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Simplify modulo offset calculations in trackimage

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This commit is contained in:
Aaron Culliney 2015-12-12 00:17:26 -08:00
parent ef1963a175
commit 0aed046b5e
1 changed files with 7 additions and 16 deletions
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23
src/disk.c
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@ -356,6 +356,8 @@ static void denibblize_track(const uint8_t * const src, int drive, uint8_t * con
unsigned int offset = 0;
int sector = -1;
const unsigned int trackwidth = disk6.disk[drive].track_width;
// iterate over 2x sectors (accounting for header and data sections)
for (unsigned int sct2=0; sct2<(NUM_SECTORS<<1)+1; sct2++) {
uint8_t prologue[3] = {0,0,0}; // D5AA..
@ -367,10 +369,7 @@ static void denibblize_track(const uint8_t * const src, int drive, uint8_t * con
prologue[idx] = byte;
++idx;
}
++offset;
if (offset >= disk6.disk[drive].track_width) {
offset = 0;
}
offset = (offset+1) % trackwidth;
if (idx >= 3) {
break;
}
@ -383,15 +382,11 @@ static void denibblize_track(const uint8_t * const src, int drive, uint8_t * con
#define SCTOFF 0x4
if (prologue[2] == 0x96) {
// found header prologue : extract sector
offset += SCTOFF;
if (offset >= disk6.disk[drive].track_width) {
RELEASE_LOG("WRAPPING PROLOGUE ...");
offset -= disk6.disk[drive].track_width;
}
offset = (offset+SCTOFF) % trackwidth;
sector = ((trackimage[offset] & 0x55) << 1);
offset = (offset+1) % disk6.disk[drive].track_width;
offset = (offset+1) % trackwidth;
sector |= (trackimage[offset] & 0x55);
offset = (offset+1) % disk6.disk[drive].track_width;
offset = (offset+1) % trackwidth;
continue;
}
if (UNLIKELY(prologue[2] != 0xAD)) {
@ -404,11 +399,7 @@ static void denibblize_track(const uint8_t * const src, int drive, uint8_t * con
uint8_t work_buf[NUM_SIXBIT_NIBS+1];
for (unsigned int idx=0; idx<(NUM_SIXBIT_NIBS+1); idx++) {
work_buf[idx] = trackimage[offset];
++offset;
if (offset >= disk6.disk[drive].track_width) {
offset = 0;
LOG("WARNING : wrapping trackimage ... trk:%d sct:%d [0]:0x%02X", (disk6.disk[drive].phase >> 1), sector, trackimage[offset]);
}
offset = (offset+1) % trackwidth;
}
assert(sector >= 0 && sector < 16 && "invalid previous nibblization");
int sec_off = 256 * disk6.disk[drive].skew_table[ sector ];