small hash table encoding function

I need small C or Cpp code to do tow tasks on data file: the data file considered a list of bytes belong to one of tow groups x and y let us assume them letters "x" and digits "y" no xx in the data file but many yy or yyy or yyyy first function: we need to unify all y series into one y using "OR" so the data file became xyxy..... no x series or y series if by mistake there was an xx the program should exit with error. second function: this series of xyxy = 32 bits we need to calculate them and result a table like this a5b3 55 d2f6 99 ... etc I prefer if the code could read the tow groups from file, but it's not critical I can accept building the hash table in the code before compiling. that is all