fixadd (3) - Linux Man Pages
fixadd: Safe function to add fixed point numbers clamping overflow. Allegro game programming library.
NAMEfixadd - Safe function to add fixed point numbers clamping overflow. Allegro game programming library.
DESCRIPTIONAlthough fixed point numbers can be added with the normal '+' integer operator, that doesn't provide any protection against overflow. If overflow is a problem, you should use this function instead. It is slower than using integer operators, but if an overflow occurs it will set `errno' and clamp the result, rather than just letting it wrap. Example:
fixed result; /* This will put 5035 into `result'. */ result = fixadd(itofix(5000), itofix(35)); /* Sets `errno' and puts -32768 into `result'. */ result = fixadd(itofix(-31000), itofix(-3000)); ASSERT(!errno); /* This will fail. */