TLA Line data Source code
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_STREAM_FILE_HPP
11 : #define BOOST_COROSIO_NATIVE_DETAIL_POSIX_POSIX_STREAM_FILE_HPP
12 :
13 : #include <boost/corosio/detail/platform.hpp>
14 :
15 : #if BOOST_COROSIO_POSIX
16 :
17 : #include <boost/corosio/detail/config.hpp>
18 : #include <boost/corosio/stream_file.hpp>
19 : #include <boost/corosio/file_base.hpp>
20 : #include <boost/corosio/detail/intrusive.hpp>
21 : #include <boost/corosio/detail/dispatch_coro.hpp>
22 : #include <boost/corosio/detail/scheduler_op.hpp>
23 : #include <boost/corosio/detail/thread_pool.hpp>
24 : #include <boost/corosio/detail/scheduler.hpp>
25 : #include <boost/corosio/detail/buffer_param.hpp>
26 : #include <boost/corosio/native/detail/make_err.hpp>
27 : #include <boost/capy/ex/executor_ref.hpp>
28 : #include <boost/capy/error.hpp>
29 : #include <boost/capy/buffers.hpp>
30 :
31 : #include <atomic>
32 : #include <coroutine>
33 : #include <cstddef>
34 : #include <cstdint>
35 : #include <filesystem>
36 : #include <limits>
37 : #include <memory>
38 : #include <optional>
39 : #include <stop_token>
40 : #include <system_error>
41 :
42 : #include <errno.h>
43 : #include <fcntl.h>
44 : #include <sys/stat.h>
45 : #include <sys/uio.h>
46 : #include <unistd.h>
47 :
48 : /*
49 : POSIX Stream File Implementation
50 : =================================
51 :
52 : Regular files cannot be monitored by epoll/kqueue/select — the kernel
53 : always reports them as ready. Blocking I/O (pread/pwrite) is dispatched
54 : to a shared thread pool, with completion posted back to the scheduler.
55 :
56 : This follows the same pattern as posix_resolver: pool_work_item for
57 : dispatch, scheduler_op for completion, shared_from_this for lifetime.
58 :
59 : Completion Flow
60 : ---------------
61 : 1. read_some() sets up file_read_op, posts to thread pool
62 : 2. Pool thread runs preadv() (blocking)
63 : 3. Pool thread stores results, posts scheduler_op to scheduler
64 : 4. Scheduler invokes op() which resumes the coroutine
65 :
66 : Single-Inflight Constraint
67 : --------------------------
68 : Only one asynchronous operation may be in flight at a time on a
69 : given file object. Concurrent read and write is not supported
70 : because both share offset_ without synchronization.
71 : */
72 :
73 : namespace boost::corosio::detail {
74 :
75 : struct scheduler;
76 : class posix_stream_file_service;
77 :
78 : /** Stream file implementation for POSIX backends.
79 :
80 : Each instance contains embedded operation objects (read_op_, write_op_)
81 : that are reused across calls. This avoids per-operation heap allocation.
82 : */
83 : class posix_stream_file final
84 : : public stream_file::implementation
85 : , public std::enable_shared_from_this<posix_stream_file>
86 : , public intrusive_list<posix_stream_file>::node
87 : {
88 : friend class posix_stream_file_service;
89 :
90 : public:
91 : static constexpr std::size_t max_buffers = 16;
92 :
93 : /** Operation state for a single file read or write. */
94 : struct file_op : scheduler_op
95 : {
96 : struct canceller
97 : {
98 : file_op* op;
99 HIT 2 : void operator()() const noexcept
100 : {
101 2 : op->request_cancel();
102 2 : }
103 : };
104 :
105 : // Coroutine state
106 : std::coroutine_handle<> h;
107 : capy::continuation cont;
108 : capy::executor_ref ex;
109 :
110 : // Output pointers
111 : std::error_code* ec_out = nullptr;
112 : std::size_t* bytes_out = nullptr;
113 :
114 : // Buffer data (copied from buffer_param at submission time)
115 : iovec iovecs[max_buffers];
116 : int iovec_count = 0;
117 :
118 : // Result storage (populated by worker thread)
119 : int errn = 0;
120 : std::size_t bytes_transferred = 0;
121 : bool is_read = false;
122 :
123 : // Thread coordination
124 : std::atomic<bool> cancelled{false};
125 : std::optional<std::stop_callback<canceller>> stop_cb;
126 :
127 : /// Prevents use-after-free when file is closed with pending ops.
128 : std::shared_ptr<void> impl_ref;
129 :
130 190 : file_op() = default;
131 :
132 55 : void reset() noexcept
133 : {
134 55 : iovec_count = 0;
135 55 : errn = 0;
136 55 : bytes_transferred = 0;
137 55 : is_read = false;
138 55 : cancelled.store(false, std::memory_order_relaxed);
139 55 : stop_cb.reset();
140 55 : impl_ref.reset();
141 55 : ec_out = nullptr;
142 55 : bytes_out = nullptr;
143 55 : }
144 :
145 : void operator()() override;
146 : void destroy() override;
147 :
148 532 : void request_cancel() noexcept
149 : {
150 532 : cancelled.store(true, std::memory_order_release);
151 532 : }
152 :
153 39 : void start(std::stop_token const& token)
154 : {
155 39 : cancelled.store(false, std::memory_order_release);
156 39 : stop_cb.reset();
157 39 : if (token.stop_possible())
158 2 : stop_cb.emplace(token, canceller{this});
159 39 : }
160 : };
161 :
162 : /** Pool work item for thread pool dispatch. */
163 : struct pool_op : pool_work_item
164 : {
165 : posix_stream_file* file_ = nullptr;
166 : std::shared_ptr<posix_stream_file> ref_;
167 : };
168 :
169 : explicit posix_stream_file(posix_stream_file_service& svc) noexcept;
170 :
171 : // -- io_stream::implementation --
172 :
173 : std::coroutine_handle<> read_some(
174 : std::coroutine_handle<>,
175 : capy::executor_ref,
176 : buffer_param,
177 : std::stop_token,
178 : std::error_code*,
179 : std::size_t*) override;
180 :
181 : std::coroutine_handle<> write_some(
182 : std::coroutine_handle<>,
183 : capy::executor_ref,
184 : buffer_param,
185 : std::stop_token,
186 : std::error_code*,
187 : std::size_t*) override;
188 :
189 : // -- stream_file::implementation --
190 :
191 302 : native_handle_type native_handle() const noexcept override
192 : {
193 302 : return fd_;
194 : }
195 :
196 265 : void cancel() noexcept override
197 : {
198 265 : read_op_.request_cancel();
199 265 : write_op_.request_cancel();
200 265 : }
201 :
202 : std::uint64_t size() const override;
203 : std::error_code resize(std::uint64_t new_size) noexcept override;
204 : std::error_code sync_data() noexcept override;
205 : std::error_code sync_all() noexcept override;
206 : native_handle_type release() override;
207 : std::error_code assign(native_handle_type handle) noexcept override;
208 : capy::io_result<std::uint64_t>
209 : seek(std::int64_t offset, file_base::seek_basis origin) noexcept override;
210 :
211 : // -- Internal --
212 :
213 : /** Open the file and store the fd. */
214 : std::error_code open_file(
215 : std::filesystem::path const& path, file_base::flags mode);
216 :
217 : /** Close the file descriptor. */
218 : void close_file() noexcept;
219 :
220 : private:
221 : posix_stream_file_service& svc_;
222 : int fd_ = -1;
223 : std::uint64_t offset_ = 0;
224 :
225 : file_op read_op_;
226 : file_op write_op_;
227 : pool_op read_pool_op_;
228 : pool_op write_pool_op_;
229 :
230 : static void do_read_work(pool_work_item*) noexcept;
231 : static void do_write_work(pool_work_item*) noexcept;
232 : };
233 :
234 : // ---------------------------------------------------------------------------
235 : // Inline implementation
236 : // ---------------------------------------------------------------------------
237 :
238 : inline
239 95 : posix_stream_file::posix_stream_file(posix_stream_file_service& svc) noexcept
240 95 : : svc_(svc)
241 : {
242 95 : }
243 :
244 : inline std::error_code
245 73 : posix_stream_file::open_file(
246 : std::filesystem::path const& path, file_base::flags mode)
247 : {
248 73 : close_file();
249 :
250 73 : int oflags = 0;
251 :
252 : // Access mode
253 73 : unsigned access = static_cast<unsigned>(mode) & 3u;
254 73 : if (access == static_cast<unsigned>(file_base::read_write))
255 4 : oflags |= O_RDWR;
256 69 : else if (access == static_cast<unsigned>(file_base::write_only))
257 24 : oflags |= O_WRONLY;
258 : else
259 45 : oflags |= O_RDONLY;
260 :
261 : // Creation flags
262 73 : if ((mode & file_base::create) != file_base::flags(0))
263 20 : oflags |= O_CREAT;
264 73 : if ((mode & file_base::exclusive) != file_base::flags(0))
265 2 : oflags |= O_EXCL;
266 73 : if ((mode & file_base::truncate) != file_base::flags(0))
267 17 : oflags |= O_TRUNC;
268 73 : if ((mode & file_base::append) != file_base::flags(0))
269 3 : oflags |= O_APPEND;
270 73 : if ((mode & file_base::sync_all_on_write) != file_base::flags(0))
271 2 : oflags |= O_SYNC;
272 :
273 73 : int fd = ::open(path.c_str(), oflags, 0666);
274 73 : if (fd < 0)
275 4 : return make_err(errno);
276 :
277 69 : fd_ = fd;
278 69 : offset_ = 0;
279 :
280 : // Append mode: position at end-of-file (preadv/pwritev use
281 : // explicit offsets, so O_APPEND alone is not sufficient).
282 69 : if ((mode & file_base::append) != file_base::flags(0))
283 : {
284 : struct stat st;
285 3 : if (::fstat(fd, &st) < 0)
286 : {
287 MIS 0 : int err = errno;
288 0 : ::close(fd);
289 0 : fd_ = -1;
290 0 : return make_err(err);
291 : }
292 HIT 3 : offset_ = static_cast<std::uint64_t>(st.st_size);
293 : }
294 :
295 : #ifdef POSIX_FADV_SEQUENTIAL
296 69 : ::posix_fadvise(fd_, 0, 0, POSIX_FADV_SEQUENTIAL);
297 : #endif
298 :
299 69 : return {};
300 : }
301 :
302 : inline void
303 342 : posix_stream_file::close_file() noexcept
304 : {
305 342 : if (fd_ >= 0)
306 : {
307 73 : ::close(fd_);
308 73 : fd_ = -1;
309 : }
310 342 : }
311 :
312 : inline std::uint64_t
313 12 : posix_stream_file::size() const
314 : {
315 : struct stat st;
316 12 : if (::fstat(fd_, &st) < 0)
317 MIS 0 : throw_system_error(make_err(errno), "stream_file::size");
318 HIT 12 : return static_cast<std::uint64_t>(st.st_size);
319 : }
320 :
321 : inline std::error_code
322 7 : posix_stream_file::resize(std::uint64_t new_size) noexcept
323 : {
324 7 : if (new_size >
325 7 : static_cast<std::uint64_t>((std::numeric_limits<off_t>::max)()))
326 2 : return make_err(EOVERFLOW);
327 5 : if (::ftruncate(fd_, static_cast<off_t>(new_size)) < 0)
328 2 : return make_err(errno);
329 3 : return {};
330 : }
331 :
332 : inline std::error_code
333 5 : posix_stream_file::sync_data() noexcept
334 : {
335 : #if BOOST_COROSIO_HAS_POSIX_SYNCHRONIZED_IO
336 5 : if (::fdatasync(fd_) < 0)
337 : #else // BOOST_COROSIO_HAS_POSIX_SYNCHRONIZED_IO
338 : if (::fsync(fd_) < 0)
339 : #endif // BOOST_COROSIO_HAS_POSIX_SYNCHRONIZED_IO
340 2 : return make_err(errno);
341 3 : return {};
342 : }
343 :
344 : inline std::error_code
345 5 : posix_stream_file::sync_all() noexcept
346 : {
347 5 : if (::fsync(fd_) < 0)
348 2 : return make_err(errno);
349 3 : return {};
350 : }
351 :
352 : inline native_handle_type
353 2 : posix_stream_file::release()
354 : {
355 2 : int fd = fd_;
356 2 : fd_ = -1;
357 2 : offset_ = 0;
358 2 : return fd;
359 : }
360 :
361 : inline std::error_code
362 6 : posix_stream_file::assign(native_handle_type handle) noexcept
363 : {
364 6 : close_file();
365 6 : fd_ = handle;
366 6 : offset_ = 0;
367 6 : return {};
368 : }
369 :
370 : inline capy::io_result<std::uint64_t>
371 20 : posix_stream_file::seek(
372 : std::int64_t offset, file_base::seek_basis origin) noexcept
373 : {
374 : // We track offset_ ourselves (not the kernel fd offset)
375 : // because preadv/pwritev use explicit offsets.
376 : std::int64_t new_pos;
377 :
378 20 : if (origin == file_base::seek_set)
379 : {
380 9 : new_pos = offset;
381 : }
382 11 : else if (origin == file_base::seek_cur)
383 : {
384 5 : new_pos = static_cast<std::int64_t>(offset_) + offset;
385 : }
386 : else
387 : {
388 : struct stat st;
389 6 : if (::fstat(fd_, &st) < 0)
390 MIS 0 : return {make_err(errno), 0};
391 HIT 6 : new_pos = st.st_size + offset;
392 : }
393 :
394 20 : if (new_pos < 0)
395 6 : return {make_err(EINVAL), 0};
396 14 : if (new_pos >
397 14 : static_cast<std::int64_t>((std::numeric_limits<off_t>::max)()))
398 MIS 0 : return {make_err(EOVERFLOW), 0};
399 :
400 HIT 14 : offset_ = static_cast<std::uint64_t>(new_pos);
401 :
402 14 : return {std::error_code{}, offset_};
403 : }
404 :
405 : // -- file_op completion handler --
406 : // (read_some, write_some, do_read_work, do_write_work are
407 : // defined in posix_stream_file_service.hpp after the service)
408 :
409 : inline void
410 39 : posix_stream_file::file_op::operator()()
411 : {
412 39 : stop_cb.reset();
413 :
414 39 : bool const was_cancelled = cancelled.load(std::memory_order_acquire);
415 :
416 39 : if (ec_out)
417 : {
418 39 : if (was_cancelled)
419 2 : *ec_out = capy::error::canceled;
420 37 : else if (errn != 0)
421 4 : *ec_out = make_err(errn);
422 33 : else if (is_read && bytes_transferred == 0)
423 3 : *ec_out = capy::error::eof;
424 : else
425 30 : *ec_out = {};
426 : }
427 :
428 39 : if (bytes_out)
429 39 : *bytes_out = was_cancelled ? 0 : bytes_transferred;
430 :
431 : // Move impl_ref to a local so members remain valid through
432 : // dispatch — impl_ref may be the last shared_ptr keeping
433 : // the parent posix_stream_file (which embeds this file_op) alive.
434 39 : auto prevent_destroy = std::move(impl_ref);
435 39 : ex.on_work_finished();
436 39 : cont.h = h;
437 39 : dispatch_coro(ex, cont).resume();
438 39 : }
439 :
440 : inline void
441 MIS 0 : posix_stream_file::file_op::destroy()
442 : {
443 0 : stop_cb.reset();
444 0 : auto local_ex = ex;
445 0 : impl_ref.reset();
446 0 : local_ex.on_work_finished();
447 0 : }
448 :
449 : } // namespace boost::corosio::detail
450 :
451 : #endif // BOOST_COROSIO_POSIX
452 :
453 : #endif // BOOST_COROSIO_NATIVE_DETAIL_POSIX_POSIX_STREAM_FILE_HPP
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