dim288.py (convert disks for misterfpga sharp x68 core)

# By Pedro Gimeno, 2020-06-26
import sys, struct

def main():
  f = open(sys.argv[1], 'rb')
  try:
    f.seek(0, 2)
    flen = f.tell()
    f.seek(0, 0)
    hdr = f.read(256)
    fmt, trkflags, id, crap = struct.unpack('<B170s11s74s', hdr)
    if id != b'DIFC HEADER':
      raise Exception('Invalid file format - not a .dim file')

    trkflags = bytearray(trkflags)

    print("DIM format: %d" % fmt)
    if fmt == 0x00:
      sectors = 8
      sectorlen = 1024
      fmt = 0x20 # ?
    elif fmt == 0x01 or fmt == 0x03:
      sectors = 9
      sectorlen = 1024
      fmt = 0x20 # ?
    elif fmt == 0x02:
      sectors = 15
      sectorlen = 512
      fmt = 0x20 # ?
    elif fmt == 0x09:
      sectors = 18
      sectorlen = 512
      fmt = 0x20 # ?
    elif fmt == 0x11:
      sectors = 26
      sectorlen = 256
      fmt = 0x20 # ?
    else:
      raise Exception('Unrecognized format: 0x%02X' % fmt)

    secdata = []
    d88_offsets = [0x2B0]
    for i, v in enumerate(trkflags):
      if v:
        for s in range(sectors):
          secdata.append(f.read(sectorlen))
        if i < 164:  # d88 only supports 164 tracks, dim supports 170
          d88_offsets.append(d88_offsets[-1] + (0x10 + sectorlen) * sectors)
        else:
          raise Exception('Data present in a track number not supported by D88, aborting')

    if f.tell() != flen:
      print(f.tell(), flen)
      raise Exception('Inconsistent sector size? Found %d tracks of %d sectors, each %d bytes'
          % (len(secdata), sectors, sectorlen))

  finally:
    f.close()

  f = open(sys.argv[2], 'wb')
  try:
    hdr = struct.pack('<17s9sBBI', b'DIM2D88', b'', 0, fmt, d88_offsets[-1])
    d88_offsets = d88_offsets[:-1]
    d88_offsets = d88_offsets + [0] * (164 - len(d88_offsets))
    f.write(hdr)
    f.write(struct.pack('<164I', *d88_offsets))
    tracknum = 0
    secptr = 0
    seclen_code = 1 if sectorlen == 256 else 2 if sectorlen == 512 else 3
    for v in trkflags[:164]:
      if v:
        h = tracknum & 1
        c = tracknum >> 1
        for s in range(sectors):
          hdr = struct.pack('<BBBBHBBB5sH', c, h, s+1, seclen_code, sectors,
              0x00,  # ? Density - 0x00 = Double, 0x40 = single
              0, 0, b'', sectorlen)
          f.write(hdr)
          f.write(secdata[secptr])
          secptr += 1

      tracknum += 1
  finally:
    f.close()

  print("Successfully converted!")

main()