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      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