用PHP捣鼓一个雪花算法

概述用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

<?PHPclass 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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