ffjavascript/src/random.js

import ChaCha from "./chacha.js";
import crypto from "crypto";

export function getRandomBytes(n) {
    let array = new Uint8Array(n);
    if (process.browser) { // Browser
        if (typeof globalThis.crypto !== "undefined") { // Supported
            globalThis.crypto.getRandomValues(array);
        } else { // fallback
            for (let i=0; i<n; i++) {
                array[i] = (Math.random()*4294967296)>>>0;
            }
        }
    }
    else { // NodeJS
        crypto.randomFillSync(array);
    }
    return array;
}

export function getRandomSeed() {
    const arr = getRandomBytes(32);
    const arrV = new Uint32Array(arr.buffer);
    const seed = [];
    for (let i=0; i<8; i++) {
        seed.push(arrV[i]);
    }
    return seed;
}

let threadRng = null;

export function getThreadRng() {
    if (threadRng) return threadRng;
    threadRng = new ChaCha(getRandomSeed());
    return threadRng;
}