1 // Copyright 2014 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 #ifndef BASE_FILES_FILE_PATH_WATCHER_FSEVENTS_H_
6 #define BASE_FILES_FILE_PATH_WATCHER_FSEVENTS_H_
7 
8 #include <CoreServices/CoreServices.h>
9 #include <stddef.h>
10 
11 #include <vector>
12 
13 #include "base/files/file_path.h"
14 #include "base/files/file_path_watcher.h"
15 #include "base/macros.h"
16 
17 namespace base {
18 
19 // Mac-specific file watcher implementation based on FSEvents.
20 // There are trade-offs between the FSEvents implementation and a kqueue
21 // implementation. The biggest issues are that FSEvents on 10.6 sometimes drops
22 // events and kqueue does not trigger for modifications to a file in a watched
23 // directory. See file_path_watcher_mac.cc for the code that decides when to
24 // use which one.
25 class FilePathWatcherFSEvents : public FilePathWatcher::PlatformDelegate {
26  public:
27   FilePathWatcherFSEvents();
28 
29   // FilePathWatcher::PlatformDelegate overrides.
30   bool Watch(const FilePath& path,
31              bool recursive,
32              const FilePathWatcher::Callback& callback) override;
33   void Cancel() override;
34 
35  private:
36   static void FSEventsCallback(ConstFSEventStreamRef stream,
37                                void* event_watcher,
38                                size_t num_events,
39                                void* event_paths,
40                                const FSEventStreamEventFlags flags[],
41                                const FSEventStreamEventId event_ids[]);
42 
43   ~FilePathWatcherFSEvents() override;
44 
45   // Called from FSEventsCallback whenever there is a change to the paths.
46   void OnFilePathsChanged(const std::vector<FilePath>& paths);
47 
48   // Called on the message_loop() thread to dispatch path events. Can't access
49   // target_ and resolved_target_ directly as those are modified on the
50   // libdispatch thread.
51   void DispatchEvents(const std::vector<FilePath>& paths,
52                       const FilePath& target,
53                       const FilePath& resolved_target);
54 
55   // Cleans up and stops the event stream.
56   void CancelOnMessageLoopThread() override;
57 
58   // (Re-)Initialize the event stream to start reporting events from
59   // |start_event|.
60   void UpdateEventStream(FSEventStreamEventId start_event);
61 
62   // Returns true if resolving the target path got a different result than
63   // last time it was done.
64   bool ResolveTargetPath();
65 
66   // Report an error watching the given target.
67   void ReportError(const FilePath& target);
68 
69   // Destroy the event stream.
70   void DestroyEventStream();
71 
72   // Start watching the FSEventStream.
73   void StartEventStream(FSEventStreamEventId start_event, const FilePath& path);
74 
75   // Callback to notify upon changes.
76   // (Only accessed from the message_loop() thread.)
77   FilePathWatcher::Callback callback_;
78 
79   // Target path to watch (passed to callback).
80   // (Only accessed from the libdispatch thread.)
81   FilePath target_;
82 
83   // Target path with all symbolic links resolved.
84   // (Only accessed from the libdispatch thread.)
85   FilePath resolved_target_;
86 
87   // Backend stream we receive event callbacks from (strong reference).
88   // (Only accessed from the libdispatch thread.)
89   FSEventStreamRef fsevent_stream_;
90 
91   DISALLOW_COPY_AND_ASSIGN(FilePathWatcherFSEvents);
92 };
93 
94 }  // namespace base
95 
96 #endif  // BASE_FILES_FILE_PATH_WATCHER_FSEVENTS_H_
97