DMK: First cut of import-only support

src/greaseweazle/image/dmk.py

@@ -0,0 +1,106 @@
+# greaseweazle/image/dmk.py
+#
+# Some of the code here is heavily inspired by Simon Owen's SAMdisk:
+# https://simonowen.com/samdisk/
+#
+# Written & released by Keir Fraser <[email protected]>
+# 
+# This is free and unencumbered software released into the public domain.
+# See the file COPYING for more details, or visit <http://unlicense.org>.
+
+from typing import Dict, Tuple, Optional, List, Union
+
+import binascii, math, struct
+import itertools as it
+from bitarray import bitarray
+
+from greaseweazle import __version__
+from greaseweazle import error
+from greaseweazle.codec.ibm import ibm
+from greaseweazle.track import MasterTrack, PLLTrack
+from .image import Image
+
+class DMKTrack:
+
+    def __init__(self, data):
+        time_per_rev = 0.2
+        dlen = len(data)
+        if dlen < 8000: dlen *= 2
+        if dlen < 11000: time_per_rev *= 5/6
+        self.track = MasterTrack(
+            bits = bytes(data),
+            time_per_rev = time_per_rev)
+
+    def master_track(self):
+        return self.track
+
+class DMK(Image):
+
+    read_only = True
+
+    def __init__(self, name: str, _fmt) -> None:
+        self.to_track: Dict[Tuple[int,int], DMKTrack] = dict()
+        self.filename = name
+
+    def from_bytes(self, dat: bytes) -> None:
+
+        ro, ncyl, tlen, flags = struct.unpack(
+            '<2BHB', dat[:5])
+        error.check(flags & 0xef == 0,
+                    'DMK: Unrecognised flags value 0x%02x' % flags)
+        nside = 1 if flags & 0x10 else 2
+
+        o = 16 # skip disk header
+        for cyl in range(ncyl):
+            for head in range(nside):
+                offs = list(map(lambda x: ((x & 0x8000) == 0x8000,
+                                           (x & 0x3fff) - 128),
+                                filter(lambda x: x != 0,
+                                       struct.unpack("<64H", dat[o:o+128]))))
+                data = dat[o+128:o+tlen]
+                o += tlen
+                if not offs:
+                    continue
+                mfm = offs[0][0]
+                if mfm:
+                    data = ibm.mfm_encode(ibm.doubler(data))
+                else:
+                    data = ibm.fm_encode(ibm.doubler(data[::2]))
+                data = bytearray(data)
+                for i, (_mfm, off) in enumerate(offs):
+                    error.check(_mfm == mfm,
+                                'DMK: Unsupported mixed-format track')
+                    if mfm:
+                        idam = off*2-6
+                        dam = data.find(b'\x44\xa9' * 3, (off+10)*2)
+                        error.check(dam != -1, 'DMK: No MFM DAM sync found')
+                        error.check(data[idam:idam+6] == b'\x44\xa9' * 3,
+                                    'DMK: Bad MFM IDAM sync')
+                        data[idam:idam+6] = b'\x44\x89' * 3
+                        data[dam:dam+6] = b'\x44\x89' * 3
+                    else:
+                        idam = (off + 1) & ~1
+                        dam = data.find(b'\xaa\xff', idam+10)
+                        if dam == -1 and i+1 == len(offs):
+                            dam = data.find(b'\xaa\xff', 0, offs[0][1]-2)
+                            print(cyl,head,i+1)
+                        error.check(dam != -1, 'DMK: No FM DAM sync found')
+                        error.check(data[idam:idam+2] == b'\xff\xfe',
+                                    'DMK: Bad FM IDAM sync')
+                        data[idam] &= 0xf5
+                        data[idam+1] &= 0x7f
+                        if dam != -1:
+                            dam += 1
+                            data[dam] &= 0xf5
+                            data[dam+1] &= 0x7f
+
+                self.to_track[cyl,head] = DMKTrack(data)
+
+    def get_track(self, cyl: int, side: int) -> Optional[MasterTrack]:
+        if (cyl,side) not in self.to_track:
+            return None
+        return self.to_track[cyl,side].master_track()
+
+# Local variables:
+# python-indent: 4
+# End:

src/greaseweazle/tools/util.py

@@ -277,6 +277,7 @@ def split_opts(seq):
       '.d88': 'D88',
       '.dcp': 'DCP',
       '.dim': 'DIM',
+      '.dmk': 'DMK',
       '.do' : ('DO','apple2'),
       '.dsd': ('DSD','acorn'),
       '.dsk': 'DSK',