Add support for watching directories to FileWatcher.

BUG=none
TEST=Unit tests in file_watcher_unittest.cc.

Review URL: http://codereview.chromium.org/3149004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@56341 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 70 insertions, 0 deletions

diff --git a/chrome/browser/file_path_watcher.h b/chrome/browser/file_path_watcher.h
new file mode 100644
index 0000000..b8c857f
--- /dev/null
+++ b/chrome/browser/file_path_watcher.h
@@ -0,0 +1,70 @@
+// Copyright (c) 2010 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.
+
+// This module provides a way to monitor a file or directory for changes.
+
+#ifndef CHROME_BROWSER_FILE_PATH_WATCHER_H_
+#define CHROME_BROWSER_FILE_PATH_WATCHER_H_
+#pragma once
+
+#include "base/basictypes.h"
+#include "base/file_path.h"
+#include "base/ref_counted.h"
+#include "chrome/browser/chrome_thread.h"
+
+// This class lets you register interest in changes on a FilePath.
+// The delegate will get called whenever the file or directory referenced by the
+// FilePath is changed, including created or deleted. Due to limitations in the
+// underlying OS APIs, spurious notifications might occur that don't relate to
+// an actual change to the watch target.
+class FilePathWatcher {
+ public:
+  // Declares the callback client code implements to receive notifications. Note
+  // that implementations of this interface should not keep a reference to the
+  // corresponding FileWatcher object to prevent a reference cycle.
+  class Delegate : public base::RefCountedThreadSafe<Delegate> {
+   public:
+    virtual ~Delegate() {}
+    virtual void OnFilePathChanged(const FilePath& path) = 0;
+    // Called when platform specific code detected an error. The watcher will
+    // not call OnFilePathChanged for future changes.
+    virtual void OnError() {}
+  };
+
+  FilePathWatcher();
+  ~FilePathWatcher() {
+    impl_->Cancel();
+  }
+
+  // Register interest in any changes on |path|. OnPathChanged will be called
+  // back for each change. Returns true on success.
+  bool Watch(const FilePath& path, Delegate* delegate) WARN_UNUSED_RESULT {
+    DCHECK(ChromeThread::CurrentlyOn(ChromeThread::FILE));
+    DCHECK(path.IsAbsolute());
+    return impl_->Watch(path, delegate);
+  }
+
+  // Used internally to encapsulate different members on different platforms.
+  class PlatformDelegate
+      : public base::RefCountedThreadSafe<PlatformDelegate,
+                                          ChromeThread::DeleteOnFileThread> {
+   public:
+    virtual ~PlatformDelegate() {}
+
+    // Start watching for the given |path| and notify |delegate| about changes.
+    virtual bool Watch(const FilePath& path, Delegate* delegate)
+        WARN_UNUSED_RESULT = 0;
+
+    // Stop watching. This is called from FilePathWatcher's dtor in order to
+    // allow to shut down properly while the object is still alive.
+    virtual void Cancel() {}
+  };
+
+ private:
+  scoped_refptr<PlatformDelegate> impl_;
+
+  DISALLOW_COPY_AND_ASSIGN(FilePathWatcher);
+};
+
+#endif  // CHROME_BROWSER_FILE_PATH_WATCHER_H_