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import { createHash } from "https://deno.land/std/hash/mod.ts";
type HashFunction = (b: Uint8Array) => Uint8Array;type HashAlgorithm = "sha1" | "sha256";
/** * I2OSP converts a nonnegative integer to an octet string of a specified length. * @param x nonnegative integer to be converted * @param length intended length of the resulting octet string */export function i2osp(x: bigint, length: number): Uint8Array {  const t = new Uint8Array(length);  for(let i = length - 1; i >= 0; i--) {    if (x === 0n) break;    t[i] = Number(x & 255n);    x = x >> 8n;  }
  return t;}
export function os2ip(m: Uint8Array): bigint {  let n = 0n;  for(const c of m) n = (n << 8n) + BigInt(c);  return n;}
/** * MGF1 is a Mask Generation Function based on a hash function. * https://tools.ietf.org/html/rfc3447#appendix-B.2.1 *  * @param seed seed from which mask is generated, an octet string * @param length intended length in octets of the mask * @param hash Hash function */export function mgf1(seed: Uint8Array, length: number, hash: HashFunction | HashAlgorithm): Uint8Array {  let counter = 0n;  let output: number[] = [];
  while(output.length < length) {    let h;    const c = i2osp(counter, 4);
    if (typeof hash === 'function') {      h = hash(new Uint8Array([...seed, ...c]))    } else {      h = new Uint8Array(createHash(hash).update(new Uint8Array([...seed, ...c])).digest());    }
    output = [...output, ...h];    counter++;  }
  return new Uint8Array(output.slice(0, length));}