include/boost/corosio/native/detail/posix/posix_random_access_file_service.hpp

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posix_random_access_file_service.hpp

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1		//
2		// Copyright (c) 2026 Michael Vandeberg
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_DETAIL_POSIX_POSIX_RANDOM_ACCESS_FILE_SERVICE_HPP
11		#define BOOST_COROSIO_NATIVE_DETAIL_POSIX_POSIX_RANDOM_ACCESS_FILE_SERVICE_HPP
12
13		#include <boost/corosio/detail/platform.hpp>
14
15		#if BOOST_COROSIO_POSIX
16
17		#include <boost/corosio/native/detail/posix/posix_random_access_file.hpp>
18		#include <boost/corosio/native/detail/reactor/reactor_scheduler.hpp>
19		#include <boost/corosio/detail/random_access_file_service.hpp>
20		#include <boost/corosio/detail/thread_pool.hpp>
21
22		#include <limits>
23		#include <mutex>
24		#include <unordered_map>
25
26		namespace boost::corosio::detail {
27
28		/** Random-access file service for POSIX backends. */
29		class BOOST_COROSIO_DECL posix_random_access_file_service final
30		: public random_access_file_service
31		{
32		public:
33	172x	explicit posix_random_access_file_service(capy::execution_context& ctx)
34	516x	: sched_(&get_scheduler(ctx))
35	172x	, pool_(ctx)
36		{
37	172x	}
38
39	344x	~posix_random_access_file_service() override = default;
40
41		posix_random_access_file_service(posix_random_access_file_service const&) =
42		delete;
43		posix_random_access_file_service&
44		operator=(posix_random_access_file_service const&) = delete;
45
46	227x	io_object::implementation* construct() override
47		{
48	227x	auto ptr = std::make_shared<posix_random_access_file>(*this);
49	227x	auto* impl = ptr.get();
50
51		{
52	227x	std::lock_guard<std::mutex> lock(mutex_);
53	227x	file_list_.push_back(impl);
54	227x	file_ptrs_[impl] = std::move(ptr);
55	227x	}
56
57	227x	return impl;
58	227x	}
59
60	225x	void destroy(io_object::implementation* p) override
61		{
62	225x	auto& impl = static_cast<posix_random_access_file&>(*p);
63	225x	impl.cancel();
64	225x	impl.close_file();
65	225x	destroy_impl(impl);
66	225x	}
67
68	421x	void close(io_object::handle& h) override
69		{
70	421x	if (h.get())
71		{
72	421x	auto& impl = static_cast<posix_random_access_file&>(*h.get());
73	421x	impl.cancel();
74	421x	impl.close_file();
75		}
76	421x	}
77
78	211x	std::error_code open_file(
79		random_access_file::implementation& impl,
80		std::filesystem::path const& path,
81		file_base::flags mode) override
82		{
83		// Unavailable in the unsafe tier: the file thread pool completes
84		// cross-thread, which the lockless scheduler cannot accept.
85	211x	if (sched_->scheduler_locking_disabled())
86	✗	return std::make_error_code(std::errc::operation_not_supported);
87	211x	return static_cast<posix_random_access_file&>(impl).open_file(
88	211x	path, mode);
89		}
90
91	172x	void shutdown() override
92		{
93	172x	std::lock_guard<std::mutex> lock(mutex_);
94	174x	for (auto* impl = file_list_.pop_front(); impl != nullptr;
95	2x	impl = file_list_.pop_front())
96		{
97	2x	impl->cancel();
98	2x	impl->close_file();
99		}
100	172x	file_ptrs_.clear();
101	172x	}
102
103	225x	void destroy_impl(posix_random_access_file& impl)
104		{
105	225x	std::lock_guard<std::mutex> lock(mutex_);
106	225x	file_list_.remove(&impl);
107	225x	file_ptrs_.erase(&impl);
108	225x	}
109
110	440x	void post(scheduler_op* op)
111		{
112	440x	sched_->post(op);
113	440x	}
114
115		void work_started() noexcept
116		{
117		sched_->work_started();
118		}
119
120		void work_finished() noexcept
121		{
122		sched_->work_finished();
123		}
124
125		/** Return the thread pool that runs this service's file work.
126
127		The pool's service is created on first use, so this can fail
128		where a plain accessor could not. Its workers start later, on
129		the first post, and a thread the system refuses there is
130		reported by that post rather than thrown here.
131
132		@throws std::bad_alloc If the service cannot be allocated.
133
134		@return The context's shared blocking-I/O pool.
135
136		@see thread_pool_ref::get
137		*/
138	444x	thread_pool& pool()
139		{
140	444x	return pool_.get();
141		}
142
143		private:
144		scheduler* sched_;
145		thread_pool_ref pool_;
146		std::mutex mutex_;
147		intrusive_list<posix_random_access_file> file_list_;
148		std::unordered_map<
149		posix_random_access_file*,
150		std::shared_ptr<posix_random_access_file>>
151		file_ptrs_;
152		};
153
154		// ---------------------------------------------------------------------------
155		// posix_random_access_file inline implementations (require complete service)
156		// ---------------------------------------------------------------------------
157
158		inline std::coroutine_handle<>
159	353x	posix_random_access_file::read_some_at(
160		std::uint64_t offset,
161		capy::continuation& cont,
162		capy::executor_ref ex,
163		buffer_param param,
164		std::stop_token token,
165		std::error_code* ec,
166		std::size_t* bytes_out)
167		{
168		// Closed-object contract outranks the zero-length no-op.
169	353x	if (fd_ < 0)
170		{
171	4x	*ec = make_error_code(std::errc::bad_file_descriptor);
172	4x	*bytes_out = 0;
173	4x	return cont.h;
174		}
175
176	349x	capy::mutable_buffer bufs[max_buffers];
177	349x	auto count = param.copy_to(bufs, max_buffers);
178
179	349x	if (count == 0)
180		{
181	2x	*ec = {};
182	2x	*bytes_out = 0;
183	2x	return cont.h;
184		}
185
186	347x	auto* op = new raf_op();
187	347x	op->is_read = true;
188	347x	op->offset = offset;
189	347x	op->fd = fd_;
190
191	347x	op->iovec_count = static_cast<int>(count);
192	694x	for (int i = 0; i < op->iovec_count; ++i)
193		{
194	347x	op->iovecs[i].iov_base = bufs[i].data();
195	347x	op->iovecs[i].iov_len = bufs[i].size();
196		}
197
198	347x	op->h = cont.h;
199	347x	op->awaiting = &cont;
200	347x	op->ex = ex;
201	347x	op->ec_out = ec;
202	347x	op->bytes_out = bytes_out;
203	347x	op->file_ = this;
204	347x	op->impl_ptr = this->shared_from_this();
205	347x	op->start(token);
206
207	347x	op->ex.on_work_started();
208
209		{
210	347x	std::lock_guard<std::mutex> lock(ops_mutex_);
211	347x	outstanding_ops_.push_back(op);
212	347x	}
213
214	347x	static_cast<pool_work_item*>(op)->func_ = &raf_op::do_work;
215	347x	if (auto pec = svc_.pool().post(static_cast<pool_work_item*>(op)))
216		{
217		// The pool is shutting down, or the system refused it a thread.
218		// Nothing of this read went cross-thread, so it answers here
219		// like the closed-descriptor and zero-length exits above rather
220		// than through a completion the scheduler has to carry back.
221		// destroy() is the discard the op never reaching the queue
222		// needs: it unlinks, unwinds the work count and frees.
223	2x	op->destroy();
224	2x	*ec = pec;
225	2x	*bytes_out = 0;
226	2x	return cont.h;
227		}
228	345x	return std::noop_coroutine();
229		}
230
231		inline std::coroutine_handle<>
232	101x	posix_random_access_file::write_some_at(
233		std::uint64_t offset,
234		capy::continuation& cont,
235		capy::executor_ref ex,
236		buffer_param param,
237		std::stop_token token,
238		std::error_code* ec,
239		std::size_t* bytes_out)
240		{
241		// Closed-object contract outranks the zero-length no-op.
242	101x	if (fd_ < 0)
243		{
244	2x	*ec = make_error_code(std::errc::bad_file_descriptor);
245	2x	*bytes_out = 0;
246	2x	return cont.h;
247		}
248
249	99x	capy::mutable_buffer bufs[max_buffers];
250	99x	auto count = param.copy_to(bufs, max_buffers);
251
252	99x	if (count == 0)
253		{
254	2x	*ec = {};
255	2x	*bytes_out = 0;
256	2x	return cont.h;
257		}
258
259	97x	auto* op = new raf_op();
260	97x	op->is_read = false;
261	97x	op->offset = offset;
262	97x	op->fd = fd_;
263
264	97x	op->iovec_count = static_cast<int>(count);
265	194x	for (int i = 0; i < op->iovec_count; ++i)
266		{
267	97x	op->iovecs[i].iov_base = bufs[i].data();
268	97x	op->iovecs[i].iov_len = bufs[i].size();
269		}
270
271	97x	op->h = cont.h;
272	97x	op->awaiting = &cont;
273	97x	op->ex = ex;
274	97x	op->ec_out = ec;
275	97x	op->bytes_out = bytes_out;
276	97x	op->file_ = this;
277	97x	op->impl_ptr = this->shared_from_this();
278	97x	op->start(token);
279
280	97x	op->ex.on_work_started();
281
282		{
283	97x	std::lock_guard<std::mutex> lock(ops_mutex_);
284	97x	outstanding_ops_.push_back(op);
285	97x	}
286
287	97x	static_cast<pool_work_item*>(op)->func_ = &raf_op::do_work;
288	97x	if (auto pec = svc_.pool().post(static_cast<pool_work_item*>(op)))
289		{
290		// The pool is shutting down, or the system refused it a thread.
291		// Nothing of this write went cross-thread, so it answers here
292		// like the closed-descriptor and zero-length exits above rather
293		// than through a completion the scheduler has to carry back.
294		// destroy() is the discard the op never reaching the queue
295		// needs: it unlinks, unwinds the work count and frees.
296	2x	op->destroy();
297	2x	*ec = pec;
298	2x	*bytes_out = 0;
299	2x	return cont.h;
300		}
301	95x	return std::noop_coroutine();
302		}
303
304		// -- raf_op thread-pool work function --
305
306		inline void
307	440x	posix_random_access_file::raf_op::do_work(pool_work_item* w) noexcept
308		{
309	440x	auto* op = static_cast<raf_op*>(w);
310	440x	auto* self = op->file_;
311
312	440x	if (op->cancelled.load(std::memory_order_acquire))
313		{
314	67x	op->errn = ECANCELED;
315	67x	op->bytes_transferred = 0;
316		}
317	373x	else if (
318	746x	op->offset >
319	373x	static_cast<std::uint64_t>(std::numeric_limits<file_off_t>::max()))
320		{
321	2x	op->errn = EOVERFLOW;
322	2x	op->bytes_transferred = 0;
323		}
324		else
325		{
326		ssize_t n;
327	371x	if (op->is_read)
328		{
329		do
330		{
331	291x	n = file_preadv(
332	291x	op->fd, op->iovecs, op->iovec_count,
333	291x	static_cast<file_off_t>(op->offset));
334		}
335	291x	while (n < 0 && errno == EINTR);
336		}
337		else
338		{
339		do
340		{
341	80x	n = file_pwritev(
342	80x	op->fd, op->iovecs, op->iovec_count,
343	80x	static_cast<file_off_t>(op->offset));
344		}
345	80x	while (n < 0 && errno == EINTR);
346		}
347
348	371x	if (n >= 0)
349		{
350	353x	op->errn = 0;
351	353x	op->bytes_transferred = static_cast<std::size_t>(n);
352		}
353		else
354		{
355	18x	op->errn = errno;
356	18x	op->bytes_transferred = 0;
357		}
358		}
359
360	440x	self->svc_.post(static_cast<scheduler_op*>(op));
361	440x	}
362
363		} // namespace boost::corosio::detail
364
365		#endif // BOOST_COROSIO_POSIX
366
367		#endif // BOOST_COROSIO_NATIVE_DETAIL_POSIX_POSIX_RANDOM_ACCESS_FILE_SERVICE_HPP
368