include/boost/corosio/native/native_random_access_file.hpp

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native_random_access_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_RANDOM_ACCESS_FILE_HPP
11		#define BOOST_COROSIO_NATIVE_NATIVE_RANDOM_ACCESS_FILE_HPP
12
13		#include <boost/corosio/random_access_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_random_access_file_service.hpp>
20		#endif
21
22		#if BOOST_COROSIO_HAS_IO_URING
23		#include <boost/corosio/native/detail/io_uring/io_uring_random_access_file.hpp>
24		#endif
25
26		#if BOOST_COROSIO_HAS_IOCP
27		#include <boost/corosio/native/detail/iocp/win_random_access_file_service.hpp>
28		#endif
29		#endif // !BOOST_COROSIO_MRDOCS
30
31		namespace boost::corosio {
32
33		/** A random-access file with devirtualized async I/O operations.
34
35		This class template inherits from @ref random_access_file and
36		shadows `read_some_at` / `write_some_at` with versions that
37		call the backend implementation directly, allowing the compiler
38		to inline through the entire call chain.
39
40		Non-async operations (`open`, `close`, `size`, `resize`,
41		`sync_data`, `sync_all`) remain unchanged and dispatch through
42		the compiled library.
43
44		A `native_random_access_file` IS-A `random_access_file` and
45		can be passed to any function expecting `random_access_file&`,
46		in which 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 random_access_file.
60
61		@par Example
62		@code
63		#include <boost/corosio/native/native_random_access_file.hpp>
64
65		native_io_context<epoll> ctx;
66		native_random_access_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_at(
70		0, capy::mutable_buffer(buf, sizeof(buf)));
71		@endcode
72
73		@see random_access_file, epoll_t, iocp_t
74		*/
75		template<auto Backend>
76		class native_random_access_file : public random_access_file
77		{
78		using backend_type = decltype(Backend);
79		using impl_type = typename backend_type::random_access_file_type;
80		using service_type =
81		typename backend_type::random_access_file_service_type;
82
83	4x	impl_type& get_impl() noexcept
84		{
85	4x	return static_cast<impl_type>(h_.get());
86		}
87
88		template<class MutableBufferSequence>
89		struct native_read_at_awaitable
90		{
91		native_random_access_file& self_;
92		std::uint64_t offset_;
93		MutableBufferSequence buffers_;
94		std::stop_token token_;
95		mutable std::error_code ec_;
96		mutable std::size_t bytes_transferred_ = 0;
97
98	2x	native_read_at_awaitable(
99		native_random_access_file& self,
100		std::uint64_t offset,
101		MutableBufferSequence buffers) noexcept
102	2x	: self_(self)
103	2x	, offset_(offset)
104	2x	, buffers_(std::move(buffers))
105		{
106	2x	}
107
108	2x	bool await_ready() const noexcept
109		{
110	2x	return token_.stop_requested();
111		}
112
113	2x	capy::io_result<std::size_t> await_resume() const noexcept
114		{
115	2x	if (token_.stop_requested())
116	✗	return {make_error_code(std::errc::operation_canceled), 0};
117	2x	return {ec_, bytes_transferred_};
118		}
119
120	2x	auto await_suspend(std::coroutine_handle<> h, capy::io_env const* env)
121		-> std::coroutine_handle<>
122		{
123	2x	token_ = env->stop_token;
124	6x	return self_.get_impl().read_some_at(
125	2x	offset_, h, env->executor, buffers_,
126	6x	token_, &ec_, &bytes_transferred_);
127		}
128		};
129
130		template<class ConstBufferSequence>
131		struct native_write_at_awaitable
132		{
133		native_random_access_file& self_;
134		std::uint64_t offset_;
135		ConstBufferSequence buffers_;
136		std::stop_token token_;
137		mutable std::error_code ec_;
138		mutable std::size_t bytes_transferred_ = 0;
139
140	2x	native_write_at_awaitable(
141		native_random_access_file& self,
142		std::uint64_t offset,
143		ConstBufferSequence buffers) noexcept
144	2x	: self_(self)
145	2x	, offset_(offset)
146	2x	, buffers_(std::move(buffers))
147		{
148	2x	}
149
150	2x	bool await_ready() const noexcept
151		{
152	2x	return token_.stop_requested();
153		}
154
155	2x	capy::io_result<std::size_t> await_resume() const noexcept
156		{
157	2x	if (token_.stop_requested())
158	✗	return {make_error_code(std::errc::operation_canceled), 0};
159	2x	return {ec_, bytes_transferred_};
160		}
161
162	2x	auto await_suspend(std::coroutine_handle<> h, capy::io_env const* env)
163		-> std::coroutine_handle<>
164		{
165	2x	token_ = env->stop_token;
166	6x	return self_.get_impl().write_some_at(
167	2x	offset_, h, env->executor, buffers_,
168	6x	token_, &ec_, &bytes_transferred_);
169		}
170		};
171
172		public:
173		/** Construct a native random-access file from an execution context.
174
175		@param ctx The execution context that will own this file.
176		*/
177	10x	explicit native_random_access_file(capy::execution_context& ctx)
178	10x	: random_access_file(create_handle<service_type>(ctx))
179		{
180	10x	}
181
182		/** Construct a native random-access file from an executor.
183
184		@param ex The executor whose context will own this file.
185		*/
186		template<class Ex>
187		requires(!std::same_as<
188		std::remove_cvref_t<Ex>,
189		native_random_access_file>) &&
190		capy::Executor<Ex>
191		explicit native_random_access_file(Ex const& ex)
192		: native_random_access_file(ex.context())
193		{
194		}
195
196		/// Move construct.
197		native_random_access_file(native_random_access_file&&) noexcept = default;
198
199		/// Move assign.
200		native_random_access_file&
201		operator=(native_random_access_file&&) noexcept = default;
202
203		native_random_access_file(native_random_access_file const&) = delete;
204		native_random_access_file&
205		operator=(native_random_access_file const&) = delete;
206
207		/** Asynchronously read at the given offset.
208
209		Calls the backend implementation directly, bypassing virtual
210		dispatch. Otherwise identical to @ref random_access_file::read_some_at.
211		*/
212		template<capy::MutableBufferSequence MB>
213	2x	auto read_some_at(std::uint64_t offset, MB const& buffers)
214		{
215	2x	return native_read_at_awaitable<MB>(*this, offset, buffers);
216		}
217
218		/** Asynchronously write at the given offset.
219
220		Calls the backend implementation directly, bypassing virtual
221		dispatch. Otherwise identical to @ref random_access_file::write_some_at.
222		*/
223		template<capy::ConstBufferSequence CB>
224	2x	auto write_some_at(std::uint64_t offset, CB const& buffers)
225		{
226	2x	return native_write_at_awaitable<CB>(*this, offset, buffers);
227		}
228		};
229
230		} // namespace boost::corosio
231
232		#endif // BOOST_COROSIO_NATIVE_NATIVE_RANDOM_ACCESS_FILE_HPP
233