1 /**
2 * Licensed to the Apache Software Foundation (ASF) under one
3 * or more contributor license agreements. See the NOTICE file
4 * distributed with this work for additional information
5 * regarding copyright ownership. The ASF licenses this file
6 * to you under the Apache License, Version 2.0 (the
7 * "License"); you may not use this file except in compliance
8 * with the License. You may obtain a copy of the License at
9 *
10 * http://www.apache.org/licenses/LICENSE-2.0
11 *
12 * Unless required by applicable law or agreed to in writing, software
13 * distributed under the License is distributed on an "AS IS" BASIS,
14 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15 * See the License for the specific language governing permissions and
16 * limitations under the License.
17 */
18 package org.apache.hadoop.hbase.util;
19
20 import org.apache.hadoop.hbase.classification.InterfaceAudience;
21 import org.apache.hadoop.hbase.classification.InterfaceStability;
22
23 /**
24 * Used to describe or modify the lexicographical sort order of a
25 * {@code byte[]}. Default ordering is considered {@code ASCENDING}. The order
26 * of a {@code byte[]} can be inverted, resulting in {@code DESCENDING} order,
27 * by replacing each byte with its 1's compliment.
28 */
29 @InterfaceAudience.Public
30 @InterfaceStability.Evolving
31 public enum Order {
32
33 ASCENDING {
34 @Override
35 public int cmp(int cmp) { /* noop */ return cmp; }
36
37 @Override
38 public byte apply(byte val) { /* noop */ return val; }
39
40 @Override
41 public void apply(byte[] val) { /* noop */ }
42
43 @Override
44 public void apply(byte[] val, int offset, int length) { /* noop */ }
45
46 @Override
47 public String toString() { return "ASCENDING"; }
48 },
49
50 DESCENDING {
51 /**
52 * A {@code byte} value is inverted by taking its 1's Complement, achieved
53 * via {@code xor} with {@code 0xff}.
54 */
55 private static final byte MASK = (byte) 0xff;
56
57 @Override
58 public int cmp(int cmp) { return -1 * cmp; }
59
60 @Override
61 public byte apply(byte val) { return (byte) (val ^ MASK); }
62
63 @Override
64 public void apply(byte[] val) {
65 for (int i = 0; i < val.length; i++) { val[i] ^= MASK; }
66 }
67
68 @Override
69 public void apply(byte[] val, int offset, int length) {
70 for (int i = 0; i < length; i++) { val[offset + i] ^= MASK; }
71 }
72
73 @Override
74 public String toString() { return "DESCENDING"; }
75 };
76
77 /**
78 * Returns the adjusted trichotomous value according to the ordering imposed by this
79 * {@code Order}.
80 */
81 public abstract int cmp(int cmp);
82
83 /**
84 * Apply order to the byte {@code val}.
85 */
86 public abstract byte apply(byte val);
87
88 /**
89 * Apply order to the byte array {@code val}.
90 */
91 public abstract void apply(byte[] val);
92
93 /**
94 * Apply order to a range within the byte array {@code val}.
95 */
96 public abstract void apply(byte[] val, int offset, int length);
97 }