Function decodeBase58

encoding/base58.ts:125–175

(b58: string)

 * ```
 */
export function decodeBase58(b58: string): Uint8Array_ {
  const splitInput = b58.trim().split("");

  let length = 0;
  let ones = 0;

  // Counting leading ones
  let index = 0;
  while (splitInput[index] === "1") {
    ones++;
    index++;
  }

  const notZeroData = splitInput.slice(index);

  const size = Math.round((b58.length * 733) / 1000 + 1);
  const output: number[] = [];

  notZeroData.forEach((char, idx) => {
    let carry = mapBase58[char];
    let i = 0;

    if (carry === undefined) {
      throw new TypeError(
        `Invalid base58 char at index ${idx} with value ${char}`,
      );
    }

    for (
      let reverseIterator = size - 1;
      (carry > 0 || i < length) && reverseIterator !== -1;
      reverseIterator--, i++
    ) {
      carry += 58 * (output[reverseIterator] ?? 0);
      output[reverseIterator] = Math.round(carry % 256);
      carry = Math.floor(carry / 256);
    }

    length = i;
  });

  const validOutput = output.filter((item) => item !== undefined);

  if (ones > 0) {
    const onesResult = Array.from({ length: ones }).fill(0, 0, ones);

    return new Uint8Array([...onesResult, ...validOutput] as number[]);
  }

  return new Uint8Array(validOutput);
}