components/drive/file_write_watcher.h

   1 // Copyright 2013 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 COMPONENTS_DRIVE_FILE_WRITE_WATCHER_H_
   6 #define COMPONENTS_DRIVE_FILE_WRITE_WATCHER_H_
   7
   8 #include "base/callback_forward.h"
   9 #include "base/memory/scoped_ptr.h"
  10 #include "base/threading/thread_checker.h"
  11 #include "components/drive/file_system_core_util.h"
  12
  13 namespace base {
  14 class FilePath;
  15 class SingleThreadTaskRunner;
  16 }  // namespace base
  17
  18 namespace drive {
  19
  20 namespace internal {
  21
  22 typedef base::Callback<void(bool)> StartWatchCallback;
  23
  24 // The class watches modification to Drive files in the cache directory.
  25 // This is used for returning a local writable snapshot of Drive files from the
  26 // Save-As file dialog, so that the callers of the dialog can save to Drive
  27 // without any special handling about Drive.
  28 class FileWriteWatcher {
  29  public:
  30   explicit FileWriteWatcher(base::SingleThreadTaskRunner* file_task_runner);
  31   ~FileWriteWatcher();
  32
  33   // Starts watching the modification to |path|. When it successfully started
  34   // watching, it runs |on_start_callback| by passing true as the argument.
  35   // Or if it failed, the callback is run with false.
  36   // Detected modification is notified by calling |on_write_callback|.
  37   //
  38   // Currently, the modification is watched in "one-shot" manner. That is, once
  39   // a modification is notified, the watch is deactivated for freeing system
  40   // resources. As a heuristic to capture the real end of write operations that
  41   // might be done by several chunked writes, the notification is fired after
  42   // 5 seconds has passed after the last write operation is detected.
  43   //
  44   // TODO(kinaba): investigate the possibility to continuously watch the whole
  45   // cache directory. http://crbug.com/269424
  46   void StartWatch(const base::FilePath& path,
  47                   const StartWatchCallback& on_start_callback,
  48                   const base::Closure& on_write_callback);
  49
  50   // For testing purpose, stops inserting delay between the write detection and
  51   // notification to the |on_write_callback|.
  52   void DisableDelayForTesting();
  53
  54  private:
  55   class FileWriteWatcherImpl;
  56   scoped_ptr<FileWriteWatcherImpl, util::DestroyHelper> watcher_impl_;
  57
  58   base::ThreadChecker thread_checker_;
  59
  60   DISALLOW_COPY_AND_ASSIGN(FileWriteWatcher);
  61 };
  62
  63 }  // namespace internal
  64 }  // namespace drive
  65
  66 #endif  // COMPONENTS_DRIVE_FILE_WRITE_WATCHER_H_