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diff --git a/src/include/fst/reverse.h b/src/include/fst/reverse.h
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+// reverse.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.
+//
+// Copyright 2005-2010 Google, Inc.
+// Author: riley@google.com (Michael Riley)
+//
+// \file
+// Functions and classes to sort arcs in an FST.
+
+#ifndef FST_LIB_REVERSE_H__
+#define FST_LIB_REVERSE_H__
+
+#include <algorithm>
+#include <vector>
+using std::vector;
+
+#include <fst/cache.h>
+
+
+namespace fst {
+
+// Reverses an FST. The reversed result is written to an output
+// MutableFst.  If A transduces string x to y with weight a, then the
+// reverse of A transduces the reverse of x to the reverse of y with
+// weight a.Reverse().
+//
+// Typically, a = a.Reverse() and Arc = RevArc (e.g. for
+// TropicalWeight or LogWeight).  In general, e.g. when the weights
+// only form a left or right semiring, the output arc type must match
+// the input arc type except having the reversed Weight type.
+template<class Arc, class RevArc>
+void Reverse(const Fst<Arc> &ifst, MutableFst<RevArc> *ofst) {
+  typedef typename Arc::StateId StateId;
+  typedef typename Arc::Weight Weight;
+  typedef typename RevArc::Weight RevWeight;
+
+  ofst->DeleteStates();
+  ofst->SetInputSymbols(ifst.InputSymbols());
+  ofst->SetOutputSymbols(ifst.OutputSymbols());
+  if (ifst.Properties(kExpanded, false))
+    ofst->ReserveStates(CountStates(ifst) + 1);
+  StateId istart = ifst.Start();
+  StateId ostart = ofst->AddState();
+  ofst->SetStart(ostart);
+
+  for (StateIterator< Fst<Arc> > siter(ifst);
+       !siter.Done();
+       siter.Next()) {
+    StateId is = siter.Value();
+    StateId os = is + 1;
+    while (ofst->NumStates() <= os)
+      ofst->AddState();
+    if (is == istart)
+      ofst->SetFinal(os, RevWeight::One());
+
+    Weight final = ifst.Final(is);
+    if (final != Weight::Zero()) {
+      RevArc oarc(0, 0, final.Reverse(), os);
+      ofst->AddArc(0, oarc);
+    }
+
+    for (ArcIterator< Fst<Arc> > aiter(ifst, is);
+         !aiter.Done();
+         aiter.Next()) {
+      const Arc &iarc = aiter.Value();
+      RevArc oarc(iarc.ilabel, iarc.olabel, iarc.weight.Reverse(), os);
+      StateId nos = iarc.nextstate + 1;
+      while (ofst->NumStates() <= nos)
+        ofst->AddState();
+      ofst->AddArc(nos, oarc);
+    }
+  }
+  uint64 iprops = ifst.Properties(kCopyProperties, false);
+  uint64 oprops = ofst->Properties(kFstProperties, false);
+  ofst->SetProperties(ReverseProperties(iprops) | oprops, kFstProperties);
+}
+
+}  // namespace fst
+
+#endif  // FST_LIB_REVERSE_H__