mirror of
https://github.com/mauiaaron/apple2.git
synced 2024-09-27 09:56:08 +00:00
Refactor various codepaths for clarity #2
This commit is contained in:
Aaron Culliney
parent
7a0255ff8b
commit
a5854a20f6
215
src/disk.c
215
src/disk.c
@ -74,10 +74,8 @@ static uint8_t rev_translate_table_6[0x80] = { 0 };
|
||||
|
||||
__attribute__((constructor(CTOR_PRIORITY_LATE)))
|
||||
static void _initialize_reverse_translate(void) {
|
||||
unsigned int loop = 0;
|
||||
while (loop < 0x40) {
|
||||
rev_translate_table_6[translate_table_6[loop]-0x80] = loop << 2;
|
||||
loop++;
|
||||
for (unsigned int i=0; i<0x40; i++) {
|
||||
rev_translate_table_6[translate_table_6[i]-0x80] = i << 2;
|
||||
}
|
||||
}
|
||||
|
||||
@ -120,73 +118,54 @@ static bool is_po(const char * const name) {
|
||||
|
||||
#define NUM_SIXBIT_NIBS 342
|
||||
|
||||
static void nibblize_sector(const uint8_t *src, uint8_t *out) {
|
||||
static void nibblize_sector(const uint8_t * const src, uint8_t *out) {
|
||||
SCOPE_TRACE_DISK("nibblize_sector");
|
||||
|
||||
uint8_t work_buf[NUM_SIXBIT_NIBS];
|
||||
uint8_t work_buf[NUM_SIXBIT_NIBS+1];
|
||||
uint8_t *nib = work_buf;
|
||||
|
||||
// Convert 256 8-bit bytes into 342 6-bit bytes
|
||||
{
|
||||
unsigned int counter = 0;
|
||||
uint8_t offset = 0xAC;
|
||||
while (offset != 0x02) {
|
||||
uint8_t value = (( (*(src+offset)) & 0x01) << 1) | (( (*(src+offset)) & 0x02) >> 1);
|
||||
offset -= 0x56;
|
||||
value = (value << 2) | (( (*(src+offset)) & 0x01) << 1) | (( (*(src+offset)) & 0x02) >> 1);
|
||||
offset -= 0x56;
|
||||
value = (value << 2) | (( (*(src+offset)) & 0x01) << 1) | (( (*(src+offset)) & 0x02) >> 1);
|
||||
offset -= 0x53;
|
||||
*(nib++) = value << 2;
|
||||
++counter;
|
||||
}
|
||||
*(nib-2) &= 0x3F;
|
||||
*(nib-1) &= 0x3F;
|
||||
|
||||
assert((counter == NUM_SIXBIT_NIBS-0x100) && "nibblizing counter about to overflow");
|
||||
memcpy(nib, src, 0x100);
|
||||
unsigned int counter = 0;
|
||||
uint8_t offset = 0xAC;
|
||||
while (offset != 0x02) {
|
||||
uint8_t value = (( (*(src+offset)) & 0x01) << 1) | (( (*(src+offset)) & 0x02) >> 1);
|
||||
offset -= 0x56;
|
||||
value = (value << 2) | (( (*(src+offset)) & 0x01) << 1) | (( (*(src+offset)) & 0x02) >> 1);
|
||||
offset -= 0x56;
|
||||
value = (value << 2) | (( (*(src+offset)) & 0x01) << 1) | (( (*(src+offset)) & 0x02) >> 1);
|
||||
offset -= 0x53;
|
||||
*(nib++) = value << 2;
|
||||
++counter;
|
||||
}
|
||||
|
||||
src = work_buf;
|
||||
uint8_t work_buf2[NUM_SIXBIT_NIBS+1];
|
||||
nib = work_buf2;
|
||||
*(nib-2) &= 0x3F;
|
||||
*(nib-1) &= 0x3F;
|
||||
assert((counter == NUM_SIXBIT_NIBS-0x100) && "nibblizing counter about to overflow");
|
||||
memcpy(nib, src, 0x100);
|
||||
|
||||
// XOR the entire data block with itself offset by one byte, creating a final checksum byte
|
||||
{
|
||||
uint8_t savedval = 0;
|
||||
int loop = NUM_SIXBIT_NIBS;
|
||||
while (loop--) {
|
||||
*(nib++) = savedval ^ *src;
|
||||
savedval = *(src++);
|
||||
}
|
||||
*nib = savedval;
|
||||
uint8_t savedval = 0;
|
||||
for (unsigned int i=0; i<NUM_SIXBIT_NIBS; i++) {
|
||||
uint8_t prevsaved = savedval ^ work_buf[i];
|
||||
savedval = work_buf[i];
|
||||
work_buf[i] = prevsaved;
|
||||
}
|
||||
|
||||
src = work_buf2;
|
||||
nib = NULL;
|
||||
work_buf[NUM_SIXBIT_NIBS] = savedval;
|
||||
|
||||
// Convert the 6-bit bytes into disk bytes using a lookup table. A valid disk byte is a byte that has the high bit
|
||||
// set, at least two adjacent bits set (excluding the high bit), and at most one pair of consecutive zero bits.
|
||||
{
|
||||
int loop = NUM_SIXBIT_NIBS+1;
|
||||
while (loop--) {
|
||||
*(out++) = translate_table_6[(*(src++)) >> 2];
|
||||
}
|
||||
for (unsigned int i=0; i<NUM_SIXBIT_NIBS+1; i++) {
|
||||
*(out++) = translate_table_6[work_buf[i] >> 2];
|
||||
}
|
||||
}
|
||||
|
||||
static void denibblize_sector(const uint8_t *src, uint8_t *out) {
|
||||
static void denibblize_sector(const uint8_t * const src, uint8_t *out) {
|
||||
SCOPE_TRACE_DISK("denibblize_sector");
|
||||
|
||||
uint8_t work_buf[NUM_SIXBIT_NIBS+1];
|
||||
uint8_t *dsk = work_buf;
|
||||
|
||||
// Convert disk bytes into 6-bit bytes
|
||||
{
|
||||
unsigned int loop = NUM_SIXBIT_NIBS+1;
|
||||
while (loop--) {
|
||||
*(dsk++) = rev_translate_table_6[*(src++) & 0x7F];
|
||||
}
|
||||
for (unsigned int i=0; i<(NUM_SIXBIT_NIBS+1); i++) {
|
||||
work_buf[i] = rev_translate_table_6[src[i] & 0x7F];
|
||||
}
|
||||
|
||||
#if DISK_TRACING
|
||||
@ -199,56 +178,47 @@ static void denibblize_sector(const uint8_t *src, uint8_t *out) {
|
||||
}
|
||||
#endif
|
||||
|
||||
src = work_buf;
|
||||
uint8_t work_buf2[NUM_SIXBIT_NIBS];
|
||||
dsk = work_buf2;
|
||||
|
||||
// XOR the entire data block with itself offset by one byte to undo checksumming
|
||||
{
|
||||
uint8_t savedval = 0;
|
||||
unsigned int loop = NUM_SIXBIT_NIBS;
|
||||
while (loop--) {
|
||||
*dsk = savedval ^ *(src++);
|
||||
savedval = *(dsk++);
|
||||
}
|
||||
uint8_t savedval = 0;
|
||||
for (unsigned int i=0; i<NUM_SIXBIT_NIBS; i++) {
|
||||
work_buf[i] = savedval ^ work_buf[i];
|
||||
savedval = work_buf[i];
|
||||
}
|
||||
|
||||
#if DISK_TRACING
|
||||
if (test_write_fp) {
|
||||
fprintf(test_write_fp, "XORNIBS:\n");
|
||||
for (unsigned int i=0; i<NUM_SIXBIT_NIBS; i++) {
|
||||
fprintf(test_write_fp, "%02X", work_buf2[i]);
|
||||
fprintf(test_write_fp, "%02X", work_buf[i]);
|
||||
}
|
||||
fprintf(test_write_fp, "\n");
|
||||
}
|
||||
#endif
|
||||
|
||||
// Convert 342 6-bit bytes into 256 8-bit bytes
|
||||
{
|
||||
uint8_t *lowbitsptr = work_buf2;
|
||||
uint8_t *sectorbase = work_buf2+0x56;
|
||||
uint8_t offset = 0xAC;
|
||||
unsigned int counter = 0;
|
||||
while (offset != 0x02) {
|
||||
assert(counter < 256 && "denibblizing counter overflow");
|
||||
if (offset >= 0xAC) {
|
||||
*(out+offset) = (*(sectorbase+offset) & 0xFC) | (((*lowbitsptr) & 0x80) >> 7) | (((*lowbitsptr) & 0x40) >> 5);
|
||||
++counter;
|
||||
}
|
||||
offset -= 0x56;
|
||||
|
||||
*(out+offset) = (*(sectorbase+offset) & 0xFC) | (((*lowbitsptr) & 0x20) >> 5) | (((*lowbitsptr) & 0x10) >> 3);
|
||||
uint8_t *lowbitsptr = work_buf;
|
||||
uint8_t *sectorbase = work_buf+0x56;
|
||||
uint8_t offset = 0xAC;
|
||||
unsigned int counter = 0;
|
||||
while (offset != 0x02) {
|
||||
assert(counter < 256 && "denibblizing counter overflow");
|
||||
if (offset >= 0xAC) {
|
||||
*(out+offset) = (*(sectorbase+offset) & 0xFC) | (((*lowbitsptr) & 0x80) >> 7) | (((*lowbitsptr) & 0x40) >> 5);
|
||||
++counter;
|
||||
offset -= 0x56;
|
||||
|
||||
*(out+offset) = (*(sectorbase+offset) & 0xFC) | (((*lowbitsptr) & 0x08) >> 3) | (((*lowbitsptr) & 0x04) >> 1);
|
||||
++counter;
|
||||
offset -= 0x53;
|
||||
|
||||
++lowbitsptr;
|
||||
}
|
||||
assert(counter == 256 && "invalid bytes count");
|
||||
offset -= 0x56;
|
||||
|
||||
*(out+offset) = (*(sectorbase+offset) & 0xFC) | (((*lowbitsptr) & 0x20) >> 5) | (((*lowbitsptr) & 0x10) >> 3);
|
||||
++counter;
|
||||
offset -= 0x56;
|
||||
|
||||
*(out+offset) = (*(sectorbase+offset) & 0xFC) | (((*lowbitsptr) & 0x08) >> 3) | (((*lowbitsptr) & 0x04) >> 1);
|
||||
++counter;
|
||||
offset -= 0x53;
|
||||
|
||||
++lowbitsptr;
|
||||
}
|
||||
assert(counter == 256 && "invalid bytes count");
|
||||
|
||||
#ifdef DISK_TRACING
|
||||
if (test_write_fp) {
|
||||
@ -370,47 +340,60 @@ static void denibblize_track(int drive, uint8_t *dst) {
|
||||
unsigned int offset = 0;
|
||||
int sector = -1;
|
||||
|
||||
// iterate over 2x sector count (header and data sections)
|
||||
// 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..
|
||||
|
||||
// Find a prologue
|
||||
unsigned int count = 0;
|
||||
unsigned int loop = NIB_TRACK_SIZE;
|
||||
while (loop && (count < 3)) {
|
||||
--loop;
|
||||
if (count || (*(trackimage+offset) == 0xD5)) {
|
||||
prologue[count] = *(trackimage+offset);
|
||||
++count;
|
||||
// Find the beginning of a header or data prologue
|
||||
for (unsigned int i=0, idx=0; i<NIB_TRACK_SIZE; i++) { // FIXME: probably can change this to NIB_SEC_SIZE*2 ...
|
||||
uint8_t byte = trackimage[offset];
|
||||
if (idx || (byte == 0xD5)) {
|
||||
prologue[idx] = byte;
|
||||
++idx;
|
||||
}
|
||||
++offset;
|
||||
if (offset >= disk6.disk[drive].track_width) {
|
||||
offset = 0;
|
||||
}
|
||||
}
|
||||
|
||||
if ((count == 3) && (prologue[1] == 0xAA)) {
|
||||
#define DATA_BYTES_LEN (256+128)
|
||||
#define SCTOFF_HI 0x4
|
||||
#define SCTOFF_LO 0x5
|
||||
unsigned int tmpoff = offset;
|
||||
uint8_t work_buf[DATA_BYTES_LEN] = { 0 };
|
||||
for (unsigned int i=0; i<DATA_BYTES_LEN; i++) {
|
||||
work_buf[i] = *(trackimage+tmpoff);
|
||||
++tmpoff;
|
||||
if (tmpoff >= disk6.disk[drive].track_width) {
|
||||
tmpoff = 0;
|
||||
}
|
||||
}
|
||||
|
||||
if (prologue[2] == 0x96) { // header
|
||||
sector = ((work_buf[SCTOFF_HI] & 0x55) << 1) | (work_buf[SCTOFF_LO] & 0x55);
|
||||
} else if (prologue[2] == 0xAD) { // data
|
||||
int sec_off = 256 * disk6.disk[drive].skew_table[ sector ];
|
||||
denibblize_sector(work_buf, dst+sec_off);
|
||||
sector = -1;
|
||||
if (idx >= 3) {
|
||||
break;
|
||||
}
|
||||
}
|
||||
|
||||
if (prologue[1] != 0xAA) {
|
||||
continue;
|
||||
}
|
||||
|
||||
#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;
|
||||
}
|
||||
sector = ((trackimage[offset++] & 0x55) << 1);
|
||||
sector |= (trackimage[offset++] & 0x55);
|
||||
continue;
|
||||
}
|
||||
if (UNLIKELY(prologue[2] != 0xAD)) {
|
||||
RELEASE_LOG("OMG, found mid-track 0xD5 byte...");
|
||||
continue;
|
||||
}
|
||||
|
||||
// found data prologue : copy and write data to sector
|
||||
|
||||
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;
|
||||
}
|
||||
}
|
||||
int sec_off = 256 * disk6.disk[drive].skew_table[ sector ];
|
||||
denibblize_sector(work_buf, dst+sec_off);
|
||||
sector = -1;
|
||||
}
|
||||
}
|
||||
|
||||
|
||||
Loading…
Reference in New Issue
Block a user