1 /* 2 * Licensed to the Apache Software Foundation (ASF) under one or more 3 * contributor license agreements. See the NOTICE file distributed with 4 * this work for additional information regarding copyright ownership. 5 * The ASF licenses this file to You under the Apache License, Version 2.0 6 * (the "License"); you may not use this file except in compliance with 7 * the License. You may obtain a copy of the License at 8 * 9 * http://www.apache.org/licenses/LICENSE-2.0 10 * 11 * Unless required by applicable law or agreed to in writing, software 12 * distributed under the License is distributed on an "AS IS" BASIS, 13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 14 * See the License for the specific language governing permissions and 15 * limitations under the License. 16 */ 17 package org.apache.commons.text.translate; 18 19 import java.io.IOException; 20 import java.io.Writer; 21 22 /** 23 * Translate escaped octal Strings back to their octal values. 24 * 25 * For example, "\45" should go back to being the specific value (a %). 26 * 27 * Note that this currently only supports the viable range of octal for Java; namely 28 * 1 to 377. This is because parsing Java is the main use case. 29 * 30 * @since 1.0 31 */ 32 public class OctalUnescaper extends CharSequenceTranslator { 33 34 /** 35 * {@inheritDoc} 36 */ 37 @Override 38 public int translate(final CharSequence input, final int index, final Writer out) throws IOException { 39 final int remaining = input.length() - index - 1; // how many characters left, ignoring the first \ 40 final StringBuilder builder = new StringBuilder(); 41 if(input.charAt(index) == '\\' && remaining > 0 && isOctalDigit(input.charAt(index + 1)) ) { 42 final int next = index + 1; 43 final int next2 = index + 2; 44 final int next3 = index + 3; 45 46 // we know this is good as we checked it in the if block above 47 builder.append(input.charAt(next)); 48 49 if(remaining > 1 && isOctalDigit(input.charAt(next2))) { 50 builder.append(input.charAt(next2)); 51 if(remaining > 2 && isZeroToThree(input.charAt(next)) && isOctalDigit(input.charAt(next3))) { 52 builder.append(input.charAt(next3)); 53 } 54 } 55 56 out.write( Integer.parseInt(builder.toString(), 8) ); 57 return 1 + builder.length(); 58 } 59 return 0; 60 } 61 62 /** 63 * Checks if the given char is an octal digit. Octal digits are the character representations of the digits 0 to 7. 64 * @param ch the char to check 65 * @return true if the given char is the character representation of one of the digits from 0 to 7 66 */ 67 private boolean isOctalDigit(final char ch) { 68 return ch >= '0' && ch <= '7'; 69 } 70 71 /** 72 * Checks if the given char is the character representation of one of the digit from 0 to 3. 73 * @param ch the char to check 74 * @return true if the given char is the character representation of one of the digits from 0 to 3 75 */ 76 private boolean isZeroToThree(final char ch) { 77 return ch >= '0' && ch <= '3'; 78 } 79 }