用PHP捣鼓一个雪花算法

本文给大家聊聊雪花算法的PHP实现，希望对需要的朋友有所帮助！

雪花算法的实现

最近看了下雪花算法，自己试着写了一下

<?php class SnowFlake {     const TWEPOCH = 0; // 时间起始标记点，作为基准，一般取系统的最近时间（一旦确定不能变动）     const WORKER_ID_BITS     = 5; // 机器标识位数     const DATACENTER_ID_BITS = 5; // 数据中心标识位数     const SEQUENCE_BITS      = 12; // 毫秒内自增位     private $workerId; // 工作机器ID     private $datacenterId; // 数据中心ID     private $sequence; // 毫秒内序列     private $maxWorkerId     = -1 ^ (-1 << self::WORKER_ID_BITS); // 机器ID最大值     private $maxDatacenterId = -1 ^ (-1 << self::DATACENTER_ID_BITS); // 数据中心ID最大值     private $workerIdShift      = self::SEQUENCE_BITS; // 机器ID偏左移位数     private $datacenterIdShift  = self::SEQUENCE_BITS + self::WORKER_ID_BITS; // 数据中心ID左移位数     private $timestampLeftShift = self::SEQUENCE_BITS + self::WORKER_ID_BITS + self::DATACENTER_ID_BITS; // 时间毫秒左移位数     private $sequenceMask       = -1 ^ (-1 << self::SEQUENCE_BITS); // 生成序列的掩码     private $lastTimestamp = -1; // 上次生产id时间戳     public function __construct($workerId, $datacenterId, $sequence = 0)     {         if ($workerId > $this->maxWorkerId || $workerId < 0) {             throw new Exception("worker Id can't be greater than {$this->maxWorkerId} or less than 0");         }         if ($datacenterId > $this->maxDatacenterId || $datacenterId < 0) {             throw new Exception("datacenter Id can't be greater than {$this->maxDatacenterId} or less than 0");         }         $this->workerId     = $workerId;         $this->datacenterId = $datacenterId;         $this->sequence     = $sequence;     }     public function createId()     {         $timestamp = $this->createTimestamp();         if ($timestamp < $this->lastTimestamp) {//当产生的时间戳小于上次的生成的时间戳时，报错             $diffTimestamp = bcsub($this->lastTimestamp, $timestamp);             throw new Exception("Clock moved backwards.  Refusing to generate id for {$diffTimestamp} milliseconds");         }         if ($this->lastTimestamp == $timestamp) {//当生成的时间戳等于上次生成的时间戳的时候             $this->sequence = ($this->sequence + 1) & $this->sequenceMask;//序列自增一次             if (0 == $this->sequence) {//当序列为0时，重新生成最新的时间戳                 $timestamp = $this->createNextTimestamp($this->lastTimestamp);             }         } else {//当生成的时间戳不等于上次的生成的时间戳的时候，序列归0             $this->sequence = 0;         }         $this->lastTimestamp = $timestamp;         return (($timestamp - self::TWEPOCH) << $this->timestampLeftShift) |             ($this->datacenterId << $this->datacenterIdShift) |             ($this->workerId << $this->workerIdShift) |             $this->sequence;     }     protected function createNextTimestamp($lastTimestamp) //生成一个大于等于 上次生成的时间戳 的时间戳     {         $timestamp = $this->createTimestamp();         while ($timestamp <= $lastTimestamp) {             $timestamp = $this->createTimestamp();         }         return $timestamp;     }     protected function createTimestamp()//生成毫秒级别的时间戳     {         return floor(microtime(true) * 1000);     } } ?>

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