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diff --git a/src/include/fst/lock.h b/src/include/fst/lock.h
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+// lock.h
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Google-compatibility locking declarations and inline definitions
+
+#ifndef FST_LIB_LOCK_H__
+#define FST_LIB_LOCK_H__
+
+#include <fst/compat.h>  // for DISALLOW_COPY_AND_ASSIGN
+
+namespace fst {
+
+using namespace std;
+
+//
+// Single initialization  - single-thread implementation
+//
+
+typedef int FstOnceType;
+
+static const int FST_ONCE_INIT = 1;
+
+inline int FstOnceInit(FstOnceType *once, void (*init)(void)) {
+  if (*once)
+    (*init)();
+  *once = 0;
+  return 0;
+}
+
+//
+// Thread locking - single-thread (non-)implementation
+//
+
+class Mutex {
+ public:
+  Mutex() {}
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(Mutex);
+};
+
+class MutexLock {
+ public:
+  MutexLock(Mutex *) {}
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(MutexLock);
+};
+
+// Reference counting - single-thread implementation
+class RefCounter {
+ public:
+  RefCounter() : count_(1) {}
+
+  int count() const { return count_; }
+  int Incr() const { return ++count_; }
+  int Decr() const {  return --count_; }
+
+ private:
+  mutable int count_;
+
+  DISALLOW_COPY_AND_ASSIGN(RefCounter);
+};
+
+}  // namespace fst
+
+#endif  // FST_LIB_LOCK_H__