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1 // Copyright (c) 2011 The Chromium Authors. All rights reserved. | |
2 // Use of this source code is governed by a BSD-style license that can be | |
3 // found in the LICENSE file. | |
4 | |
5 #include "base/files/file_path_watcher.h" | |
6 | |
7 #include <fcntl.h> | |
8 #include <sys/event.h> | |
9 #include <sys/param.h> | |
10 | |
11 #include <vector> | |
12 | |
13 #include "base/bind.h" | |
14 #include "base/file_util.h" | |
15 #include "base/message_loop.h" | |
16 #include "base/message_loop_proxy.h" | |
17 #include "base/stringprintf.h" | |
18 | |
19 namespace base { | |
20 namespace files { | |
21 | |
22 namespace { | |
23 | |
24 // Mac-specific file watcher implementation based on kqueue. | |
25 // Originally it was based on FSEvents so that the semantics were equivalent | |
26 // on Linux, OSX and Windows where it was able to detect: | |
27 // - file creation/deletion/modification in a watched directory | |
28 // - file creation/deletion/modification for a watched file | |
29 // - modifications to the paths to a watched object that would affect the | |
30 // object such as renaming/attibute changes etc. | |
31 // The FSEvents version did all of the above except handling attribute changes | |
32 // to path components. Unfortunately FSEvents appears to have an issue where the | |
33 // current implementation (Mac OS X 10.6.7) sometimes drops events and doesn't | |
34 // send notifications. See | |
35 // http://code.google.com/p/chromium/issues/detail?id=54822#c31 for source that | |
36 // will reproduce the problem. FSEvents also required having a CFRunLoop | |
37 // backing the thread that it was running on, that caused added complexity | |
38 // in the interfaces. | |
39 // The kqueue implementation will handle all of the items in the list above | |
40 // except for detecting modifications to files in a watched directory. It will | |
41 // detect the creation and deletion of files, just not the modification of | |
42 // files. It does however detect the attribute changes that the FSEvents impl | |
43 // would miss. | |
44 class FilePathWatcherImpl : public FilePathWatcher::PlatformDelegate, | |
45 public MessageLoopForIO::Watcher, | |
46 public MessageLoop::DestructionObserver { | |
47 public: | |
48 FilePathWatcherImpl() : kqueue_(-1) {} | |
49 virtual ~FilePathWatcherImpl() {} | |
50 | |
51 // MessageLoopForIO::Watcher overrides. | |
52 virtual void OnFileCanReadWithoutBlocking(int fd) OVERRIDE; | |
53 virtual void OnFileCanWriteWithoutBlocking(int fd) OVERRIDE; | |
54 | |
55 // MessageLoop::DestructionObserver overrides. | |
56 virtual void WillDestroyCurrentMessageLoop() OVERRIDE; | |
57 | |
58 // FilePathWatcher::PlatformDelegate overrides. | |
59 virtual bool Watch(const FilePath& path, | |
60 FilePathWatcher::Delegate* delegate) OVERRIDE; | |
61 virtual void Cancel() OVERRIDE; | |
62 | |
63 private: | |
64 class EventData { | |
65 public: | |
66 EventData(const FilePath& path, const FilePath::StringType& subdir) | |
67 : path_(path), subdir_(subdir) { } | |
68 FilePath path_; // Full path to this item. | |
69 FilePath::StringType subdir_; // Path to any sub item. | |
70 }; | |
71 typedef std::vector<struct kevent> EventVector; | |
72 | |
73 // Can only be called on |io_message_loop_|'s thread. | |
74 virtual void CancelOnMessageLoopThread() OVERRIDE; | |
75 | |
76 // Returns true if the kevent values are error free. | |
77 bool AreKeventValuesValid(struct kevent* kevents, int count); | |
78 | |
79 // Respond to a change of attributes of the path component represented by | |
80 // |event|. Sets |target_file_affected| to true if |target_| is affected. | |
81 // Sets |update_watches| to true if |events_| need to be updated. | |
82 void HandleAttributesChange(const EventVector::iterator& event, | |
83 bool* target_file_affected, | |
84 bool* update_watches); | |
85 | |
86 // Respond to a move of deletion of the path component represented by | |
87 // |event|. Sets |target_file_affected| to true if |target_| is affected. | |
88 // Sets |update_watches| to true if |events_| need to be updated. | |
89 void HandleDeleteOrMoveChange(const EventVector::iterator& event, | |
90 bool* target_file_affected, | |
91 bool* update_watches); | |
92 | |
93 // Respond to a creation of an item in the path component represented by | |
94 // |event|. Sets |target_file_affected| to true if |target_| is affected. | |
95 // Sets |update_watches| to true if |events_| need to be updated. | |
96 void HandleCreateItemChange(const EventVector::iterator& event, | |
97 bool* target_file_affected, | |
98 bool* update_watches); | |
99 | |
100 // Update |events_| with the current status of the system. | |
101 // Sets |target_file_affected| to true if |target_| is affected. | |
102 // Returns false if an error occurs. | |
103 bool UpdateWatches(bool* target_file_affected); | |
104 | |
105 // Fills |events| with one kevent per component in |path|. | |
106 // Returns the number of valid events created where a valid event is | |
107 // defined as one that has a ident (file descriptor) field != -1. | |
108 static int EventsForPath(FilePath path, EventVector *events); | |
109 | |
110 // Release a kevent generated by EventsForPath. | |
111 static void ReleaseEvent(struct kevent& event); | |
112 | |
113 // Returns a file descriptor that will not block the system from deleting | |
114 // the file it references. | |
115 static int FileDescriptorForPath(const FilePath& path); | |
116 | |
117 // Closes |*fd| and sets |*fd| to -1. | |
118 static void CloseFileDescriptor(int* fd); | |
119 | |
120 // Returns true if kevent has open file descriptor. | |
121 static bool IsKeventFileDescriptorOpen(const struct kevent& event) { | |
122 return event.ident != static_cast<uintptr_t>(-1); | |
123 } | |
124 | |
125 static EventData* EventDataForKevent(const struct kevent& event) { | |
126 return reinterpret_cast<EventData*>(event.udata); | |
127 } | |
128 | |
129 EventVector events_; | |
130 scoped_refptr<base::MessageLoopProxy> io_message_loop_; | |
131 MessageLoopForIO::FileDescriptorWatcher kqueue_watcher_; | |
132 scoped_refptr<FilePathWatcher::Delegate> delegate_; | |
133 FilePath target_; | |
134 int kqueue_; | |
135 | |
136 DISALLOW_COPY_AND_ASSIGN(FilePathWatcherImpl); | |
137 }; | |
138 | |
139 void FilePathWatcherImpl::ReleaseEvent(struct kevent& event) { | |
140 CloseFileDescriptor(reinterpret_cast<int*>(&event.ident)); | |
141 EventData* entry = EventDataForKevent(event); | |
142 delete entry; | |
143 event.udata = NULL; | |
144 } | |
145 | |
146 int FilePathWatcherImpl::EventsForPath(FilePath path, EventVector* events) { | |
147 DCHECK(MessageLoopForIO::current()); | |
148 // Make sure that we are working with a clean slate. | |
149 DCHECK(events->empty()); | |
150 | |
151 std::vector<FilePath::StringType> components; | |
152 path.GetComponents(&components); | |
153 | |
154 if (components.size() < 1) { | |
155 return -1; | |
156 } | |
157 | |
158 int last_existing_entry = 0; | |
159 FilePath built_path; | |
160 bool path_still_exists = true; | |
161 for(std::vector<FilePath::StringType>::iterator i = components.begin(); | |
162 i != components.end(); ++i) { | |
163 if (i == components.begin()) { | |
164 built_path = FilePath(*i); | |
165 } else { | |
166 built_path = built_path.Append(*i); | |
167 } | |
168 int fd = -1; | |
169 if (path_still_exists) { | |
170 fd = FileDescriptorForPath(built_path); | |
171 if (fd == -1) { | |
172 path_still_exists = false; | |
173 } else { | |
174 ++last_existing_entry; | |
175 } | |
176 } | |
177 FilePath::StringType subdir = (i != (components.end() - 1)) ? *(i + 1) : ""; | |
178 EventData* data = new EventData(built_path, subdir); | |
179 struct kevent event; | |
180 EV_SET(&event, fd, EVFILT_VNODE, (EV_ADD | EV_CLEAR | EV_RECEIPT), | |
181 (NOTE_DELETE | NOTE_WRITE | NOTE_ATTRIB | | |
182 NOTE_RENAME | NOTE_REVOKE | NOTE_EXTEND), 0, data); | |
183 events->push_back(event); | |
184 } | |
185 return last_existing_entry; | |
186 } | |
187 | |
188 int FilePathWatcherImpl::FileDescriptorForPath(const FilePath& path) { | |
189 return HANDLE_EINTR(open(path.value().c_str(), O_EVTONLY)); | |
190 } | |
191 | |
192 void FilePathWatcherImpl::CloseFileDescriptor(int *fd) { | |
193 if (*fd == -1) { | |
194 return; | |
195 } | |
196 | |
197 if (HANDLE_EINTR(close(*fd)) != 0) { | |
198 PLOG(ERROR) << "close"; | |
199 } | |
200 *fd = -1; | |
201 } | |
202 | |
203 bool FilePathWatcherImpl::AreKeventValuesValid(struct kevent* kevents, | |
204 int count) { | |
205 if (count < 0) { | |
206 PLOG(ERROR) << "kevent"; | |
207 return false; | |
208 } | |
209 bool valid = true; | |
210 for (int i = 0; i < count; ++i) { | |
211 if (kevents[i].flags & EV_ERROR && kevents[i].data) { | |
212 // Find the kevent in |events_| that matches the kevent with the error. | |
213 EventVector::iterator event = events_.begin(); | |
214 for (; event != events_.end(); ++event) { | |
215 if (event->ident == kevents[i].ident) { | |
216 break; | |
217 } | |
218 } | |
219 std::string path_name; | |
220 if (event != events_.end()) { | |
221 EventData* event_data = EventDataForKevent(*event); | |
222 if (event_data != NULL) { | |
223 path_name = event_data->path_.value(); | |
224 } | |
225 } | |
226 if (path_name.empty()) { | |
227 path_name = base::StringPrintf( | |
228 "fd %d", *reinterpret_cast<int*>(&kevents[i].ident)); | |
229 } | |
230 LOG(ERROR) << "Error: " << kevents[i].data << " for " << path_name; | |
231 valid = false; | |
232 } | |
233 } | |
234 return valid; | |
235 } | |
236 | |
237 void FilePathWatcherImpl::HandleAttributesChange( | |
238 const EventVector::iterator& event, | |
239 bool* target_file_affected, | |
240 bool* update_watches) { | |
241 EventVector::iterator next_event = event + 1; | |
242 EventData* next_event_data = EventDataForKevent(*next_event); | |
243 // Check to see if the next item in path is still accessible. | |
244 int have_access = FileDescriptorForPath(next_event_data->path_); | |
245 if (have_access == -1) { | |
246 *target_file_affected = true; | |
247 *update_watches = true; | |
248 EventVector::iterator local_event(event); | |
249 for (; local_event != events_.end(); ++local_event) { | |
250 // Close all nodes from the event down. This has the side effect of | |
251 // potentially rendering other events in |updates| invalid. | |
252 // There is no need to remove the events from |kqueue_| because this | |
253 // happens as a side effect of closing the file descriptor. | |
254 CloseFileDescriptor(reinterpret_cast<int*>(&local_event->ident)); | |
255 } | |
256 } else { | |
257 CloseFileDescriptor(&have_access); | |
258 } | |
259 } | |
260 | |
261 void FilePathWatcherImpl::HandleDeleteOrMoveChange( | |
262 const EventVector::iterator& event, | |
263 bool* target_file_affected, | |
264 bool* update_watches) { | |
265 *target_file_affected = true; | |
266 *update_watches = true; | |
267 EventVector::iterator local_event(event); | |
268 for (; local_event != events_.end(); ++local_event) { | |
269 // Close all nodes from the event down. This has the side effect of | |
270 // potentially rendering other events in |updates| invalid. | |
271 // There is no need to remove the events from |kqueue_| because this | |
272 // happens as a side effect of closing the file descriptor. | |
273 CloseFileDescriptor(reinterpret_cast<int*>(&local_event->ident)); | |
274 } | |
275 } | |
276 | |
277 void FilePathWatcherImpl::HandleCreateItemChange( | |
278 const EventVector::iterator& event, | |
279 bool* target_file_affected, | |
280 bool* update_watches) { | |
281 // Get the next item in the path. | |
282 EventVector::iterator next_event = event + 1; | |
283 EventData* next_event_data = EventDataForKevent(*next_event); | |
284 | |
285 // Check to see if it already has a valid file descriptor. | |
286 if (!IsKeventFileDescriptorOpen(*next_event)) { | |
287 // If not, attempt to open a file descriptor for it. | |
288 next_event->ident = FileDescriptorForPath(next_event_data->path_); | |
289 if (IsKeventFileDescriptorOpen(*next_event)) { | |
290 *update_watches = true; | |
291 if (next_event_data->subdir_.empty()) { | |
292 *target_file_affected = true; | |
293 } | |
294 } | |
295 } | |
296 } | |
297 | |
298 bool FilePathWatcherImpl::UpdateWatches(bool* target_file_affected) { | |
299 // Iterate over events adding kevents for items that exist to the kqueue. | |
300 // Then check to see if new components in the path have been created. | |
301 // Repeat until no new components in the path are detected. | |
302 // This is to get around races in directory creation in a watched path. | |
303 bool update_watches = true; | |
304 while (update_watches) { | |
305 size_t valid; | |
306 for (valid = 0; valid < events_.size(); ++valid) { | |
307 if (!IsKeventFileDescriptorOpen(events_[valid])) { | |
308 break; | |
309 } | |
310 } | |
311 if (valid == 0) { | |
312 // The root of the file path is inaccessible? | |
313 return false; | |
314 } | |
315 | |
316 EventVector updates(valid); | |
317 int count = HANDLE_EINTR(kevent(kqueue_, &events_[0], valid, &updates[0], | |
318 valid, NULL)); | |
319 if (!AreKeventValuesValid(&updates[0], count)) { | |
320 return false; | |
321 } | |
322 update_watches = false; | |
323 for (; valid < events_.size(); ++valid) { | |
324 EventData* event_data = EventDataForKevent(events_[valid]); | |
325 events_[valid].ident = FileDescriptorForPath(event_data->path_); | |
326 if (IsKeventFileDescriptorOpen(events_[valid])) { | |
327 update_watches = true; | |
328 if (event_data->subdir_.empty()) { | |
329 *target_file_affected = true; | |
330 } | |
331 } else { | |
332 break; | |
333 } | |
334 } | |
335 } | |
336 return true; | |
337 } | |
338 | |
339 void FilePathWatcherImpl::OnFileCanReadWithoutBlocking(int fd) { | |
340 DCHECK(MessageLoopForIO::current()); | |
341 CHECK_EQ(fd, kqueue_); | |
342 CHECK(events_.size()); | |
343 | |
344 // Request the file system update notifications that have occurred and return | |
345 // them in |updates|. |count| will contain the number of updates that have | |
346 // occurred. | |
347 EventVector updates(events_.size()); | |
348 struct timespec timeout = {0, 0}; | |
349 int count = HANDLE_EINTR(kevent(kqueue_, NULL, 0, &updates[0], updates.size(), | |
350 &timeout)); | |
351 | |
352 // Error values are stored within updates, so check to make sure that no | |
353 // errors occurred. | |
354 if (!AreKeventValuesValid(&updates[0], count)) { | |
355 delegate_->OnFilePathError(target_); | |
356 Cancel(); | |
357 return; | |
358 } | |
359 | |
360 bool update_watches = false; | |
361 bool send_notification = false; | |
362 | |
363 // Iterate through each of the updates and react to them. | |
364 for (int i = 0; i < count; ++i) { | |
365 // Find our kevent record that matches the update notification. | |
366 EventVector::iterator event = events_.begin(); | |
367 for (; event != events_.end(); ++event) { | |
368 if (!IsKeventFileDescriptorOpen(*event) || | |
369 event->ident == updates[i].ident) { | |
370 break; | |
371 } | |
372 } | |
373 if (!IsKeventFileDescriptorOpen(*event) || event == events_.end()) { | |
374 // The event may no longer exist in |events_| because another event | |
375 // modified |events_| in such a way to make it invalid. For example if | |
376 // the path is /foo/bar/bam and foo is deleted, NOTE_DELETE events for | |
377 // foo, bar and bam will be sent. If foo is processed first, then | |
378 // the file descriptors for bar and bam will already be closed and set | |
379 // to -1 before they get a chance to be processed. | |
380 continue; | |
381 } | |
382 | |
383 EventData* event_data = EventDataForKevent(*event); | |
384 | |
385 // If the subdir is empty, this is the last item on the path and is the | |
386 // target file. | |
387 bool target_file_affected = event_data->subdir_.empty(); | |
388 if ((updates[i].fflags & NOTE_ATTRIB) && !target_file_affected) { | |
389 HandleAttributesChange(event, &target_file_affected, &update_watches); | |
390 } | |
391 if (updates[i].fflags & (NOTE_DELETE | NOTE_REVOKE | NOTE_RENAME)) { | |
392 HandleDeleteOrMoveChange(event, &target_file_affected, &update_watches); | |
393 } | |
394 if ((updates[i].fflags & NOTE_WRITE) && !target_file_affected) { | |
395 HandleCreateItemChange(event, &target_file_affected, &update_watches); | |
396 } | |
397 send_notification |= target_file_affected; | |
398 } | |
399 | |
400 if (update_watches) { | |
401 if (!UpdateWatches(&send_notification)) { | |
402 delegate_->OnFilePathError(target_); | |
403 Cancel(); | |
404 } | |
405 } | |
406 | |
407 if (send_notification) { | |
408 delegate_->OnFilePathChanged(target_); | |
409 } | |
410 } | |
411 | |
412 void FilePathWatcherImpl::OnFileCanWriteWithoutBlocking(int fd) { | |
413 NOTREACHED(); | |
414 } | |
415 | |
416 void FilePathWatcherImpl::WillDestroyCurrentMessageLoop() { | |
417 CancelOnMessageLoopThread(); | |
418 } | |
419 | |
420 bool FilePathWatcherImpl::Watch(const FilePath& path, | |
421 FilePathWatcher::Delegate* delegate) { | |
422 DCHECK(MessageLoopForIO::current()); | |
423 DCHECK(target_.value().empty()); // Can only watch one path. | |
424 DCHECK(delegate); | |
425 DCHECK_EQ(kqueue_, -1); | |
426 | |
427 delegate_ = delegate; | |
428 target_ = path; | |
429 | |
430 MessageLoop::current()->AddDestructionObserver(this); | |
431 io_message_loop_ = base::MessageLoopProxy::current(); | |
432 | |
433 kqueue_ = kqueue(); | |
434 if (kqueue_ == -1) { | |
435 PLOG(ERROR) << "kqueue"; | |
436 return false; | |
437 } | |
438 | |
439 int last_entry = EventsForPath(target_, &events_); | |
440 CHECK_NE(last_entry, 0); | |
441 | |
442 EventVector responses(last_entry); | |
443 | |
444 int count = HANDLE_EINTR(kevent(kqueue_, &events_[0], last_entry, | |
445 &responses[0], last_entry, NULL)); | |
446 if (!AreKeventValuesValid(&responses[0], count)) { | |
447 // Calling Cancel() here to close any file descriptors that were opened. | |
448 // This would happen in the destructor anyways, but FilePathWatchers tend to | |
449 // be long lived, and if an error has occurred, there is no reason to waste | |
450 // the file descriptors. | |
451 Cancel(); | |
452 return false; | |
453 } | |
454 | |
455 return MessageLoopForIO::current()->WatchFileDescriptor( | |
456 kqueue_, true, MessageLoopForIO::WATCH_READ, &kqueue_watcher_, this); | |
457 } | |
458 | |
459 void FilePathWatcherImpl::Cancel() { | |
460 base::MessageLoopProxy* proxy = io_message_loop_.get(); | |
461 if (!proxy) { | |
462 set_cancelled(); | |
463 return; | |
464 } | |
465 if (!proxy->BelongsToCurrentThread()) { | |
466 proxy->PostTask(FROM_HERE, | |
467 base::Bind(&FilePathWatcherImpl::Cancel, this)); | |
468 return; | |
469 } | |
470 CancelOnMessageLoopThread(); | |
471 } | |
472 | |
473 void FilePathWatcherImpl::CancelOnMessageLoopThread() { | |
474 DCHECK(MessageLoopForIO::current()); | |
475 if (!is_cancelled()) { | |
476 set_cancelled(); | |
477 kqueue_watcher_.StopWatchingFileDescriptor(); | |
478 CloseFileDescriptor(&kqueue_); | |
479 std::for_each(events_.begin(), events_.end(), ReleaseEvent); | |
480 events_.clear(); | |
481 io_message_loop_ = NULL; | |
482 MessageLoop::current()->RemoveDestructionObserver(this); | |
483 delegate_ = NULL; | |
484 } | |
485 } | |
486 | |
487 } // namespace | |
488 | |
489 FilePathWatcher::FilePathWatcher() { | |
490 impl_ = new FilePathWatcherImpl(); | |
491 } | |
492 | |
493 } // namespace files | |
494 } // namespace base | |
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