Index/include / boost / corosio / io / io_write_stream.hpp

include/boost/corosio/io/io_write_stream.hpp

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include/boost/corosio/io/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/io/io_object.hpp>
15 #include <boost/corosio/io_buffer_param.hpp>
16 #include <boost/capy/io_result.hpp>
17 #include <boost/capy/ex/executor_ref.hpp>
18 #include <boost/capy/ex/io_env.hpp>
19
20 #include <coroutine>
21 #include <cstddef>
22 #include <stop_token>
23 #include <system_error>
24
25 namespace boost::corosio {
26
27 /** Abstract base for streams that support async writes.
28
29 Provides the `write_some` operation via a pure virtual
30 `do_write_some` dispatch point. Concrete classes override
31 `do_write_some` to route through their implementation.
32
33 Uses virtual inheritance from @ref io_object so that
34 @ref io_stream can combine this with @ref io_read_stream
35 without duplicating the `io_object` base.
36
37 @par Thread Safety
38 Distinct objects: Safe.
39 Shared objects: Unsafe.
40
41 @see io_read_stream, io_stream, io_object
42 */
43 class BOOST_COROSIO_DECL io_write_stream : virtual public io_object
44 {
45 protected:
46 /// Awaitable for async write operations.
47 template<class ConstBufferSequence>
48 struct write_some_awaitable
49 {
50 io_write_stream& ios_;
51 ConstBufferSequence buffers_;
52 std::stop_token token_;
53 mutable std::error_code ec_;
54 mutable std::size_t bytes_transferred_ = 0;
55
56 234522 write_some_awaitable(
57 io_write_stream& ios, ConstBufferSequence buffers) noexcept
58 234522 : ios_(ios)
59 234522 , buffers_(std::move(buffers))
60 {
61 234522 }
62
63 234522 bool await_ready() const noexcept
64 {
65 234522 return token_.stop_requested();
66 }
67
68 234522 capy::io_result<std::size_t> await_resume() const noexcept
69 {
70
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 234522 if (token_.stop_requested())
71 2 return {make_error_code(std::errc::operation_canceled), 0};
72 234520 return {ec_, bytes_transferred_};
73 }
74
75 234522 auto await_suspend(std::coroutine_handle<> h, capy::io_env const* env)
76 -> std::coroutine_handle<>
77 {
78 234522 token_ = env->stop_token;
79
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 469044 return ios_.do_write_some(
80 703566 h, env->executor, buffers_, token_, &ec_, &bytes_transferred_);
81 }
82 };
83
84 /** Dispatch a write through the concrete implementation.
85
86 @param h Coroutine handle to resume on completion.
87 @param ex Executor for dispatching the completion.
88 @param buffers Source buffer sequence.
89 @param token Stop token for cancellation.
90 @param ec Output error code.
91 @param bytes Output bytes transferred.
92
93 @return Coroutine handle to resume immediately.
94 */
95 virtual std::coroutine_handle<> do_write_some(
96 std::coroutine_handle<>,
97 capy::executor_ref,
98 io_buffer_param,
99 std::stop_token,
100 std::error_code*,
101 std::size_t*) = 0;
102
103 4778 io_write_stream() noexcept = default;
104
105 /// Construct from a handle.
106 explicit io_write_stream(handle h) noexcept : io_object(std::move(h)) {}
107
108 public:
109 /** Asynchronously write data to the stream.
110
111 Suspends the calling coroutine and initiates a kernel-level
112 write. The coroutine resumes when at least one byte is written,
113 an error occurs, or the operation is cancelled.
114
115 This stream must outlive the returned awaitable. The memory
116 referenced by @p buffers must remain valid until the operation
117 completes.
118
119 @param buffers The buffer sequence containing data to write.
120
121 @return An awaitable yielding `(error_code, std::size_t)`.
122
123 @see io_stream::read_some
124 */
125 template<capy::ConstBufferSequence CB>
126 234522 auto write_some(CB const& buffers)
127 {
128 234522 return write_some_awaitable<CB>(*this, buffers);
129 }
130 };
131
132 } // namespace boost::corosio
133
134 #endif
135