diff --git a/src/diff-state.cpp b/src/diff-state.cpp
new file mode 100644
index 0000000..f5813bf
--- /dev/null
+++ b/src/diff-state.cpp
@@ -0,0 +1,43 @@
+/* -*- Mode: C++; c-file-style: "gnu"; indent-tabs-mode:nil -*- */
+/*
+ * Copyright (c) 2012-2014 University of California, Los Angeles
+ *
+ * This file is part of ChronoSync, synchronization library for distributed realtime
+ * applications for NDN.
+ *
+ * ChronoSync is free software: you can redistribute it and/or modify it under the terms
+ * of the GNU General Public License as published by the Free Software Foundation, either
+ * version 3 of the License, or (at your option) any later version.
+ *
+ * ChronoSync is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
+ * without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
+ * PURPOSE.  See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * ChronoSync, e.g., in COPYING.md file.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * @author Zhenkai Zhu <http://irl.cs.ucla.edu/~zhenkai/>
+ * @author Chaoyi Bian <bcy@pku.edu.cn>
+ * @author Alexander Afanasyev <http://lasr.cs.ucla.edu/afanasyev/index.html>
+ * @author Yingdi Yu <yingdi@cs.ucla.edu>
+ */
+
+#include "diff-state.hpp"
+
+namespace chronosync {
+
+ConstStatePtr
+DiffState::diff() const
+{
+  StatePtr result = make_shared<State>();
+
+  ConstDiffStatePtr state = m_next;
+  while (static_cast<bool>(state)) {
+    *result += *state;
+    state = state->m_next;
+  }
+
+  return result;
+}
+
+} // namespace chronosync