First-time sync: asymptotic running time improvement

chrome/browser/sync/syncable/syncable_id.cc

 // Copyright (c) 2009 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.
 
 #include "chrome/browser/sync/syncable/syncable_id.h"
 
 #include <iosfwd>
 
 #include "base/string_util.h"
 
@@ skipping 27 matching lines @@
 
 Id Id::CreateFromClientString(const string& local_id) {
   Id id;
   if (local_id == "0")
     id.s_ = "r";
   else
     id.s_ = string("c") + local_id;
   return id;
 }
 
+Id Id::GetLexicographicSuccessor() const {
+  // The successor of a string is given by appending the least
+  // character in the alphabet.
+  Id id = *this;
+  id.s_.push_back(std::numeric_limits<std::string::value_type>::min());
+  return id;
+}
+
+// static
+Id Id::GetLeastIdForLexicographicComparison() {
+  Id id;
+  id.s_.clear();
+  return id;
+}
+
 }  // namespace syncable