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

include/boost/corosio/io/io_read_stream.hpp

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include/boost/corosio/io/io_read_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_READ_STREAM_HPP
11 #define BOOST_COROSIO_IO_IO_READ_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 reads.
28
29 Provides the `read_some` operation via a pure virtual
30 `do_read_some` dispatch point. Concrete classes override
31 `do_read_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_write_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_write_stream, io_stream, io_object
42 */
43 class BOOST_COROSIO_DECL io_read_stream : virtual public io_object
44 {
45 protected:
46 /// Awaitable for async read operations.
47 template<class MutableBufferSequence>
48 struct read_some_awaitable
49 {
50 io_read_stream& ios_;
51 MutableBufferSequence buffers_;
52 std::stop_token token_;
53 mutable std::error_code ec_;
54 mutable std::size_t bytes_transferred_ = 0;
55
56 305551 read_some_awaitable(
57 io_read_stream& ios, MutableBufferSequence buffers) noexcept
58 305551 : ios_(ios)
59 305551 , buffers_(std::move(buffers))
60 {
61 305551 }
62
63 305551 bool await_ready() const noexcept
64 {
65 305551 return token_.stop_requested();
66 }
67
68 305551 capy::io_result<std::size_t> await_resume() const noexcept
69 {
70 305551 if (token_.stop_requested())
71 198 return {make_error_code(std::errc::operation_canceled), 0};
72 305353 return {ec_, bytes_transferred_};
73 }
74
75 305551 auto await_suspend(std::coroutine_handle<> h, capy::io_env const* env)
76 -> std::coroutine_handle<>
77 {
78 305551 token_ = env->stop_token;
79 611102 return ios_.do_read_some(
80 916653 h, env->executor, buffers_, token_, &ec_, &bytes_transferred_);
81 }
82 };
83
84 /** Dispatch a read 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 Target 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_read_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 15652 io_read_stream() noexcept = default;
104
105 /// Construct from a handle.
106 explicit io_read_stream(handle h) noexcept : io_object(std::move(h)) {}
107
108 io_read_stream(io_read_stream&&) noexcept = default;
109 io_read_stream& operator=(io_read_stream&&) noexcept = delete;
110 io_read_stream(io_read_stream const&) = delete;
111 io_read_stream& operator=(io_read_stream const&) = delete;
112
113 public:
114 /** Asynchronously read data from the stream.
115
116 Suspends the calling coroutine and initiates a kernel-level
117 read. The coroutine resumes when at least one byte is read,
118 an error occurs, or the operation is cancelled.
119
120 This stream must outlive the returned awaitable. The memory
121 referenced by @p buffers must remain valid until the operation
122 completes.
123
124 @param buffers The buffer sequence to read data into.
125
126 @return An awaitable yielding `(error_code, std::size_t)`.
127
128 @see io_stream::write_some
129 */
130 template<capy::MutableBufferSequence MB>
131 305551 auto read_some(MB const& buffers)
132 {
133 305551 return read_some_awaitable<MB>(*this, buffers);
134 }
135 };
136
137 } // namespace boost::corosio
138
139 #endif
140