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extend/util/Snowflake.php

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