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		/** Writes bytes to a stream asynchronously.
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		private:
53		friend io_write_stream;
54
55	212061x	write_some_awaitable(
56		io_write_stream& ios, ConstBufferSequence buffers) noexcept
57	212061x	: ios_(ios)
58	212061x	, buffers_(std::move(buffers))
59		{
60	212061x	}
61
62		friend detail::bytes_op_base<write_some_awaitable<ConstBufferSequence>>;
63		io_write_stream& ios_;
64		ConstBufferSequence buffers_;
65
66		std::coroutine_handle<>
67	212055x	dispatch(std::coroutine_handle<> h, capy::executor_ref ex) const
68		{
69	424110x	return ios_.do_write_some(
70	636165x	h, ex, buffers_, this->token_, &this->ec_, &this->bytes_);
71		}
72		};
73
74		/** Dispatch a write through the concrete implementation.
75
76		@param h Coroutine handle to resume on completion.
77		@param ex Executor for dispatching the completion.
78		@param buffers Source buffer sequence.
79		@param token Stop token for cancellation.
80		@param ec Output error code.
81		@param bytes Output bytes transferred.
82
83		@return Coroutine handle to resume immediately.
84		*/
85		virtual std::coroutine_handle<> do_write_some(
86		std::coroutine_handle<> h,
87		capy::executor_ref ex,
88		buffer_param buffers,
89		std::stop_token token,
90		std::error_code* ec,
91		std::size_t* bytes) = 0;
92
93		/// Default construct; the handle is supplied through @ref io_object.
94	10432x	io_write_stream() noexcept = default;
95
96		/// Move construct; the handle moves with @ref io_object.
97		io_write_stream(io_write_stream&&) noexcept = default;
98		/// Move assignment is disabled; reseating a live stream is not supported.
99		io_write_stream& operator=(io_write_stream&&) noexcept = delete;
100		/// Copy construction is disabled; the handle is uniquely owned.
101		io_write_stream(io_write_stream const&) = delete;
102		/// Copy assignment is disabled; the handle is uniquely owned.
103		io_write_stream& operator=(io_write_stream const&) = delete;
104
105		public:
106		/** Asynchronously write data to the stream.
107
108		Suspends the calling coroutine and initiates a kernel-level
109		write. The coroutine resumes when at least one byte is written,
110		an error occurs, or the operation is cancelled.
111
112		This stream must outlive the returned awaitable. The memory
113		referenced by @p buffers must remain valid until the operation
114		completes.
115
116		A closed stream completes with `errc::bad_file_descriptor`.
117
118		@param buffers The buffer sequence containing data to write.
119
120		@return An awaitable yielding `(error_code, std::size_t)`.
121
122		@see io_stream::read_some
123		*/
124		template<capy::ConstBufferSequence CB>
125	212061x	[[nodiscard]] auto write_some(CB const& buffers)
126		{
127	212061x	return write_some_awaitable<CB>(*this, buffers);
128		}
129		};
130
131		} // namespace boost::corosio
132
133		#endif
134