mirror of https://github.com/JorjBauer/aiie.git
404 lines
12 KiB
C++
404 lines
12 KiB
C++
#include "nibutil.h"
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#include <unistd.h>
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#include <fcntl.h>
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#include <stdlib.h>
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#include <string.h>
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#include <time.h>
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#include <stdio.h>
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#include "disktypes.h"
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// Default disk volume identifier
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#define DISK_VOLUME 254
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// 4-and-4 encoding handlers
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#define nib1(a) (((a & 0xAA) >> 1) | 0xAA)
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#define nib2(b) (((b & 0x55) ) | 0xAA)
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#define denib(a, b) ((((a) & ~0xAA) << 1) | ((b) & ~0xAA))
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// In 6-and-2 encoding, there are 86 (0x56) 6-bit values
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#define SIXBIT_SPAN 0x56
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#define INCIDX(p) { p->bitIdx >>= 1; if (!p->bitIdx) {p->bitIdx = 0x80; p->idx++;} }
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// This is the DOS 3.3 RWTS Write Table (UTA2E, p. 9-26).
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const static uint8_t _trans[64] = {0x96, 0x97, 0x9a, 0x9b, 0x9d, 0x9e, 0x9f, 0xa6,
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0xa7, 0xab, 0xac, 0xad, 0xae, 0xaf, 0xb2, 0xb3,
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0xb4, 0xb5, 0xb6, 0xb7, 0xb9, 0xba, 0xbb, 0xbc,
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0xbd, 0xbe, 0xbf, 0xcb, 0xcd, 0xce, 0xcf, 0xd3,
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0xd6, 0xd7, 0xd9, 0xda, 0xdb, 0xdc, 0xdd, 0xde,
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0xdf, 0xe5, 0xe6, 0xe7, 0xe9, 0xea, 0xeb, 0xec,
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0xed, 0xee, 0xef, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6,
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0xf7, 0xf9, 0xfa, 0xfb, 0xfc, 0xfd, 0xfe, 0xff};
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// This is the inverted DOS 3.3 RWTS Write Table (high bit
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// stripped). Any "bad" value is stored as 0xFF.
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const static uint8_t _detrans[0x80] = {0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
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0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
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0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0x00, 0x04,
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0xFF, 0xFF, 0x08, 0x0C, 0xFF, 0x10, 0x14, 0x18,
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0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0x1C, 0x20,
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0xFF, 0xFF, 0xFF, 0x24, 0x28, 0x2C, 0x30, 0x34,
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0xFF, 0xFF, 0x38, 0x3C, 0x40, 0x44, 0x48, 0x4C,
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0xFF, 0x50, 0x54, 0x58, 0x5C, 0x60, 0x64, 0x68,
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0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
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0xFF, 0xFF, 0xFF, 0x6C, 0xFF, 0x70, 0x74, 0x78,
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0xFF, 0xFF, 0xFF, 0x7C, 0xFF, 0xFF, 0x80, 0x84,
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0xFF, 0x88, 0x8C, 0x90, 0x94, 0x98, 0x9C, 0xA0,
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0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xA4, 0xA8, 0xAC,
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0xFF, 0xB0, 0xB4, 0xB8, 0xBC, 0xC0, 0xC4, 0xC8,
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0xFF, 0xFF, 0xCC, 0xD0, 0xD4, 0xD8, 0xDC, 0xE0,
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0xFF, 0xE4, 0xE8, 0xEC, 0xF0, 0xF4, 0xF8, 0xFC };
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// dos 3.3 to physical sector conversion
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const static uint8_t dephys[16] = {
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0x00, 0x07, 0x0e, 0x06, 0x0d, 0x05, 0x0c, 0x04,
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0x0b, 0x03, 0x0a, 0x02, 0x09, 0x01, 0x08, 0x0f };
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// Prodos to physical sector conversion
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const uint8_t deProdosPhys[] = {
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0x00, 0x08, 0x01, 0x09, 0x02, 0x0a, 0x03, 0x0b,
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0x04, 0x0c, 0x05, 0x0d, 0x06, 0x0e, 0x07, 0x0f };
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uint8_t de44(uint8_t nibs[2])
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{
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return denib(nibs[0], nibs[1]);
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}
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static void _packBit(uint8_t *output, bitPtr *ptr, uint8_t isOn)
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{
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if (isOn)
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output[ptr->idx] |= ptr->bitIdx;
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INCIDX(ptr);
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}
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static void _packGap(uint8_t *output, bitPtr *ptr)
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{
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// A gap byte has two sync bits after it.
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for (int i=0; i<8; i++)
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_packBit(output, ptr, 1);
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_packBit(output, ptr, 0);
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_packBit(output, ptr, 0);
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}
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static void _packByte(uint8_t *output, bitPtr *ptr, uint8_t v)
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{
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for (int i=0; i<8; i++) {
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_packBit(output, ptr, v & (1 << (7-i)));
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}
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}
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// Take 256 bytes of input and turn it in to 343 bytes of nibblized output
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void _encode62Data(uint8_t outputBuffer[343], const uint8_t input[256])
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{
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memset(outputBuffer, 0, 342);
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int idx2 = 0x55;
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for (int idx6 = 0x101; idx6 >= 0; idx6--) {
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int val6 = input[idx6 & 0xFF];
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int val2 = outputBuffer[idx2];
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val2 = (val2 << 1) | (val6 & 1);
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val6 >>= 1;
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val2 = (val2 << 1) | (val6 & 1);
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val6 >>= 1;
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outputBuffer[idx2] = val2;
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if (idx6 < 0x100) {
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outputBuffer[0x56 + idx6] = val6;
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}
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if (--idx2 < 0) {
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idx2 = 0x55;
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}
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}
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// mask out the "extra" 2-nyb data from above. Note that the Apple
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// decoders don't care about the extra bits, so taking these back
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// out isn't operationally important. Just don't overflow
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// _trans[]...
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outputBuffer[0x54] &= 0x0F;
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outputBuffer[0x55] &= 0x0F;
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int lastv = 0;
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for (int idx = 0; idx < 0x156; idx++) {
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int val = outputBuffer[idx];
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outputBuffer[idx] = _trans[lastv^val];
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lastv = val;
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}
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outputBuffer[342] = _trans[lastv];
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}
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static uint8_t _whichBit(uint8_t bitIdx)
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{
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switch (bitIdx) {
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case 0x80:
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return 0;
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case 0x40:
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return 1;
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case 0x20:
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return 2;
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case 0x10:
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return 3;
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case 0x08:
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return 4;
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case 0x04:
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return 5;
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case 0x02:
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return 6;
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case 0x01:
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return 7;
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default:
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return 0; // not used
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}
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/* NOTREACHED */
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}
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// rawTrackBuffer is input (dsk/po format); outputBuffer is encoded
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// nibbles (416*16 bytes). Returns the number of bits actually
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// encoded.
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uint32_t nibblizeTrack(uint8_t outputBuffer[NIBTRACKSIZE], const uint8_t rawTrackBuffer[256*16],
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uint8_t diskType, int8_t track)
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{
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int checksum;
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bitPtr ptr = { 0, 0x80 };
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for (uint8_t sector=0; sector<16; sector++) {
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for (uint8_t i=0; i<16; i++) {
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_packGap(outputBuffer, &ptr);
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}
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_packByte(outputBuffer, &ptr, 0xD5); // prolog
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_packByte(outputBuffer, &ptr, 0xAA);
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_packByte(outputBuffer, &ptr, 0x96);
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_packByte(outputBuffer, &ptr, nib1(DISK_VOLUME));
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_packByte(outputBuffer, &ptr, nib2(DISK_VOLUME));
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_packByte(outputBuffer, &ptr, nib1(track));
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_packByte(outputBuffer, &ptr, nib2(track));
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_packByte(outputBuffer, &ptr, nib1(sector));
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_packByte(outputBuffer, &ptr, nib2(sector));
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checksum = DISK_VOLUME ^ track ^ sector;
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_packByte(outputBuffer, &ptr, nib1(checksum));
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_packByte(outputBuffer, &ptr, nib2(checksum));
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_packByte(outputBuffer, &ptr, 0xDE); // epilog
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_packByte(outputBuffer, &ptr, 0xAA);
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_packByte(outputBuffer, &ptr, 0xEB);
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for (uint8_t i=0; i<5; i++) {
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_packGap(outputBuffer, &ptr);
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}
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_packByte(outputBuffer, &ptr, 0xD5); // data prolog
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_packByte(outputBuffer, &ptr, 0xAA);
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_packByte(outputBuffer, &ptr, 0xAD);
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uint8_t physicalSector = (diskType == T_PO ? deProdosPhys[sector] : dephys[sector]);
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uint8_t nibData[343];
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_encode62Data(nibData, &rawTrackBuffer[physicalSector * 256]);
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for (int i=0; i<343; i++) {
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_packByte(outputBuffer, &ptr, nibData[i]);
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}
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_packByte(outputBuffer, &ptr, 0xDE); // data epilog
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_packByte(outputBuffer, &ptr, 0xAA);
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_packByte(outputBuffer, &ptr, 0xEB);
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for (uint8_t i=0; i<16; i++) {
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_packGap(outputBuffer, &ptr);
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}
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}
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return (ptr.idx*8 + _whichBit(ptr.bitIdx));
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}
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// Pop the next 343 bytes off of trackBuffer, which should be 342
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// 6:2-bit GCR encoded values, which we decode back in to 256 8-byte
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// output values; and one checksum byte.
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//
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// Return true if we've successfully consumed 343 bytes from
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// trackBuf.
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bool _decode62Data(const uint8_t trackBuffer[343], uint8_t output[256])
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{
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static uint8_t workbuf[342];
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for (int i=0; i<342; i++) {
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uint8_t in = *(trackBuffer++) & 0x7F; // strip high bit
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workbuf[i] = _detrans[in];
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if (workbuf[i] == 0xFF) // bad data is untranslatable
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return false;
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}
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// fixme: collapse this in to the previous loop
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uint8_t prev = 0;
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for (int i=0; i<342; i++) {
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workbuf[i] = prev ^ workbuf[i];
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prev = workbuf[i];
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}
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#if 0
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if (prev != trackBuffer[342]) {
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printf("ERROR: checksum of sector is incorrect [0x%X v 0x%X]\n", prev, trackBuffer[342]);
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return false;
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}
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#endif
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// Start with all of the bytes with 6 bits of data
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for (uint16_t i=0; i<256; i++) {
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output[i] = workbuf[SIXBIT_SPAN + i] & 0xFC; // 6 bits
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}
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// Then pull in all of the 2-bit values, which are stuffed 3 to a byte. That gives us
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// 4 bits more than we need - the last two skip two of the bits.
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for (uint8_t i=0; i<SIXBIT_SPAN; i++) {
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// This byte (workbuf[i]) has 2 bits for each of 3 output bytes:
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// i, SIXBIT_SPAN+i, and 2*SIXBIT_SPAN+i
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uint8_t thisbyte = workbuf[i];
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output[ i] |= ((thisbyte & 0x08) >> 3) | ((thisbyte & 0x04) >> 1);
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output[ SIXBIT_SPAN + i] |= ((thisbyte & 0x20) >> 5) | ((thisbyte & 0x10) >> 3);
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if (i < SIXBIT_SPAN-2) {
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output[2*SIXBIT_SPAN + i] |= ((thisbyte & 0x80) >> 7) | ((thisbyte & 0x40) >> 5);
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}
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}
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return true;
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}
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// trackBuffer is input NIB data; rawTrackBuffer is output DSK/PO data
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nibErr denibblizeTrack(const uint8_t input[NIBTRACKSIZE], uint8_t rawTrackBuffer[256*16],
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uint8_t diskType)
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{
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// bitmask of the sectors that we've found while decoding. We should
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// find all 16.
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uint16_t sectorsUpdated = 0;
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// loop through the data twice, so we make sure we read anything
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// that crosses the end/start boundary
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for (uint16_t i=0; i<2*416*16; i++) {
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// Find the prolog
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if (input[i % NIBTRACKSIZE] != 0xD5)
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continue;
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i++;
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if (input[i % NIBTRACKSIZE] != 0xAA)
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continue;
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i++;
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if (input[i % NIBTRACKSIZE] != 0x96)
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continue;
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i++;
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// And now we should be in the header section
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uint8_t volumeID = denib(input[i % NIBTRACKSIZE],
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input[(i+1) % NIBTRACKSIZE]);
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i += 2;
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uint8_t trackID = denib(input[i % NIBTRACKSIZE],
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input[(i+1) % NIBTRACKSIZE]);
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i += 2;
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uint8_t sectorNum = denib(input[i % NIBTRACKSIZE],
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input[(i+1) % NIBTRACKSIZE]);
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i += 2;
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uint8_t headerChecksum = denib(input[i % NIBTRACKSIZE],
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input[(i+1) % NIBTRACKSIZE]);
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i += 2;
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if (headerChecksum != (volumeID ^ trackID ^ sectorNum)) {
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continue;
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}
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// check for the epilog
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if (input[i % NIBTRACKSIZE] != 0xDE) {
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continue;
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}
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i++;
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if (input[i % NIBTRACKSIZE] != 0xAA) {
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continue;
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}
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i++;
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// Skip to the data prolog
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while (input[i % NIBTRACKSIZE] != 0xD5) {
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i++;
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}
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i++;
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if (input[i % NIBTRACKSIZE] != 0xAA)
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continue;
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i++;
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if (input[i % NIBTRACKSIZE] != 0xAD)
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continue;
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i++;
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// Decode the data in to a temporary buffer: we don't want to overwrite
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// something valid with partial data
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uint8_t output[256];
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// create a new nibData (in case it wraps around our track data)
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uint8_t nibData[343];
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for (int j=0; j<343; j++) {
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nibData[j] = input[(i+j)%NIBTRACKSIZE];
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}
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if (!_decode62Data(nibData, output)) {
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return errorBadData;
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}
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i += 343;
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// Check the data epilog
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if (input[i % NIBTRACKSIZE] != 0xDE)
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continue;
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i++;
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if (input[i % NIBTRACKSIZE] != 0xAA)
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continue;
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i++;
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if (input[i % NIBTRACKSIZE] != 0xEB)
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continue;
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i++;
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// We've got a whole block! Put it in the rawTrackBuffer and mark
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// the bit for it in sectorsUpdated.
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// FIXME: if trackID != curTrack, that's an error?
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uint8_t targetSector;
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if (diskType == T_PO) {
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targetSector = deProdosPhys[sectorNum];
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} else {
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targetSector = dephys[sectorNum];
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}
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if (targetSector > 16)
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return errorBadData;
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memcpy(&rawTrackBuffer[targetSector * 256],
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output,
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256);
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sectorsUpdated |= (1 << sectorNum);
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}
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// Check that we found all of the sectors for this track
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if (sectorsUpdated != 0xFFFF) {
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return errorMissingSectors;
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}
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return errorNone;
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}
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nibErr nibblizeSector(uint8_t dataIn[256], uint8_t dataOut[343])
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{
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_encode62Data(dataOut, dataIn);
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return errorNone;
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}
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nibErr denibblizeSector(nibSector input, uint8_t dataOut[256])
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{
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if (_decode62Data((uint8_t *)(input.data62), dataOut)) {
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return errorNone;
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}
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return errorBadData;
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}
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