Byte32 Decoding

In v2.1 we introduced byte32 encoding for function and event variables (to save storage and gas costs). We provide examples to decode them.

Decode amountsIn or amountsOut from the Swap event

The parameter amountsIn is packed with the amounts in for both tokens X and Y and encoded into bytes32. Below is an example of how to decode them. The same is true for amountsOut.

function decodeAmounts(amounts: Bytes): [bigint, bigint] {
  /**
   * Decodes the amounts bytes input as 2 integers.
   *
   * @param amounts - amounts to decode.
   * @return tuple of BigInts with the values decoded.
   */

  // Convert amounts to a BigInt
  const amountsBigInt = BigInt(`0x${Buffer.from(amounts).toString('hex')}`);

  // Read the right 128 bits of the 256 bits
  const amountsX = amountsBigInt & ((BigInt(2) ** BigInt(128)) - BigInt(1));

  // Read the left 128 bits of the 256 bits
  const amountsY = amountsBigInt >> BigInt(128);

  return [amountsX, amountsY];
}

def decodeAmounts(amounts: bytes) -> tuple:
    """
    Decodes the amounts bytes input as 2 integers.

    :param amounts: amounts to decode.
    :return: tuple of ints with the values decoded.
    """
    
    amounts = bytes.fromhex(amounts)

    # Read the right 128 bits of the 256 bits
    amountsX = int.from_bytes(random_bytes, byteorder="big") & (2 ** 128 - 1)

    # Read the left 128 bits of the 256 bits
    amountsY = int.from_bytes(random_bytes, byteorder="big") >> 128

    return (amountsX, amountsY)

Decode totalFees and protocolFees from Swap Event

The following functions return the decoded values of the Fees of the LBPair contract.

function decodeFees(feesBytes: Bytes): bigint {
  /**
   * Decode the fee value from the bytes input and return it as in integer.
   * Fee values are stored in the first 128 bits of the input.
   *
   * @param feesBytes - Bytes containing the encoded value.
   * @return Fee values.
   */

  // Convert feesBytes to a BigInt
  const feesBigInt = BigInt(`0x${Buffer.from(feesBytes).toString('hex')}`);

  // Retrieve the fee value from the right 128 bits
  return feesBigInt & ((BigInt(2) ** BigInt(128)) - BigInt(1));
}

def decodeFees(fees_bytes: bytes) -> int:
    """
    Decode the fee value from the bytes input and return it as in integer.
    Fee values are stored in the first 128bits ofthe input.

    :param fees_bytes: Bytes containing the encoded value.
    :return: Fee values.
    """

    fees_bytes = bytes.fromhex(fees_bytes)
    
    # Retrieve the fee value from the right 128 bits
    return int.from_bytes(fees_bytes, byteorder="big") & (2 ** 128 - 1)