Building off of this question How to get this PRNG to generate numbers within the range? , I am making it support BigInt (big values) in JavaScript, and I think I have it right (please correct me if I did it incorrectly):

const fetch = (x, o) => {
  if (x >= o) {
    return x
  } else {
    const v = (x * x) % o
    return (x <= (o / 2n)) ? v : o - v
  }
}

const fetchLarge = (x) => fetch(x, 43214321432143214321432143214321432143214321n)

// the last number can be anything.
const buildLarge = (x, o) => fetchLarge((fetchLarge(x)   o) % BigInt(Math.pow(32, 31)) ^ 101010101010104321432143214321n)

const j = 432143213214321432143214321432143214321n; // If you don't want duplicates, either i or j should stay fixed
let i = 1n
let invalid = [];
let valid = new Set;
while (i) {
  let x = buildLarge(i, j);
  if (valid.has(x)) {
    invalid.push([i, j, x]);
  } else {
    valid.add(x);
  }
  console.log(x)
  i  ;
}

console.log("invalid:", invalid);
console.log("valid:", [...valid]);
console.log("count of valid:", valid.size);

Sidenote: There should never be an invalid value.

But the main question is, given a value of x such as 40531205068036774067539981357810868028938588n, how can you divide it into an array of 5-bit values (array of integers between 0-31)?

Is it just as simple as doing x.toString(32) and then converting those letters to indices or something? Not sure if I'm doing this correctly.

CodePudding user response：

To create an array with numbers between 0-31 you can just divide and collect the remainders (which you would then convert to standard number):

function createArray(n, mod=32n) {
    if (!n) return [0];
    let arr = [];
    while (n) {
        arr.push(Number(n % mod));
        n /= mod;
    }
    return arr;
}

let result = createArray(40531205068036774067539981357810868028938588n);

console.log(result);