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			//
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_IO_IO_WRITE_STREAM_HPP
11			#define BOOST_COROSIO_IO_IO_WRITE_STREAM_HPP
12
13			#include <boost/corosio/detail/config.hpp>
14			#include <boost/corosio/detail/op_base.hpp>
15			#include <boost/corosio/io/io_object.hpp>
16			#include <boost/corosio/detail/buffer_param.hpp>
17			#include <boost/capy/io_result.hpp>
18			#include <boost/capy/ex/executor_ref.hpp>
19			#include <boost/capy/ex/io_env.hpp>
20
21			#include <coroutine>
22			#include <cstddef>
23			#include <stop_token>
24			#include <system_error>
25
26			namespace boost::corosio {
27
28			/** Abstract base for streams that support async writes.
29
30			Provides the `write_some` operation via a pure virtual
31			`do_write_some` dispatch point. Concrete classes override
32			`do_write_some` to route through their implementation.
33
34			Uses virtual inheritance from @ref io_object so that
35			@ref io_stream can combine this with @ref io_read_stream
36			without duplicating the `io_object` base.
37
38			@par Thread Safety
39			Distinct objects: Safe.
40			Shared objects: Unsafe.
41
42			@see io_read_stream, io_stream, io_object
43			*/
44			class BOOST_COROSIO_DECL io_write_stream : virtual public io_object
45			{
46			protected:
47			/// Awaitable for async write operations.
48			template<class ConstBufferSequence>
49			struct write_some_awaitable
50			: detail::bytes_op_base<write_some_awaitable<ConstBufferSequence>>
51			{
52			io_write_stream& ios_;
53			ConstBufferSequence buffers_;
54
55		1005578x	write_some_awaitable(
56			io_write_stream& ios, ConstBufferSequence buffers) noexcept
57		502789x	: ios_(ios)
58		502789x	, buffers_(std::move(buffers))
59		502789x	{
60		1005578x	}
61
62			std::coroutine_handle<>
63		502789x	dispatch(std::coroutine_handle<> h, capy::executor_ref ex) const
64			{
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66		502789x	h, ex, buffers_, this->token_, &this->ec_, &this->bytes_);
67		✗	}
68			};
69
70			/** Dispatch a write through the concrete implementation.
71
72			@param h Coroutine handle to resume on completion.
73			@param ex Executor for dispatching the completion.
74			@param buffers Source buffer sequence.
75			@param token Stop token for cancellation.
76			@param ec Output error code.
77			@param bytes Output bytes transferred.
78
79			@return Coroutine handle to resume immediately.
80			*/
81			virtual std::coroutine_handle<> do_write_some(
82			std::coroutine_handle<>,
83			capy::executor_ref,
84			buffer_param,
85			std::stop_token,
86			std::error_code*,
87			std::size_t*) = 0;
88
89		16480x	io_write_stream() noexcept = default;
90
91			io_write_stream(io_write_stream&&) noexcept = default;
92			io_write_stream& operator=(io_write_stream&&) noexcept = delete;
93			io_write_stream(io_write_stream const&) = delete;
94			io_write_stream& operator=(io_write_stream const&) = delete;
95
96			public:
97			/** Asynchronously write data to the stream.
98
99			Suspends the calling coroutine and initiates a kernel-level
100			write. The coroutine resumes when at least one byte is written,
101			an error occurs, or the operation is cancelled.
102
103			This stream must outlive the returned awaitable. The memory
104			referenced by @p buffers must remain valid until the operation
105			completes.
106
107			A closed stream completes with `errc::bad_file_descriptor`.
108
109			@param buffers The buffer sequence containing data to write.
110
111			@return An awaitable yielding `(error_code, std::size_t)`.
112
113			@see io_stream::read_some
114			*/
115			template<capy::ConstBufferSequence CB>
116		502789x	[[nodiscard]] auto write_some(CB const& buffers)
117			{
118		502789x	return write_some_awaitable<CB>(*this, buffers);
119			}
120			};
121
122			} // namespace boost::corosio
123
124			#endif
125