<?php class SnowFlake { const TWEPOCH = 1288834974657; //
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 nextId() { $timestamp =
$this->timeGen(); if ($timestamp < $this->lastTimestamp) { $diffTimestamp =
bcsub($this->lastTimestamp, $timestamp); throw new Exception("Clock moved
backwards. Refusing to generate id for {$diffTimestamp} milliseconds"); } if
($this->lastTimestamp == $timestamp) { $this->sequence = ($this->sequence + 1)
& $this->sequenceMask; if (0 == $this->sequence) { $timestamp =
$this->tilNextMillis($this->lastTimestamp); } } else { $this->sequence = 0; }
$this->lastTimestamp = $timestamp; /*$gmpTimestamp =
gmp_init($this->leftShift(bcsub($timestamp, self::TWEPOCH),
$this->timestampLeftShift)); $gmpDatacenterId =
gmp_init($this->leftShift($this->datacenterId, $this->datacenterIdShift));
$gmpWorkerId = gmp_init($this->leftShift($this->workerId,
$this->workerIdShift)); $gmpSequence = gmp_init($this->sequence); return
gmp_strval(gmp_or(gmp_or(gmp_or($gmpTimestamp, $gmpDatacenterId),
$gmpWorkerId), $gmpSequence));*/ return (($timestamp - self::TWEPOCH) <<
$this->timestampLeftShift) | ($this->datacenterId << $this->datacenterIdShift)
| ($this->workerId << $this->workerIdShift) | $this->sequence; } protected
function tilNextMillis($lastTimestamp) { $timestamp = $this->timeGen(); while
($timestamp <= $lastTimestamp) { $timestamp = $this->timeGen(); } return
$timestamp; } protected function timeGen() { return floor(microtime(true) *
1000); } // 左移 << protected function leftShift($a, $b) { return bcmul($a,
bcpow(2, $b)); } }
 
 

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