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/detail/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		272247x	read_some_awaitable(
57			io_read_stream& ios, MutableBufferSequence buffers) noexcept
58		272247x	: ios_(ios)
59		272247x	, buffers_(std::move(buffers))
60			{
61		272247x	}
62
63		272247x	bool await_ready() const noexcept
64			{
65		272247x	return token_.stop_requested();
66			}
67
68		272247x	capy::io_result<std::size_t> await_resume() const noexcept
69			{
70	2/2 ✓ Branch 3 → 4 taken 800 times. ✓ Branch 3 → 6 taken 271447 times.	272247x	if (token_.stop_requested())
71		800x	return {make_error_code(std::errc::operation_canceled), 0};
72		271447x	return {ec_, bytes_transferred_};
73			}
74
75		272247x	auto await_suspend(std::coroutine_handle<> h, capy::io_env const* env)
76			-> std::coroutine_handle<>
77			{
78		272247x	token_ = env->stop_token;
79	1/1 ✓ Branch 5 → 6 taken 272247 times.	544494x	return ios_.do_read_some(
80		816741x	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			buffer_param,
99			std::stop_token,
100			std::error_code*,
101			std::size_t*) = 0;
102
103		4832x	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		272247x	auto read_some(MB const& buffers)
132			{
133		272247x	return read_some_awaitable<MB>(*this, buffers);
134			}
135			};
136
137			} // namespace boost::corosio
138
139			#endif
140