include/boost/corosio/native/native_stream_file.hpp

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native_stream_file.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_NATIVE_NATIVE_STREAM_FILE_HPP
11		#define BOOST_COROSIO_NATIVE_NATIVE_STREAM_FILE_HPP
12
13		#include <boost/corosio/stream_file.hpp>
14		#include <boost/corosio/backend.hpp>
15
16		#ifndef BOOST_COROSIO_MRDOCS
17		#if BOOST_COROSIO_HAS_EPOLL \|\| BOOST_COROSIO_HAS_SELECT \|\| \
18		BOOST_COROSIO_HAS_KQUEUE
19		#include <boost/corosio/native/detail/posix/posix_stream_file_service.hpp>
20		#endif
21
22		#if BOOST_COROSIO_HAS_IO_URING
23		#include <boost/corosio/native/detail/io_uring/io_uring_stream_file.hpp>
24		#endif
25
26		#if BOOST_COROSIO_HAS_IOCP
27		#include <boost/corosio/native/detail/iocp/win_file_service.hpp>
28		#endif
29		#endif // !BOOST_COROSIO_MRDOCS
30
31		namespace boost::corosio {
32
33		/** A sequential file with devirtualized async I/O operations.
34
35		This class template inherits from @ref stream_file and shadows
36		`read_some` / `write_some` with versions that call the backend
37		implementation directly, allowing the compiler to inline through
38		the entire call chain.
39
40		Non-async operations (`open`, `close`, `size`, `resize`, `seek`,
41		`sync_data`, `sync_all`) remain unchanged and dispatch through
42		the compiled library.
43
44		A `native_stream_file` IS-A `stream_file` and can be passed to
45		any function expecting `stream_file&` or `io_stream&`, in which
46		case virtual dispatch is used transparently.
47
48		@note On POSIX platforms, file I/O is dispatched to a thread
49		pool regardless of the chosen reactor backend, so all three
50		reactor tags (`epoll`, `select`, `kqueue`) resolve to the same
51		underlying implementation. The `Backend` template parameter
52		exists for API symmetry with @ref native_tcp_socket and friends.
53		The vtable savings are smaller relative to the thread-pool /
54		overlapped-I/O cost than they are for socket operations.
55
56		@tparam Backend A backend tag value (e.g., `epoll`, `iocp`).
57
58		@par Thread Safety
59		Same as @ref stream_file.
60
61		@par Example
62		@code
63		#include <boost/corosio/native/native_stream_file.hpp>
64
65		native_io_context<epoll> ctx;
66		native_stream_file<epoll> f(ctx);
67		f.open("data.bin", file_base::read_only);
68		char buf[4096];
69		auto [ec, n] = co_await f.read_some(
70		capy::mutable_buffer(buf, sizeof(buf)));
71		@endcode
72
73		@see stream_file, epoll_t, iocp_t
74		*/
75		template<auto Backend>
76		class native_stream_file : public stream_file
77		{
78		using backend_type = decltype(Backend);
79		using impl_type = typename backend_type::stream_file_type;
80		using service_type = typename backend_type::stream_file_service_type;
81
82	4x	impl_type& get_impl() noexcept
83		{
84	4x	return static_cast<impl_type>(h_.get());
85		}
86
87		template<class MutableBufferSequence>
88		struct native_read_awaitable
89		{
90		native_stream_file& self_;
91		MutableBufferSequence buffers_;
92		std::stop_token token_;
93		mutable std::error_code ec_;
94		mutable std::size_t bytes_transferred_ = 0;
95
96	2x	native_read_awaitable(
97		native_stream_file& self,
98		MutableBufferSequence buffers) noexcept
99	2x	: self_(self)
100	2x	, buffers_(std::move(buffers))
101		{
102	2x	}
103
104	2x	bool await_ready() const noexcept
105		{
106	2x	return token_.stop_requested();
107		}
108
109	2x	capy::io_result<std::size_t> await_resume() const noexcept
110		{
111	2x	if (token_.stop_requested())
112	✗	return {make_error_code(std::errc::operation_canceled), 0};
113	2x	return {ec_, bytes_transferred_};
114		}
115
116	2x	auto await_suspend(std::coroutine_handle<> h, capy::io_env const* env)
117		-> std::coroutine_handle<>
118		{
119	2x	token_ = env->stop_token;
120	6x	return self_.get_impl().read_some(
121	6x	h, env->executor, buffers_, token_, &ec_, &bytes_transferred_);
122		}
123		};
124
125		template<class ConstBufferSequence>
126		struct native_write_awaitable
127		{
128		native_stream_file& self_;
129		ConstBufferSequence buffers_;
130		std::stop_token token_;
131		mutable std::error_code ec_;
132		mutable std::size_t bytes_transferred_ = 0;
133
134	2x	native_write_awaitable(
135		native_stream_file& self,
136		ConstBufferSequence buffers) noexcept
137	2x	: self_(self)
138	2x	, buffers_(std::move(buffers))
139		{
140	2x	}
141
142	2x	bool await_ready() const noexcept
143		{
144	2x	return token_.stop_requested();
145		}
146
147	2x	capy::io_result<std::size_t> await_resume() const noexcept
148		{
149	2x	if (token_.stop_requested())
150	✗	return {make_error_code(std::errc::operation_canceled), 0};
151	2x	return {ec_, bytes_transferred_};
152		}
153
154	2x	auto await_suspend(std::coroutine_handle<> h, capy::io_env const* env)
155		-> std::coroutine_handle<>
156		{
157	2x	token_ = env->stop_token;
158	6x	return self_.get_impl().write_some(
159	6x	h, env->executor, buffers_, token_, &ec_, &bytes_transferred_);
160		}
161		};
162
163		public:
164		/** Construct a native stream file from an execution context.
165
166		@param ctx The execution context that will own this file.
167		*/
168	10x	explicit native_stream_file(capy::execution_context& ctx)
169	10x	: io_object(create_handle<service_type>(ctx))
170		{
171	10x	}
172
173		/** Construct a native stream file from an executor.
174
175		@param ex The executor whose context will own this file.
176		*/
177		template<class Ex>
178		requires(!std::same_as<std::remove_cvref_t<Ex>, native_stream_file>) &&
179		capy::Executor<Ex>
180		explicit native_stream_file(Ex const& ex) : native_stream_file(ex.context())
181		{
182		}
183
184		/// Move construct.
185		native_stream_file(native_stream_file&&) noexcept = default;
186
187		/// Move assign.
188		native_stream_file& operator=(native_stream_file&&) noexcept = default;
189
190		native_stream_file(native_stream_file const&) = delete;
191		native_stream_file& operator=(native_stream_file const&) = delete;
192
193		/** Asynchronously read data from the file.
194
195		Calls the backend implementation directly, bypassing virtual
196		dispatch. Otherwise identical to @ref io_stream::read_some.
197		*/
198		template<capy::MutableBufferSequence MB>
199	2x	auto read_some(MB const& buffers)
200		{
201	2x	return native_read_awaitable<MB>(*this, buffers);
202		}
203
204		/** Asynchronously write data to the file.
205
206		Calls the backend implementation directly, bypassing virtual
207		dispatch. Otherwise identical to @ref io_stream::write_some.
208		*/
209		template<capy::ConstBufferSequence CB>
210	2x	auto write_some(CB const& buffers)
211		{
212	2x	return native_write_awaitable<CB>(*this, buffers);
213		}
214		};
215
216		} // namespace boost::corosio
217
218		#endif // BOOST_COROSIO_NATIVE_NATIVE_STREAM_FILE_HPP
219