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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 205784 read_some_awaitable(
57 io_read_stream& ios, MutableBufferSequence buffers) noexcept
58 205784 : ios_(ios)
59 205784 , buffers_(std::move(buffers))
60 {
61 205784 }
62
63 205784 bool await_ready() const noexcept
64 {
65 205784 return token_.stop_requested();
66 }
67
68 205784 capy::io_result<std::size_t> await_resume() const noexcept
69 {
70 205784 if (token_.stop_requested())
71 195 return {make_error_code(std::errc::operation_canceled), 0};
72 205589 return {ec_, bytes_transferred_};
73 }
74
75 205784 auto await_suspend(std::coroutine_handle<> h, capy::io_env const* env)
76 -> std::coroutine_handle<>
77 {
78 205784 token_ = env->stop_token;
79 411568 return ios_.do_read_some(
80 617352 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 14773 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 public:
109 /** Asynchronously read data from the stream.
110
111 Suspends the calling coroutine and initiates a kernel-level
112 read. The coroutine resumes when at least one byte is read,
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 to read data into.
120
121 @return An awaitable yielding `(error_code, std::size_t)`.
122
123 @see io_stream::write_some
124 */
125 template<capy::MutableBufferSequence MB>
126 205784 auto read_some(MB const& buffers)
127 {
128 205784 return read_some_awaitable<MB>(*this, buffers);
129 }
130 };
131
132 } // namespace boost::corosio
133
134 #endif
135