base/files/file_path_watcher_fsevents.h

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