1 files changed, 67 insertions, 0 deletions
diff --git a/chrome/browser/sync/notification_method.h b/chrome/browser/sync/notification_method.h
new file mode 100644
index 0000000..4e1bcd1
--- /dev/null
+++ b/chrome/browser/sync/notification_method.h
@@ -0,0 +1,67 @@
+// 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.
+
+#ifndef CHROME_BROWSER_SYNC_NOTIFICATION_METHOD_H_
+#define CHROME_BROWSER_SYNC_NOTIFICATION_METHOD_H_
+
+#include <string>
+
+namespace browser_sync {
+
+// This is the matrix for the interaction between clients with
+// different notification methods (except for NOTIFICATION_SERVER):
+//
+//          Listen
+//          L T N
+//        +-------+
+//      L | E E E |
+// Send T | Y Y Y |
+//      N | E Y Y |
+//        +-------+
+//
+// 'Y' means a client listening with the column notification method
+// will receive notifications from a client sending with the row
+// notification method. 'E' means means that the notification will be
+// an empty one, which may be dropped by the server in the future.
+//
+// As for NOTIFICATION_SERVER, server-issued notifications will also
+// simulate a peer-issued notification, so that any client with
+// NOTIFICATION_TRANSITIONAL or NOTIFICATION_NEW will be able to
+// receive those, too.  This support will be removed once everyone is
+// on NOTIFICATION_SERVER.
+
+enum NotificationMethod {
+  // Old, broken notification method.  Works only if notification
+  // servers don't drop empty notifications.
+  NOTIFICATION_LEGACY,
+  // Compatible with new notifications.  Also compatible with legacy
+  // notifications if the notification servers don't drop empty
+  // notifications.
+  NOTIFICATION_TRANSITIONAL,
+  // New notification method.  Compatible only with transitional
+  // notifications.
+  //
+  // NOTE: "New" is kind of a misnomer, as it refers only to
+  // peer-issued notifications; the plan is to migrate everyone to
+  // using NOTIFICATION_SERVER.
+  NOTIFICATION_NEW,
+
+  // Server-issued notifications.  Compatible only with transitional
+  // notifications.
+  NOTIFICATION_SERVER,
+};
+
+extern const NotificationMethod kDefaultNotificationMethod;
+
+std::string NotificationMethodToString(
+    NotificationMethod notification_method);
+
+// If the given string is not one of "legacy", "transitional", "new",
+// or "server", returns kDefaultNotificationMethod.
+NotificationMethod StringToNotificationMethod(const std::string& str);
+
+}  // namespace browser_sync
+
+#endif  // CHROME_BROWSER_SYNC_NOTIFICATION_METHOD_H_
+