text: //
  //  GTMFileSystemKQueue.h
  //
  //  Copyright 2008 Google Inc.
  //
  //  Licensed under the Apache License, Version 2.0 (the "License"); you may not
  //  use this file except in compliance with the License.  You may obtain a copy
  //  of the License at
  // 
  //  http://www.apache.org/licenses/LICENSE-2.0
  // 
  //  Unless required by applicable law or agreed to in writing, software
  //  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
  //  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
  //  License for the specific language governing permissions and limitations under
  //  the License.
  //
  
  #import <Foundation/Foundation.h>
  
  #import <sys/event.h>  // for kqueue() and kevent and the NOTE_* constants
  
  //  Event constants
  enum {
    kGTMFileSystemKQueueDeleteEvent = NOTE_DELETE,
    kGTMFileSystemKQueueWriteEvent = NOTE_WRITE,
    kGTMFileSystemKQueueExtendEvent = NOTE_EXTEND,
    kGTMFileSystemKQueueAttributeChangeEvent = NOTE_ATTRIB,
    kGTMFileSystemKQueueLinkChangeEvent = NOTE_LINK,
    kGTMFileSystemKQueueRenameEvent = NOTE_RENAME,
    kGTMFileSystemKQueueRevokeEvent = NOTE_REVOKE,
    kGTMFileSystemKQueueAllEvents = NOTE_DELETE | NOTE_WRITE | NOTE_EXTEND |
                                    NOTE_ATTRIB | NOTE_LINK | NOTE_RENAME |
                                    NOTE_REVOKE,
  };
  typedef unsigned int GTMFileSystemKQueueEvents;
  
  // GTMFileSystemKQueue.
  //
  // This is a very simple, easy-to-use class for registering handlers that get
  // called when a events happen to a given file system path.
  //
  // The default runloop for the first path kqueued is used for notification
  // delivery, so keep that in mind when you're using this class.  This class
  // explicitly does not handle arbitrary runloops and threading.
  //
  @interface GTMFileSystemKQueue : NSObject {
   @private
    NSString *path_;
    int fd_;
    GTMFileSystemKQueueEvents events_;
    BOOL acrossReplace_;
    __weak id target_;
    SEL action_;
  }
  
  // |path| is the full path to monitor.  |events| is a combination of events
  // listed above that you want notification of.  |acrossReplace| will cause this
  // object to reattach when a the file is deleted & recreated or moved out of the
  // way and a new one put in place.  |selector| should be of the signature:
  //    - (void)fileSystemKQueue:(GTMFileSystemKQueue *)fskq
  //                      events:(GTMFileSystemKQueueEvents)events;
  // where the events can be one or more of the events listed above ORed together.
  //
  // NOTE: |acrossReplace| is not fool proof.  If the file is renamed/deleted,
  // then the object will make one attempt at the time it gets the rename/delete
  // to reopen the file.  If the new file has not been created, no more action is
  // taken.  To handle the file coming into existance later, you need to monitor
  // the directory in some other way.
  - (id)initWithPath:(NSString *)path
           forEvents:(GTMFileSystemKQueueEvents)events
       acrossReplace:(BOOL)acrossReplace
              target:(id)target
              action:(SEL)action;
  
  - (NSString *)path;
  
  @end
  