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 */ 017package org.apache.commons.text.translate; 018 019import java.io.IOException; 020import java.io.Writer; 021 022/** 023 * Translates escaped Unicode values of the form \\u+\d\d\d\d back to 024 * Unicode. It supports multiple 'u' characters and will work with or 025 * without the +. 026 * 027 * @since 1.0 028 */ 029public class UnicodeUnescaper extends CharSequenceTranslator { 030 031 /** 032 * Constructs a new instance. 033 */ 034 public UnicodeUnescaper() { 035 // empty 036 } 037 038 /** 039 * {@inheritDoc} 040 */ 041 @Override 042 public int translate(final CharSequence input, final int index, final Writer writer) throws IOException { 043 if (input.charAt(index) == '\\' && index + 1 < input.length() && input.charAt(index + 1) == 'u') { 044 // consume optional additional 'u' chars 045 int i = 2; 046 while (index + i < input.length() && input.charAt(index + i) == 'u') { 047 i++; 048 } 049 050 if (index + i < input.length() && input.charAt(index + i) == '+') { 051 i++; 052 } 053 054 if (index + i + 4 <= input.length()) { 055 // Get 4 hex digits 056 final CharSequence unicode = input.subSequence(index + i, index + i + 4); 057 058 try { 059 final int value = Integer.parseInt(unicode.toString(), 16); 060 writer.write((char) value); 061 } catch (final NumberFormatException nfe) { 062 throw new IllegalArgumentException("Unable to parse unicode value: " + unicode, nfe); 063 } 064 return i + 4; 065 } 066 throw new IllegalArgumentException("Less than 4 hex digits in unicode value: '" 067 + input.subSequence(index, input.length()) 068 + "' due to end of CharSequence"); 069 } 070 return 0; 071 } 072}