xid-js/lib/xid.js

unique id generator for Node.js

'use strict';

const os = require('os');
const crypto = require('crypto');
const base32 = require('./base32');

function randInt() {
  return crypto.randomBytes(3).readUIntBE(0, 3);
}

function machineId() {
  const hostname = os.hostname();
  if (undefined === hostname) {
    return randInt();
  }
  return crypto.createHash('md5')
    .update(hostname)
    .digest()
    .slice(0, 3)
    .readUIntBE(0, 3);
}

const mid = machineId();
const pid = process.pid & 0xffff;
let seq = randInt();
let time = Date.now() / 1000 | 0;

const buff = Buffer.allocUnsafe(12).fill(0);
buff.writeUInt32BE(time, 0);
buff.writeUIntBE(mid, 4, 3);
buff.writeUInt16BE(pid, 7);

/**
 * Generate a unique id.
 *
 * @returns {string}
 */
function next() {
  const now = Date.now() / 1000 | 0;
  if (time !== now) {
    buff.writeUInt32BE(now, 0);
    time = now;
  }
  const c = seq & 0xffffff;
  seq += 1;
  buff.writeUIntBE(c, 9, 3);
  return base32.encodeString(buff).substring(0, 20);
}

module.exports = {
  next,
};