base/files/file_path_watcher_kqueue.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_KQUEUE_H_
   6 #define BASE_FILES_FILE_PATH_WATCHER_KQUEUE_H_
   7
   8 #include <sys/event.h>
   9 #include <vector>
  10
  11 #include "base/files/file_path.h"
  12 #include "base/files/file_path_watcher.h"
  13 #include "base/message_loop/message_loop.h"
  14 #include "base/single_thread_task_runner.h"
  15
  16 namespace base {
  17
  18 // Mac-specific file watcher implementation based on kqueue.
  19 // The Linux and Windows versions are able to detect:
  20 // - file creation/deletion/modification in a watched directory
  21 // - file creation/deletion/modification for a watched file
  22 // - modifications to the paths to a watched object that would affect the
  23 //   object such as renaming/attibute changes etc.
  24 // The kqueue implementation will handle all of the items in the list above
  25 // except for detecting modifications to files in a watched directory. It will
  26 // detect the creation and deletion of files, just not the modification of
  27 // files. It does however detect the attribute changes that the FSEvents impl
  28 // would miss.
  29 class FilePathWatcherKQueue : public FilePathWatcher::PlatformDelegate,
  30                               public MessageLoopForIO::Watcher,
  31                               public MessageLoop::DestructionObserver {
  32  public:
  33   FilePathWatcherKQueue();
  34
  35   // MessageLoopForIO::Watcher overrides.
  36   void OnFileCanReadWithoutBlocking(int fd) override;
  37   void OnFileCanWriteWithoutBlocking(int fd) override;
  38
  39   // MessageLoop::DestructionObserver overrides.
  40   void WillDestroyCurrentMessageLoop() override;
  41
  42   // FilePathWatcher::PlatformDelegate overrides.
  43   bool Watch(const FilePath& path,
  44              bool recursive,
  45              const FilePathWatcher::Callback& callback) override;
  46   void Cancel() override;
  47
  48  protected:
  49   ~FilePathWatcherKQueue() override;
  50
  51  private:
  52   class EventData {
  53    public:
  54     EventData(const FilePath& path, const FilePath::StringType& subdir)
  55         : path_(path), subdir_(subdir) { }
  56     FilePath path_;  // Full path to this item.
  57     FilePath::StringType subdir_;  // Path to any sub item.
  58   };
  59
  60   typedef std::vector<struct kevent> EventVector;
  61
  62   // Can only be called on |io_task_runner_|'s thread.
  63   void CancelOnMessageLoopThread() override;
  64
  65   // Returns true if the kevent values are error free.
  66   bool AreKeventValuesValid(struct kevent* kevents, int count);
  67
  68   // Respond to a change of attributes of the path component represented by
  69   // |event|. Sets |target_file_affected| to true if |target_| is affected.
  70   // Sets |update_watches| to true if |events_| need to be updated.
  71   void HandleAttributesChange(const EventVector::iterator& event,
  72                               bool* target_file_affected,
  73                               bool* update_watches);
  74
  75   // Respond to a move or deletion of the path component represented by
  76   // |event|. Sets |target_file_affected| to true if |target_| is affected.
  77   // Sets |update_watches| to true if |events_| need to be updated.
  78   void HandleDeleteOrMoveChange(const EventVector::iterator& event,
  79                                 bool* target_file_affected,
  80                                 bool* update_watches);
  81
  82   // Respond to a creation of an item in the path component represented by
  83   // |event|. Sets |target_file_affected| to true if |target_| is affected.
  84   // Sets |update_watches| to true if |events_| need to be updated.
  85   void HandleCreateItemChange(const EventVector::iterator& event,
  86                               bool* target_file_affected,
  87                               bool* update_watches);
  88
  89   // Update |events_| with the current status of the system.
  90   // Sets |target_file_affected| to true if |target_| is affected.
  91   // Returns false if an error occurs.
  92   bool UpdateWatches(bool* target_file_affected);
  93
  94   // Fills |events| with one kevent per component in |path|.
  95   // Returns the number of valid events created where a valid event is
  96   // defined as one that has a ident (file descriptor) field != -1.
  97   static int EventsForPath(FilePath path, EventVector *events);
  98
  99   // Release a kevent generated by EventsForPath.
 100   static void ReleaseEvent(struct kevent& event);
 101
 102   // Returns a file descriptor that will not block the system from deleting
 103   // the file it references.
 104   static uintptr_t FileDescriptorForPath(const FilePath& path);
 105
 106   static const uintptr_t kNoFileDescriptor = static_cast<uintptr_t>(-1);
 107
 108   // Closes |*fd| and sets |*fd| to -1.
 109   static void CloseFileDescriptor(uintptr_t* fd);
 110
 111   // Returns true if kevent has open file descriptor.
 112   static bool IsKeventFileDescriptorOpen(const struct kevent& event) {
 113     return event.ident != kNoFileDescriptor;
 114   }
 115
 116   static EventData* EventDataForKevent(const struct kevent& event) {
 117     return reinterpret_cast<EventData*>(event.udata);
 118   }
 119
 120   EventVector events_;
 121   scoped_refptr<base::SingleThreadTaskRunner> io_task_runner_;
 122   MessageLoopForIO::FileDescriptorWatcher kqueue_watcher_;
 123   FilePathWatcher::Callback callback_;
 124   FilePath target_;
 125   int kqueue_;
 126
 127   DISALLOW_COPY_AND_ASSIGN(FilePathWatcherKQueue);
 128 };
 129
 130 }  // namespace base
 131
 132 #endif  // BASE_FILES_FILE_PATH_WATCHER_KQUEUE_H_