package com.wms_admin.utils;
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import java.util.Date;
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import java.util.UUID;
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public class IdGenerator {
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private static IdGenerator instance = new IdGenerator(0);
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public static IdGenerator initDefaultInstance(int machineId) {
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instance = new IdGenerator(machineId);
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return instance;
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}
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public static IdGenerator getInstance() {
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return instance;
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}
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public static long generateId() {
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return instance.nextId();
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}
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// total bits=53(max 2^53-1：9007199254740992-1)
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// private final static long TIME_BIT = 40; // max: 2318-06-04
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private final static long MACHINE_BIT = 5; // max 31
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private final static long SEQUENCE_BIT = 8; // 256/10ms
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/**
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* mask/max value
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*/
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private final static long MAX_MACHINE_NUM = -1L ^ (-1L << MACHINE_BIT);
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private final static long MAX_SEQUENCE = -1L ^ (-1L << SEQUENCE_BIT);
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private final static long MACHINE_LEFT = SEQUENCE_BIT;
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private final static long TIMESTMP_LEFT = MACHINE_BIT + SEQUENCE_BIT;
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private long machineId;
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private long sequence = 0L;
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private long lastStmp = -1L;
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private IdGenerator(long machineId) {
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if (machineId > MAX_MACHINE_NUM || machineId < 0) {
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throw new IllegalArgumentException(
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"machineId can't be greater than " + MAX_MACHINE_NUM + " or less than 0");
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}
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this.machineId = machineId;
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}
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/**
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* generate new ID
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*
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* @return
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*/
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public synchronized long nextId() {
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long currStmp = getTimestamp();
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if (currStmp < lastStmp) {
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throw new RuntimeException("Clock moved backwards. Refusing to generate id");
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}
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if (currStmp == lastStmp) {
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sequence = (sequence + 1) & MAX_SEQUENCE;
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if (sequence == 0L) {
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currStmp = getNextTimestamp();
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}
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} else {
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sequence = 0L;
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}
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lastStmp = currStmp;
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return currStmp << TIMESTMP_LEFT //
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| machineId << MACHINE_LEFT //
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| sequence;
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}
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private long getNextTimestamp() {
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long mill = getTimestamp();
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while (mill <= lastStmp) {
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mill = getTimestamp();
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}
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return mill;
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}
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private long getTimestamp() {
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// per 10ms
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return System.currentTimeMillis() / 10;// 10ms
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}
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public static Date parseIdTimestamp(long id) {
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return new Date((id >>> TIMESTMP_LEFT) * 10);
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}
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public static String uuid() {
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return UUID.randomUUID().toString().replaceAll("-", "");
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}
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}
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