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		// Copyright (c) 2026 Michael Vandeberg
4		//
5		// Distributed under the Boost Software License, Version 1.0. (See accompanying
6		// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
7		//
8		// Official repository: https://github.com/cppalliance/corosio
9		//
10
11		#ifndef BOOST_COROSIO_IO_IO_READ_STREAM_HPP
12		#define BOOST_COROSIO_IO_IO_READ_STREAM_HPP
13
14		#include <boost/corosio/detail/config.hpp>
15		#include <boost/corosio/detail/op_base.hpp>
16		#include <boost/corosio/io/io_object.hpp>
17		#include <boost/corosio/detail/buffer_param.hpp>
18		#include <boost/capy/results.hpp>
19		#include <boost/capy/ex/executor_ref.hpp>
20		#include <boost/capy/ex/await_context.hpp>
21
22		#include <boost/capy/continuation.hpp>
23
24		#include <coroutine>
25		#include <cstddef>
26		#include <stop_token>
27		#include <system_error>
28
29		namespace boost::corosio {
30
31		/** Reads bytes from a stream asynchronously.
32
33		Provides the `read_some` operation via a pure virtual
34		`do_read_some` dispatch point. Concrete classes override
35		`do_read_some` to route through their implementation.
36
37		Uses virtual inheritance from @ref io_object so that
38		@ref io_stream can combine this with @ref io_write_stream
39		without duplicating the `io_object` base.
40
41		@par Thread Safety
42		Distinct objects: Safe.
43		Shared objects: Unsafe.
44
45		@see @ref io_write_stream, @ref io_stream, @ref io_object
46		*/
47		class BOOST_COROSIO_DECL io_read_stream : virtual public io_object
48		{
49		protected:
50		/// Awaitable for async read operations.
51		template<class MutableBufferSequence>
52		struct read_some_awaitable
53		: detail::bytes_op_base<read_some_awaitable<MutableBufferSequence>>
54		{
55		private:
56		friend io_read_stream;
57
58	235386x	read_some_awaitable(
59		io_read_stream& ios, MutableBufferSequence buffers) noexcept
60	235386x	: ios_(ios)
61	235386x	, buffers_(std::move(buffers))
62		{
63	235386x	}
64
65		friend detail::bytes_op_base<
66		read_some_awaitable<MutableBufferSequence>>;
67		io_read_stream& ios_;
68		MutableBufferSequence buffers_;
69
70		std::coroutine_handle<>
71	235359x	dispatch(capy::continuation& cont, capy::executor_ref ex) const
72		{
73	470718x	return ios_.do_read_some(
74	706077x	cont, ex, buffers_, this->token_, &this->ec_, &this->bytes_);
75		}
76		};
77
78		/** Dispatch a read through the concrete implementation.
79
80		@param cont Continuation to resume on completion; it lives in
81		the awaiting frame until then.
82		@param ex Executor for dispatching the completion.
83		@param buffers Target buffer sequence.
84		@param token Stop token for cancellation.
85		@param ec Output error code.
86		@param bytes Output bytes transferred.
87
88		@return Coroutine handle to resume immediately.
89		*/
90		virtual std::coroutine_handle<> do_read_some(
91		capy::continuation& cont,
92		capy::executor_ref ex,
93		buffer_param buffers,
94		std::stop_token token,
95		std::error_code* ec,
96		std::size_t* bytes) = 0;
97
98		/// Default construct; the handle is supplied through @ref io_object.
99	25997x	io_read_stream() noexcept = default;
100
101		/// Move construct; the handle moves with @ref io_object.
102		io_read_stream(io_read_stream&&) noexcept = default;
103		/// Move assignment is disabled; reseating a live stream is not supported.
104		io_read_stream& operator=(io_read_stream&&) noexcept = delete;
105		/// Copy construction is disabled; the handle is uniquely owned.
106		io_read_stream(io_read_stream const&) = delete;
107		/// Copy assignment is disabled; the handle is uniquely owned.
108		io_read_stream& operator=(io_read_stream const&) = delete;
109
110		public:
111		/** Asynchronously read data from the stream.
112
113		Suspends the calling coroutine and initiates a kernel-level
114		read. The coroutine resumes when at least one byte is read,
115		an error occurs, or the operation is cancelled.
116
117		This stream must outlive the returned awaitable. The memory
118		referenced by @p buffers must remain valid until the operation
119		completes.
120
121		A closed stream completes with `errc::bad_file_descriptor`.
122
123		@param buffers The buffer sequence to read data into.
124
125		@return An awaitable yielding `(error_code, std::size_t)`.
126
127		@see @ref io_stream::write_some
128		*/
129		template<capy::MutableBufferSequence MB>
130	235386x	[[nodiscard]] auto read_some(MB const& buffers)
131		{
132	235386x	return read_some_awaitable<MB>(*this, buffers);
133		}
134		};
135
136		} // namespace boost::corosio
137
138		#endif
139