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 * Tests if the given char is an octal digit. Octal digits are the character representations of the digits 0 to 7. 36 * 37 * @param ch the char to check 38 * @return true if the given char is the character representation of one of the digits from 0 to 7 39 */ 40 private boolean isOctalDigit(final char ch) { 41 return ch >= '0' && ch <= '7'; 42 } 43 44 /** 45 * Tests if the given char is the character representation of one of the digit from 0 to 3. 46 * 47 * @param ch the char to check 48 * @return true if the given char is the character representation of one of the digits from 0 to 3 49 */ 50 private boolean isZeroToThree(final char ch) { 51 return ch >= '0' && ch <= '3'; 52 } 53 54 /** 55 * {@inheritDoc} 56 */ 57 @Override 58 public int translate(final CharSequence input, final int index, final Writer writer) throws IOException { 59 final int remaining = input.length() - index - 1; // how many characters left, ignoring the first \ 60 final StringBuilder builder = new StringBuilder(); 61 if (input.charAt(index) == '\\' && remaining > 0 && isOctalDigit(input.charAt(index + 1))) { 62 final int next = index + 1; 63 final int next2 = index + 2; 64 final int next3 = index + 3; 65 66 // we know this is good as we checked it in the if block above 67 builder.append(input.charAt(next)); 68 69 if (remaining > 1 && isOctalDigit(input.charAt(next2))) { 70 builder.append(input.charAt(next2)); 71 if (remaining > 2 && isZeroToThree(input.charAt(next)) && isOctalDigit(input.charAt(next3))) { 72 builder.append(input.charAt(next3)); 73 } 74 } 75 76 writer.write(Integer.parseInt(builder.toString(), 8)); 77 return 1 + builder.length(); 78 } 79 return 0; 80 } 81 }