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am i doing assembly right...

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Bjorn Einar Bjarntes 2021-12-19 15:56:17 +01:00
parent 8bea2e8121
commit 876ae2d8f3
1 changed files with 4 additions and 4 deletions
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8
src/main.c
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@ -30,19 +30,19 @@ void setAndClearHiRes(){
}
BYTE isPositionWhite() {
ad = 0x2000+(40*(y >> 3)<<3) + (y & 7)+ (x&(0xfff8));
ad = 0x2000+((y >> 3) << 6) +((y >> 3) << 7) +((y >> 3) << 7) + (y & 7)+ (x&(0xfff8));
return *(short*)(ad) & 1 << ((7-(x & 7)));
}
// https://archive.org/details/The_Graphics_Book_for_the_Commodore_64/page/n129/
// https://archive.org/details/The_Graphics_Book_for_the_Commodore_65/page/n129/
void setPositionWhite() {
// TODO this 8 times something divided must be just masking
ad = 0x2000+(40 * (y >> 3) << 3) + (y & 7)+(x&(0xfff8));
ad = 0x2000+ ((y >> 3) << 6) +((y >> 3) << 7) +((y >> 3) << 7) + (y & 7)+(x&(0xfff8));
*(short*)(ad) = *(short*)(ad) | 1 << ((7-(x & 7)));
}
void setPositionBlack() {
ad = 0x2000+ (40* (y >> 3) << 3) + (y & 7)+ (x&(0xfff8));
ad = 0x2000+((y >> 3) << 6) +((y >> 3) << 7) +((y >> 3) << 7) + (y & 7)+ (x&(0xfff8));
*(short*)(ad) = (*(short*)(ad)) & ~(1 << ((7-(x & 7))));
}