[apple2] / src / floppydrive.cpp

//
// Apple 2 floppy disk support
//
// by James Hammons
// (c) 2005-2018 Underground Software
//
// JLH = James Hammons <jlhamm@acm.org>
//
// WHO  WHEN        WHAT
// ---  ----------  -----------------------------------------------------------
// JLH  12/03/2005  Created this file
// JLH  12/15/2005  Fixed nybblization functions to work properly
// JLH  12/27/2005  Added blank disk creation, fixed saving to work properly
//

#include "floppydrive.h"

#include <stdio.h>
#include <string.h>
#include "apple2.h"
#include "crc32.h"
#include "firmware.h"
#include "log.h"
#include "mmu.h"
#include "video.h"              // For message spawning... Though there's probably a
                                                // better approach than this!

// Useful enums

enum { IO_MODE_READ, IO_MODE_WRITE };

// FloppyDrive class variable initialization

uint8_t FloppyDrive::doSector[16] = {
        0x0, 0x7, 0xE, 0x6, 0xD, 0x5, 0xC, 0x4, 0xB, 0x3, 0xA, 0x2, 0x9, 0x1, 0x8, 0xF };
uint8_t FloppyDrive::poSector[16] = {
        0x0, 0x8, 0x1, 0x9, 0x2, 0xA, 0x3, 0xB, 0x4, 0xC, 0x5, 0xD, 0x6, 0xE, 0x7, 0xF };
uint8_t FloppyDrive::wozHeader[9] = "WOZ1\xFF\x0A\x0D\x0A";
uint8_t FloppyDrive::wozHeader2[9] = "WOZ2\xFF\x0A\x0D\x0A";
uint8_t FloppyDrive::standardTMAP[141] = {
        0, 0, 0xFF, 1, 1, 1, 0xFF, 2, 2, 2, 0xFF, 3, 3, 3, 0xFF, 4, 4, 4, 0xFF,
        5, 5, 5, 0xFF, 6, 6, 6, 0xFF, 7, 7, 7, 0xFF, 8, 8, 8, 0xFF, 9, 9, 9, 0xFF,
        10, 10, 10, 0xFF, 11, 11, 11, 0xFF, 12, 12, 12, 0xFF, 13, 13, 13, 0xFF,
        14, 14, 14, 0xFF, 15, 15, 15, 0xFF, 16, 16, 16, 0xFF, 17, 17, 17, 0xFF,
        18, 18, 18, 0xFF, 19, 19, 19, 0xFF, 20, 20, 20, 0xFF, 21, 21, 21, 0xFF,
        22, 22, 22, 0xFF, 23, 23, 23, 0xFF, 24, 24, 24, 0xFF, 25, 25, 25, 0xFF,
        26, 26, 26, 0xFF, 27, 27, 27, 0xFF, 28, 28, 28, 0xFF, 29, 29, 29, 0xFF,
        30, 30, 30, 0xFF, 31, 31, 31, 0xFF, 32, 32, 32, 0xFF, 33, 33, 33, 0xFF,
        34, 34, 34, 0xFF, 0xFF, 0xFF
};
uint8_t FloppyDrive::bitMask[8] = { 0x80, 0x40, 0x20, 0x10, 0x08, 0x04, 0x02, 0x01 };
uint8_t FloppyDrive::sequencerROM[256] = {
0x18, 0x18, 0x18, 0x18, 0x0A, 0x0A, 0x0A, 0x0A, 0x18, 0x18, 0x18, 0x18, 0x18, 0x18, 0x18, 0x18,
0x2D, 0x38, 0x2D, 0x38, 0x0A, 0x0A, 0x0A, 0x0A, 0x28, 0x28, 0x28, 0x28, 0x28, 0x28, 0x28, 0x28,
0x38, 0x28, 0xD8, 0x08, 0x0A, 0x0A, 0x0A, 0x0A, 0x39, 0x39, 0x39, 0x39, 0x3B, 0x3B, 0x3B, 0x3B,
0x48, 0x48, 0xD8, 0x48, 0x0A, 0x0A, 0x0A, 0x0A, 0x48, 0x48, 0x48, 0x48, 0x48, 0x48, 0x48, 0x48,
0x58, 0x58, 0xD8, 0xD8, 0x0A, 0x0A, 0x0A, 0x0A, 0x58, 0x58, 0x58, 0x58, 0x58, 0x58, 0x58, 0x58,
0x68, 0x68, 0xD8, 0xD8, 0x0A, 0x0A, 0x0A, 0x0A, 0x68, 0x68, 0x68, 0x68, 0x68, 0x68, 0x68, 0x68,
0x78, 0x78, 0xD8, 0xD8, 0x0A, 0x0A, 0x0A, 0x0A, 0x78, 0x78, 0x78, 0x78, 0x78, 0x78, 0x78, 0x78,
0x88, 0x88, 0xD8, 0xD8, 0x0A, 0x0A, 0x0A, 0x0A, 0x08, 0x88, 0x08, 0x88, 0x08, 0x88, 0x08, 0x88,
0x98, 0x98, 0xD8, 0xD8, 0x0A, 0x0A, 0x0A, 0x0A, 0x98, 0x98, 0x98, 0x98, 0x98, 0x98, 0x98, 0x98,
0x29, 0xA8, 0xD8, 0xD8, 0x0A, 0x0A, 0x0A, 0x0A, 0xA8, 0xA8, 0xA8, 0xA8, 0xA8, 0xA8, 0xA8, 0xA8,
0xBD, 0xB8, 0xCD, 0xD8, 0x0A, 0x0A, 0x0A, 0x0A, 0xB9, 0xB9, 0xB9, 0xB9, 0xBB, 0xBB, 0xBB, 0xBB,
0x59, 0xC8, 0xD9, 0xD8, 0x0A, 0x0A, 0x0A, 0x0A, 0xC8, 0xC8, 0xC8, 0xC8, 0xC8, 0xC8, 0xC8, 0xC8,
0xD9, 0xA0, 0xD9, 0xD8, 0x0A, 0x0A, 0x0A, 0x0A, 0xD8, 0xD8, 0xD8, 0xD8, 0xD8, 0xD8, 0xD8, 0xD8,
0x08, 0xE8, 0xD8, 0xE8, 0x0A, 0x0A, 0x0A, 0x0A, 0xE8, 0xE8, 0xE8, 0xE8, 0xE8, 0xE8, 0xE8, 0xE8,
0xFD, 0xF8, 0xFD, 0xF8, 0x0A, 0x0A, 0x0A, 0x0A, 0xF8, 0xF8, 0xF8, 0xF8, 0xF8, 0xF8, 0xF8, 0xF8,
0x4D, 0xE0, 0xDD, 0xE0, 0x0A, 0x0A, 0x0A, 0x0A, 0x88, 0x08, 0x88, 0x08, 0x88, 0x08, 0x88, 0x08
};

char FloppyDrive::nameBuf[MAX_PATH];


// Static in-line functions, for clarity & speed, mostly for reading values out
// of the WOZ struct, which stores its data in LE; some for swapping variables
static inline uint16_t Uint16LE(uint16_t v)
{
#if SDL_BYTEORDER == SDL_BIG_ENDIAN
        return ((v & 0xFF) << 8) | ((v & 0xFF00) >> 8);
#else
        return v;
#endif
}


static inline uint32_t Uint32LE(uint32_t v)
{
#if SDL_BYTEORDER == SDL_BIG_ENDIAN
        return ((v & 0xFF) << 24) | ((v & 0xFF00) << 8)
                | ((v & 0xFF0000) >> 8) | ((v & 0xFF000000) >> 24);
#else
        return v;
#endif
}


static inline void Swap(uint8_t & a, uint8_t & b)
{
        uint8_t t = a;
        a = b;
        b = t;
}


static inline void Swap(uint32_t & a, uint32_t & b)
{
        uint32_t t = a;
        a = b;
        b = t;
}


static inline void Swap(bool & a, bool & b)
{
        bool t = a;
        a = b;
        b = t;
}


static inline void Swap(uint8_t * & a, uint8_t * & b)
{
        uint8_t * t = a;
        a = b;
        b = t;
}


static inline void Swap(WOZ * & a, WOZ * & b)
{
        WOZ * t = a;
        a = b;
        b = t;
}


// FloppyDrive class implementation...

FloppyDrive::FloppyDrive(): motorOn(0), activeDrive(0), ioMode(IO_MODE_READ),  ioHappened(false)
{
        phase[0] = phase[1] = 0;
        headPos[0] = headPos[1] = 0;
        trackLength[0] = trackLength[1] = 51200;
        disk[0] = disk[1] = NULL;
        woz[0] = woz[1] = NULL;
        diskSize[0] = diskSize[1] = 0;
        diskType[0] = diskType[1] = DT_EMPTY;
        imageDirty[0] = imageDirty[1] = false;
        imageName[0][0] = imageName[1][0] = 0;                  // Zero out filenames
}


FloppyDrive::~FloppyDrive()
{
        if (disk[0])
                delete[] disk[0];

        if (disk[1])
                delete[] disk[1];
}


bool FloppyDrive::LoadImage(const char * filename, uint8_t driveNum/*= 0*/)
{
        WriteLog("FLOPPY: Attempting to load image '%s' in drive #%u.\n", filename, driveNum);

        if (driveNum > 1)
        {
                WriteLog("FLOPPY: Attempted to load image to drive #%u!\n", driveNum);
                return false;
        }

        // Zero out filename, in case it doesn't load
        imageName[driveNum][0] = 0;

        FILE * fp = fopen(filename, "rb");

        if (fp == NULL)
        {
                WriteLog("FLOPPY: Failed to open image file '%s' for reading...\n", filename);
                return false;
        }

        if (disk[driveNum])
                delete[] disk[driveNum];

        fseek(fp, 0, SEEK_END);
        diskSize[driveNum] = ftell(fp);
        fseek(fp, 0, SEEK_SET);
        disk[driveNum] =  new uint8_t[diskSize[driveNum]];
        woz[driveNum] = (WOZ *)disk[driveNum];
        fread(disk[driveNum], 1, diskSize[driveNum], fp);

        fclose(fp);
//printf("Read disk image: %u bytes.\n", diskSize);
        DetectImageType(filename, driveNum);
        strcpy(imageName[driveNum], filename);

        WriteLog("FLOPPY: Loaded image '%s' for drive #%u.\n", filename, driveNum);

        return true;
}


bool FloppyDrive::SaveImage(uint8_t driveNum/*= 0*/)
{
// comment out for now...
#if 0
        // Various sanity checks...
        if (driveNum > 1)
        {
                WriteLog("FLOPPY: Attempted to save image to drive #%u!\n", driveNum);
                return false;
        }

        if (!imageDirty[driveNum])
        {
                WriteLog("FLOPPY: No need to save unchanged image...\n");
                return false;
        }

        if (imageName[driveNum][0] == 0)
        {
                WriteLog("FLOPPY: Attempted to save non-existant image!\n");
                return false;
        }

        // Finally, write the damn image
        FILE * fp = fopen(imageName[driveNum], "wb");

        if (fp == NULL)
        {
                WriteLog("FLOPPY: Failed to open image file '%s' for writing...\n", imageName[driveNum]);
                return false;
        }

        fwrite(disk[driveNum], 1, diskSize[driveNum], fp);
        fclose(fp);

        WriteLog("FLOPPY: Successfully wrote image file '%s'...\n", imageName[driveNum]);

        return true;
#else
        char * ext = strrchr(imageName[driveNum], '.');

        if ((ext != NULL) && (diskType[driveNum] != DT_WOZ))
                memcpy(ext, ".woz", 4);

        return SaveWOZ(driveNum);
#endif
}


bool FloppyDrive::SaveImageAs(const char * filename, uint8_t driveNum/*= 0*/)
{
        strncpy(imageName[driveNum], filename, MAX_PATH);
        // Ensure a NULL terminated string here, as strncpy() won't terminate the
        // string if the source length is >= MAX_PATH
        imageName[driveNum][MAX_PATH - 1] = 0;
        return SaveImage(driveNum);
}


void FloppyDrive::CreateBlankImage(uint8_t driveNum/*= 0*/)
{
        if (disk[driveNum] != NULL)
                delete disk[driveNum];

        InitWOZ(driveNum);
        diskType[driveNum] = DT_WOZ;
        strcpy(imageName[driveNum], "newblank.woz");
        SpawnMessage("New blank image inserted in drive %u...", driveNum);
}


void FloppyDrive::SwapImages(void)
{
#if 0
WriteLog("SwapImages BEFORE:\n");
WriteLog("\tdisk[0]=%X, disk[1]=%X\n", disk[0], disk[1]);
WriteLog("\twoz[0]=%X, woz[1]=%X\n", woz[0], woz[1]);
WriteLog("\tdiskSize[0]=%X, diskSize[1]=%X\n", diskSize[0], diskSize[1]);
WriteLog("\tdiskType[0]=%X, diskType[1]=%X\n", diskType[0], diskType[1]);
WriteLog("\timageDirty[0]=%X, imageDirty[1]=%X\n", imageDirty[0], imageDirty[1]);
WriteLog("\tphase[0]=%X, phase[1]=%X\n", phase[0], phase[1]);
WriteLog("\theadPos[0]=%X, headPos[1]=%X\n", headPos[0], headPos[1]);
WriteLog("\tcurrentPos[0]=%X, currentPos[1]=%X\n", currentPos[0], currentPos[1]);
#endif
        char imageNameTmp[MAX_PATH];

        memcpy(imageNameTmp, imageName[0], MAX_PATH);
        memcpy(imageName[0], imageName[1], MAX_PATH);
        memcpy(imageName[1], imageNameTmp, MAX_PATH);

        Swap(disk[0], disk[1]);
        Swap(woz[0], woz[1]);
        Swap(diskSize[0], diskSize[1]);
        Swap(diskType[0], diskType[1]);
        Swap(imageDirty[0], imageDirty[1]);

        Swap(phase[0], phase[1]);
        Swap(headPos[0], headPos[1]);
        Swap(currentPos[0], currentPos[1]);
SpawnMessage("Drive 0: %s...", imageName[0]);
#if 0
WriteLog("SwapImages AFTER:\n");
WriteLog("\tdisk[0]=%X, disk[1]=%X\n", disk[0], disk[1]);
WriteLog("\twoz[0]=%X, woz[1]=%X\n", woz[0], woz[1]);
WriteLog("\tdiskSize[0]=%X, diskSize[1]=%X\n", diskSize[0], diskSize[1]);
WriteLog("\tdiskType[0]=%X, diskType[1]=%X\n", diskType[0], diskType[1]);
WriteLog("\timageDirty[0]=%X, imageDirty[1]=%X\n", imageDirty[0], imageDirty[1]);
WriteLog("\tphase[0]=%X, phase[1]=%X\n", phase[0], phase[1]);
WriteLog("\theadPos[0]=%X, headPos[1]=%X\n", headPos[0], headPos[1]);
WriteLog("\tcurrentPos[0]=%X, currentPos[1]=%X\n", currentPos[0], currentPos[1]);
#endif
}


/*
Need to add some type of error checking here, so we can report back on bad images, etc.
*/
void FloppyDrive::DetectImageType(const char * filename, uint8_t driveNum)
{
        diskType[driveNum] = DFT_UNKNOWN;

        if (memcmp(disk[driveNum], wozHeader, 8) == 0)
        {
                diskType[driveNum] = DT_WOZ;
                /*bool r =*/ CheckWOZ(disk[driveNum], diskSize[driveNum], driveNum);
        }
        else if (diskSize[driveNum] == 143360)
        {
                const char * ext = strrchr(filename, '.');

                if (ext == NULL)
                        return;

                WriteLog("FLOPPY: Found extension [%s]...\n", ext);

                if (strcasecmp(ext, ".po") == 0)
                        diskType[driveNum] = DT_PRODOS;
                else if ((strcasecmp(ext, ".do") == 0) || (strcasecmp(ext, ".dsk") == 0))
                {
                        // We assume this, but check for a PRODOS fingerprint. Trust, but
                        // verify. ;-)
                        diskType[driveNum] = DT_DOS33;

                        uint8_t fingerprint[4][4] = {
                                { 0x00, 0x00, 0x03, 0x00 },             // @ $400
                                { 0x02, 0x00, 0x04, 0x00 },             // @ $600
                                { 0x03, 0x00, 0x05, 0x00 },             // @ $800
                                { 0x04, 0x00, 0x00, 0x00 }              // @ $A00
                        };

                        bool foundProdos = true;

                        for(uint32_t i=0; i<4; i++)
                        {
                                for(uint32_t j=0; j<4; j++)
                                {
                                        if (disk[driveNum][0x400 + (i * 0x200) + j] != fingerprint[i][j])
                                        {
                                                foundProdos = false;
                                                break;
                                        }
                                }
                        }

                        if (foundProdos)
                                diskType[driveNum] = DT_PRODOS;
                }

// Actually, it just might matter WRT to nybblyzing/denybblyzing
// (and, it does... :-P)
                WOZifyImage(driveNum);
        }
        else if (diskSize[driveNum] == 143488)
        {
                diskType[driveNum] = DT_DOS33_HDR;
                WOZifyImage(driveNum);
        }

#warning "Should we attempt to nybblize unknown images here? Definitely SHOULD issue a warning!"
// No, we don't nybblize anymore.  But we should tell the user that the loading failed with a return value

        WriteLog("FLOPPY: Detected image type %s...\n", (diskType[driveNum] == DT_DOS33 ?
                "DOS 3.3 image" : (diskType[driveNum] == DT_DOS33_HDR ?
                "DOS 3.3 image (headered)" : (diskType[driveNum] == DT_PRODOS ? "ProDOS image" : (diskType[driveNum] == DT_WOZ ? "WOZ image" : "unknown")))));
}


//
// Write a bitstream (source left justified to bit 7) to destination buffer.
// Writes 'bits' number of bits to 'dest', starting at bit position 'dstPtr',
// updating 'dstPtr' for the caller.
//
void FloppyDrive::WriteBits(uint8_t * dest, uint8_t * src, uint16_t bits, uint16_t * dstPtr)
{
        for(uint16_t i=0; i<bits; i++)
        {
                // Get the destination location's bitmask
                uint8_t dstMask = bitMask[*dstPtr % 8];

                // Set the bit to one if there's a corresponding one in the source
                // data, otherwise set it to zero
                if (src[i / 8] & bitMask[i % 8])
                        dest[*dstPtr / 8] |= dstMask;
                else
                        dest[*dstPtr / 8] &= ~dstMask;

                (*dstPtr)++;
        }
}


void FloppyDrive::WOZifyImage(uint8_t driveNum)
{
        // hdr (21) + nybbles (343) + footer (48) = 412 bytes per sector
        // (not incl. 64 byte track marker)
// let's try 394 per sector... & see what happens
// let's go back to what we had, and see what happens  :-)
// [still need to expand them back to what they were]

        uint8_t ff10[2] = { 0xFF, 0x00 };
        uint8_t addressHeader[14] = {
                0xD5, 0xAA, 0x96, 0xFF, 0xFE, 0x00, 0x00, 0x00,
                0x00, 0x00, 0x00, 0xDE, 0xAA, 0xEB };
        uint8_t sectorHeader[3] = { 0xD5, 0xAA, 0xAD };
        uint8_t footer[3] = { 0xDE, 0xAA, 0xEB };
        uint8_t diskbyte[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,
                0xBD, 0xBE, 0xBF, 0xCB, 0xCD, 0xCE, 0xCF, 0xD3,
                0xD6, 0xD7, 0xD9, 0xDA, 0xDB, 0xDC, 0xDD, 0xDE,
                0xDF, 0xE5, 0xE6, 0xE7, 0xE9, 0xEA, 0xEB, 0xEC,
                0xED, 0xEE, 0xEF, 0xF2, 0xF3, 0xF4, 0xF5, 0xF6,
                0xF7, 0xF9, 0xFA, 0xFB, 0xFC, 0xFD, 0xFE, 0xFF };

        uint8_t tmpNib[343];
//      memcpy(tmpDisk, disk[driveNum], diskSize[driveNum]);
//      delete[] disk[driveNum];
        uint8_t * tmpDisk = disk[driveNum];
        disk[driveNum] = NULL;//new uint8_t[diskSize[driveNum]];

        // Set up track index...
//      memcpy(woz[driveNum]->tmap, standardTMAP, 141);
        InitWOZ(driveNum);

        // Upconvert data from DSK & friends format to WOZ tracks  :-)
        for(uint8_t trk=0; trk<35; trk++)
        {
                uint16_t dstBitPtr = 0;
                uint8_t * img = woz[driveNum]->track[trk].bits;
//already done
//              memset(img, 0, 6646);

                // Write self-sync header bytes (16, should it be 64? Dunno.)
                for(int i=0; i<64; i++)
                        WriteBits(img, ff10, 10, &dstBitPtr);

                // Write out the following sectors
                for(uint8_t sector=0; sector<16; sector++)
                {
                        // Set up the sector address header
                        addressHeader[5] = ((trk >> 1) & 0x55) | 0xAA;
                        addressHeader[6] =  (trk       & 0x55) | 0xAA;
                        addressHeader[7] = ((sector >> 1) & 0x55) | 0xAA;
                        addressHeader[8] =  (sector       & 0x55) | 0xAA;
                        addressHeader[9] = (((trk ^ sector ^ 0xFE) >> 1) & 0x55) | 0xAA;
                        addressHeader[10] = ((trk ^ sector ^ 0xFE)       & 0x55) | 0xAA;

                        WriteBits(img, addressHeader, 14 * 8, &dstBitPtr);

                        // Write 5 self-sync bytes for actual sector header
                        for(int i=0; i<5; i++)
                                WriteBits(img, ff10, 10, &dstBitPtr);

                        // Write sector header (D5 AA AD)
                        WriteBits(img, sectorHeader, 3 * 8, &dstBitPtr);
//                      uint8_t * bytes = disk[driveNum];
                        uint8_t * bytes = tmpDisk;

//Need to fix this so it writes the correct sector in the correct place *and* put the correct sector # into the header above as well.  !!! FIX !!!
                        // Figure out location of sector data in disk image
                        if (diskType[driveNum] == DT_DOS33)
                                bytes += (doSector[sector] * 256) + (trk * 256 * 16);
                        else if (diskType[driveNum] == DT_DOS33_HDR)
                                bytes += (doSector[sector] * 256) + (trk * 256 * 16) + 128;
                        else if (diskType[driveNum] == DT_PRODOS)
                                bytes += (poSector[sector] * 256) + (trk * 256 * 16);
                        else
                                bytes += (sector * 256) + (trk * 256 * 16);

                        // Convert the 256 8-bit bytes into 342 6-bit bytes.
                        for(uint16_t i=0; i<0x56; i++)
                        {
                                tmpNib[i] = ((bytes[(i + 0xAC) & 0xFF] & 0x01) << 7)
                                        | ((bytes[(i + 0xAC) & 0xFF] & 0x02) << 5)
                                        | ((bytes[(i + 0x56) & 0xFF] & 0x01) << 5)
                                        | ((bytes[(i + 0x56) & 0xFF] & 0x02) << 3)
                                        | ((bytes[(i + 0x00) & 0xFF] & 0x01) << 3)
                                        | ((bytes[(i + 0x00) & 0xFF] & 0x02) << 1);
                        }

                        tmpNib[0x54] &= 0x3F;
                        tmpNib[0x55] &= 0x3F;
                        memcpy(tmpNib + 0x56, bytes, 256);

                        // XOR the data block with itself, offset by one byte, creating a
                        // 343rd byte which is used as a checksum.
                        tmpNib[342] = 0x00;

                        for(uint16_t i=342; i>0; i--)
                                tmpNib[i] = tmpNib[i] ^ tmpNib[i - 1];

                        // Using a lookup table, convert the 6-bit bytes into disk bytes.
                        for(uint16_t i=0; i<343; i++)
                                tmpNib[i] = diskbyte[tmpNib[i] >> 2];

                        WriteBits(img, tmpNib, 343 * 8, &dstBitPtr);

                        // Done with the nybblization, now add the epilogue...
                        WriteBits(img, footer, 3 * 8, &dstBitPtr);

                        // (Should the footer be 30 or 48? would be 45 FF10s here for 48)
                        for(int i=0; i<27; i++)
                                WriteBits(img, ff10, 10, &dstBitPtr);
                }

                // Set the proper bit/byte lengths in the WOZ for this track
                woz[driveNum]->track[trk].bitCount = Uint16LE(dstBitPtr);
                woz[driveNum]->track[trk].byteCount = Uint16LE((dstBitPtr + 7) / 8);
        }

        delete[] tmpDisk;
}


const char * FloppyDrive::ImageName(uint8_t driveNum/*= 0*/)
{
        // Set up a zero-length string for return value
        nameBuf[0] = 0;

        if (driveNum > 1)
        {
                WriteLog("FLOPPY: Attempted to get image name for drive #%u!\n", driveNum);
                return nameBuf;
        }

        // Now we attempt to strip out extraneous paths/extensions to get just the filename
        const char * startOfFile = strrchr(imageName[driveNum], '/');
        const char * startOfExt = strrchr(imageName[driveNum], '.');

        // If there isn't a path, assume we're starting at the beginning
        if (startOfFile == NULL)
                startOfFile = &imageName[driveNum][0];
        else
                startOfFile++;

        // If there isn't an extension, assume it's at the terminating NULL
        if (startOfExt == NULL)
                startOfExt = &imageName[driveNum][0] + strlen(imageName[driveNum]);

        // Now copy the filename (may copy nothing!)
        int j = 0;

        for(const char * i=startOfFile; i<startOfExt; i++)
                nameBuf[j++] = *i;

        nameBuf[j] = 0;

        return nameBuf;
}


void FloppyDrive::EjectImage(uint8_t driveNum/*= 0*/)
{
        // Sanity check
        if (diskType[driveNum] == DT_EMPTY)
                return;

        // Probably want to save a dirty image... ;-)
        if (SaveImage(driveNum))
                WriteLog("FLOPPY: Ejected image file '%s' from drive %u...\n", imageName[driveNum], driveNum);

        if (disk[driveNum])
                delete[] disk[driveNum];

        disk[driveNum] = NULL;
        woz[driveNum] = NULL;
        diskSize[driveNum] = 0;
        diskType[driveNum] = DT_EMPTY;
        imageDirty[driveNum] = false;
        imageName[driveNum][0] = 0;                     // Zero out filenames
}


bool FloppyDrive::IsEmpty(uint8_t driveNum/*= 0*/)
{
        if (driveNum > 1)
        {
                WriteLog("FLOPPY: Attempted DriveIsEmtpy() for drive #%u!\n", driveNum);
                return true;
        }

        return (diskType[driveNum] == DT_EMPTY ? true : false);
}


bool FloppyDrive::IsWriteProtected(uint8_t driveNum/*= 0*/)
{
        if (driveNum > 1)
        {
                WriteLog("FLOPPY: Attempted DiskIsWriteProtected() for drive #%u!\n", driveNum);
                return true;
        }

        return (bool)woz[driveNum]->writeProtected;
}


void FloppyDrive::SetWriteProtect(bool state, uint8_t driveNum/*= 0*/)
{
        if (driveNum > 1)
        {
                WriteLog("FLOPPY: Attempted set write protect for drive #%u!\n", driveNum);
                return;
        }

        woz[driveNum]->writeProtected = (uint8_t)state;
}


int FloppyDrive::DriveLightStatus(uint8_t driveNum/*= 0*/)
{
        int retval = DLS_OFF;

        if (activeDrive != driveNum)
                return DLS_OFF;

        if (ioHappened)
                retval = (ioMode == IO_MODE_READ ? DLS_READ : DLS_WRITE);

        ioHappened = false;
        return retval;
}


void FloppyDrive::SaveState(FILE * file)
{
        // Internal state vars
        fputc(motorOn, file);
        fputc(activeDrive, file);
        fputc(ioMode, file);
        fputc(dataRegister, file);
        fputc((ioHappened ? 1 : 0), file);

        // Disk #1
        if (disk[0] != NULL)
        {
                WriteLong(file, diskSize[0]);
                WriteLong(file, diskType[0]);
                fputc(phase[0], file);
                fputc(headPos[0], file);
                WriteLong(file, currentPos[0]);
                fputc((imageDirty[0] ? 1 : 0), file);
                fwrite(disk[0], 1, diskSize[0], file);
                fwrite(imageName[0], 1, MAX_PATH, file);
        }
        else
                WriteLong(file, 0);

        // Disk #2
        if (disk[1] != NULL)
        {
                WriteLong(file, diskSize[1]);
                WriteLong(file, diskType[1]);
                fputc(phase[1], file);
                fputc(headPos[1], file);
                WriteLong(file, currentPos[1]);
                fputc((imageDirty[1] ? 1 : 0), file);
                fwrite(disk[1], 1, diskSize[1], file);
                fwrite(imageName[1], 1, MAX_PATH, file);
        }
        else
                WriteLong(file, 0);
}


void FloppyDrive::LoadState(FILE * file)
{
        // Eject images if they're loaded
        EjectImage(0);
        EjectImage(1);

        // Read internal state variables
        motorOn = fgetc(file);
        activeDrive = fgetc(file);
        ioMode = fgetc(file);
        dataRegister = fgetc(file);
        ioHappened = (fgetc(file) == 1 ? true : false);

        diskSize[0] = ReadLong(file);

        if (diskSize[0])
        {
                disk[0] = new uint8_t[diskSize[0]];
                diskType[0] = (uint8_t)ReadLong(file);
                phase[0] = fgetc(file);
                headPos[0] = fgetc(file);
                currentPos[0] = ReadLong(file);
                imageDirty[0] = (fgetc(file) == 1 ? true : false);
                fread(disk[0], 1, diskSize[0], file);
                fread(imageName[0], 1, MAX_PATH, file);
                woz[0] = (WOZ *)disk[0];
        }

        diskSize[1] = ReadLong(file);

        if (diskSize[1])
        {
                disk[1] = new uint8_t[diskSize[1]];
                diskType[1] = (uint8_t)ReadLong(file);
                phase[1] = fgetc(file);
                headPos[1] = fgetc(file);
                currentPos[1] = ReadLong(file);
                imageDirty[1] = (fgetc(file) == 1 ? true : false);
                fread(disk[1], 1, diskSize[1], file);
                fread(imageName[1], 1, MAX_PATH, file);
                woz[1] = (WOZ *)disk[1];
        }
}


uint32_t FloppyDrive::ReadLong(FILE * file)
{
        uint32_t r = 0;

        for(int i=0; i<4; i++)
                r = (r << 8) | fgetc(file);

        return r;
}


void FloppyDrive::WriteLong(FILE * file, uint32_t l)
{
        for(int i=0; i<4; i++)
        {
                fputc((l >> 24) & 0xFF, file);
                l = l << 8;
        }
}


void FloppyDrive::WriteLongLE(FILE * file, uint32_t l)
{
        for(int i=0; i<4; i++)
        {
                fputc(l & 0xFF, file);
                l >>= 8;
        }
}


void FloppyDrive::WriteWordLE(FILE * file, uint16_t w)
{
        fputc(w & 0xFF, file);
        fputc((w >> 8) & 0xFF, file);
}


void FloppyDrive::WriteZeroes(FILE * file, uint32_t num)
{
        for(uint32_t i=0; i<num; i++)
                fputc(0, file);
}


// Memory mapped I/O functions + Logic State Sequencer

/*
The DSK format is a byte-for-byte image of a 16-sector Apple II floppy disk: 35
tracks of 16 sectors of 256 bytes each, making 143,360 bytes in total. The PO
format is exactly the same size as DSK and is also organized as 35 sequential
tracks, but the sectors within each track are in a different sequence. The NIB
format is a nybblized format: a more direct representation of the disk's data
as encoded by the Apple II floppy drive hardware. NIB contains 35 tracks of
6656 bytes each, for a total size of 232,960 bytes. Although this format is
much larger, it is also more versatile and can represent the older 13-sector
disks, many copy-protected disks, and other unusual encodings.

N.B.: Though the NIB format is *closer* to the representation of the disk's
      data, it's not *quite* 100% as there can be zero bits lurking in the
      interstices of the bytes written to the disk.  There's room for another
      format that takes this into account (possibly even take phase 1 & 3
      tracks into account as well).

      As luck would have it, not long after I wrote that, I found out that some enterprising people have created it already--WOZ format.  Which is now supported by apple2.  :-D

According to Beneath Apple DOS, DOS checks the data register to see if it changes when spinning up a drive: "A sufficient delay should be provided to allow the motor time to come up to speed.  Shugart recommends one second, but DOS is able to reduce this delay by watching the read latch until data starts to change."  Which means, we can simulate an empty/off drive by leaving the data register alone.
*/

void FloppyDrive::ControlStepper(uint8_t addr)
{
        // $C0E0 - 7
/*
How It Works
------------
The stepper motor has 4 phase solenoids (numbered 0-3) which corresponds to bits 1-2 of the address.  Bit 0 tells the phase solenoid to either energize (1) or de-energize (0).  By energizing the phase solenoids in ascending order, the stepper motor moves the head from a low numbered track to a higher numbered track; conversely, by energizing the solenoids in descending order, the stepper motor moves the head from a high numbered track to a lower one.  Given that this is a mechanical device, it takes a certain amount of time for the drum in the stepper motor to move from place to place--though pretty much all software written for the Disk II takes this into account.

Tracks can apparently go from 0 to 79, though typically only 0 to 69 are usuable.  Further, because of the limitations of the read/write head of the drive, not every track can be written to, so typically (about 99.99% of the time in my guesstimation) only every *other* track is written to (phases 0 and 2); some disks exist that have tracks written on phase 1 or 3, but these tend to be the exception rather than the rule.
*/
        // Sanity check
        if (diskType[activeDrive] == DT_EMPTY)
                return;

        // Convert phase solenoid number into a bit from 1 through 8:
        uint8_t phaseBit = 1 << ((addr >> 1) & 0x03);

        // Set the state of the phase solenoid accessed using the phase bit
        if (addr & 0x01)
                phase[activeDrive] |= phaseBit;
        else
                phase[activeDrive] &= ~phaseBit;

        // See if the new phase solenoid is energized, & move the stepper/head
        // appropriately.
        // N.B.: The head stub is located by bits 1 & 2 of the headPos variable
        uint8_t oldHeadPos = headPos[activeDrive];
        uint8_t nextUp     = 1 << (((oldHeadPos >> 1) + 1) & 0x03);
        uint8_t nextDown   = 1 << (((oldHeadPos >> 1) - 1) & 0x03);

        // We simulate cogging here by seeing if there's a valid up and/or down
        // position to go to.  If both are valid, the head goes nowhere.
        if (phase[activeDrive] & nextUp)
                headPos[activeDrive] += (headPos[activeDrive] < 140 ? 2 : 0);

        if (phase[activeDrive] & nextDown)
                headPos[activeDrive] -= (headPos[activeDrive] > 0 ? 2 : 0);

        if (oldHeadPos != headPos[activeDrive])
        {
                uint8_t newTIdx = woz[activeDrive]->tmap[headPos[activeDrive]];
                float newBitLen = (newTIdx == 0xFF ? 51200.0f
                        : Uint16LE(woz[activeDrive]->track[newTIdx].bitCount));

                uint8_t oldTIdx = woz[activeDrive]->tmap[oldHeadPos];
                float oldBitLen = (oldTIdx == 0xFF ? 51200.0f
                        : Uint16LE(woz[activeDrive]->track[oldTIdx].bitCount));
                currentPos[activeDrive] = (uint32_t)((float)currentPos[activeDrive] * (newBitLen / oldBitLen));

                trackLength[activeDrive] = (uint16_t)newBitLen;
                SpawnMessage("Stepping to track %u...", headPos[activeDrive] >> 2);
        }

WriteLog("FLOPPY: Stepper phase %d set to %s [%c%c%c%c] (track=%2.2f)\n", (addr >> 1) & 0x03, (addr & 0x01 ? "ON " : "off"), (phase[activeDrive] & 0x08 ? '|' : '.'), (phase[activeDrive] & 0x04 ? '|' : '.'), (phase[activeDrive] & 0x02 ? '|' : '.'), (phase[activeDrive] & 0x01 ? '|' : '.'), (float)headPos[activeDrive] / 4.0f);
}


void FloppyDrive::ControlMotor(uint8_t addr)
{
        // $C0E8 - 9
        motorOn = addr;

        if (motorOn)
                readPulse = 0;
        else
                driveOffTimeout = 2000000;

WriteLog("FLOPPY: Turning drive motor %s\n", (motorOn ? "ON" : "off"));
}


void FloppyDrive::DriveEnable(uint8_t addr)
{
        // $C0EA - B
        activeDrive = addr;
WriteLog("FLOPPY: Selecting drive #%hhd\n", addr + 1);
}


/*
So for $C08C-F, we have two switches (Q6 & Q7) which combine to make four states ($C-D is off/on for Q6, $E-F is off/on for Q7).

So it forms a matrix like so:

       $C08E                        $C08F
      +-----------------------------------------------------------------------
$C08C |Enable READ sequencing      |Data reg SHL every 8th clock while writing
      +----------------------------+------------------------------------------
$C08D |Check write prot./init write|Data reg LOAD every 8th clk while writing

Looks like reads from even addresses in $C080-F block transfer data from the sequencer to the MPU, does write from odd do the inverse (transfer from MPU to sequencer)?  Looks like it.

*/


void FloppyDrive::SetShiftLoadSwitch(uint8_t state)
{
        // $C0EC - D
        slSwitch = state;
}


void FloppyDrive::SetReadWriteSwitch(uint8_t state)
{
        // $C0EE - F
        rwSwitch = state;
}


// MMIO: Reads from $C08x to $C0XX on even addresses
uint8_t FloppyDrive::DataRegister(void)
{
        // Sanity check
        if (diskType[activeDrive] != DT_EMPTY)
        {
                uint8_t tIdx = woz[activeDrive]->tmap[headPos[activeDrive]];
                uint32_t bitLen = (tIdx == 0xFF ? 51200
                        : Uint16LE(woz[activeDrive]->track[tIdx].bitCount));
                SpawnMessage("%u:Reading $%02X from track %u, sector %u...",
                        activeDrive, dataRegister, headPos[activeDrive] >> 2, (uint32_t)(((float)currentPos[activeDrive] / (float)bitLen) * 16.0f));
                ioMode = IO_MODE_READ;
                ioHappened = true;
        }

        return dataRegister;
}


// MMIO: Writes from $C08x to $C0XX on odd addresses
void FloppyDrive::DataRegister(uint8_t data)
{
        cpuDataBus = data;
        ioMode = IO_MODE_WRITE;
        ioHappened = true;
}


/*
        OFF switches                ON switches
Switch  Addr   Func                 Addr   Func
Q0      $C080  Phase 0 off          $C081  Phase 0 on
Q1      $C082  Phase 1 off          $C083  Phase 1 on
Q2      $C084  Phase 2 off          $C085  Phase 2 on
Q3      $C086  Phase 3 off          $C087  Phase 3 on
Q4      $C088  Drive off            $C089  Drive on
Q5      $C08A  Select Drive 1       $C08B  Select Drive 2
Q6      $C08C  Shift data register  $C08D  Load data register
Q7      $C08E  Read                 $C08F  Write

From "Beneath Apple ProDOS", description of combinations of $C0EC-EF

$C08C, $C08E: Enable read sequencing
$C08C, $C08F: Shift data register every four cycles while writing
$C08D, $C08E: Check write protect and initialize sequencer for writing
$C08D, $C08F: Load data register every four cycles while writing


Sense Write Protect:

        LDX #SLOT               Put slot number times 16 in X-register.
        LDA $C08D, X
        LDA $C08E, X    Sense write protect.
        BMI ERROR               If high bit set, protected.

*/

/*
PRODOS 8 MLI ERROR CODES

$00:    No error
$01:    Bad system call number
$04:    Bad system call parameter count
$25:    Interrupt table full
$27:    I/O error
$28:    No device connected
$2B:    Disk write protected
$2E:    Disk switched
$40:    Invalid pathname
$42:    Maximum number of files open
$43:    Invalid reference number
$44:    Directory not found
$45:    Volume not found
$46:    File not found
$47:    Duplicate filename
$48:    Volume full
$49:    Volume directory full
$4A:    Incompatible file format, also a ProDOS directory
$4B:    Unsupported storage_type
$4C:    End of file encountered
$4D:    Position out of range
$4E:    File access error, also file locked
$50:    File is open
$51:    Directory structure damaged
$52:    Not a ProDOS volume
$53:    Invalid system call parameter
$55:    Volume Control Block table full
$56:    Bad buffer address
$57:    Duplicate volume
$5A:    File structure damaged
*/


//
// This is used mainly to initialize blank disks and upconvert non-WOZ disks
//
void FloppyDrive::InitWOZ(uint8_t driveNum/*= 0*/)
{
        // Sanity check
        if (disk[driveNum] != NULL)
        {
                WriteLog("FLOPPY: Attempted to initialize non-NULL WOZ structure\n");
                return;
        }

        diskSize[driveNum] = 256 + (35 * sizeof(WOZTrack));
        disk[driveNum] = new uint8_t[diskSize[driveNum]];
        woz[driveNum] = (WOZ *)disk[driveNum];

        // Zero out WOZ image in memory
        memset(woz[driveNum], 0, diskSize[driveNum]);

        // Set up header (leave CRC as 0 for now)
        memcpy(woz[driveNum]->magic, wozHeader, 8);

        // INFO header
        memcpy(woz[driveNum]->infoTag, "INFO", 4);
        woz[driveNum]->infoSize = Uint32LE(60);
        woz[driveNum]->infoVersion = 1;
        woz[driveNum]->diskType = 1;
        woz[driveNum]->writeProtected = 0;
        woz[driveNum]->synchronized = 0;
        woz[driveNum]->cleaned = 1;
        memset(woz[driveNum]->creator, ' ', 32);
        memcpy(woz[driveNum]->creator, "Apple2 emulator v1.0.0", 22);

        // TMAP header
        memcpy(woz[driveNum]->tmapTag, "TMAP", 4);
        woz[driveNum]->tmapSize = Uint32LE(160);
        memcpy(woz[driveNum]->tmap, standardTMAP, 141);

        // TRKS header
        memcpy(woz[driveNum]->trksTag, "TRKS", 4);
        woz[driveNum]->trksSize = Uint32LE(35 * sizeof(WOZTrack));

        for(int i=0; i<35; i++)
        {
                woz[driveNum]->track[i].bitCount = Uint16LE(51200);
                woz[driveNum]->track[i].byteCount = Uint16LE((51200 + 7) / 8);
        }

        // META header (how to handle? prolly with a separate pointer)
}


//
// Do basic sanity checks on the passed in contents (file loaded elsewhere).
// Returns true if successful, false on failure.
//
bool FloppyDrive::CheckWOZ(const uint8_t * wozData, uint32_t wozSize, uint8_t driveNum/*= 0*/)
{
        // Hey!  This reference works!!  :-D
        WOZ & woz1 = *((WOZ *)wozData);
        woz[driveNum] = (WOZ *)wozData;

        // Basic sanity checking
        if (wozData == NULL)
        {
                WriteLog("FLOPPY: NULL pointer passed in to CheckWOZ()...\n");
                return false;
        }

        if (memcmp(woz1.magic, wozHeader, 8) != 0)
        {
                WriteLog("FLOPPY: Invalid WOZ header in file\n");
                return false;
        }

        uint32_t crc = CRC32(&wozData[12], wozSize - 12);
        uint32_t wozCRC = Uint32LE(woz1.crc32);

        if ((wozCRC != 0) && (wozCRC != crc))
        {
                WriteLog("FLOPPY: Corrupted data found in WOZ. CRC32: %08X, computed: %08X\n", wozCRC, crc);
                return false;
        }
        else if (wozCRC == 0)
                WriteLog("FLOPPY: Warning--WOZ file has no CRC...\n");

#if 1
        WriteLog("Track map:\n");
        WriteLog("                                        1   1   1   1   1   1   1   1\n");
        WriteLog("0.,.1.,.2.,.3.,.4.,.5.,.6.,.7.,.8.,.9.,.0.,.1.,.2.,.3.,.4.,.5.,.6.,.7.,.\n");
        WriteLog("------------------------------------------------------------------------\n");

        for(uint8_t j=0; j<2; j++)
        {
                for(uint8_t i=0; i<72; i++)
                {
                        char buf[64] = "..";
                        buf[0] = buf[1] = '.';

                        if (woz1.tmap[i] != 0xFF)
                                sprintf(buf, "%02d", woz1.tmap[i]);

                        WriteLog("%c", buf[j]);
                }

                WriteLog("\n");
        }

        WriteLog("\n1   1   2   2   2   2   2   2   2   2   2   2   3   3   3   3   3   3\n");
        WriteLog("8.,.9.,.0.,.1.,.2.,.3.,.4.,.5.,.6.,.7.,.8.,.9.,.0.,.1.,.2.,.3.,.4.,.5\n");
        WriteLog("---------------------------------------------------------------------\n");

        for(uint8_t j=0; j<2; j++)
        {
                for(uint8_t i=72; i<141; i++)
                {
                        char buf[64] = "..";

                        if (woz1.tmap[i] != 0xFF)
                                sprintf(buf, "%02d", woz1.tmap[i]);

                        WriteLog("%c", buf[j]);
                }

                WriteLog("\n");
        }

        WriteLog("\n");

        uint8_t numTracks = woz1.trksSize / sizeof(WOZTrack);

        // N.B.: Need to check the track[] to have this tell the correct track...  Right now, it doesn't
        for(uint8_t i=0; i<numTracks; i++)
        {
                WriteLog("WOZ: Track %2.2f: %d bits (packed into %d bytes)\n", (float)i / 4.0f, woz1.track[i].bitCount, woz1.track[i].byteCount);
        }
#endif

        WriteLog("FLOPPY: Well formed WOZ file found\n");
        return true;
}


bool FloppyDrive::SaveWOZ(uint8_t driveNum)
{
        // Various sanity checks...
        if (driveNum > 1)
        {
                WriteLog("FLOPPY: Attempted to save image to drive #%u!\n", driveNum);
                return false;
        }

        if (diskType[driveNum] == DT_EMPTY)
        {
                WriteLog("FLOPPY: No image in drive #%u to save\n", driveNum);
                return false;
        }

        if (!imageDirty[driveNum])
        {
                WriteLog("FLOPPY: No need to save unchanged image in drive #%u...\n", driveNum);
                return false;
        }

        // Set up CRC32 before writing
        woz[driveNum]->crc32 = Uint32LE(CRC32(&disk[driveNum][12], diskSize[driveNum] - 12));

        // META header (skip for now) (actually, should be in the disk[] image already)

        // Finally, write the damn image
        FILE * fp = fopen(imageName[driveNum], "wb");

        if (fp == NULL)
        {
                WriteLog("FLOPPY: Failed to open image file '%s' for writing...\n", imageName[driveNum]);
                return false;
        }

        fwrite(disk[driveNum], 1, diskSize[driveNum], fp);
        fclose(fp);

        WriteLog("FLOPPY: Successfully wrote image file '%s'...\n", imageName[driveNum]);

        return true;
}


// N.B.: The WOZ documentation says that the bitstream is normalized to 4µs.
//       Which means on the //e that you would have to run it at that clock
//       rate (instead of the //e clock rate 0.9799µs/cycle) to get the
//       simulated drive running at 300 RPM.  So, instead of doing that, we're
//       just gonna run it at twice the clock rate of the base 6502 clock,
//       which will make the simulated drive run in the neighborhood of around
//       306 RPM.  Should be close enough to get away with it.  :-)  (And it
//       seems to run OK, for the most part.)


static bool logSeq = false;
//
// Logic State Sequencer & Data Register
//
void FloppyDrive::RunSequencer(uint32_t cyclesToRun)
{
        static uint32_t prng = 1;

        // Sanity checks
        if (diskType[activeDrive] == DT_EMPTY)
                return;
        else if (motorOn == false)
        {
                if (driveOffTimeout == 0)
                        return;
                else
                        driveOffTimeout--;
        }

        // It's x2 because the sequencer clock runs twice as fast as the CPU clock.
        cyclesToRun *= 2;

//extern bool dumpDis;
//static bool tripwire = false;
uint8_t chop = 0;
//static uint32_t lastPos = 0;
if (logSeq)
{
        WriteLog("DISKSEQ: Running for %d cycles [rw=%hhd, sl=%hhd, reg=%02X, bus=%02X]\n", cyclesToRun, rwSwitch, slSwitch, dataRegister, cpuDataBus);
}

        while (cyclesToRun-- > 0)
        {
                pulseClock = (pulseClock + 1) & 0x07;

                if (pulseClock == 0)
                {
                        uint16_t bytePos = currentPos[activeDrive] / 8;
                        uint8_t bitPos = currentPos[activeDrive] % 8;
                        uint8_t tIdx = woz[activeDrive]->tmap[headPos[activeDrive]];

                        if (tIdx != 0xFF)
                        {
                                if (woz[activeDrive]->track[tIdx].bits[bytePos] & bitMask[bitPos])
                                {
                                        // According to Jim Sather (Understanding the Apple II),
                                        // the Read Pulse, when it happens, is 1µs long, which is 2
                                        // sequencer clock pulses long.
                                        readPulse = 2;
                                        zeroBitCount = 0;
                                }
                                else
                                        zeroBitCount++;
#if 0
                                currentPos[activeDrive] = (currentPos[activeDrive] + 1) % Uint16LE(woz[activeDrive]->track[tIdx].bitCount);
                        }
                        else
                                currentPos[activeDrive] = (currentPos[activeDrive] + 1) % 51200;
#else
                        }

//this doesn't work reliably for some reason...
//seems to work OK now...
                        currentPos[activeDrive] = (currentPos[activeDrive] + 1) % trackLength[activeDrive];
#endif

                        // If we hit more than 2 zero bits in a row, simulate the disk head
                        // reader's Automatic Gain Control (AGC) turning itself up too high
                        // by stuffing random bits in the bitstream.  We also do this if
                        // the current track is marked as unformatted.
/*
N.B.: Had to up this to 3 because Up N' Down had some weird sync bytes (FE10).  May have to up it some more.
*/
                        if ((zeroBitCount > 3) || (tIdx == 0xFF))
                        {
                                if (prng & 0x00001)
                                {
                                        // This PRNG is called the "Galois configuration".
                                        prng ^= 0x24000;
                                        readPulse = 2;
                                }

                                prng >>= 1;
                        }
                }

                // Find and run the Sequencer's next state
                uint8_t nextState = (sequencerState & 0xF0) | (rwSwitch << 3)
                        | (slSwitch << 2) | (readPulse ? 0x02 : 0)
                        | ((dataRegister & 0x80) >> 7);
if (logSeq)
        WriteLog("[%02X:%02X]%s", sequencerState, nextState, (chop == 15 ? "\n" : ""));
chop = (chop + 1) % 20;
                sequencerState = sequencerROM[nextState];

                switch (sequencerState & 0x0F)
                {
                case 0x00:
                case 0x01:
                case 0x02:
                case 0x03:
                case 0x04:
                case 0x05:
                case 0x06:
                case 0x07:
                        // CLR (clear data register)
                        dataRegister = 0;
                        break;
                case 0x08:
                case 0x0C:
                        // NOP (no operation)
                        break;
                case 0x09:
                        // SL0 (shift left, 0 fill LSB)
                        dataRegister <<= 1;
//if (!stopWriting)
{
                        uint8_t tIdx = woz[activeDrive]->tmap[headPos[activeDrive]];

                        if (rwSwitch && (tIdx != 0xFF)
                                && !woz[activeDrive]->writeProtected)
                        {
                                imageDirty[activeDrive] = true;
                                uint16_t bytePos = currentPos[activeDrive] / 8;
                                uint8_t bitPos = currentPos[activeDrive] % 8;

                                if (dataRegister & 0x80)
                                        // Fill in the one, if necessary
                                        woz[activeDrive]->track[tIdx].bits[bytePos] |= bitMask[bitPos];
                                else
                                        // Otherwise, punch in the zero
                                        woz[activeDrive]->track[tIdx].bits[bytePos] &= ~bitMask[bitPos];

#if 0
if (dumpDis || tripwire)
{
tripwire = true;
WriteLog("[%s]", (dataRegister & 0x80 ? "1" : "0"));
if (lastPos == currentPos[activeDrive])
        WriteLog("{STOMP}");
else if ((lastPos + 1) != currentPos[activeDrive])
        WriteLog("{LAG}");
lastPos = currentPos[activeDrive];
}
#endif
                        }
}
                        break;
                case 0x0A:
                case 0x0E:
                        // SR (shift right write protect bit)
                        dataRegister >>= 1;
                        dataRegister |= (woz[activeDrive]->writeProtected ? 0x80 : 0x00);
                        break;
                case 0x0B:
                case 0x0F:
                        // LD (load data register from data bus)
                        dataRegister = cpuDataBus;
//if (!stopWriting)
{
                        uint8_t tIdx = woz[activeDrive]->tmap[headPos[activeDrive]];

                        if (rwSwitch && (tIdx != 0xFF)
                                && !woz[activeDrive]->writeProtected)
                        {
                                imageDirty[activeDrive] = true;
                                uint16_t bytePos = currentPos[activeDrive] / 8;
                                uint8_t bitPos = currentPos[activeDrive] % 8;
                                woz[activeDrive]->track[tIdx].bits[bytePos] |= bitMask[bitPos];
#if 0
if (dumpDis || tripwire)
{
tripwire = true;
WriteLog("[%s]", (dataRegister & 0x80 ? "1" : "0"));
if (lastPos == currentPos[activeDrive])
        WriteLog("{STOMP}");
else if ((lastPos + 1) != currentPos[activeDrive])
        WriteLog("{LAG}");
lastPos = currentPos[activeDrive];
}
#endif
                        }
}
                        break;
                case 0x0D:
                        // SL1 (shift left, 1 fill LSB)
                        dataRegister <<= 1;
                        dataRegister |= 0x01;
                        break;
                }

                if (readPulse > 0)
                        readPulse--;
        }

if (logSeq)
        WriteLog("\n");
}


FloppyDrive floppyDrive[2];

static uint8_t SlotIOR(uint16_t address)
{
        uint8_t state = address & 0x0F;

        switch (state)
        {
        case 0x00:
        case 0x01:
        case 0x02:
        case 0x03:
        case 0x04:
        case 0x05:
        case 0x06:
        case 0x07:
                floppyDrive[0].ControlStepper(state);
                break;
        case 0x08:
        case 0x09:
                floppyDrive[0].ControlMotor(state & 0x01);
                break;
        case 0x0A:
        case 0x0B:
                floppyDrive[0].DriveEnable(state & 0x01);
                break;
        case 0x0C:
        case 0x0D:
                floppyDrive[0].SetShiftLoadSwitch(state & 0x01);
                break;
        case 0x0E:
        case 0x0F:
                floppyDrive[0].SetReadWriteSwitch(state & 0x01);
                break;
        }

        // Even addresses return the data register, odd (we suppose) returns a
        // floating bus read...
        return (address & 0x01 ? ReadFloatingBus(0) : floppyDrive[0].DataRegister());
}


static void SlotIOW(uint16_t address, uint8_t byte)
{
        uint8_t state = address & 0x0F;

        switch (state)
        {
        case 0x00:
        case 0x01:
        case 0x02:
        case 0x03:
        case 0x04:
        case 0x05:
        case 0x06:
        case 0x07:
                floppyDrive[0].ControlStepper(state);
                break;
        case 0x08:
        case 0x09:
                floppyDrive[0].ControlMotor(state & 0x01);
                break;
        case 0x0A:
        case 0x0B:
                floppyDrive[0].DriveEnable(state & 0x01);
                break;
        case 0x0C:
        case 0x0D:
                floppyDrive[0].SetShiftLoadSwitch(state & 0x01);
                break;
        case 0x0E:
        case 0x0F:
                floppyDrive[0].SetReadWriteSwitch(state & 0x01);
                break;
        }

        // Odd addresses write to the Data register, even addresses (we assume) go
        // into the ether
        if (state & 0x01)
                floppyDrive[0].DataRegister(byte);
}


// This slot function doesn't need to differentiate between separate instances
// of FloppyDrive
static uint8_t SlotROM(uint16_t address)
{
        return diskROM[address];
}


void InstallFloppy(uint8_t slot)
{
        SlotData disk = { SlotIOR, SlotIOW, SlotROM, 0, 0, 0 };
        InstallSlotHandler(slot, &disk);
}