@iden3/js-crypto/src/base58.ts

Crypto primitives for iden3

// Original js implementation https://gist.github.com/diafygi/90a3e80ca1c2793220e5/

const base58 = '123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz';

export const base58FromBytes = (
  input: Uint8Array //Uint8Array raw byte input
): string => {
  const d = []; //the array for storing the stream of base58 digits
  let s = ''; //the result string variable that will be returned
  let j = 0; //the iterator variable for the base58 digit array (d)
  let c = 0; //the carry amount variable that is used to overflow from the current base58 digit to the next base58 digit
  let n: number; //a temporary placeholder variable for the current base58 digit
  for (let i = 0; i < input.length; i++) {
    //loop through each byte in the input stream
    j = 0; //reset the base58 digit iterator
    c = input[i]; //set the initial carry amount equal to the current byte amount
    s += c || s.length ^ i ? '' : '1'; //prepend the result string with a "1" (0 in base58) if the byte stream is zero and non-zero bytes haven't been seen yet (to ensure correct decode length)
    while (j in d || c) {
      //start looping through the digits until there are no more digits and no carry amount
      n = d[j]; //set the placeholder for the current base58 digit
      n = n ? n * 256 + c : c; //shift the current base58 one byte and add the carry amount (or just add the carry amount if this is a new digit)
      c = (n / 58) | 0; //find the new carry amount (floored integer of current digit divided by 58)
      d[j] = n % 58; //reset the current base58 digit to the remainder (the carry amount will pass on the overflow)
      j++; //iterate to the next base58 digit
    }
  }
  while (j--)
    //since the base58 digits are backwards, loop through them in reverse order
    s += base58[d[j]]; //lookup the character associated with each base58 digit
  return s; //return the final base58 string
};

export const base58ToBytes = (
  str: string //Base58 encoded string input
): Uint8Array => {
  const d = []; //the array for storing the stream of decoded bytes
  const b = []; //the result byte array that will be returned
  let j = 0; //the iterator variable for the byte array (d)
  let c = 0; //the carry amount variable that is used to overflow from the current byte to the next byte
  let n = 0; //a temporary placeholder variable for the current byte
  for (let i = 0; i < str.length; i++) {
    //loop through each base58 character in the input string
    j = 0; //reset the byte iterator
    c = base58.indexOf(str[i]); //set the initial carry amount equal to the current base58 digit
    if (c < 0)
      //see if the base58 digit lookup is invalid (-1)
      throw new Error(`Can't convert base58 string ${str} to bytes`);
    // eslint-disable-next-line @typescript-eslint/no-unused-expressions
    c || b.length ^ i ? i : b.push(0); //prepend the result array with a zero if the base58 digit is zero and non-zero characters haven't been seen yet (to ensure correct decode length)
    while (j in d || c) {
      //start looping through the bytes until there are no more bytes and no carry amount
      n = d[j]; //set the placeholder for the current byte
      n = n ? n * 58 + c : c; //shift the current byte 58 units and add the carry amount (or just add the carry amount if this is a new byte)
      c = n >> 8; //find the new carry amount (1-byte shift of current byte value)
      d[j] = n % 256; //reset the current byte to the remainder (the carry amount will pass on the overflow)
      j++; //iterate to the next byte
    }
  }
  while (j--)
    //since the byte array is backwards, loop through it in reverse order
    b.push(d[j]); //append each byte to the result
  return new Uint8Array(b); //return the final byte array in Uint8Array format
};