On 2/26/07, Luc Le Blanc <[EMAIL PROTECTED]> wrote:
I'm surprised the RGBColorType was not declared as a union of UInt32
and other elements. But to copy or compare RGBColorTypes quickly
without having to resort to MemMove or Compare, is there a
CPU-effective smart cast I can use (( UInt32 ) is refused by the
compiler)? Is this cost-free (CPU-wise):
you have a point, it should have been:
typedef struct RGBColorType
{
union
{
struct
{
uint8 r;
uint8 g
uint8 b;
} elements;
uint32 rgb;
} data;
} RGBColorType ;
but to your question. yes.
RGBColorType a, b;
*( UInt32 * ) &a = 0xffffffffL;
*( UInt32 * ) &b = 0x80800101L;
*((UInt32 *)&a) = 0xffffffffL;
may help the compiler understand better - why not use a macro to make
your code easier to understand at the same time :)
#define RGBColorTypeSet(a, val) (*((UInt32 *)(a)) = (val)
#define RGBColorTypeCompare(a, b) ( (*((UInt32 *)(a)) == *((UInt32 *)(b))) )
then do:
RGBColorTypeSet(&a, 0xffffffffL);
RGBColorTypeSet(&b, 0x80800101L);
if (RGBColorTypeCompare(&a, &b))
{
.. same
}
else
{
.. different
}
C/C++ can be pretty nasty about how you code your pointer casts;
so, just put extra brackets in there to help. it all comes down to memory;
as long as the RGBColorType components are after each other; it'll work.
you can do a lot of cool tricks like color averaging etc with this too.
--
// Aaron Ardiri
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