\framework\components\uniqueidUniqueId

<?php
namespace framework\components\uniqueid;
use framework\base\Component;

class UniqueId extends Component
{
    //开始时间,固定一个小于当前时间的毫秒数即可  
    const twepoch =  1474992000000;//2016/9/28 0:0:0  

    //机器标识占的位数  
    const workerIdBits = 10;

    //毫秒内自增数点的位数  
    const sequenceBits = 12;

    protected $workId = 0;

    protected $lastTimestamp = -1;
    protected $sequence = 0;

    protected function init()
    {
        if(SYSTEM_WORK_ID< 0){
            $this->triggerThrowable(new \Exception("workerId can't be  less than 0", 500));
        }
        //赋值
        $this->workId = SYSTEM_WORK_ID;
    }

    //生成一个ID
    public function nextId()
    {
        $timestamp = $this->timeGen();
        $lastTimestamp = $this->lastTimestamp;
        //判断时钟是否正常
        if ($timestamp < $lastTimestamp) {
            $time = $lastTimestamp - $timestamp;
            $this->triggerThrowable(new \Exception("Clock moved backwards.  Refusing to generate id for $time milliseconds", 500));
        }
        //生成唯一序列
        if ($lastTimestamp == $timestamp) {
            $sequenceMask = -1 ^ (-1 << self::sequenceBits);
            $this->sequence = ($this->sequence + 1) & $sequenceMask;
            if ($this->sequence == 0) {
                $timestamp = $this->tilNextMillis($lastTimestamp);
            }
        } else {
            $this->sequence = 0;
        }
        $this->lastTimestamp = $timestamp;
        //
        //时间毫秒/数据中心ID/机器ID,要左移的位数
        $timestampLeftShift = self::sequenceBits + self::workerIdBits;
        $workerIdShift = self::sequenceBits;
        //组合3段数据返回: 时间戳.工作机器.序列
        $nextId = (($timestamp - self::twepoch) << $timestampLeftShift) | ($this->workId << $workerIdShift) | $this->sequence;
        return $nextId;
    }

    //取当前时间毫秒  
    protected function timeGen()
    {
        $timestramp = (float)\sprintf("%.0f", \microtime(true) * 1000);
        return  $timestramp;
    }

    //取下一毫秒  
    protected function tilNextMillis($lastTimestamp)
    {
        $timestamp = $this->timeGen();
        while ($timestamp <= $lastTimestamp) {
            $timestamp = $this->timeGen();
        }
        return $timestamp;
    }
}