1 /**
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with this
4 * work for additional information regarding copyright ownership. The ASF
5 * licenses this file to you under the Apache License, Version 2.0 (the
6 * "License"); you may not use this file except in compliance with the License.
7 * 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, WITHOUT
13 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
14 * License for the specific language governing permissions and limitations under
15 * the License.
16 */
17 package org.apache.hadoop.hbase.io.hfile;
18
19 import java.util.Random;
20
21 import org.apache.hadoop.io.BytesWritable;
22 import org.apache.hadoop.hbase.io.hfile.RandomDistribution.DiscreteRNG;
23
24 /*
25 * <p>
26 * Copied from
27 * <a href="https://issues.apache.org/jira/browse/HADOOP-3315">hadoop-3315 tfile</a>.
28 * Remove after tfile is committed and use the tfile version of this class
29 * instead.</p>
30 */
31 class KeySampler {
32 Random random;
33 int min, max;
34 DiscreteRNG keyLenRNG;
35 private static final int MIN_KEY_LEN = 4;
36
37 public KeySampler(Random random, byte [] first, byte [] last,
38 DiscreteRNG keyLenRNG) {
39 this.random = random;
40 min = keyPrefixToInt(first);
41 max = keyPrefixToInt(last);
42 this.keyLenRNG = keyLenRNG;
43 }
44
45 private int keyPrefixToInt(byte [] key) {
46 byte[] b = key;
47 int o = 0;
48 return (b[o] & 0xff) << 24 | (b[o + 1] & 0xff) << 16
49 | (b[o + 2] & 0xff) << 8 | (b[o + 3] & 0xff);
50 }
51
52 public void next(BytesWritable key) {
53 key.setSize(Math.max(MIN_KEY_LEN, keyLenRNG.nextInt()));
54 random.nextBytes(key.get());
55 int n = random.nextInt(max - min) + min;
56 byte[] b = key.get();
57 b[0] = (byte) (n >> 24);
58 b[1] = (byte) (n >> 16);
59 b[2] = (byte) (n >> 8);
60 b[3] = (byte) n;
61 }
62 }