UUID draft

uuiddraft.js

const crypto = require('crypto')

const rnds8Pool = new Uint8Array(256); // # of random values to pre-allocate
let poolPtr = rnds8Pool.length;

function rng(size) {
    if (poolPtr > rnds8Pool.length - size) {
        crypto.randomFillSync(rnds8Pool);
        poolPtr = 0;
    }
    return rnds8Pool.slice(poolPtr, (poolPtr += size));
}

const MILLISECOND_IN_NANOSECONDS = 1000 * 1000;
const MASK_32 = Math.pow(2, 32);

const storage = {
    seq: -1,
    lastTime: 0,
}

function uuid() {
    const now = Date.now();

    if (now <= storage.lastTime) {
        storage.seq = (storage.seq + 1) % (1024 * MILLISECOND_IN_NANOSECONDS)
    } else {
        storage.lastTime = now
        storage.seq = 0
    }

    let nowHigh = Math.floor(now / MASK_32)

    let nowLow = now % MASK_32
    nowHigh = (nowHigh * MILLISECOND_IN_NANOSECONDS) + Math.floor((nowLow * MILLISECOND_IN_NANOSECONDS) / MASK_32)
    nowLow = ((nowLow * MILLISECOND_IN_NANOSECONDS) % MASK_32) + Math.floor(storage.seq / Math.pow(2, 10))

    const arr8 = new Uint8Array(16)

    arr8[0] = nowHigh >> 24
    arr8[1] = nowHigh >> 16 & 0xff
    arr8[2] = nowHigh >> 8 & 0xff
    arr8[3] = nowHigh & 0xff

    arr8[4] = nowLow >> 24
    arr8[5] = nowLow >> 16 & 0xff
    arr8[6] = (nowLow >> 12 & 0x0f) | 0x70 // version
    arr8[7] = nowLow >> 4 & 0xff

    arr8[8] = (storage.seq >> 8 & 0x03) | (nowLow & 0x3c) | 0x80 // variant
    arr8[9] = storage.seq & 0xff

    const rand = rng(6)

    for (let i = 0; i < rand.length; i++) {
        arr8[10 + i] = rand[i]
    }

    return {
        toString: () => {
            let hex = Buffer.from(arr8).toString('hex').padStart(32, '0');
            return hex.substring(0, 8)
                + '-' + hex.substring(8, 12)
                + '-' + hex.substring(12, 16)
                + '-' + hex.substring(16);
        },
        get buffer() {
            return arr8.buffer
        },
    }
}

let n = 50;
const ids = new Array(n)
for (let i = 0; i < n; i++) {
    ids[i] = uuid()
}

ids.forEach((id, i) => {
    console.log(id.toString())
})