*
* ulong ul2int ULONG => INT can fail if >INT_MAX
* ulong int2ul INT => ULONG can fail if <0
* ulong mask A B => A & B
* ulong add A B => A + B (mod 2^32)
* ulong subtract A B => A - B (mod 2^32)
*
* ulong ul2int ULONG => INT can fail if >INT_MAX
* ulong int2ul INT => ULONG can fail if <0
* ulong mask A B => A & B
* ulong add A B => A + B (mod 2^32)
* ulong subtract A B => A - B (mod 2^32)