@levabala/react-native-uuid/src/v1.ts

react-native-uuid is a zero-dependency TypeScript implementation of RFC4122.

/* eslint-disable no-bitwise */
import {stringify} from './stringify';
import {rng} from './rng';

type V1Options = {
  node: number[];
  clockseq: number;
  msecs: number;
  nsecs: number;
  random: number[];
  rng: () => number[];
};

// **`v1()` - Generate time-based UUID**
//
// Inspired by https://github.com/LiosK/UUID.js
// and http://docs.python.org/library/uuid.html

let _nodeId: number[];
let _clockseq: number;

// Previous uuid creation time
let _lastMSecs = 0;
let _lastNSecs = 0;

// See https://github.com/uuidjs/uuid for API details
export const v1 = (
  options?: V1Options,
  buf?: Uint8Array,
  offset: number = 0,
) => {
  let i = (buf && offset) || 0;
  const b = buf || new Uint8Array(16);

  let node = options && options.node ? options.node : _nodeId;
  let clockseq = options && options.clockseq ? options.clockseq : _clockseq;

  // node and clockseq need to be initialized to random values if they're not
  // specified.  We do this lazily to minimize issues related to insufficient
  // system entropy.  See #189
  if (node == null || clockseq == null) {
    const seedBytes =
      options && options.random
        ? options.random
        : options && options.rng
        ? options.rng()
        : rng();

    if (node == null) {
      // Per 4.5, create and 48-bit node id, (47 random bits + multicast bit = 1)
      node = _nodeId = [
        seedBytes[0] | 0x01,
        seedBytes[1],
        seedBytes[2],
        seedBytes[3],
        seedBytes[4],
        seedBytes[5],
      ];
    }

    if (clockseq == null) {
      // Per 4.2.2, randomize (14 bit) clockseq
      clockseq = _clockseq = ((seedBytes[6] << 8) | seedBytes[7]) & 0x3fff;
    }
  }

  // UUID timestamps are 100 nano-second units since the Gregorian epoch,
  // (1582-10-15 00:00).  JSNumbers aren't precise enough for this, so
  // time is handled internally as 'msecs' (integer milliseconds) and 'nsecs'
  // (100-nanoseconds offset from msecs) since unix epoch, 1970-01-01 00:00.
  let msecs: number = options && options.msecs ? options.msecs : Date.now();

  // Per 4.2.1.2, use count of uuid's generated during the current clock
  // cycle to simulate higher resolution clock
  let nsecs: number = options && options.nsecs ? options.nsecs : _lastNSecs + 1;

  // Time since last uuid creation (in msecs)
  const dt: number = msecs - _lastMSecs + (nsecs - _lastNSecs) / 10000;

  // Per 4.2.1.2, Bump clockseq on clock regression
  if (dt < 0 && options && !options.clockseq) {
    clockseq = (clockseq + 1) & 0x3fff;
  }

  // Reset nsecs if clock regresses (new clockseq) or we've moved onto a new
  // time interval
  if ((dt < 0 || msecs > _lastMSecs) && options && !options.nsecs) {
    nsecs = 0;
  }

  // Per 4.2.1.2 Throw error if too many uuids are requested
  if (nsecs >= 10000) {
    throw new Error("uuid.v1(): Can't create more than 10M uuids/sec");
  }

  _lastMSecs = msecs;
  _lastNSecs = nsecs;
  _clockseq = clockseq;

  // Per 4.1.4 - Convert from unix epoch to Gregorian epoch
  msecs += 12219292800000;

  // `time_low`
  const tl = ((msecs & 0xfffffff) * 10000 + nsecs) % 0x100000000;
  b[i++] = (tl >>> 24) & 0xff;
  b[i++] = (tl >>> 16) & 0xff;
  b[i++] = (tl >>> 8) & 0xff;
  b[i++] = tl & 0xff;

  // `time_mid`
  const tmh = ((msecs / 0x100000000) * 10000) & 0xfffffff;
  b[i++] = (tmh >>> 8) & 0xff;
  b[i++] = tmh & 0xff;

  // `time_high_and_version`
  b[i++] = ((tmh >>> 24) & 0xf) | 0x10; // include version
  b[i++] = (tmh >>> 16) & 0xff;

  // `clock_seq_hi_and_reserved` (Per 4.2.2 - include variant)
  b[i++] = (clockseq >>> 8) | 0x80;

  // `clock_seq_low`
  b[i++] = clockseq & 0xff;

  // `node`
  for (let n = 0; n < 6; ++n) {
    b[i + n] = node[n];
  }

  return buf || stringify(b);
};