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bradgrantham-apple2e
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read sectors from disk instead of reading whole floppy

This commit is contained in:
Brad Grantham 2020-12-12 08:38:58 -08:00
parent d20991ae8e
commit b99576c1e0
1 changed files with 72 additions and 33 deletions
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105
apple2e.cpp
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@ -266,22 +266,34 @@ struct backed_region : region
const region io_region = {"io", 0xC000, 0x100};
const unsigned char floppy_sectorHeader[21] = {
namespace floppy
{
/*
5 1/2" floppy disk images are 35 tracks of 16 sectors of 256 bytes = 143360 bytes
*/
constexpr int sectorSize = 256;
constexpr int sectorsPerTrack = 16;
constexpr int tracksPerFloppy = 35;
const unsigned char sectorHeader[21] = {
0xD5, 0xAA, 0x96, 0xFF, 0xFE, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0xDE, 0xAA, 0xFF, 0xFF, 0xFF,
0xFF, 0xFF, 0xD5, 0xAA, 0xAD };
const unsigned char floppy_doSector[16] = {
const unsigned char doSectorSkew[16] = {
0x0, 0x7, 0xE, 0x6, 0xD, 0x5, 0xC, 0x4, 0xB, 0x3, 0xA, 0x2, 0x9, 0x1, 0x8, 0xF };
const unsigned char floppy_poSector[16] = {
const unsigned char poSectorSkew[16] = {
0x0, 0x8, 0x1, 0x9, 0x2, 0xA, 0x3, 0xB, 0x4, 0xC, 0x5, 0xD, 0x6, 0xE, 0x7, 0xF };
const unsigned char floppy_sectorFooter[48] = {
const unsigned char sectorFooter[48] = {
0xDE, 0xAA, 0xEB, 0xFF, 0xEB, 0xFF, 0xFF, 0xFF,
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF };
const unsigned char floppy_6BitsToBytes[0x40] = {
const unsigned char SixBitsToBytes[0x40] = {
0x96, 0x97, 0x9A, 0x9B, 0x9D, 0x9E, 0x9F, 0xA6,
0xA7, 0xAB, 0xAC, 0xAD, 0xAE, 0xAF, 0xB2, 0xB3,
0xB4, 0xB5, 0xB6, 0xB7, 0xB9, 0xBA, 0xBB, 0xBC,
@ -291,9 +303,9 @@ const unsigned char floppy_6BitsToBytes[0x40] = {
0xED, 0xEE, 0xEF, 0xF2, 0xF3, 0xF4, 0xF5, 0xF6,
0xF7, 0xF9, 0xFA, 0xFB, 0xFC, 0xFD, 0xFE, 0xFF };
constexpr size_t floppy_trackGapSize = 64;
constexpr size_t trackGapSize = 64;
constexpr size_t nybblizedSectorSize = 21 + 343 + 48;
constexpr size_t nybblizedTrackSize = floppy_trackGapSize + 16 * nybblizedSectorSize;
constexpr size_t nybblizedTrackSize = trackGapSize + sectorsPerTrack * nybblizedSectorSize;
void nybblizeSector(int trackIndex, int sectorIndex, const uint8_t *sectorBytes, uint8_t *sectorNybblized)
{
@ -301,7 +313,7 @@ void nybblizeSector(int trackIndex, int sectorIndex, const uint8_t *sectorBytes,
uint8_t *p = sectorNybblized;
memcpy(p, floppy_sectorHeader, sizeof(floppy_sectorHeader)); // Set up the sectorIndex header
memcpy(p, sectorHeader, sizeof(sectorHeader)); // Set up the sectorIndex header
p[5] = ((trackIndex >> 1) & 0x55) | 0xAA;
p[6] = (trackIndex & 0x55) | 0xAA;
@ -339,16 +351,16 @@ void nybblizeSector(int trackIndex, int sectorIndex, const uint8_t *sectorBytes,
// Using a lookup table, convert the 6-bit bytes into disk bytes.
for(int i=0; i<343; i++)
p[i] = floppy_6BitsToBytes[p[i] >> 2];
p[i] = SixBitsToBytes[p[i] >> 2];
p += 343;
// Done with the nybblization, now for the epilogue...
memcpy(p, floppy_sectorFooter, sizeof(floppy_sectorFooter));
memcpy(p, sectorFooter, sizeof(sectorFooter));
// p += 48;
}
void floppy_NybblizeImage(const unsigned char *floppyByteImage, unsigned char *nybblizedImage, const unsigned char *skew)
bool nybblizeImage(FILE *floppyImageFile, unsigned char *nybblizedImage, const unsigned char *skew)
{
// Format of a sector is header (23) + nybbles (343) + footer (30) = 396
// (short by 20 bytes of 416 [413 if 48 byte header is one time only])
@ -359,16 +371,32 @@ void floppy_NybblizeImage(const unsigned char *floppyByteImage, unsigned char *n
{
unsigned char *nybblizedTrack = nybblizedImage + trackIndex * nybblizedTrackSize;
memset(nybblizedTrack, 0xFF, floppy_trackGapSize); // Write gap 1, 64 bytes (self-sync)
memset(nybblizedTrack, 0xFF, trackGapSize); // Write gap 1, 64 bytes (self-sync)
for(unsigned char sectorIndex = 0; sectorIndex < 16; sectorIndex++)
{
const unsigned char * sectorBytes = floppyByteImage + (skew[sectorIndex] * 256) + (trackIndex * 256 * 16);
long sectorOffset = (skew[sectorIndex] + trackIndex * sectorsPerTrack) * sectorSize;
int seeked = fseek(floppyImageFile, sectorOffset, SEEK_SET);
if(seeked == -1) {
fprintf(stderr, "failed to seek to sector in floppy disk image\n");
return false;
}
unsigned char sectorBytes[256];
size_t wasRead = fread(sectorBytes, 1, sectorSize, floppyImageFile);
if(wasRead != sectorSize) {
fprintf(stderr, "failed to read sector from floppy disk image\n");
return false;
}
nybblizeSector(trackIndex, sectorIndex, sectorBytes, nybblizedTrack + sectorIndex * nybblizedSectorSize);
}
}
return true;
}
};
// XXX readonly at this time
struct DISKIIboard : board_base
{
@ -404,10 +432,10 @@ struct DISKIIboard : board_base
backed_region rom_C600 = {"rom_C600", 0xC600, 0x0100, ROM, nullptr, [&]{return true;}};
unsigned char *floppy_image[2]; // [143360];
unsigned char *floppy_nybblized[2]; // [232960];
const unsigned int bytes_per_nybblized_track = 6656;
bool floppy_present[2];
FILE *floppyImageFiles[2] = {nullptr, nullptr};
int drive_selected = 0;
bool drive_motor_enabled[2];
@ -421,19 +449,36 @@ struct DISKIIboard : board_base
void set_floppy(int number, const char *name) // number 0 or 1; name = NULL to eject
{
floppy_present[number] = false;
if(name) {
if(!read_blob(name, floppy_image[number], 143360 /*sizeof(floppy_image[0])*/))
throw "Couldn't read floppy";
floppy_present[number] = true;
const unsigned char *skew;
if(strcmp(name + strlen(name) - 3, ".po") == 0) {
printf("ProDOS floppy\n");
skew = floppy_poSector;
} else {
skew = floppy_doSector;
if(floppyImageFiles[number]) {
fclose(floppyImageFiles[number]);
}
floppyImageFiles[number] = fopen(name, "rb");
if(!floppyImageFiles[number]) {
fprintf(stderr, "Couldn't open floppy disk image \"%s\"\n", name);
} else {
const unsigned char *skew;
if(strcmp(name + strlen(name) - 3, ".po") == 0) {
printf("ProDOS floppy\n");
skew = floppy::poSectorSkew;
} else {
skew = floppy::doSectorSkew;
}
bool success = floppy::nybblizeImage(floppyImageFiles[number], floppy_nybblized[number], skew);
if(!success) {
floppyImageFiles[number] = nullptr;
fprintf(stderr, "unexpected failure reading sector from disk \"%s\"\n", name);
}
floppy_present[number] = true;
}
floppy_NybblizeImage(floppy_image[number], floppy_nybblized[number], skew);
}
}
@ -445,10 +490,6 @@ struct DISKIIboard : board_base
{
std::copy(diskII_rom, diskII_rom + 0x100, rom_C600.memory.begin());
if(floppy0_name) {
floppy_image[0] = new (std::nothrow) unsigned char[143360];
if(!floppy_image[0]) {
throw "failed to allocate floppy_image[0]";
}
floppy_nybblized[0] = new (std::nothrow) unsigned char[232960];
if(!floppy_nybblized[0]) {
throw "failed to allocate floppy_nybblized[0]";
@ -456,10 +497,6 @@ struct DISKIIboard : board_base
set_floppy(0, floppy0_name);
}
if(floppy1_name) {
floppy_image[1] = new (std::nothrow) unsigned char[143360];
if(!floppy_image[1]) {
throw "failed to allocate floppy_image[1]";
}
floppy_nybblized[1] = new (std::nothrow) unsigned char[232960];
if(!floppy_nybblized[1]) {
throw "failed to allocate floppy_nybblized[1]";
@ -489,9 +526,11 @@ struct DISKIIboard : board_base
if(state == 1) { // turn stepper motor phase on
if(head_stepper_most_recent_phase == (((phase - 1) + 4) % 4)) { // stepping up
track_number = min(track_number + 1, 70);
// XXX load track
if(debug & DEBUG_FLOPPY) printf("track number now %d\n", track_number);
} else if(head_stepper_most_recent_phase == ((phase + 1) % 4)) { // stepping down
track_number = max(0, track_number - 1);
// XXX load track
if(debug & DEBUG_FLOPPY) printf("track number now %d\n", track_number);
} else if(head_stepper_most_recent_phase == phase) { // unexpected condition
if(debug & DEBUG_FLOPPY) printf("track head stepper no change\n");