From 7a2544b5ca0946ca192c7d177c5826da4d21facd Mon Sep 17 00:00:00 2001
From: niushuai233 <niushuai951101@gmail.com>
Date: Mon, 24 Oct 2022 15:54:49 +0800
Subject: [PATCH] =?UTF-8?q?feat:=20=E6=96=B0=E5=A2=9Eidworker=E9=9B=AA?=
 =?UTF-8?q?=E8=8A=B1=E7=AE=97=E6=B3=95=E5=AE=9E=E7=8E=B0?=
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---
 .../devcontrol/base/util/IdWorker.java        | 132 ++++++++++++++++++
 1 file changed, 132 insertions(+)
 create mode 100644 app/src/main/java/cc/niushuai/project/devcontrol/base/util/IdWorker.java

diff --git a/app/src/main/java/cc/niushuai/project/devcontrol/base/util/IdWorker.java b/app/src/main/java/cc/niushuai/project/devcontrol/base/util/IdWorker.java
new file mode 100644
index 0000000..ef1c375
--- /dev/null
+++ b/app/src/main/java/cc/niushuai/project/devcontrol/base/util/IdWorker.java
@@ -0,0 +1,132 @@
+package cc.niushuai.project.devcontrol.base.util;
+
+public class IdWorker {
+
+    private static final IdWorker INSTANCE = new IdWorker(1, 1, 1);
+
+    //下面两个每个5位，加起来就是10位的工作机器id
+    private long workerId;    //工作id
+    private long datacenterId;   //数据id
+    //12位的序列号
+    private long sequence;
+
+    public IdWorker(long workerId, long datacenterId, long sequence) {
+        // sanity check for workerId
+        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));
+        }
+        System.out.printf("worker starting. timestamp left shift %d, datacenter id bits %d, worker id bits %d, sequence bits %d, workerid %d",
+                timestampLeftShift, datacenterIdBits, workerIdBits, sequenceBits, workerId);
+
+        this.workerId = workerId;
+        this.datacenterId = datacenterId;
+        this.sequence = sequence;
+    }
+
+    //初始时间戳
+    private long twepoch = 1288834974657L;
+
+    //长度为5位
+    private long workerIdBits = 5L;
+    private long datacenterIdBits = 5L;
+    //最大值
+    private long maxWorkerId = -1L ^ (-1L << workerIdBits);
+    private long maxDatacenterId = -1L ^ (-1L << datacenterIdBits);
+    //序列号id长度
+    private long sequenceBits = 12L;
+    //序列号最大值
+    private long sequenceMask = -1L ^ (-1L << sequenceBits);
+
+    //工作id需要左移的位数，12位
+    private long workerIdShift = sequenceBits;
+    //数据id需要左移位数 12+5=17位
+    private long datacenterIdShift = sequenceBits + workerIdBits;
+    //时间戳需要左移位数 12+5+5=22位
+    private long timestampLeftShift = sequenceBits + workerIdBits + datacenterIdBits;
+
+    //上次时间戳，初始值为负数
+    private long lastTimestamp = -1L;
+
+    public long getWorkerId() {
+        return workerId;
+    }
+
+    public long getDatacenterId() {
+        return datacenterId;
+    }
+
+    public long getTimestamp() {
+        return System.currentTimeMillis();
+    }
+
+    //下一个ID生成算法
+    public synchronized long nextId() {
+        long timestamp = timeGen();
+
+        //获取当前时间戳如果小于上次时间戳，则表示时间戳获取出现异常
+        if (timestamp < lastTimestamp) {
+            System.err.printf("clock is moving backwards.  Rejecting requests until %d.", lastTimestamp);
+            throw new RuntimeException(String.format("Clock moved backwards.  Refusing to generate id for %d milliseconds",
+                    lastTimestamp - timestamp));
+        }
+
+        //获取当前时间戳如果等于上次时间戳（同一毫秒内），则在序列号加一；否则序列号赋值为0，从0开始。
+        if (lastTimestamp == timestamp) {
+            sequence = (sequence + 1) & sequenceMask;
+            if (sequence == 0) {
+                timestamp = tilNextMillis(lastTimestamp);
+            }
+        } else {
+            sequence = 0;
+        }
+
+        //将上次时间戳值刷新
+        lastTimestamp = timestamp;
+
+        /**
+         * 返回结果：
+         * (timestamp - twepoch) << timestampLeftShift) 表示将时间戳减去初始时间戳，再左移相应位数
+         * (datacenterId << datacenterIdShift) 表示将数据id左移相应位数
+         * (workerId << workerIdShift) 表示将工作id左移相应位数
+         * | 是按位或运算符，例如：x | y，只有当x，y都为0的时候结果才为0，其它情况结果都为1。
+         * 因为个部分只有相应位上的值有意义，其它位上都是0，所以将各部分的值进行 | 运算就能得到最终拼接好的id
+         */
+        return ((timestamp - twepoch) << timestampLeftShift) |
+                (datacenterId << datacenterIdShift) |
+                (workerId << workerIdShift) |
+                sequence;
+    }
+
+    //获取时间戳，并与上次时间戳比较
+    private long tilNextMillis(long lastTimestamp) {
+        long timestamp = timeGen();
+        while (timestamp <= lastTimestamp) {
+            timestamp = timeGen();
+        }
+        return timestamp;
+    }
+
+    //获取系统时间戳
+    private long timeGen() {
+        return System.currentTimeMillis();
+    }
+
+    //---------------测试---------------
+    public static void main(String[] args) {
+        IdWorker worker = new IdWorker(1, 1, 1);
+        for (int i = 0; i < 30; i++) {
+            System.out.println(worker.nextId());
+        }
+    }
+
+    public static long getNextId() {
+        return INSTANCE.nextId();
+    }
+
+    public static String getNextIdStr() {
+        return getNextId() + "";
+    }
+}
\ No newline at end of file