Update from Google.
--
MOE_MIGRATED_REVID=85702957
diff --git a/src/main/java/com/google/devtools/build/lib/util/StringIndexer.java b/src/main/java/com/google/devtools/build/lib/util/StringIndexer.java
new file mode 100644
index 0000000..cf345d2
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/util/StringIndexer.java
@@ -0,0 +1,61 @@
+// Copyright 2014 Google Inc. All rights reserved.
+//
+// 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.
+package com.google.devtools.build.lib.util;
+
+/**
+ * An object that provides bidirectional String <-> unique integer mapping.
+ */
+public interface StringIndexer {
+
+ /**
+ * Removes all mappings.
+ */
+ public void clear();
+
+ /**
+ * @return some measure of the size of the index.
+ */
+ public int size();
+
+ /**
+ * Creates new mapping for the given string if necessary and returns
+ * string index. Also, as a side effect, zero or more additional mappings
+ * may be created for various prefixes of the given string.
+ *
+ * @return a unique index.
+ */
+ public int getOrCreateIndex(String s);
+
+ /**
+ * @return a unique index for the given string or -1 if string
+ * was not added.
+ */
+ public int getIndex(String s);
+
+ /**
+ * Creates mapping for the given string if necessary.
+ * Also, as a side effect, zero or more additional mappings may be
+ * created for various prefixes of the given string.
+ *
+ * @return true if new mapping was created, false if mapping already existed.
+ */
+ public boolean addString(String s);
+
+ /**
+ * @return string associated with the given index or null if
+ * mapping does not exist.
+ */
+ public String getStringForIndex(int i);
+
+}
