@polkadot/util/cjs/hex/toU8a.js

A collection of useful utilities for @polkadot

"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.hexToU8a = hexToU8a;

var _alphabet = require("./alphabet");

var _stripPrefix = require("./stripPrefix");

// Copyright 2017-2022 @polkadot/util authors & contributors
// SPDX-License-Identifier: Apache-2.0

/**
 * @name hexToU8a
 * @summary Creates a Uint8Array object from a hex string.
 * @description
 * `null` inputs returns an empty `Uint8Array` result. Hex input values return the actual bytes value converted to a Uint8Array. Anything that is not a hex string (including the `0x` prefix) throws an error.
 * @example
 * <BR>
 *
 * ```javascript
 * import { hexToU8a } from '@polkadot/util';
 *
 * hexToU8a('0x80001f'); // Uint8Array([0x80, 0x00, 0x1f])
 * hexToU8a('0x80001f', 32); // Uint8Array([0x00, 0x80, 0x00, 0x1f])
 * ```
 */
function hexToU8a(_value) {
  let bitLength = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : -1;

  if (!_value) {
    return new Uint8Array();
  }

  const value = (0, _stripPrefix.hexStripPrefix)(_value).toLowerCase();
  const valLength = value.length / 2;
  const endLength = Math.ceil(bitLength === -1 ? valLength : bitLength / 8);
  const result = new Uint8Array(endLength);
  const offset = endLength > valLength ? endLength - valLength : 0;
  const dv = new DataView(result.buffer, offset);
  const mod = (endLength - offset) % 2;
  const length = endLength - offset - mod;

  for (let i = 0; i < length; i += 2) {
    const idx = i * 2;
    dv.setUint16(i, _alphabet.HEX_TO_U16[value.substring(idx, idx + 4)]);
  }

  if (mod) {
    dv.setUint8(length, _alphabet.HEX_TO_U8[value.substring(value.length - 2)]);
  }

  return result;
}