NAME¶
fixmul - Multiplies two fixed point values together. Allegro game programming
library.
SYNOPSIS¶
#include <allegro.h>
fixed fixmul(fixed x, fixed y);
DESCRIPTION¶
A fixed point value can be multiplied or divided by an integer with the normal
`*' and `/' operators. To multiply two fixed point values, though, you must
use this function.
If an overflow occurs, `errno' will be set and the maximum possible value will
be returned, but `errno' is not cleared if the operation is successful. This
means that if you are going to test for overflow you should set `errno=0'
before calling fixmul(). Example:
fixed result;
/* This will put 30000 into `result'. */
result = fixmul(itofix(10), itofix(3000));
/* But this overflows, and sets `errno'. */
result = fixmul(itofix(100), itofix(3000));
ASSERT(!errno);
RETURN VALUE¶
Returns the clamped result of multiplying `x' by `y', setting `errno' to ERANGE
if there was an overflow.
SEE ALSO¶
fixadd(3alleg4),
fixsub(3alleg4),
fixdiv(3alleg4),
ex3buf(3alleg4),
excustom(3alleg4),
exfixed(3alleg4),
exspline(3alleg4),
exstars(3alleg4),
exupdate(3alleg4)