/**

* ID 生成策略

* 毫秒级时间41位+机器ID 10位+毫秒内序列12位。

* 0 41 51 64

+-----------+------+------+

|time |pc |inc |

+-----------+------+------+

* 前41bits是以微秒为单位的timestamp。

* 接着10bits是事先配置好的机器ID。

* 最后12bits是累加计数器。

* macheine id(10bits)标明最多只能有1024台机器同时产生ID，sequence number(12bits)也标明1台机器1ms中最多产生4096个ID，

*

* auth: zhouyuan

*/

class idwork

{

const debug = 1;

static $workerId;

static $twepoch = 1361775855078;

static $sequence = 0;

const workerIdBits = 4;

static $maxWorkerId = 15;

const sequenceBits = 10;

static $workerIdShift = 10;

static $timestampLeftShift = 14;

static $sequenceMask = 1023;

private static $lastTimestamp = -1;

function __construct($params){

$workId = $params['workId'];

if($workId > self::$maxWorkerId || $workId< 0 )

{

throw new Exception("worker Id can't be greater than 15 or less than 0");

}

self::$workerId=$workId;

}

function timeGen(){

//获得当前时间戳

$time = explode(' ', microtime());

$time2= substr($time[0], 2, 3);

return $time[1].$time2;

}

function tilNextMillis($lastTimestamp) {

$timestamp = $this->timeGen();

while ($timestamp <= $lastTimestamp) {

$timestamp = $this->timeGen();

}

return $timestamp;

}

function nextId()

{

$timestamp=$this->timeGen();

if(self::$lastTimestamp == $timestamp) {

self::$sequence = (self::$sequence + 1) & self::$sequenceMask;

if (self::$sequence == 0) {

$timestamp = $this->tilNextMillis(self::$lastTimestamp);

}

} else {

self::$sequence = 0;

}

if ($timestamp < self::$lastTimestamp) {

throw new Excwption("Clock moved backwards. Refusing to generate id for ".(self::$lastTimestamp-$timestamp)." milliseconds");

}

self::$lastTimestamp = $timestamp;

$nextId = ((sprintf('%.0f', $timestamp) - sprintf('%.0f', self::$twepoch) )<< self::$timestampLeftShift ) | ( self::$workerId << self::$workerIdShift ) | self::$sequence;

return $nextId;

}

}

?>

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