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		1769656x	write_some_awaitable(
56			io_write_stream& ios, ConstBufferSequence buffers) noexcept
57		1769656x	: ios_(ios), buffers_(std::move(buffers)) {}
58
59		884828x	std::coroutine_handle<> dispatch(
60			std::coroutine_handle<> h, capy::executor_ref ex) const
61			{
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63		884828x	h, ex, buffers_, this->token_, &this->ec_, &this->bytes_);
64		✗	}
65			};
66
67			/** Dispatch a write through the concrete implementation.
68
69			@param h Coroutine handle to resume on completion.
70			@param ex Executor for dispatching the completion.
71			@param buffers Source buffer sequence.
72			@param token Stop token for cancellation.
73			@param ec Output error code.
74			@param bytes Output bytes transferred.
75
76			@return Coroutine handle to resume immediately.
77			*/
78			virtual std::coroutine_handle<> do_write_some(
79			std::coroutine_handle<>,
80			capy::executor_ref,
81			buffer_param,
82			std::stop_token,
83			std::error_code*,
84			std::size_t*) = 0;
85
86		19488x	io_write_stream() noexcept = default;
87
88			io_write_stream(io_write_stream&&) noexcept = default;
89			io_write_stream& operator=(io_write_stream&&) noexcept = delete;
90			io_write_stream(io_write_stream const&) = delete;
91			io_write_stream& operator=(io_write_stream const&) = delete;
92
93			public:
94			/** Asynchronously write data to the stream.
95
96			Suspends the calling coroutine and initiates a kernel-level
97			write. The coroutine resumes when at least one byte is written,
98			an error occurs, or the operation is cancelled.
99
100			This stream must outlive the returned awaitable. The memory
101			referenced by @p buffers must remain valid until the operation
102			completes.
103
104			A closed stream completes with `errc::bad_file_descriptor`.
105
106			@param buffers The buffer sequence containing data to write.
107
108			@return An awaitable yielding `(error_code, std::size_t)`.
109
110			@see io_stream::read_some
111			*/
112			template<capy::ConstBufferSequence CB>
113		884828x	[[nodiscard]] auto write_some(CB const& buffers)
114			{
115		884828x	return write_some_awaitable<CB>(*this, buffers);
116			}
117			};
118
119			} // namespace boost::corosio
120
121			#endif
122