@polkadot/util/u8a/cmp.js

// Copyright 2017-2022 @polkadot/util authors & contributors
// SPDX-License-Identifier: Apache-2.0
import { u8aToU8a } from "./toU8a.js";
/**
 * @name u8aCmp
 * @summary Compares two Uint8Arrays for sorting.
 * @description
 * For `UInt8Array` (or hex string) input values returning -1, 0 or +1
 * @example
 * <BR>
 *
 * ```javascript
 * import { u8aCmp } from '@polkadot/util';
 *
 * u8aCmp(new Uint8Array([0x67, 0x65]), new Uint8Array([0x68, 0x65])); // -1
 * u8aCmp(new Uint8Array([0x68, 0x65]), new Uint8Array([0x68, 0x65])); // 0
 * u8aCmp(new Uint8Array([0x69, 0x65]), new Uint8Array([0x68, 0x65])); // +1
 * ```
 */

export function u8aCmp(a, b) {
  const u8aa = u8aToU8a(a);
  const u8ab = u8aToU8a(b);
  let i = 0;

  while (true) {
    const overA = i >= u8aa.length;
    const overB = i >= u8ab.length;

    if (overA && overB) {
      // both ends reached
      return 0;
    } else if (overA) {
      // a has no more data, b has data
      return -1;
    } else if (overB) {
      // b has no more data, a has data
      return 1;
    } else if (u8aa[i] !== u8ab[i]) {
      // the number in this index doesn't match
      // (we don't use u8aa[i] - u8ab[i] since that doesn't match with localeCompare)
      return u8aa[i] > u8ab[i] ? 1 : -1;
    }

    i++;
  }
}