fixadd

NAME

fixadd − Safe function to add fixed point numbers clamping overflow. Allegro game programming library.

SYNOPSIS

#include <allegro.h>

fixed fixadd(fixed x, fixed y);

DESCRIPTION

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. */

RETURN VALUE

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

SEE ALSO

fixsub(3), fixmul(3), fixdiv(3)