add SnowflakeIdWorker

Author: 15045120

src/main/java/com/github/myibu/algorithm/id/SnowflakeIdWorker.java

@@ -0,0 +1,87 @@
+package com.github.myibu.algorithm.id;
+
+/**
+ * Twitter Snowflake
+ * see <a href="https://github.com/twitter-archive/snowflake/blob/scala_28/src/main/scala/com/twitter/service/snowflake/IdWorker.scala">snowflake's IdWorker</a>
+ * @author myibu
+ * Created on 2022/10/12
+ */
+public class SnowflakeIdWorker {
+    private final static long twepoch = 1598598185157L;
+
+    private long sequence = 0L;
+    private final static long workerIdBits = 5L;
+    private final static long datacenterIdBits = 5L;
+    private final static long maxWorkerId = -1L ^ (-1L << workerIdBits);
+    private final static long maxDatacenterId = -1L ^ (-1L << datacenterIdBits);
+    private final static long sequenceBits = 12L;
+
+    private final static long workerIdShift = sequenceBits;
+    private final static long datacenterIdShift = sequenceBits + workerIdBits;
+    private final static long timestampLeftShift = sequenceBits + workerIdBits + datacenterIdBits;
+    private final static long sequenceMask = -1L ^ (-1L << sequenceBits);
+
+    private long lastTimestamp = -1L;
+
+    private final long workerId;
+    private final long datacenterId;
+
+    public SnowflakeIdWorker(long workerId, long datacenterId) {
+        if (workerId > maxWorkerId || workerId < 0) {
+            throw new IllegalArgumentException(String.format("worker Id can't be greater than %d or less than 0", maxWorkerId));
+        }
+        if (datacenterId > maxDatacenterId || datacenterId < 0) {
+            throw new IllegalArgumentException(String.format("datacenter Id can't be greater than %d or less than 0", maxDatacenterId));
+        }
+        this.workerId = workerId;
+        this.datacenterId = datacenterId;
+    }
+
+    public long getWorkerId() {
+        return workerId;
+    }
+
+    public long getDatacenterId() {
+        return datacenterId;
+    }
+
+    public long getTimestamp() {
+        return System.currentTimeMillis();
+    }
+
+    public synchronized long nextId() {
+        long timestamp = timeGen();
+
+        if (lastTimestamp == timestamp) {
+            sequence = (sequence + 1) & sequenceMask;
+            if (sequence == 0) {
+                timestamp = tilNextMillis(lastTimestamp);
+            }
+        } else {
+            sequence = 0L;
+        }
+
+        if (timestamp < lastTimestamp) {
+            throw new RuntimeException(String.format("Clock moved backwards.  Refusing to generate id for %d milliseconds", lastTimestamp - timestamp));
+        }
+
+        lastTimestamp = timestamp;
+
+        return ((timestamp - twepoch) << timestampLeftShift)
+                | (datacenterId << datacenterIdShift)
+                | (workerId << workerIdShift)
+                | sequence;
+    }
+
+    protected long tilNextMillis(long lastTimestamp) {
+        long timestamp = timeGen();
+        while (timestamp <= lastTimestamp) {
+            timestamp = timeGen();
+        }
+        return timestamp;
+    }
+
+    protected long timeGen() {
+        return System.currentTimeMillis();
+    }
+}

src/test/java/com/github/myibu/algorithm/AlgorithmTest.java

@@ -9,6 +9,7 @@
 import com.github.myibu.algorithm.hash.MurmurHash2;
 import com.github.myibu.algorithm.hash.SHA256;
 import com.github.myibu.algorithm.hash.SipHash;
+import com.github.myibu.algorithm.id.SnowflakeIdWorker;
 import com.github.myibu.algorithm.random.LinearCongruentialRandom;
 import com.github.myibu.algorithm.random.MersenneTwisterRandom;
 import com.github.myibu.algorithm.random.Random;
@@ -379,4 +380,13 @@ public void testBitsEncoder() {
         Assert.assertEquals(-2, Bits.Decoder.decodeZigzagValue(3));
         Assert.assertEquals(-1, Bits.Decoder.decodeZigzagValue(1));
     }
+
+    @Test
+    public void testSnowflakeIdWorker() {
+        SnowflakeIdWorker idWorker = new SnowflakeIdWorker(0, 0);
+        for (int i = 0; i < 1000; i++) {
+            long id = idWorker.nextId();
+            System.out.println(id);
+        }
+    }
 }