fix: Cbor.encode(BigInt(n)) possible failure

[neeboo]

Fix Cbor.encode(BigInt(n)) possible failure

Description

When use Cbor.encode, if passed value is BigInt, first will run the BigInt encoder and transform BigInt value to be a hex string. However this BigInt(n).toString(16) would probrably generate a hex string length not to be even, which won't pass the RegTest in the fromHex function.

const hexRe = new RegExp(/^([0-9A-F]{2})*$/i);

Fixes # (issue)

Added a zero-padding while passing hex string length is not even.

export function fromHex(hex: string): ArrayBuffer {
  //FIXME: always padding hex string length to be even
  // then run the reg test
  if (hex.length % 2 !== 0) {
    hex = '0' + hex;
  }

  if (!hexRe.test(hex)) {
    throw new Error('Invalid hexadecimal string.');
  }
  const buffer = [...hex]
    .reduce((acc, curr, i) => {
      // tslint:disable-next-line:no-bitwise
      acc[(i / 2) | 0] = (acc[(i / 2) | 0] || '') + curr;
      return acc;
    }, [] as string[])
    .map(x => Number.parseInt(x, 16));

  return new Uint8Array(buffer).buffer;
}

How Has This Been Tested?

test cases are in cbor.tests.ts

Checklist:

• [x] My changes follow the guidelines in CONTRIBUTING.md.
• [x] The title of this PR complies with Conventional Commits.
• [ ] I have edited the CHANGELOG accordingly.
• [ ] I have made corresponding changes to the documentation.

[dfinity-droid-prod[bot]]

Dear @neeboo,

In order to potentially merge your code in this open-source repository and therefore proceed with your contribution, we need to have your approval on DFINITY's CLA[^1].

If you decide to agree with it, please visit this issue and read the instructions there.

— The DFINITY Foundation [^1]: Contributor License Agreement

[dfinity-droid-prod[bot]]

Dear @neeboo,

In order to potentially merge your code in this open-source repository and therefore proceed with your contribution, we need to have your approval on DFINITY's CLA[^1].

If you decide to agree with it, please visit this issue and read the instructions there.

— The DFINITY Foundation [^1]: Contributor License Agreement

[ilbertt]

When serializing objects that contain BigInts, I'm getting the error:

Invalid hexadecimal string.

Has some progress been made on this?