fixadd(3) Safe function to add fixed point numbers clamping overflow. Allegro game programming library.


#include <allegro.h>

fixed fixadd(fixed x, fixed y);


Although 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. */


Returns the clamped result of adding `x' to `y', setting `errno' to ERANGE if there was an overflow.