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	212812x	read_some_awaitable(
56		io_read_stream& ios, MutableBufferSequence buffers) noexcept
57	212812x	: ios_(ios)
58	212812x	, buffers_(std::move(buffers))
59		{
60	212812x	}
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	212803x	dispatch(std::coroutine_handle<> h, capy::executor_ref ex) const
69		{
70	425606x	return ios_.do_read_some(
71	638409x	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	10432x	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	212812x	[[nodiscard]] auto read_some(MB const& buffers)
127		{
128	212812x	return read_some_awaitable<MB>(*this, buffers);
129		}
130		};
131
132		} // namespace boost::corosio
133
134		#endif
135