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		2118032x	write_some_awaitable(
56			io_write_stream& ios, ConstBufferSequence buffers) noexcept
57		1059016x	: ios_(ios)
58		1059016x	, buffers_(std::move(buffers))
59		1059016x	{
60		2118032x	}
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		1059009x	dispatch(std::coroutine_handle<> h, capy::executor_ref ex) const
68			{
69	8/16 ✓ Branch 0 taken 1058955 times. ✗ Branch 1 not taken. ✓ Branch 2 taken 1058955 times. ✗ Branch 3 not taken. ✓ Branch 4 taken 49 times. ✗ Branch 5 not taken. ✓ Branch 6 taken 49 times. ✗ Branch 7 not taken. ✓ Branch 8 taken 4 times. ✗ Branch 9 not taken. ✓ Branch 10 taken 4 times. ✗ Branch 11 not taken. ✓ Branch 12 taken 1 time. ✗ Branch 13 not taken. ✓ Branch 14 taken 1 time. ✗ Branch 15 not taken.	2118018x	return ios_.do_write_some(
70		1059009x	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		22146x	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		1059016x	[[nodiscard]] auto write_some(CB const& buffers)
126			{
127		1059016x	return write_some_awaitable<CB>(*this, buffers);
128			}
129			};
130
131			} // namespace boost::corosio
132
133			#endif
134