solana/web3.js/test/shortvec-encoding.test.js

// @flow

import {decodeLength, encodeLength} from '../src/util/shortvec-encoding';

function checkDecodedArray(array: Array<number>, expectedValue: number) {
  expect(decodeLength(array)).toEqual(expectedValue);
  expect(array.length).toEqual(0);
}

test('shortvec decodeLength', () => {
  let array = [];
  checkDecodedArray(array, 0);

  array = [5];
  checkDecodedArray(array, 5);

  array = [0x7f];
  checkDecodedArray(array, 0x7f);

  array = [0x80, 0x01];
  checkDecodedArray(array, 0x80);

  array = [0xff, 0x01];
  checkDecodedArray(array, 0xff);

  array = [0x80, 0x02];
  checkDecodedArray(array, 0x100);

  array = [0xff, 0xff, 0x01];
  checkDecodedArray(array, 0x7fff);

  array = [0x80, 0x80, 0x80, 0x01];
  checkDecodedArray(array, 0x200000);
});

function checkEncodedArray(
  array: Array<number>,
  len: number,
  prevLength: number,
  addedLength: number,
  expectedArray: Array<number>,
) {
  encodeLength(array, len);
  expect(array.length).toEqual(prevLength);
  expect(array.slice(-addedLength)).toEqual(expectedArray);
}

test('shortvec encodeLength', () => {
  let array = [];
  let prevLength = 1;
  checkEncodedArray(array, 0, prevLength, 1, [0]);

  checkEncodedArray(array, 5, (prevLength += 1), 1, [5]);

  checkEncodedArray(array, 0x7f, (prevLength += 1), 1, [0x7f]);

  checkEncodedArray(array, 0x80, (prevLength += 2), 2, [0x80, 0x01]);

  checkEncodedArray(array, 0xff, (prevLength += 2), 2, [0xff, 0x01]);

  checkEncodedArray(array, 0x100, (prevLength += 2), 2, [0x80, 0x02]);

  checkEncodedArray(array, 0x7fff, (prevLength += 3), 3, [0xff, 0xff, 0x01]);

  prevLength = checkEncodedArray(array, 0x200000, (prevLength += 4), 4, [
    0x80,
    0x80,
    0x80,
    0x01,
  ]);
});