private static void fnvHash(final int[] mix, final int[] cache, final int offset) {
    for (int i = 0; i < mix.length; i++) {
      mix[i] = fnv(mix[i], cache[offset + i]);
    }
  }
Calculates EthHash DataSet size at a given epoch.

@param epoch EthHash Epoch
@return DataSet size
ethereum/core/src/main/java/org/hyperledger/besu/ethereum/mainnet/EthHash.java