如何用PHP实现雪花算法，代码怎样写呢

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);

    }

}
    
?>