雪花ID | 订单编号 生成类

<?php

namespace app\extend;
/**
 * 雪花算法分布式ID生成器
 */
class SnowFlake
{
    const EPOCH = 1479533469598; // 自定义纪元起点 (2016-11-20)
    const MAX_MACHINE_ID = 1023; // 10位机器ID最大值
    const MAX_SEQUENCE = 4095;   // 12位序列号最大值
    private static int $machineId = 0;   // 机器ID (0-1023)
    private static int $lastTimestamp = 0; // 上次生成时间戳
    private static int $sequence = 0;    // 序列号

    /**
     * 设置机器ID
     * @param int $mId 0-1023
     */
    public static function setMachineId(int $mId): void
    {
        if ($mId < 0 || $mId > self::MAX_MACHINE_ID) {
            throw new \InvalidArgumentException("机器ID范围0-1023");
        }
        self::$machineId = $mId;
    }

    /**
     * 生成分布式ID (64位长整型字符串)
     * @return string
     */
    public static function generateId(): string
    {
        $timestamp = self::getCurrentTimestamp();
        if ($timestamp < self::$lastTimestamp) {
            throw new \RuntimeException("时钟回退，拒绝生成ID");
        }
        if ($timestamp === self::$lastTimestamp) {
            self::$sequence = (self::$sequence + 1) & self::MAX_SEQUENCE;
            if (self::$sequence === 0) {
                $timestamp = self::waitNextMillis(self::$lastTimestamp);
            }
        } else {
            self::$sequence = 0;
        }
        self::$lastTimestamp = $timestamp;
        // 组合64位二进制 (时间戳42位 + 机器ID10位 + 序列号12位)
        $binary = sprintf(
            "%042b%010b%012b",
            $timestamp - self::EPOCH,
            self::$machineId,
            self::$sequence
        );
        return self::binaryToDecimal($binary);
    }

    /**
     * 从ID解析生成时间戳 (毫秒)
     * @param string $id
     * @return int
     */
    public static function parseTime(string $id): int
    {
        $binary = self::decimalToBinary($id);
        $timeBits = substr($binary, 0, 42);
        return (int)bindec($timeBits) + self::EPOCH;
    }

    //--------------------- 私有方法 ---------------------
    private static function getCurrentTimestamp(): int
    {
        return (int)round(microtime(true) * 1000);
    }

    private static function waitNextMillis(int $lastTimestamp): int
    {
        $timestamp = self::getCurrentTimestamp();
        while ($timestamp <= $lastTimestamp) {
            usleep(1000);
            $timestamp = self::getCurrentTimestamp();
        }
        return $timestamp;
    }

    private static function binaryToDecimal(string $binary): string
    {
        $decimal = '0';
        $length = strlen($binary);
        for ($i = 0; $i < $length; $i++) {
            $decimal = bcmul($decimal, '2');
            $decimal = bcadd($decimal, $binary[$i]);
        }
        return $decimal;
    }

    private static function decimalToBinary(string $decimal): string
    {
        $binary = '';
        $num = $decimal;
        while ($num !== '0') {
            $binary = bcmod($num, '2') . $binary;
            $num = bcdiv($num, '2', 0);
        }
        return str_pad($binary, 64, '0', STR_PAD_LEFT);
    }
}