Snowflake

Snowflake.php

<?php


define('EPOCH', 1414213562373);
define('NUMWORKERBITS', 10);
define('NUMSEQUENCEBITS', 12);
define('MAXWORKERID', (-1 ^ (-1 << NUMWORKERBITS)));
define('MAXSEQUENCE', (-1 ^ (-1 << NUMSEQUENCEBITS)));

class Snowflake
{
	private $_lastTimestamp;
	private $_sequence = 0;
	private $_workerId = 1;
	public function __construct($workerId)
	{
		if (($workerId < 0) || ($workerId > MAXWORKERID)) {
			return null;
		}
		$this->workerId = $workerId;
	}
	public function next()
	{
		$ts = $this->timestamp();
		if ($ts == $this->_lastTimestamp) {
			$this->_sequence = ($this->_sequence + 1) & MAXSEQUENCE;
			if ($this->_sequence == 0) {
				$ts = $this->waitNextMilli($ts);
			}
		} else {
			$this->_sequence = 0;
		}
		if ($ts < $this->_lastTimestamp) {
			return 0;
		}
		$this->_lastTimestamp = $ts;
		return $this->pack();
	}
	private function pack()
	{
		return ($this->_lastTimestamp << (NUMWORKERBITS + NUMSEQUENCEBITS)) | ($this->_workerId << NUMSEQUENCEBITS) | $this->_sequence;
	}
	private function waitNextMilli($ts)
	{
		if ($ts = $this->_lastTimestamp) {
			sleep(0.1);
			$ts = $this->timestamp();
		}
		return $ts;
	}
	private function timestamp()
	{
		return $this->millitime() - EPOCH;
	}
	private function millitime()
	{
		$microtime = microtime();
		$comps = explode(' ', $microtime);
		// Note: Using a string here to prevent loss of precision
		// in case of "overflow" (PHP converts it to a double)
		return sprintf('%d%03d', $comps[1], $comps[0] * 1000);
	}
}

$snowflake = new Snowflake(1);

$a = $snowflake->next();
usleep(rand(1000, 6000));
$b = $snowflake->next();
usleep(rand(1000, 6000));
$c = $snowflake->next();