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mode7: comment gr-sim rle unpack a bit better

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Vince Weaver 2017-12-15 11:29:20 -05:00
parent 20dfdcc36e
commit e60974a9ef
1 changed files with 24 additions and 10 deletions
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34
gr-sim/gr-sim.c
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@ -700,28 +700,24 @@ int home(void) {
int grsim_unrle(unsigned char *rle_data, int address) { int grsim_unrle(unsigned char *rle_data, int address) {
// int xoffset=0;
// int yoffset=0;
unsigned char s; unsigned char s;
// int out_pointer;
ram[GBASL]=0; // input address ram[GBASL]=0; /* input address */
ram[GBASH]=0; ram[GBASH]=0; /* we fake this in this environment */
x=0; x=0; /* Set X and Y registers to 0 */
y=0; y=0;
ram[BASL]=address&0xff; ram[BASL]=address&0xff; /* output address? */
ram[BASH]=(address>>8)&0xff; ram[BASH]=(address>>8)&0xff;
ram[CV]=0; ram[CV]=0;
/* CH = xsize */ /* Read xsize, put in CH */
ram[CH]=rle_data[y_indirect(GBASL,y)]; ram[CH]=rle_data[y_indirect(GBASL,y)];
y++; y++;
/* Skip ysize */ /* Skip ysize, we won't need it */
y++; y++;
while(1) { while(1) {
@ -730,23 +726,38 @@ int grsim_unrle(unsigned char *rle_data, int address) {
/* 0xff is a special value meaning end */ /* 0xff is a special value meaning end */
if (a==0xff) break; if (a==0xff) break;
/* Store run length into TEMP */
ram[TEMP]=a; ram[TEMP]=a;
/* 16-bit increment of GBASL:GBASH */
y++; y++;
if (y==0) ram[GBASH]++; if (y==0) ram[GBASH]++;
/* Get the color into A */
a=rle_data[y_indirect(GBASL,y)]; a=rle_data[y_indirect(GBASL,y)];
/* 16-bit increment of GBASL:GBASH */
y++; y++;
if (y==0) ram[GBASH]++; if (y==0) ram[GBASH]++;
/* Push y on stack */
s=y; s=y;
y=0; y=0;
while(1) { while(1) {
/* store out color */
ram[y_indirect(BASL,y)]=a; ram[y_indirect(BASL,y)]=a;
/* 16-bit increment of output pointer */
ram[BASL]++; ram[BASL]++;
if (ram[BASL]==0) ram[BASH]++; if (ram[BASL]==0) ram[BASH]++;
/* increment size */
x++; x++;
/* if size longer than width, adjust */
if (x>=ram[CH]) { if (x>=ram[CH]) {
if (ram[BASL]>0xa7) ram[BASH]++; if (ram[BASL]>0xa7) ram[BASH]++;
ram[BASL]+=0x58; ram[BASL]+=0x58;
@ -764,9 +775,12 @@ int grsim_unrle(unsigned char *rle_data, int address) {
} }
x=0; x=0;
} }
/* repeat until use up all of run length */
ram[TEMP]--; ram[TEMP]--;
if (ram[TEMP]==0) break; if (ram[TEMP]==0) break;
} }
/* restore y from stack */
y=s; y=s;
} }