file_path_watcher_fsevents.h

// Copyright 2014 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef BASE_FILES_FILE_PATH_WATCHER_FSEVENTS_H_
#define BASE_FILES_FILE_PATH_WATCHER_FSEVENTS_H_

#include <CoreServices/CoreServices.h>

#include <vector>

#include "butil/files/file_path.h"
#include "butil/files/file_path_watcher.h"

namespace butil {

// Mac-specific file watcher implementation based on FSEvents.
// There are trade-offs between the FSEvents implementation and a kqueue
// implementation. The biggest issues are that FSEvents on 10.6 sometimes drops
// events and kqueue does not trigger for modifications to a file in a watched
// directory. See file_path_watcher_mac.cc for the code that decides when to
// use which one.
class FilePathWatcherFSEvents : public FilePathWatcher::PlatformDelegate {
 public:
  FilePathWatcherFSEvents();

  // Called from the FSEvents callback whenever there is a change to the paths.
  void OnFilePathsChanged(const std::vector<FilePath>& paths);

  // (Re-)Initialize the event stream to start reporting events from
  // |start_event|.
  void UpdateEventStream(FSEventStreamEventId start_event);

  // Returns true if resolving the target path got a different result than
  // last time it was done.
  bool ResolveTargetPath();

  // FilePathWatcher::PlatformDelegate overrides.
  virtual bool Watch(const FilePath& path,
                     bool recursive,
                     const FilePathWatcher::Callback& callback) OVERRIDE;
  virtual void Cancel() OVERRIDE;

 private:
  virtual ~FilePathWatcherFSEvents();

  // Destroy the event stream.
  void DestroyEventStream();

  // Start watching the FSEventStream.
  void StartEventStream(FSEventStreamEventId start_event);

  // Cleans up and stops the event stream.
  virtual void CancelOnMessageLoopThread() OVERRIDE;

  // Callback to notify upon changes.
  FilePathWatcher::Callback callback_;

  // Target path to watch (passed to callback).
  FilePath target_;

  // Target path with all symbolic links resolved.
  FilePath resolved_target_;

  // Backend stream we receive event callbacks from (strong reference).
  FSEventStreamRef fsevent_stream_;

  DISALLOW_COPY_AND_ASSIGN(FilePathWatcherFSEvents);
};

}  // namespace butil

#endif  // BASE_FILES_FILE_PATH_WATCHER_FSEVENTS_H_