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		// 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_NATIVE_NATIVE_RANDOM_ACCESS_FILE_HPP
12		#define BOOST_COROSIO_NATIVE_NATIVE_RANDOM_ACCESS_FILE_HPP
13
14		#include <boost/corosio/random_access_file.hpp>
15		#include <boost/corosio/backend.hpp>
16
17		#ifndef BOOST_COROSIO_MRDOCS
18		#if BOOST_COROSIO_HAS_EPOLL \|\| BOOST_COROSIO_HAS_SELECT \|\| \
19		BOOST_COROSIO_HAS_KQUEUE
20		#include <boost/corosio/native/detail/posix/posix_random_access_file_service.hpp>
21		#endif
22
23		#if BOOST_COROSIO_HAS_IO_URING
24		#include <boost/corosio/native/detail/io_uring/io_uring_random_access_file.hpp>
25		#endif
26
27		#if BOOST_COROSIO_HAS_IOCP
28		#include <boost/corosio/native/detail/iocp/win_random_access_file_service.hpp>
29		#endif
30		#endif // !BOOST_COROSIO_MRDOCS
31
32		namespace boost::corosio {
33
34		/** A random-access file with devirtualized async I/O operations.
35
36		This class template inherits from @ref random_access_file and
37		shadows `read_some_at` / `write_some_at` with versions that
38		call the backend implementation directly, allowing the compiler
39		to inline through the entire call chain.
40
41		Non-async operations (`open`, `close`, `size`, `resize`,
42		`sync_data`, `sync_all`) remain unchanged and dispatch through
43		the compiled library.
44
45		A `native_random_access_file` IS-A `random_access_file` and
46		can be passed to any function expecting `random_access_file&`,
47		in which case virtual dispatch is used transparently.
48
49		@note On POSIX platforms, file I/O is dispatched to a thread
50		pool regardless of the chosen reactor backend, so all three
51		reactor tags (`epoll`, `select`, `kqueue`) resolve to the same
52		underlying implementation. The `Backend` template parameter
53		exists for API symmetry with @ref native_tcp_socket and friends.
54		The vtable savings are smaller relative to the thread-pool /
55		overlapped-I/O cost than they are for socket operations.
56
57		@tparam Backend A backend tag value (e.g., `epoll`, `iocp`).
58
59		@par Thread Safety
60		Same as @ref random_access_file.
61
62		@par Example
63		@par !example native_random_access_file
64
65		@see random_access_file, epoll_t, iocp_t
66		*/
67		template<auto Backend>
68		class native_random_access_file : public random_access_file
69		{
70		using backend_type = decltype(Backend);
71		using impl_type = typename backend_type::random_access_file_type;
72		using service_type =
73		typename backend_type::random_access_file_service_type;
74
75	14x	impl_type& get_impl() noexcept
76		{
77	14x	return static_cast<impl_type>(h_.get());
78		}
79
80		template<class MutableBufferSequence>
81		struct native_read_at_awaitable
82		{
83		native_random_access_file& self_;
84		std::uint64_t offset_;
85		MutableBufferSequence buffers_;
86		std::stop_token token_;
87		mutable std::error_code ec_;
88		mutable std::size_t bytes_transferred_ = 0;
89
90	8x	native_read_at_awaitable(
91		native_random_access_file& self,
92		std::uint64_t offset,
93		MutableBufferSequence buffers) noexcept
94	8x	: self_(self)
95	8x	, offset_(offset)
96	8x	, buffers_(std::move(buffers))
97		{
98	8x	}
99
100	8x	bool await_ready() const noexcept
101		{
102		// A pre-set ec_ means the initiator failed before
103		// dispatch (e.g. a closed object).
104	8x	return static_cast<bool>(ec_) \|\| token_.stop_requested();
105		}
106
107	8x	[[nodiscard]] capy::io_result<std::size_t> await_resume() const noexcept
108		{
109	8x	if (token_.stop_requested())
110	2x	return {make_error_code(std::errc::operation_canceled), 0};
111	6x	return {ec_, bytes_transferred_};
112		}
113
114	8x	auto await_suspend(std::coroutine_handle<> h, capy::io_env const* env)
115		-> std::coroutine_handle<>
116		{
117	8x	token_ = env->stop_token;
118	24x	return self_.get_impl().read_some_at(
119	8x	offset_, h, env->executor, buffers_,
120	24x	token_, &ec_, &bytes_transferred_);
121		}
122		};
123
124		template<class ConstBufferSequence>
125		struct native_write_at_awaitable
126		{
127		native_random_access_file& self_;
128		std::uint64_t offset_;
129		ConstBufferSequence buffers_;
130		std::stop_token token_;
131		mutable std::error_code ec_;
132		mutable std::size_t bytes_transferred_ = 0;
133
134	6x	native_write_at_awaitable(
135		native_random_access_file& self,
136		std::uint64_t offset,
137		ConstBufferSequence buffers) noexcept
138	6x	: self_(self)
139	6x	, offset_(offset)
140	6x	, buffers_(std::move(buffers))
141		{
142	6x	}
143
144	6x	bool await_ready() const noexcept
145		{
146		// A pre-set ec_ means the initiator failed before
147		// dispatch (e.g. a closed object).
148	6x	return static_cast<bool>(ec_) \|\| token_.stop_requested();
149		}
150
151	6x	[[nodiscard]] capy::io_result<std::size_t> await_resume() const noexcept
152		{
153	6x	if (token_.stop_requested())
154	2x	return {make_error_code(std::errc::operation_canceled), 0};
155	4x	return {ec_, bytes_transferred_};
156		}
157
158	6x	auto await_suspend(std::coroutine_handle<> h, capy::io_env const* env)
159		-> std::coroutine_handle<>
160		{
161	6x	token_ = env->stop_token;
162	18x	return self_.get_impl().write_some_at(
163	6x	offset_, h, env->executor, buffers_,
164	18x	token_, &ec_, &bytes_transferred_);
165		}
166		};
167
168		public:
169		/** Construct a native random-access file from an execution context.
170
171		@param ctx The execution context that will own this file.
172		*/
173	16x	explicit native_random_access_file(capy::execution_context& ctx)
174	16x	: random_access_file(create_handle<service_type>(ctx))
175		{
176	16x	}
177
178		/** Construct a native random-access file from an executor.
179
180		@param ex The executor whose context will own this file.
181		*/
182		template<class Ex>
183		requires(!std::same_as<
184		std::remove_cvref_t<Ex>,
185		native_random_access_file>) &&
186		capy::Executor<Ex>
187		explicit native_random_access_file(Ex const& ex)
188		: native_random_access_file(ex.context())
189		{
190		}
191
192		/// Move construct.
193		native_random_access_file(native_random_access_file&&) noexcept = default;
194
195		/// Move assign.
196		native_random_access_file&
197		operator=(native_random_access_file&&) noexcept = default;
198
199		native_random_access_file(native_random_access_file const&) = delete;
200		native_random_access_file&
201		operator=(native_random_access_file const&) = delete;
202
203		/** Asynchronously read at the given offset.
204
205		Calls the backend implementation directly, bypassing virtual
206		dispatch. Otherwise identical to @ref random_access_file::read_some_at.
207		*/
208		template<capy::MutableBufferSequence MB>
209	8x	[[nodiscard]] auto read_some_at(std::uint64_t offset, MB const& buffers)
210		{
211	8x	return native_read_at_awaitable<MB>(*this, offset, buffers);
212		}
213
214		/** Asynchronously write at the given offset.
215
216		Calls the backend implementation directly, bypassing virtual
217		dispatch. Otherwise identical to @ref random_access_file::write_some_at.
218		*/
219		template<capy::ConstBufferSequence CB>
220	6x	[[nodiscard]] auto write_some_at(std::uint64_t offset, CB const& buffers)
221		{
222	6x	return native_write_at_awaitable<CB>(*this, offset, buffers);
223		}
224		};
225
226		} // namespace boost::corosio
227
228		#endif // BOOST_COROSIO_NATIVE_NATIVE_RANDOM_ACCESS_FILE_HPP
229