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
18 package org.apache.commons.codec.net;
19
20 import org.apache.commons.codec.DecoderException;
21
22 /**
23 * Utility methods for this package.
24 *
25 * <p>This class is immutable and thread-safe.</p>
26 *
27 * @since 1.4
28 */
29 final class Utils {
30
31 /**
32 * Radix used in encoding and decoding.
33 */
34 private static final int RADIX = 16;
35
36 /**
37 * Returns the numeric value of the character {@code b} in radix 16.
38 *
39 * @param b
40 * The byte to be converted.
41 * @return The numeric value represented by the character in radix 16.
42 *
43 * @throws DecoderException
44 * Thrown when the byte is not valid per {@link Character#digit(char,int)}
45 */
46 static int digit16(final byte b) throws DecoderException {
47 final int i = Character.digit((char) b, RADIX);
48 if (i == -1) {
49 throw new DecoderException("Invalid URL encoding: not a valid digit (radix " + RADIX + "): " + b);
50 }
51 return i;
52 }
53
54 /**
55 * Returns the upper case hexadecimal digit of the lower 4 bits of the int.
56 *
57 * @param b the input int
58 * @return the upper case hexadecimal digit of the lower 4 bits of the int.
59 */
60 static char hexDigit(final int b) {
61 return Character.toUpperCase(Character.forDigit(b & 0xF, RADIX));
62 }
63
64 }