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(ppu) Minor optimisation

This commit is contained in:
neauoire 2021-12-24 09:29:26 -08:00
parent 5af50c7ca0
commit 668eab05bf
1 changed files with 8 additions and 6 deletions
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14
src/devices/ppu.c
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@ -12,6 +12,8 @@ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
WITH REGARD TO THIS SOFTWARE.
*/
/* byte: p0-bg | p0-fg | p1-bg | p1-fg */
static Uint8 blending[5][16] = {
{0, 0, 0, 0, 1, 0, 1, 1, 2, 2, 0, 2, 3, 3, 3, 0},
{0, 1, 2, 3, 0, 1, 2, 3, 0, 1, 2, 3, 0, 1, 2, 3},
@ -46,7 +48,7 @@ ppu_resize(Ppu *p, Uint16 width, Uint16 height)
p->pixels = pixels;
p->width = width;
p->height = height;
ppu_clear(p, 0x00);
ppu_clear(p, CLEAR_BOTH);
}
void
@ -61,11 +63,11 @@ Uint8
ppu_read(Ppu *p, Uint16 x, Uint16 y)
{
if(x < p->width && y < p->height) {
Uint32 row = (x + y * p->width) / 2;
Uint8 shift = !(x & 0x1) << 2;
Uint32 row = (x + y * p->width) >> 1;
Uint8 shift = (x & 0x1) << 2;
Uint8 pix = p->pixels[row] >> shift;
if(pix & 0x0c)
pix = pix >> 2;
pix >>= 2;
return pix & 0x3;
}
return 0x0;
@ -75,8 +77,8 @@ void
ppu_write(Ppu *p, Uint8 layer, Uint16 x, Uint16 y, Uint8 color)
{
if(x < p->width && y < p->height) {
Uint32 row = (x + y * p->width) / 2;
Uint8 shift = (!(x & 0x1) << 2) + (layer << 1);
Uint32 row = (x + y * p->width) >> 1;
Uint8 shift = ((x & 0x1) << 2) + (layer << 1);
Uint8 pix = p->pixels[row];
Uint8 mask = ~(0x3 << shift);
Uint8 pixnew = (pix & mask) + (color << shift);