@polkadot/util/bn/toU8a.js

A collection of useful utilities for @polkadot

// Copyright 2017-2022 @polkadot/util authors & contributors
// SPDX-License-Identifier: Apache-2.0
import { isNumber } from "../is/number.js";
import { objectSpread } from "../object/spread.js";
import { bnToBn } from "./toBn.js";
const DEFAULT_OPTS = {
  bitLength: -1,
  isLe: true,
  isNegative: false
};
/**
 * @name bnToU8a
 * @summary Creates a Uint8Array object from a BN.
 * @description
 * `null`/`undefined`/`NaN` inputs returns an empty `Uint8Array` result. `BN` input values return the actual bytes value converted to a `Uint8Array`. Optionally convert using little-endian format if `isLE` is set.
 * @example
 * <BR>
 *
 * ```javascript
 * import { bnToU8a } from '@polkadot/util';
 *
 * bnToU8a(new BN(0x1234)); // => [0x12, 0x34]
 * ```
 */

/** @deprecated Use bnToU8a(value?: ExtToBn | BN | bigint | number | null, options?: NumberOptions) */
function bnToU8a(value, arg1 = DEFAULT_OPTS, arg2) {
  const {
    bitLength,
    isLe,
    isNegative
  } = objectSpread({
    bitLength: -1,
    isLe: true,
    isNegative: false
  }, isNumber(arg1) ? {
    bitLength: arg1,
    isLe: arg2
  } : arg1);
  const valueBn = bnToBn(value);
  const byteLength = bitLength === -1 ? Math.ceil(valueBn.bitLength() / 8) : Math.ceil((bitLength || 0) / 8);

  if (!value) {
    return bitLength === -1 ? new Uint8Array() : new Uint8Array(byteLength);
  }

  const output = new Uint8Array(byteLength);
  const bn = isNegative ? valueBn.toTwos(byteLength * 8) : valueBn;
  output.set(bn.toArray(isLe ? 'le' : 'be', byteLength), 0);
  return output;
}

export { bnToU8a };