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	197288x	read_some_awaitable(
56		io_read_stream& ios, MutableBufferSequence buffers) noexcept
57	197288x	: ios_(ios), buffers_(std::move(buffers)) {}
58
59	197288x	std::coroutine_handle<> dispatch(
60		std::coroutine_handle<> h, capy::executor_ref ex) const
61		{
62	394576x	return ios_.do_read_some(
63	591864x	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	16314x	io_read_stream() noexcept = default;
87
88		/// Construct from a handle.
89		explicit io_read_stream(handle h) noexcept : io_object(std::move(h)) {}
90
91		io_read_stream(io_read_stream&&) noexcept = default;
92		io_read_stream& operator=(io_read_stream&&) noexcept = delete;
93		io_read_stream(io_read_stream const&) = delete;
94		io_read_stream& operator=(io_read_stream const&) = delete;
95
96		public:
97		/** Asynchronously read data from the stream.
98
99		Suspends the calling coroutine and initiates a kernel-level
100		read. The coroutine resumes when at least one byte is read,
101		an error occurs, or the operation is cancelled.
102
103		This stream must outlive the returned awaitable. The memory
104		referenced by @p buffers must remain valid until the operation
105		completes.
106
107		@param buffers The buffer sequence to read data into.
108
109		@par Cancellation
110		Supports cancellation via the awaitable's stop_token or by
111		calling the owning stream's `cancel()` member. On cancellation,
112		yields `errc::operation_canceled`.
113
114		@return An awaitable yielding `(error_code, std::size_t)`.
115
116		@see io_stream::write_some
117		*/
118		template<capy::MutableBufferSequence MB>
119	197288x	auto read_some(MB const& buffers)
120		{
121	197288x	return read_some_awaitable<MB>(*this, buffers);
122		}
123		};
124
125		} // namespace boost::corosio
126
127		#endif
128