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			/** Abstract base for streams that support async reads.
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			io_read_stream& ios_;
53			MutableBufferSequence buffers_;
54
55		1521794x	read_some_awaitable(
56			io_read_stream& ios, MutableBufferSequence buffers) noexcept
57		1521794x	: ios_(ios), buffers_(std::move(buffers)) {}
58
59		760897x	std::coroutine_handle<> dispatch(
60			std::coroutine_handle<> h, capy::executor_ref ex) const
61			{
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63		760897x	h, ex, buffers_, this->token_, &this->ec_, &this->bytes_);
64		✗	}
65			};
66
67			/** Dispatch a read through the concrete implementation.
68
69			@param h Coroutine handle to resume on completion.
70			@param ex Executor for dispatching the completion.
71			@param buffers Target buffer sequence.
72			@param token Stop token for cancellation.
73			@param ec Output error code.
74			@param bytes Output bytes transferred.
75
76			@return Coroutine handle to resume immediately.
77			*/
78			virtual std::coroutine_handle<> do_read_some(
79			std::coroutine_handle<>,
80			capy::executor_ref,
81			buffer_param,
82			std::stop_token,
83			std::error_code*,
84			std::size_t*) = 0;
85
86		19488x	io_read_stream() noexcept = default;
87
88			io_read_stream(io_read_stream&&) noexcept = default;
89			io_read_stream& operator=(io_read_stream&&) noexcept = delete;
90			io_read_stream(io_read_stream const&) = delete;
91			io_read_stream& operator=(io_read_stream const&) = delete;
92
93			public:
94			/** Asynchronously read data from the stream.
95
96			Suspends the calling coroutine and initiates a kernel-level
97			read. The coroutine resumes when at least one byte is read,
98			an error occurs, or the operation is cancelled.
99
100			This stream must outlive the returned awaitable. The memory
101			referenced by @p buffers must remain valid until the operation
102			completes.
103
104			A closed stream completes with `errc::bad_file_descriptor`.
105
106			@param buffers The buffer sequence to read data into.
107
108			@return An awaitable yielding `(error_code, std::size_t)`.
109
110			@see io_stream::write_some
111			*/
112			template<capy::MutableBufferSequence MB>
113		760897x	[[nodiscard]] auto read_some(MB const& buffers)
114			{
115		760897x	return read_some_awaitable<MB>(*this, buffers);
116			}
117			};
118
119			} // namespace boost::corosio
120
121			#endif
122