fixmul (3) - Linux Man Pages
fixmul: Multiplies two fixed point values together. Allegro game programming library.
NAMEfixmul - Multiplies two fixed point values together. Allegro game programming library.
DESCRIPTIONA 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);