//
2			// Copyright (c) 2026 Steve Gerbino
3			// Copyright (c) 2026 Michael Vandeberg
4			//
5			// Distributed under the Boost Software License, Version 1.0. (See accompanying
6			// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
7			//
8			// Official repository: https://github.com/cppalliance/corosio
9			//
10
11			#ifndef BOOST_COROSIO_IO_IO_WRITE_STREAM_HPP
12			#define BOOST_COROSIO_IO_IO_WRITE_STREAM_HPP
13
14			#include <boost/corosio/detail/config.hpp>
15			#include <boost/corosio/detail/op_base.hpp>
16			#include <boost/corosio/io/io_object.hpp>
17			#include <boost/corosio/detail/buffer_param.hpp>
18			#include <boost/capy/results.hpp>
19			#include <boost/capy/ex/executor_ref.hpp>
20			#include <boost/capy/ex/await_context.hpp>
21
22			#include <boost/capy/continuation.hpp>
23
24			#include <coroutine>
25			#include <cstddef>
26			#include <stop_token>
27			#include <system_error>
28
29			namespace boost::corosio {
30
31			/** Writes bytes to a stream asynchronously.
32
33			Provides the `write_some` operation via a pure virtual
34			`do_write_some` dispatch point. Concrete classes override
35			`do_write_some` to route through their implementation.
36
37			Uses virtual inheritance from @ref io_object so that
38			@ref io_stream can combine this with @ref io_read_stream
39			without duplicating the `io_object` base.
40
41			@par Thread Safety
42			Distinct objects: Safe.
43			Shared objects: Unsafe.
44
45			@see @ref io_read_stream, @ref io_stream, @ref io_object
46			*/
47			class BOOST_COROSIO_DECL io_write_stream : virtual public io_object
48			{
49			protected:
50			/// Awaitable for async write operations.
51			template<class ConstBufferSequence>
52			struct write_some_awaitable
53			: detail::bytes_op_base<write_some_awaitable<ConstBufferSequence>>
54			{
55			private:
56			friend io_write_stream;
57
58		1488566x	write_some_awaitable(
59			io_write_stream& ios, ConstBufferSequence buffers) noexcept
60		744283x	: ios_(ios)
61		744283x	, buffers_(std::move(buffers))
62		744283x	{
63		1488566x	}
64
65			friend detail::bytes_op_base<write_some_awaitable<ConstBufferSequence>>;
66			io_write_stream& ios_;
67			ConstBufferSequence buffers_;
68
69			std::coroutine_handle<>
70		744256x	dispatch(capy::continuation& cont, capy::executor_ref ex) const
71			{
72	6/12 ✓ Branch 0 taken 744202 times. ✗ Branch 1 not taken. ✓ Branch 2 taken 744202 times. ✗ Branch 3 not taken. ✓ Branch 4 taken 51 times. ✗ Branch 5 not taken. ✓ Branch 6 taken 51 times. ✗ Branch 7 not taken. ✓ Branch 8 taken 3 times. ✗ Branch 9 not taken. ✓ Branch 10 taken 3 times. ✗ Branch 11 not taken.	1488512x	return ios_.do_write_some(
73		744256x	cont, ex, buffers_, this->token_, &this->ec_, &this->bytes_);
74		✗	}
75			};
76
77			/** Dispatch a write through the concrete implementation.
78
79			@param cont Continuation to resume on completion; it lives in
80			the awaiting frame until then.
81			@param ex Executor for dispatching the completion.
82			@param buffers Source buffer sequence.
83			@param token Stop token for cancellation.
84			@param ec Output error code.
85			@param bytes Output bytes transferred.
86
87			@return Coroutine handle to resume immediately.
88			*/
89			virtual std::coroutine_handle<> do_write_some(
90			capy::continuation& cont,
91			capy::executor_ref ex,
92			detail::buffer_param buffers,
93			std::stop_token token,
94			std::error_code* ec,
95			std::size_t* bytes) = 0;
96
97			/// Default construct; the handle is supplied through @ref io_object.
98		44299x	io_write_stream() noexcept = default;
99
100			/// Move construct; the handle moves with @ref io_object.
101			io_write_stream(io_write_stream&&) noexcept = default;
102			/// Move assignment is disabled; reseating a live stream is not supported.
103			io_write_stream& operator=(io_write_stream&&) noexcept = delete;
104			/// Copy construction is disabled; the handle is uniquely owned.
105			io_write_stream(io_write_stream const&) = delete;
106			/// Copy assignment is disabled; the handle is uniquely owned.
107			io_write_stream& operator=(io_write_stream const&) = delete;
108
109			public:
110			/** Asynchronously write data to the stream.
111
112			Suspends the calling coroutine and initiates a kernel-level
113			write. The coroutine resumes when at least one byte is written,
114			an error occurs, or the operation is cancelled.
115
116			This stream must outlive the returned awaitable. The memory
117			referenced by @p buffers must remain valid until the operation
118			completes.
119
120			A closed stream completes with `errc::bad_file_descriptor`.
121
122			@param buffers The buffer sequence containing data to write.
123
124			@return An awaitable yielding `(error_code, std::size_t)`.
125
126			@see @ref io_stream::read_some
127			*/
128			template<capy::ConstBufferSequence CB>
129		744283x	[[nodiscard]] auto write_some(CB const& buffers)
130			{
131		744283x	return write_some_awaitable<CB>(*this, buffers);
132			}
133			};
134
135			} // namespace boost::corosio
136
137			#endif
138