C#版本

/// <summary>/// 根據(jù)twitter的snowflake算法生成唯一ID/// snowflake算法 64 位/// 0---0000000000 0000000000 0000000000 0000000000 0 --- 00000 ---00000 ---000000000000/// 第一位為未使用(實(shí)際上也可作為long的符號位)，接下來的41位為毫秒級時(shí)間，然后5位datacenter標(biāo)識位，5位機(jī)器ID(并不算標(biāo)識符，實(shí)際是為線程標(biāo)識)，然后12位該毫秒內(nèi)的當(dāng)前毫秒內(nèi)的計(jì)數(shù)，加起來剛好64位，為一個Long型。/// 其中datacenter標(biāo)識位起始是機(jī)器位，機(jī)器ID其實(shí)是線程標(biāo)識，可以同一一個10位來表示不同機(jī)器/// </summary>public class IdWorker{//機(jī)器IDprivate static long workerId = 1;private static long twepoch = 687888001020L; //唯一時(shí)間，這是一個避免重復(fù)的隨機(jī)量，自行設(shè)定不要大于當(dāng)前時(shí)間戳private static long sequence = 0L;private static int workerIdBits = 4; //機(jī)器碼字節(jié)數(shù)。4個字節(jié)用來保存機(jī)器碼public static long maxWorkerId = -1L ^ -1L << workerIdBits; //最大機(jī)器IDprivate static int sequenceBits = 10; //計(jì)數(shù)器字節(jié)數(shù)，10個字節(jié)用來保存計(jì)數(shù)碼private static int workerIdShift = sequenceBits; //機(jī)器碼數(shù)據(jù)左移位數(shù)，就是后面計(jì)數(shù)器占用的位數(shù)private static int timestampLeftShift = sequenceBits + workerIdBits; //時(shí)間戳左移動位數(shù)就是機(jī)器碼和計(jì)數(shù)器總字節(jié)數(shù)public static long sequenceMask = -1L ^ -1L << sequenceBits; //一微秒內(nèi)可以產(chǎn)生計(jì)數(shù)，如果達(dá)到該值則等到下一微妙在進(jìn)行生成private long lastTimestamp = -1L;public long nextId(){lock (this){long timestamp = timeGen();if (this.lastTimestamp == timestamp){ //同一微妙中生成IDIdWorker.sequence = (IdWorker.sequence + 1) & IdWorker.sequenceMask; //用&運(yùn)算計(jì)算該微秒內(nèi)產(chǎn)生的計(jì)數(shù)是否已經(jīng)到達(dá)上限if (IdWorker.sequence == 0){//一微妙內(nèi)產(chǎn)生的ID計(jì)數(shù)已達(dá)上限，等待下一微妙timestamp = tillNextMillis(this.lastTimestamp);}}else{ //不同微秒生成IDIdWorker.sequence = 0; //計(jì)數(shù)清0}if (timestamp < lastTimestamp){ //如果當(dāng)前時(shí)間戳比上一次生成ID時(shí)時(shí)間戳還小，拋出異常，因?yàn)椴荒鼙ＷC現(xiàn)在生成的ID之前沒有生成過throw new Exception(string.Format("Clock moved backwards. Refusing to generate id for {0} milliseconds",this.lastTimestamp - timestamp));}this.lastTimestamp = timestamp; //把當(dāng)前時(shí)間戳保存為最后生成ID的時(shí)間戳long nextId = (timestamp - twepoch << timestampLeftShift) | IdWorker.workerId << IdWorker.workerIdShift | IdWorker.sequence;return nextId;}}/// <summary>/// 獲取下一微秒時(shí)間戳/// </summary>/// <param name="lastTimestamp"></param>/// <returns></returns>private long tillNextMillis(long lastTimestamp){long timestamp = timeGen();while (timestamp <= lastTimestamp){timestamp = timeGen();}return timestamp;}/// <summary>/// 生成當(dāng)前時(shí)間戳/// </summary>/// <returns></returns>private long timeGen(){return (long)(DateTime.UtcNow - new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc)).TotalMilliseconds;}}

JAVA版本

import org.slf4j.Logger; import org.slf4j.LoggerFactory; import org.springframework.stereotype.Component;public class IdWorker {protected static final Logger LOG = LoggerFactory.getLogger(IdWorker.class);private long workerId;private long datacenterId;private long sequence = 0L;private long twepoch = 1288834974657L;private long workerIdBits = 5L;private long datacenterIdBits = 5L;private long maxWorkerId = -1L ^ (-1L << workerIdBits);private long maxDatacenterId = -1L ^ (-1L << datacenterIdBits);private long sequenceBits = 12L;private long workerIdShift = sequenceBits;private long datacenterIdShift = sequenceBits + workerIdBits;private long timestampLeftShift = sequenceBits + workerIdBits + datacenterIdBits;private long sequenceMask = -1L ^ (-1L << sequenceBits);private long lastTimestamp = -1L;public IdWorker(long workerId, long datacenterId) {// sanity check for workerIdif (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;LOG.info(String.format("worker starting. timestamp left shift %d, datacenter id bits %d, worker id bits %d, sequence bits %d, workerid %d", timestampLeftShift, datacenterIdBits, workerIdBits, sequenceBits, workerId));}public synchronized long nextId() {long timestamp = timeGen();if (timestamp < lastTimestamp) {LOG.error(String.format("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));}if (lastTimestamp == timestamp) {sequence = (sequence + 1) & sequenceMask;if (sequence == 0) {timestamp = tilNextMillis(lastTimestamp);}} else {sequence = 0L;}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();}}

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