81 lines
2.0 KiB
PHP
81 lines
2.0 KiB
PHP
<?php
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namespace extend\util;
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use Exception;
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class Snowflake
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{
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// 起始的时间戳
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const START_EPOCH = 1609459200000; // 2021-01-01 00:00:00
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// 各部分所占位数
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const SEQUENCE_BITS = 12;
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const MACHINE_ID_BITS = 0;
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const DATA_CENTER_ID_BITS = 0;
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// 最大值
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const MAX_SEQUENCE = 4095;
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const MAX_MACHINE_ID = 31;
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const MAX_DATA_CENTER_ID = 31;
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private $data_center_id;
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private $machine_id;
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private $last_timestamp;
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private $sequence;
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public function __construct($data_center_id, $machine_id)
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{
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$this->last_timestamp = 0;
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$this->sequence = 0;
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}
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/**
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* @throws Exception
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*/
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public function generateId()
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{
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$timestamp = $this->getTimestamp();
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// 当前时间小于上一次生成时间，发生时钟回拨
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if ($timestamp < $this->last_timestamp) {
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throw new Exception('Clock moved backwards.');
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}
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// 当前时间与上一次生成时间相同
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if ($timestamp == $this->last_timestamp) {
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$this->sequence = ($this->sequence + 1) & self::MAX_SEQUENCE;
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// 当前毫秒的序列已经达到最大值，等待下一毫秒
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if ($this->sequence == 0) {
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$timestamp = $this->nextMillis($this->last_timestamp);
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}
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} else {
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// 新的一毫秒，序列从0开始
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$this->sequence = 0;
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}
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$this->last_timestamp = $timestamp;
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return (($timestamp - self::START_EPOCH) << (self::SEQUENCE_BITS))
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// | ($this->data_center_id << (self::SEQUENCE_BITS + self::MACHINE_ID_BITS))
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// | ($this->machine_id << self::SEQUENCE_BITS)
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| $this->sequence;
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}
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private function getTimestamp()
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{
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return floor(microtime(true) * 1000);
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}
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private function nextMillis($last_timestamp)
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{
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$timestamp = $this->getTimestamp();
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while ($timestamp <= $last_timestamp) {
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$timestamp = $this->getTimestamp();
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}
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return $timestamp;
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}
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} |