/*

  * Licensed to the Apache Software Foundation (ASF) under one or more

  * contributor license agreements.  See the NOTICE file distributed with

  * this work for additional information regarding copyright ownership.

  * The ASF licenses this file to You 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 org.apache.commons.lang3.text.translate;

 import java.io.IOException;

 import java.io.Writer;

 /**

  * Translate escaped octal Strings back to their octal values.

  *

  * For example, "\45" should go back to being the specific value (a %).

  *

  * Note that this currently only supports the viable range of octal for Java; namely 

  * 1 to 377. This is both because parsing Java is the main use case and Integer.parseInt

  * throws an exception when values are larger than octal 377.

  * 

  * @since 3.0

  * @version $Id: OctalUnescaper.java 967237 2010-07-23 20:08:57Z mbenson $

  */

 public class OctalUnescaper extends CharSequenceTranslator {

     private static int OCTAL_MAX = 377;

     /**

      * {@inheritDoc}

      */

     @Override

     public int translate(final CharSequence input, final int index, final Writer out) throws IOException {

         if(input.charAt(index) == '\\' && index < (input.length() - 1) && Character.isDigit(input.charAt(index + 1)) ) {

             final int start = index + 1;

             int end = index + 2;

             while ( end < input.length() && Character.isDigit(input.charAt(end)) ) {

                 end++;

                 if ( Integer.parseInt(input.subSequence(start, end).toString(), 10) > OCTAL_MAX) {

                     end--; // rollback

                     break;

                 }

             }

             out.write( Integer.parseInt(input.subSequence(start, end).toString(), 8) );

             return 1 + end - start;

         }

         return 0;

     }

 }