001    /*
002     * Licensed to the Apache Software Foundation (ASF) under one or more
003     * contributor license agreements.  See the NOTICE file distributed with
004     * this work for additional information regarding copyright ownership.
005     * The ASF licenses this file to You under the Apache License, Version 2.0
006     * (the "License"); you may not use this file except in compliance with
007     * the License.  You may obtain a copy of the License at
008     * 
009     *      http://www.apache.org/licenses/LICENSE-2.0
010     * 
011     * Unless required by applicable law or agreed to in writing, software
012     * distributed under the License is distributed on an "AS IS" BASIS,
013     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014     * See the License for the specific language governing permissions and
015     * limitations under the License.
016     */
017    package org.apache.commons.lang3.text.translate;
018    
019    import java.io.IOException;
020    import java.io.Writer;
021    
022    /**
023     * Translate escaped octal Strings back to their octal values.
024     *
025     * For example, "\45" should go back to being the specific value (a %).
026     *
027     * Note that this currently only supports the viable range of octal for Java; namely 
028     * 1 to 377. This is both because parsing Java is the main use case and Integer.parseInt
029     * throws an exception when values are larger than octal 377.
030     * 
031     * @since 3.0
032     * @version $Id: OctalUnescaper.java 967237 2010-07-23 20:08:57Z mbenson $
033     */
034    public class OctalUnescaper extends CharSequenceTranslator {
035    
036        private static int OCTAL_MAX = 377;
037    
038        /**
039         * {@inheritDoc}
040         */
041        @Override
042        public int translate(CharSequence input, int index, Writer out) throws IOException {
043            if(input.charAt(index) == '\\' && index < (input.length() - 1) && Character.isDigit(input.charAt(index + 1)) ) {
044                int start = index + 1;
045    
046                int end = index + 2;
047                while ( end < input.length() && Character.isDigit(input.charAt(end)) ) {
048                    end++;
049                    if ( Integer.parseInt(input.subSequence(start, end).toString(), 10) > OCTAL_MAX) {
050                        end--; // rollback
051                        break;
052                    }
053                }
054    
055                out.write( Integer.parseInt(input.subSequence(start, end).toString(), 8) );
056                return 1 + end - start;
057            }
058            return 0;
059        }
060    }