@polkadot/util/bn/toU8a.js

A collection of useful utilities for @polkadot

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]
 * ```
 */
export function bnToU8a(value, { bitLength = -1, isLe = true, isNegative = false } = DEFAULT_OPTS) {
    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(1)
            : 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;
}