Mail Archives: djgpp/1999/07/03/12:25:51
I actually worked out some protracted method of doing it myself using
dosmemput(), but I will take both pieces of advice into account because I
don't think my version is very well optimised at present. Thanks muchly
though.
Are the near pointer hacks really that bad? Surely its just the same as
programming in real mode rather than protected mode?
Nate Eldredge <nate AT cartsys DOT com> wrote in message
news:377D4C68 DOT 16AD5C62 AT cartsys DOT com...
> David Mitchell wrote:
> >
> > This is how I do it.
> > Note: This code can be very much optimised! And the putPixel method is
> > missing the clipping code.
>
> I suggest that flipping be done as:
>
> dosmemput(vscreen, 0xa0000, 64000);
>
> instead. It's much safer and all of maybe 3 cycles slower (and
> nearptr_enable is an expensive DPMI call itself, although it isn't in
> the inner loop).
>
> If you insist on using the nearptr hack, then for the sake of your
> sanity use __djgpp_nearptr_disable whenever you can.
>
> >
> > char vscreen[64000];
> > char *scrptr;
> >
> > void putPixel(int x, int y, char color) {
> > int offs;
> >
> > offs = 320*y + x;
> >
> > vscreen[offs] = color;
> > }
> >
> > void flip(void) {
> > memcpy(scrptr, virt, 64000); // #include <mem.h>
> > }
> >
> > int main(void) {
> > .
> > .
> > .
> > __djgpp_nearptr_enable(); // #include
<sys/nearptr.h>
> > for this.
> > scrptr = (char*) (__djgpp_conventional_base + 0xa0000); // note 4
> > zeros because of
> >
> > // pmode
> > .
> > .
> > .
> > }
> >
> > David.
> >
> > PS the flip takes less than 1ms on a P200
>
> --
>
> Nate Eldredge
> nate AT cartsys DOT com
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