sync/syncable/syncable_changes_version.h

   1 // Copyright (c) 2012 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 SYNC_SYNCABLE_SYNCABLE_CHANGES_VERSION_H_
   6 #define SYNC_SYNCABLE_SYNCABLE_CHANGES_VERSION_H_
   7 #pragma once
   8
   9 namespace syncable {
  10
  11 // For the most part, the sync engine treats version numbers as opaque values.
  12 // However, there are parts of our code base that break this abstraction, and
  13 // depend on the following two invariants:
  14 //
  15 //  1.  CHANGES_VERSION is less than 0.
  16 //  2.  The server only issues positive version numbers.
  17 //
  18 // Breaking these abstractions makes some operations 10 times
  19 // faster.  If either of these invariants change, then those queries
  20 // must be revisited.
  21
  22 enum {
  23   CHANGES_VERSION = -1
  24 };
  25
  26 #define CHANGES_VERSION_STRING "-1"
  27
  28 }  // namespace syncable
  29
  30 #endif  // SYNC_SYNCABLE_SYNCABLE_CHANGES_VERSION_H_