js雪花代码

class Snowflake {
  constructor(workerId, datacenterId, sequence = 0) {
    this.twepoch = 1288834974657n;
    this.workerIdBits = 5n;
    this.datacenterIdBits = 5n;
    this.maxWorkerId = -1n ^ (-1n << this.workerIdBits);
    this.maxDatacenterId = -1n ^ (-1n << this.datacenterIdBits);
    this.sequenceBits = 12n;

    this.workerIdShift = this.sequenceBits;
    this.datacenterIdShift = this.sequenceBits + this.workerIdBits;
    this.timestampLeftShift = this.sequenceBits + this.workerIdBits + this.datacenterIdBits;
    this.sequenceMask = -1n ^ (-1n << this.sequenceBits);

    if (workerId > this.maxWorkerId || workerId < 0) {
      throw new Error(`workerId can't be greater than ${this.maxWorkerId} or less than 0`);
    }
    if (datacenterId > this.maxDatacenterId || datacenterId < 0) {
      throw new Error(`datacenterId can't be greater than ${this.maxDatacenterId} or less than 0`);
    }

    this.workerId = BigInt(workerId);
    this.datacenterId = BigInt(datacenterId);
    this.sequence = BigInt(sequence);

    this.lastTimestamp = -1n;
  }

  tilNextMillis(lastTimestamp) {
    let timestamp = this.timeGen();
    while (timestamp <= lastTimestamp) {
      timestamp = this.timeGen();
    }
    return BigInt(timestamp);
  }

  timeGen() {
    return BigInt(Date.now());
  }

  nextId() {
    let timestamp = this.timeGen();

    if (timestamp < this.lastTimestamp) {
      throw new Error(`Clock moved backwards. Refusing to generate id for ${this.lastTimestamp - timestamp} milliseconds`);
    }

    if (this.lastTimestamp === timestamp) {
      this.sequence = (this.sequence + 1n) & this.sequenceMask;
      if (this.sequence === 0n) {
        timestamp = this.tilNextMillis(this.lastTimestamp);
      }
    } else {
      this.sequence = 0n;
    }

    this.lastTimestamp = timestamp;

    return ((timestamp - this.twepoch) << this.timestampLeftShift) |
           (this.datacenterId << this.datacenterIdShift) |
           (this.workerId << this.workerIdShift) |
           this.sequence;
  }
}

// Usage
const snowflake = new Snowflake(1, 1);
console.log(snowflake.nextId());