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<pre><span class="sourceLineNo">001</span>/*<a name="line.1"></a>
<span class="sourceLineNo">002</span> * Licensed to the Apache Software Foundation (ASF) under one<a name="line.2"></a>
<span class="sourceLineNo">003</span> * or more contributor license agreements. See the NOTICE file<a name="line.3"></a>
<span class="sourceLineNo">004</span> * distributed with this work for additional information<a name="line.4"></a>
<span class="sourceLineNo">005</span> * regarding copyright ownership. The ASF licenses this file<a name="line.5"></a>
<span class="sourceLineNo">006</span> * to you under the Apache License, Version 2.0 (the<a name="line.6"></a>
<span class="sourceLineNo">007</span> * "License"); you may not use this file except in compliance<a name="line.7"></a>
<span class="sourceLineNo">008</span> * with the License. You may obtain a copy of the License at<a name="line.8"></a>
<span class="sourceLineNo">009</span> *<a name="line.9"></a>
<span class="sourceLineNo">010</span> * http://www.apache.org/licenses/LICENSE-2.0<a name="line.10"></a>
<span class="sourceLineNo">011</span> *<a name="line.11"></a>
<span class="sourceLineNo">012</span> * Unless required by applicable law or agreed to in writing, software<a name="line.12"></a>
<span class="sourceLineNo">013</span> * distributed under the License is distributed on an "AS IS" BASIS,<a name="line.13"></a>
<span class="sourceLineNo">014</span> * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.<a name="line.14"></a>
<span class="sourceLineNo">015</span> * See the License for the specific language governing permissions and<a name="line.15"></a>
<span class="sourceLineNo">016</span> * limitations under the License.<a name="line.16"></a>
<span class="sourceLineNo">017</span> */<a name="line.17"></a>
<span class="sourceLineNo">018</span>package org.apache.hadoop.hbase.util;<a name="line.18"></a>
<span class="sourceLineNo">019</span><a name="line.19"></a>
<span class="sourceLineNo">020</span>import java.util.HashSet;<a name="line.20"></a>
<span class="sourceLineNo">021</span>import java.util.Random;<a name="line.21"></a>
<span class="sourceLineNo">022</span>import java.util.Set;<a name="line.22"></a>
<span class="sourceLineNo">023</span>import java.util.concurrent.atomic.AtomicLong;<a name="line.23"></a>
<span class="sourceLineNo">024</span>import org.apache.yetus.audience.InterfaceAudience;<a name="line.24"></a>
<span class="sourceLineNo">025</span><a name="line.25"></a>
<span class="sourceLineNo">026</span>import org.apache.hbase.thirdparty.com.google.common.base.Preconditions;<a name="line.26"></a>
<span class="sourceLineNo">027</span><a name="line.27"></a>
<span class="sourceLineNo">028</span>/**<a name="line.28"></a>
<span class="sourceLineNo">029</span> * An instance of this class is used to generate a stream of pseudorandom numbers. The class uses a<a name="line.29"></a>
<span class="sourceLineNo">030</span> * 64-bit seed, which is modified using a linear congruential formula. see<a name="line.30"></a>
<span class="sourceLineNo">031</span> * https://en.wikipedia.org/wiki/Linear_congruential_generator<a name="line.31"></a>
<span class="sourceLineNo">032</span> */<a name="line.32"></a>
<span class="sourceLineNo">033</span>@InterfaceAudience.Private<a name="line.33"></a>
<span class="sourceLineNo">034</span>public class Random64 {<a name="line.34"></a>
<span class="sourceLineNo">035</span><a name="line.35"></a>
<span class="sourceLineNo">036</span> private static final long multiplier = 6364136223846793005L;<a name="line.36"></a>
<span class="sourceLineNo">037</span> private static final long addend = 1442695040888963407L;<a name="line.37"></a>
<span class="sourceLineNo">038</span><a name="line.38"></a>
<span class="sourceLineNo">039</span> private static final AtomicLong seedUniquifier = new AtomicLong(8682522807148012L);<a name="line.39"></a>
<span class="sourceLineNo">040</span><a name="line.40"></a>
<span class="sourceLineNo">041</span> private long seed;<a name="line.41"></a>
<span class="sourceLineNo">042</span><a name="line.42"></a>
<span class="sourceLineNo">043</span> /**<a name="line.43"></a>
<span class="sourceLineNo">044</span> * Copy from {@link Random#seedUniquifier()}<a name="line.44"></a>
<span class="sourceLineNo">045</span> */<a name="line.45"></a>
<span class="sourceLineNo">046</span> private static long seedUniquifier() {<a name="line.46"></a>
<span class="sourceLineNo">047</span> for (;;) {<a name="line.47"></a>
<span class="sourceLineNo">048</span> long current = seedUniquifier.get();<a name="line.48"></a>
<span class="sourceLineNo">049</span> long next = current * 181783497276652981L;<a name="line.49"></a>
<span class="sourceLineNo">050</span> if (seedUniquifier.compareAndSet(current, next)) {<a name="line.50"></a>
<span class="sourceLineNo">051</span> return next;<a name="line.51"></a>
<span class="sourceLineNo">052</span> }<a name="line.52"></a>
<span class="sourceLineNo">053</span> }<a name="line.53"></a>
<span class="sourceLineNo">054</span> }<a name="line.54"></a>
<span class="sourceLineNo">055</span><a name="line.55"></a>
<span class="sourceLineNo">056</span> public Random64() {<a name="line.56"></a>
<span class="sourceLineNo">057</span> this(seedUniquifier() ^ System.nanoTime());<a name="line.57"></a>
<span class="sourceLineNo">058</span> }<a name="line.58"></a>
<span class="sourceLineNo">059</span><a name="line.59"></a>
<span class="sourceLineNo">060</span> public Random64(long seed) {<a name="line.60"></a>
<span class="sourceLineNo">061</span> this.seed = seed;<a name="line.61"></a>
<span class="sourceLineNo">062</span> }<a name="line.62"></a>
<span class="sourceLineNo">063</span><a name="line.63"></a>
<span class="sourceLineNo">064</span> public long nextLong() {<a name="line.64"></a>
<span class="sourceLineNo">065</span> return next64(64);<a name="line.65"></a>
<span class="sourceLineNo">066</span> }<a name="line.66"></a>
<span class="sourceLineNo">067</span><a name="line.67"></a>
<span class="sourceLineNo">068</span> public void nextBytes(byte[] bytes) {<a name="line.68"></a>
<span class="sourceLineNo">069</span> for (int i = 0, len = bytes.length; i &lt; len;) {<a name="line.69"></a>
<span class="sourceLineNo">070</span> // We regard seed as unsigned long, therefore used '&gt;&gt;&gt;' instead of '&gt;&gt;'.<a name="line.70"></a>
<span class="sourceLineNo">071</span> for (long rnd = nextLong(), n = Math.min(len - i, Long.SIZE / Byte.SIZE); n-- &gt; 0; rnd &gt;&gt;&gt;=<a name="line.71"></a>
<span class="sourceLineNo">072</span> Byte.SIZE) {<a name="line.72"></a>
<span class="sourceLineNo">073</span> bytes[i++] = (byte) rnd;<a name="line.73"></a>
<span class="sourceLineNo">074</span> }<a name="line.74"></a>
<span class="sourceLineNo">075</span> }<a name="line.75"></a>
<span class="sourceLineNo">076</span> }<a name="line.76"></a>
<span class="sourceLineNo">077</span><a name="line.77"></a>
<span class="sourceLineNo">078</span> private long next64(int bits) {<a name="line.78"></a>
<span class="sourceLineNo">079</span> seed = seed * multiplier + addend;<a name="line.79"></a>
<span class="sourceLineNo">080</span> return seed &gt;&gt;&gt; (64 - bits);<a name="line.80"></a>
<span class="sourceLineNo">081</span> }<a name="line.81"></a>
<span class="sourceLineNo">082</span><a name="line.82"></a>
<span class="sourceLineNo">083</span> /**<a name="line.83"></a>
<span class="sourceLineNo">084</span> * Random64 is a pseudorandom algorithm(LCG). Therefore, we will get same sequence if seeds are<a name="line.84"></a>
<span class="sourceLineNo">085</span> * the same. This main will test how many calls nextLong() it will get the same seed. We do not<a name="line.85"></a>
<span class="sourceLineNo">086</span> * need to save all numbers (that is too large). We could save once every 100000 calls nextLong().<a name="line.86"></a>
<span class="sourceLineNo">087</span> * If it get a same seed, we can detect this by calling nextLong() 100000 times continuously.<a name="line.87"></a>
<span class="sourceLineNo">088</span> */<a name="line.88"></a>
<span class="sourceLineNo">089</span> public static void main(String[] args) {<a name="line.89"></a>
<span class="sourceLineNo">090</span> long defaultTotalTestCnt = 1000000000000L; // 1 trillion<a name="line.90"></a>
<span class="sourceLineNo">091</span><a name="line.91"></a>
<span class="sourceLineNo">092</span> if (args.length == 1) {<a name="line.92"></a>
<span class="sourceLineNo">093</span> defaultTotalTestCnt = Long.parseLong(args[0]);<a name="line.93"></a>
<span class="sourceLineNo">094</span> }<a name="line.94"></a>
<span class="sourceLineNo">095</span><a name="line.95"></a>
<span class="sourceLineNo">096</span> Preconditions.checkArgument(defaultTotalTestCnt &gt; 0, "totalTestCnt &lt;= 0");<a name="line.96"></a>
<span class="sourceLineNo">097</span><a name="line.97"></a>
<span class="sourceLineNo">098</span> final int precision = 100000;<a name="line.98"></a>
<span class="sourceLineNo">099</span> final long totalTestCnt = defaultTotalTestCnt + precision;<a name="line.99"></a>
<span class="sourceLineNo">100</span> final int reportPeriod = 100 * precision;<a name="line.100"></a>
<span class="sourceLineNo">101</span> final long startTime = EnvironmentEdgeManager.currentTime();<a name="line.101"></a>
<span class="sourceLineNo">102</span><a name="line.102"></a>
<span class="sourceLineNo">103</span> System.out.println("Do collision test, totalTestCnt=" + totalTestCnt);<a name="line.103"></a>
<span class="sourceLineNo">104</span><a name="line.104"></a>
<span class="sourceLineNo">105</span> Random64 rand = new Random64();<a name="line.105"></a>
<span class="sourceLineNo">106</span> Set&lt;Long&gt; longSet = new HashSet&lt;&gt;();<a name="line.106"></a>
<span class="sourceLineNo">107</span><a name="line.107"></a>
<span class="sourceLineNo">108</span> for (long cnt = 1; cnt &lt;= totalTestCnt; cnt++) {<a name="line.108"></a>
<span class="sourceLineNo">109</span> final long randLong = rand.nextLong();<a name="line.109"></a>
<span class="sourceLineNo">110</span><a name="line.110"></a>
<span class="sourceLineNo">111</span> if (longSet.contains(randLong)) {<a name="line.111"></a>
<span class="sourceLineNo">112</span> System.err.println("Conflict! count=" + cnt);<a name="line.112"></a>
<span class="sourceLineNo">113</span> System.exit(1);<a name="line.113"></a>
<span class="sourceLineNo">114</span> }<a name="line.114"></a>
<span class="sourceLineNo">115</span><a name="line.115"></a>
<span class="sourceLineNo">116</span> if (cnt % precision == 0) {<a name="line.116"></a>
<span class="sourceLineNo">117</span> if (!longSet.add(randLong)) {<a name="line.117"></a>
<span class="sourceLineNo">118</span> System.err.println("Conflict! count=" + cnt);<a name="line.118"></a>
<span class="sourceLineNo">119</span> System.exit(1);<a name="line.119"></a>
<span class="sourceLineNo">120</span> }<a name="line.120"></a>
<span class="sourceLineNo">121</span><a name="line.121"></a>
<span class="sourceLineNo">122</span> if (cnt % reportPeriod == 0) {<a name="line.122"></a>
<span class="sourceLineNo">123</span> long cost = EnvironmentEdgeManager.currentTime() - startTime;<a name="line.123"></a>
<span class="sourceLineNo">124</span> long remainingMs = (long) (1.0 * (totalTestCnt - cnt) * cost / cnt);<a name="line.124"></a>
<span class="sourceLineNo">125</span> System.out.println(String.format("Progress: %.3f%%, remaining %d minutes",<a name="line.125"></a>
<span class="sourceLineNo">126</span> 100.0 * cnt / totalTestCnt, remainingMs / 60000));<a name="line.126"></a>
<span class="sourceLineNo">127</span> }<a name="line.127"></a>
<span class="sourceLineNo">128</span> }<a name="line.128"></a>
<span class="sourceLineNo">129</span><a name="line.129"></a>
<span class="sourceLineNo">130</span> }<a name="line.130"></a>
<span class="sourceLineNo">131</span><a name="line.131"></a>
<span class="sourceLineNo">132</span> System.out.println("No collision!");<a name="line.132"></a>
<span class="sourceLineNo">133</span> }<a name="line.133"></a>
<span class="sourceLineNo">134</span><a name="line.134"></a>
<span class="sourceLineNo">135</span>}<a name="line.135"></a>
</pre>
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