include/boost/corosio/io/io_read_stream.hpp

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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/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			/** Reads bytes from a stream asynchronously.
29
30			Provides the `read_some` operation via a pure virtual
31			`do_read_some` dispatch point. Concrete classes override
32			`do_read_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_write_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_write_stream, io_stream, io_object
43			*/
44			class BOOST_COROSIO_DECL io_read_stream : virtual public io_object
45			{
46			protected:
47			/// Awaitable for async read operations.
48			template<class MutableBufferSequence>
49			struct read_some_awaitable
50			: detail::bytes_op_base<read_some_awaitable<MutableBufferSequence>>
51			{
52			private:
53			friend io_read_stream;
54
55		1875722x	read_some_awaitable(
56			io_read_stream& ios, MutableBufferSequence buffers) noexcept
57		937861x	: ios_(ios)
58		937861x	, buffers_(std::move(buffers))
59		937861x	{
60		1875722x	}
61
62			friend detail::bytes_op_base<
63			read_some_awaitable<MutableBufferSequence>>;
64			io_read_stream& ios_;
65			MutableBufferSequence buffers_;
66
67			std::coroutine_handle<>
68		937851x	dispatch(std::coroutine_handle<> h, capy::executor_ref ex) const
69			{
70	8/16 ✓ Branch 0 taken 937785 times. ✗ Branch 1 not taken. ✓ Branch 2 taken 937785 times. ✗ Branch 3 not taken. ✓ Branch 4 taken 43 times. ✗ Branch 5 not taken. ✓ Branch 6 taken 43 times. ✗ Branch 7 not taken. ✓ Branch 8 taken 22 times. ✗ Branch 9 not taken. ✓ Branch 10 taken 22 times. ✗ Branch 11 not taken. ✓ Branch 12 taken 1 time. ✗ Branch 13 not taken. ✓ Branch 14 taken 1 time. ✗ Branch 15 not taken.	1875702x	return ios_.do_read_some(
71		937851x	h, ex, buffers_, this->token_, &this->ec_, &this->bytes_);
72		✗	}
73			};
74
75			/** Dispatch a read through the concrete implementation.
76
77			@param h Coroutine handle to resume on completion.
78			@param ex Executor for dispatching the completion.
79			@param buffers Target buffer sequence.
80			@param token Stop token for cancellation.
81			@param ec Output error code.
82			@param bytes Output bytes transferred.
83
84			@return Coroutine handle to resume immediately.
85			*/
86			virtual std::coroutine_handle<> do_read_some(
87			std::coroutine_handle<> h,
88			capy::executor_ref ex,
89			buffer_param buffers,
90			std::stop_token token,
91			std::error_code* ec,
92			std::size_t* bytes) = 0;
93
94			/// Default construct; the handle is supplied through @ref io_object.
95		22146x	io_read_stream() noexcept = default;
96
97			/// Move construct; the handle moves with @ref io_object.
98			io_read_stream(io_read_stream&&) noexcept = default;
99			/// Move assignment is disabled; reseating a live stream is not supported.
100			io_read_stream& operator=(io_read_stream&&) noexcept = delete;
101			/// Copy construction is disabled; the handle is uniquely owned.
102			io_read_stream(io_read_stream const&) = delete;
103			/// Copy assignment is disabled; the handle is uniquely owned.
104			io_read_stream& operator=(io_read_stream const&) = delete;
105
106			public:
107			/** Asynchronously read data from the stream.
108
109			Suspends the calling coroutine and initiates a kernel-level
110			read. The coroutine resumes when at least one byte is read,
111			an error occurs, or the operation is cancelled.
112
113			This stream must outlive the returned awaitable. The memory
114			referenced by @p buffers must remain valid until the operation
115			completes.
116
117			A closed stream completes with `errc::bad_file_descriptor`.
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		937861x	[[nodiscard]] auto read_some(MB const& buffers)
127			{
128		937861x	return read_some_awaitable<MB>(*this, buffers);
129			}
130			};
131
132			} // namespace boost::corosio
133
134			#endif
135