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diff --git a/kaldi_io/src/tools/openfst/include/fst/symbol-table.h b/kaldi_io/src/tools/openfst/include/fst/symbol-table.h
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+
+// 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.
+// All Rights Reserved.
+//
+// Author : Johan Schalkwyk
+//
+// \file
+// Classes to provide symbol-to-integer and integer-to-symbol mappings.
+
+#ifndef FST_LIB_SYMBOL_TABLE_H__
+#define FST_LIB_SYMBOL_TABLE_H__
+
+#include <cstring>
+#include <string>
+#include <utility>
+using std::pair; using std::make_pair;
+#include <vector>
+using std::vector;
+
+
+#include <fst/compat.h>
+#include <iostream>
+#include <fstream>
+#include <sstream>
+
+
+#include <map>
+
+DECLARE_bool(fst_compat_symbols);
+
+namespace fst {
+
+// WARNING: Reading via symbol table read options should
+//          not be used. This is a temporary work around for
+//          reading symbol ranges of previously stored symbol sets.
+struct SymbolTableReadOptions {
+  SymbolTableReadOptions() { }
+
+  SymbolTableReadOptions(vector<pair<int64, int64> > string_hash_ranges_,
+                         const string& source_)
+      : string_hash_ranges(string_hash_ranges_),
+        source(source_) { }
+
+  vector<pair<int64, int64> > string_hash_ranges;
+  string source;
+};
+
+struct SymbolTableTextOptions {
+  SymbolTableTextOptions();
+
+  bool allow_negative;
+  string fst_field_separator;
+};
+
+class SymbolTableImpl {
+ public:
+  SymbolTableImpl(const string &name)
+      : name_(name),
+        available_key_(0),
+        dense_key_limit_(0),
+        check_sum_finalized_(false) {}
+
+  explicit SymbolTableImpl(const SymbolTableImpl& impl)
+      : name_(impl.name_),
+        available_key_(0),
+        dense_key_limit_(0),
+        check_sum_finalized_(false) {
+    for (size_t i = 0; i < impl.symbols_.size(); ++i) {
+      AddSymbol(impl.symbols_[i], impl.Find(impl.symbols_[i]));
+    }
+  }
+
+  ~SymbolTableImpl() {
+    for (size_t i = 0; i < symbols_.size(); ++i)
+      delete[] symbols_[i];
+  }
+
+  // TODO(johans): Add flag to specify whether the symbol
+  //               should be indexed as string or int or both.
+  int64 AddSymbol(const string& symbol, int64 key);
+
+  int64 AddSymbol(const string& symbol) {
+    int64 key = Find(symbol);
+    return (key == -1) ? AddSymbol(symbol, available_key_++) : key;
+  }
+
+  static SymbolTableImpl* ReadText(
+      istream &strm, const string &name,
+      const SymbolTableTextOptions &opts = SymbolTableTextOptions());
+
+  static SymbolTableImpl* Read(istream &strm,
+                               const SymbolTableReadOptions& opts);
+
+  bool Write(ostream &strm) const;
+
+  //
+  // Return the string associated with the key. If the key is out of
+  // range (<0, >max), return an empty string.
+  string Find(int64 key) const {
+    if (key >=0 && key < dense_key_limit_)
+      return string(symbols_[key]);
+
+    map<int64, const char*>::const_iterator it =
+        key_map_.find(key);
+    if (it == key_map_.end()) {
+      return "";
+    }
+    return string(it->second);
+  }
+
+  //
+  // Return the key associated with the symbol. If the symbol
+  // does not exists, return SymbolTable::kNoSymbol.
+  int64 Find(const string& symbol) const {
+    return Find(symbol.c_str());
+  }
+
+  //
+  // Return the key associated with the symbol. If the symbol
+  // does not exists, return SymbolTable::kNoSymbol.
+  int64 Find(const char* symbol) const {
+    map<const char *, int64, StrCmp>::const_iterator it =
+        symbol_map_.find(symbol);
+    if (it == symbol_map_.end()) {
+      return -1;
+    }
+    return it->second;
+  }
+
+  int64 GetNthKey(ssize_t pos) const {
+    if ((pos < 0) || (pos >= symbols_.size())) return -1;
+    else return Find(symbols_[pos]);
+  }
+
+  const string& Name() const { return name_; }
+
+  int IncrRefCount() const {
+    return ref_count_.Incr();
+  }
+  int DecrRefCount() const {
+    return ref_count_.Decr();
+  }
+  int RefCount() const {
+    return ref_count_.count();
+  }
+
+  string CheckSum() const {
+    MaybeRecomputeCheckSum();
+    return check_sum_string_;
+  }
+
+  string LabeledCheckSum() const {
+    MaybeRecomputeCheckSum();
+    return labeled_check_sum_string_;
+  }
+
+  int64 AvailableKey() const {
+    return available_key_;
+  }
+
+  size_t NumSymbols() const {
+    return symbols_.size();
+  }
+
+ private:
+  // Recomputes the checksums (both of them) if we've had changes since the last
+  // computation (i.e., if check_sum_finalized_ is false).
+  // Takes ~2.5 microseconds (dbg) or ~230 nanoseconds (opt) on a 2.67GHz Xeon
+  // if the checksum is up-to-date (requiring no recomputation).
+  void MaybeRecomputeCheckSum() const;
+
+  struct StrCmp {
+    bool operator()(const char *s1, const char *s2) const {
+      return strcmp(s1, s2) < 0;
+    }
+  };
+
+  string name_;
+  int64 available_key_;
+  int64 dense_key_limit_;
+  vector<const char *> symbols_;
+  map<int64, const char*> key_map_;
+  map<const char *, int64, StrCmp> symbol_map_;
+
+  mutable RefCounter ref_count_;
+  mutable bool check_sum_finalized_;
+  mutable string check_sum_string_;
+  mutable string labeled_check_sum_string_;
+  mutable Mutex check_sum_mutex_;
+};
+
+//
+// \class SymbolTable
+// \brief Symbol (string) to int and reverse mapping
+//
+// The SymbolTable implements the mappings of labels to strings and reverse.
+// SymbolTables are used to describe the alphabet of the input and output
+// labels for arcs in a Finite State Transducer.
+//
+// SymbolTables are reference counted and can therefore be shared across
+// multiple machines. For example a language model grammar G, with a
+// SymbolTable for the words in the language model can share this symbol
+// table with the lexical representation L o G.
+//
+class SymbolTable {
+ public:
+  static const int64 kNoSymbol = -1;
+
+  // Construct symbol table with an unspecified name.
+  SymbolTable() : impl_(new SymbolTableImpl("<unspecified>")) {}
+
+  // Construct symbol table with a unique name.
+  SymbolTable(const string& name) : impl_(new SymbolTableImpl(name)) {}
+
+  // Create a reference counted copy.
+  SymbolTable(const SymbolTable& table) : impl_(table.impl_) {
+    impl_->IncrRefCount();
+  }
+
+  // Derefence implentation object. When reference count hits 0, delete
+  // implementation.
+  virtual ~SymbolTable() {
+    if (!impl_->DecrRefCount()) delete impl_;
+  }
+
+  // Copys the implemenation from one symbol table to another.
+  void operator=(const SymbolTable &st) {
+    if (impl_ != st.impl_) {
+      st.impl_->IncrRefCount();
+      if (!impl_->DecrRefCount()) delete impl_;
+      impl_ = st.impl_;
+    }
+  }
+
+  // Read an ascii representation of the symbol table from an istream. Pass a
+  // name to give the resulting SymbolTable.
+  static SymbolTable* ReadText(
+      istream &strm, const string& name,
+      const SymbolTableTextOptions &opts = SymbolTableTextOptions()) {
+    SymbolTableImpl* impl = SymbolTableImpl::ReadText(strm, name, opts);
+    if (!impl)
+      return 0;
+    else
+      return new SymbolTable(impl);
+  }
+
+  // read an ascii representation of the symbol table
+  static SymbolTable* ReadText(const string& filename,
+      const SymbolTableTextOptions &opts = SymbolTableTextOptions()) {
+    ifstream strm(filename.c_str(), ifstream::in);
+    if (!strm) {
+      LOG(ERROR) << "SymbolTable::ReadText: Can't open file " << filename;
+      return 0;
+    }
+    return ReadText(strm, filename, opts);
+  }
+
+
+  // WARNING: Reading via symbol table read options should
+  //          not be used. This is a temporary work around.
+  static SymbolTable* Read(istream &strm,
+                           const SymbolTableReadOptions& opts) {
+    SymbolTableImpl* impl = SymbolTableImpl::Read(strm, opts);
+    if (!impl)
+      return 0;
+    else
+      return new SymbolTable(impl);
+  }
+
+  // read a binary dump of the symbol table from a stream
+  static SymbolTable* Read(istream &strm, const string& source) {
+    SymbolTableReadOptions opts;
+    opts.source = source;
+    return Read(strm, opts);
+  }
+
+  // read a binary dump of the symbol table
+  static SymbolTable* Read(const string& filename) {
+    ifstream strm(filename.c_str(), ifstream::in | ifstream::binary);
+    if (!strm) {
+      LOG(ERROR) << "SymbolTable::Read: Can't open file " << filename;
+      return 0;
+    }
+    return Read(strm, filename);
+  }
+
+  //--------------------------------------------------------
+  // Derivable Interface (final)
+  //--------------------------------------------------------
+  // create a reference counted copy
+  virtual SymbolTable* Copy() const {
+    return new SymbolTable(*this);
+  }
+
+  // Add a symbol with given key to table. A symbol table also
+  // keeps track of the last available key (highest key value in
+  // the symbol table).
+  virtual int64 AddSymbol(const string& symbol, int64 key) {
+    MutateCheck();
+    return impl_->AddSymbol(symbol, key);
+  }
+
+  // Add a symbol to the table. The associated value key is automatically
+  // assigned by the symbol table.
+  virtual int64 AddSymbol(const string& symbol) {
+    MutateCheck();
+    return impl_->AddSymbol(symbol);
+  }
+
+  // Add another symbol table to this table. All key values will be offset
+  // by the current available key (highest key value in the symbol table).
+  // Note string symbols with the same key value with still have the same
+  // key value after the symbol table has been merged, but a different
+  // value. Adding symbol tables do not result in changes in the base table.
+  virtual void AddTable(const SymbolTable& table);
+
+  // return the name of the symbol table
+  virtual const string& Name() const {
+    return impl_->Name();
+  }
+
+  // Return the label-agnostic MD5 check-sum for this table.  All new symbols
+  // added to the table will result in an updated checksum.
+  // DEPRECATED.
+  virtual string CheckSum() const {
+    return impl_->CheckSum();
+  }
+
+  // Same as CheckSum(), but this returns an label-dependent version.
+  virtual string LabeledCheckSum() const {
+    return impl_->LabeledCheckSum();
+  }
+
+  virtual bool Write(ostream &strm) const {
+    return impl_->Write(strm);
+  }
+
+  bool Write(const string& filename) const {
+    ofstream strm(filename.c_str(), ofstream::out | ofstream::binary);
+    if (!strm) {
+      LOG(ERROR) << "SymbolTable::Write: Can't open file " << filename;
+      return false;
+    }
+    return Write(strm);
+  }
+
+  // Dump an ascii text representation of the symbol table via a stream
+  virtual bool WriteText(
+      ostream &strm,
+      const SymbolTableTextOptions &opts = SymbolTableTextOptions()) const;
+
+  // Dump an ascii text representation of the symbol table
+  bool WriteText(const string& filename) const {
+    ofstream strm(filename.c_str());
+    if (!strm) {
+      LOG(ERROR) << "SymbolTable::WriteText: Can't open file " << filename;
+      return false;
+    }
+    return WriteText(strm);
+  }
+
+  // Return the string associated with the key. If the key is out of
+  // range (<0, >max), log error and return an empty string.
+  virtual string Find(int64 key) const {
+    return impl_->Find(key);
+  }
+
+  // Return the key associated with the symbol. If the symbol
+  // does not exists, log error and  return SymbolTable::kNoSymbol
+  virtual int64 Find(const string& symbol) const {
+    return impl_->Find(symbol);
+  }
+
+  // Return the key associated with the symbol. If the symbol
+  // does not exists, log error and  return SymbolTable::kNoSymbol
+  virtual int64 Find(const char* symbol) const {
+    return impl_->Find(symbol);
+  }
+
+  // Return the current available key (i.e highest key number+1) in
+  // the symbol table
+  virtual int64 AvailableKey(void) const {
+    return impl_->AvailableKey();
+  }
+
+  // Return the current number of symbols in table (not necessarily
+  // equal to AvailableKey())
+  virtual size_t NumSymbols(void) const {
+    return impl_->NumSymbols();
+  }
+
+  virtual int64 GetNthKey(ssize_t pos) const {
+    return impl_->GetNthKey(pos);
+  }
+
+ private:
+  explicit SymbolTable(SymbolTableImpl* impl) : impl_(impl) {}
+
+  void MutateCheck() {
+    // Copy on write
+    if (impl_->RefCount() > 1) {
+      impl_->DecrRefCount();
+      impl_ = new SymbolTableImpl(*impl_);
+    }
+  }
+
+  const SymbolTableImpl* Impl() const {
+    return impl_;
+  }
+
+ private:
+  SymbolTableImpl* impl_;
+};
+
+
+//
+// \class SymbolTableIterator
+// \brief Iterator class for symbols in a symbol table
+class SymbolTableIterator {
+ public:
+  SymbolTableIterator(const SymbolTable& table)
+      : table_(table),
+        pos_(0),
+        nsymbols_(table.NumSymbols()),
+        key_(table.GetNthKey(0)) { }
+
+  ~SymbolTableIterator() { }
+
+  // is iterator done
+  bool Done(void) {
+    return (pos_ == nsymbols_);
+  }
+
+  // return the Value() of the current symbol (int64 key)
+  int64 Value(void) {
+    return key_;
+  }
+
+  // return the string of the current symbol
+  string Symbol(void) {
+    return table_.Find(key_);
+  }
+
+  // advance iterator forward
+  void Next(void) {
+    ++pos_;
+    if (pos_ < nsymbols_) key_ = table_.GetNthKey(pos_);
+  }
+
+  // reset iterator
+  void Reset(void) {
+    pos_ = 0;
+    key_ = table_.GetNthKey(0);
+  }
+
+ private:
+  const SymbolTable& table_;
+  ssize_t pos_;
+  size_t nsymbols_;
+  int64 key_;
+};
+
+
+// Tests compatibilty between two sets of symbol tables
+inline bool CompatSymbols(const SymbolTable *syms1, const SymbolTable *syms2,
+                          bool warning = true) {
+  if (!FLAGS_fst_compat_symbols) {
+    return true;
+  } else if (!syms1 && !syms2) {
+    return true;
+  } else if (syms1 && !syms2) {
+    if (warning)
+      LOG(WARNING) <<
+          "CompatSymbols: first symbol table present but second missing";
+    return false;
+  } else if (!syms1 && syms2) {
+    if (warning)
+      LOG(WARNING) <<
+          "CompatSymbols: second symbol table present but first missing";
+    return false;
+  } else if (syms1->LabeledCheckSum() != syms2->LabeledCheckSum()) {
+    if (warning)
+      LOG(WARNING) << "CompatSymbols: Symbol table check sums do not match";
+    return false;
+  } else {
+    return true;
+  }
+}
+
+
+// Relabels a symbol table as specified by the input vector of pairs
+// (old label, new label). The new symbol table only retains symbols
+// for which a relabeling is *explicitely* specified.
+// TODO(allauzen): consider adding options to allow for some form
+// of implicit identity relabeling.
+template <class Label>
+SymbolTable *RelabelSymbolTable(const SymbolTable *table,
+                                const vector<pair<Label, Label> > &pairs) {
+  SymbolTable *new_table = new SymbolTable(
+      table->Name().empty() ? string() :
+      (string("relabeled_") + table->Name()));
+
+  for (size_t i = 0; i < pairs.size(); ++i)
+    new_table->AddSymbol(table->Find(pairs[i].first), pairs[i].second);
+
+  return new_table;
+}
+
+// Symbol Table Serialization
+inline void SymbolTableToString(const SymbolTable *table, string *result) {
+  ostringstream ostrm;
+  table->Write(ostrm);
+  *result = ostrm.str();
+}
+
+inline SymbolTable *StringToSymbolTable(const string &s) {
+  istringstream istrm(s);
+  return SymbolTable::Read(istrm, SymbolTableReadOptions());
+}
+
+
+
+}  // namespace fst
+
+#endif  // FST_LIB_SYMBOL_TABLE_H__