Is there a similar function on Arduino?
There is a one line command to do it.
byte msb;
byte lsb;
int theInt = (int)msb << 8 + lsb;
The only question is which of the two bytes you read is msb and which is lsb.
But, I thought you were sending one byte in and one byte out, so msb should be 0 and lsb should be the byte you send/receive.
It is not clear why the nibbles seem to be reversed in the lsb.