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 * Translates escaped Unicode values of the form \\u+\d\d\d\d back to
24 * Unicode. It supports multiple 'u' characters and will work with or
25 * without the +.
26 *
27 * @since 1.0
28 */
29 public class UnicodeUnescaper extends CharSequenceTranslator {
30
31 /**
32 * {@inheritDoc}
33 */
34 @Override
35 public int translate(final CharSequence input, final int index, final Writer writer) throws IOException {
36 if (input.charAt(index) == '\\' && index + 1 < input.length() && input.charAt(index + 1) == 'u') {
37 // consume optional additional 'u' chars
38 int i = 2;
39 while (index + i < input.length() && input.charAt(index + i) == 'u') {
40 i++;
41 }
42
43 if (index + i < input.length() && input.charAt(index + i) == '+') {
44 i++;
45 }
46
47 if (index + i + 4 <= input.length()) {
48 // Get 4 hex digits
49 final CharSequence unicode = input.subSequence(index + i, index + i + 4);
50
51 try {
52 final int value = Integer.parseInt(unicode.toString(), 16);
53 writer.write((char) value);
54 } catch (final NumberFormatException nfe) {
55 throw new IllegalArgumentException("Unable to parse unicode value: " + unicode, nfe);
56 }
57 return i + 4;
58 }
59 throw new IllegalArgumentException("Less than 4 hex digits in unicode value: '"
60 + input.subSequence(index, input.length())
61 + "' due to end of CharSequence");
62 }
63 return 0;
64 }
65 }