Floppy image 2us to 4us conversion

diff --git a/disk.cpp b/disk.cpp
index 89066a00911ee415f4fccc7a64f3f90f436de59c..34e184ecb4cc73988e1ce9746ddec05cf5c069ec 100644 (file)
--- a/disk.cpp
+++ b/disk.cpp
@@ -219,6 +219,7 @@ typedef struct {
        int lastdataacesstrack;
        int lastrev;
        bool track_access_done;
+       bool fourms;
 #endif
 } drive;
 
@@ -571,12 +572,14 @@ static int get_floppy_speed_from_image(drive *drv)
        
        m = get_floppy_speed();
        l = drv->tracklen;
+       drv->fourms = false;
        if (!drv->tracktiming[0]) {
                m = m * l / (2 * 8 * FLOPPY_WRITE_LEN * drv->ddhd);
        }
        // 4us track?
        if (l < (FLOPPY_WRITE_LEN_PAL * 8) * 4 / 6) {
                m *= 2;
+               drv->fourms = true;
        }
        if (m <= 0) {
                m = 1;
@@ -3298,11 +3301,37 @@ static bool unformatted (drive *drv)
        return false;
 }
 
-/* get one bit from MFM bit stream */
-STATIC_INLINE uae_u32 getonebit (uae_u16 * mfmbuf, int mfmpos)
+static int nextbit(drive *drv)
+{
+       return drv && !drv->fourms && !(adkcon & 0x0100) ? 2 : 1;
+}
+
+/* get one bit from bit stream */
+static uae_u32 getonebit(drive *drv, uae_u16 *mfmbuf, int mfmpos, int *inc)
 {
        uae_u16 *buf;
 
+       if (inc)
+               *inc = 1;
+       if (inc && nextbit(drv) == 2) {
+               // 2us -> 4us
+               int b1 = getonebit(NULL, mfmbuf, mfmpos, NULL);
+               int b2 = getonebit(NULL, mfmbuf, (mfmpos + 1) % drv->tracklen, NULL);
+               if (!b1 && b2) {
+                       *inc = 3;
+                       return 1;
+               }
+               if (b1 && !b2) {
+                       *inc = 2;
+                       return 1;
+               }
+               if (b1 && b2) {
+                       *inc = 3;
+                       return 1;
+               }
+               *inc = 2;
+               return 0;
+       }
        buf = &mfmbuf[mfmpos >> 4];
        return (buf[0] & (1 << (15 - (mfmpos & 15)))) ? 1 : 0;
 }
@@ -3326,7 +3355,7 @@ void dumpdisk (const TCHAR *name)
                                                if (pos < 0)
                                                        pos += drv->tracklen;
                                                w <<= 1;
-                                               w |= getonebit (drv->bigmfmbuf, pos);
+                                               w |= getonebit(NULL, drv->bigmfmbuf, pos, NULL);
                                        }
                                        console_out_f(_T("%04X%c"), w, j == -1 ? '|' : ' ');
                                }
@@ -3541,6 +3570,7 @@ static void disk_doupdate_predict (int startcycle)
                noselected = false;
                int countcycle = startcycle;
                while (countcycle < (maxhpos << 8)) {
+                       int inc = nextbit(drv);
                        if (drv->tracktiming[0])
                                updatetrackspeed (drv, mfmpos);
                        countcycle += drv->trackspeed;
@@ -3550,12 +3580,12 @@ static void disk_doupdate_predict (int startcycle)
                                        if (unformatted (drv))
                                                tword |= (uaerand () & 0x1000) ? 1 : 0;
                                        else
-                                               tword |= getonebit (drv->bigmfmbuf, mfmpos);
+                                               tword |= getonebit(drv, drv->bigmfmbuf, mfmpos, &inc);
                                }
                                if (dskdmaen != DSKDMA_READ && (tword & 0xffff) == dsksync && dsksync != 0)
                                        diskevent_flag |= DISK_WORDSYNC;
                        }
-                       mfmpos++;
+                       mfmpos += inc;
                        mfmpos %= drv->tracklen;
                        if (!dskdmaen) {
                                if (mfmpos == 0)
@@ -3713,6 +3743,7 @@ static void disk_doupdate_read (drive * drv, int floppybits)
        */
        while (floppybits >= drv->trackspeed) {
                bool skipbit = false;
+               int inc = nextbit(drv);
 
                if (drv->tracktiming[0])
                        updatetrackspeed (drv, drv->mfmpos);
@@ -3723,7 +3754,7 @@ static void disk_doupdate_read (drive * drv, int floppybits)
                        if (unformatted (drv))
                                word |= (uaerand () & 0x1000) ? 1 : 0;
                        else
-                               word |= getonebit (drv->bigmfmbuf, drv->mfmpos);
+                               word |= getonebit(drv, drv->bigmfmbuf, drv->mfmpos, &inc);
                }
 
                //write_log (_T("%08X bo=%d so=%d mfmpos=%d dma=%d\n"), (word & 0xffffff), bitoffset, syncoffset, drv->mfmpos, dma_enable);
@@ -3731,7 +3762,7 @@ static void disk_doupdate_read (drive * drv, int floppybits)
                        word >>= 1;
                        return;
                }
-               drv->mfmpos++;
+               drv->mfmpos += inc;
                drv->mfmpos %= drv->tracklen;
                if (drv->mfmpos == drv->indexoffset) {
                        if (disk_debug_logging > 2 && drv->indexhack)
@@ -3747,7 +3778,7 @@ static void disk_doupdate_read (drive * drv, int floppybits)
                if (drv->mfmpos == drv->skipoffset) {
                        int skipcnt = disk_jitter;
                        while (skipcnt-- > 0) {
-                               drv->mfmpos++;
+                               drv->mfmpos += nextbit(drv);
                                drv->mfmpos %= drv->tracklen;
                                if (drv->mfmpos == drv->indexoffset) {
                                        if (disk_debug_logging > 2 && drv->indexhack)