1 #!/usr/bin/python

2 # mk_adf.py <bootblock> <payload> <output_adf>

3 #

4 # Stuff a given bootblock and payload into an output ADF image.

5 #

6 # Written & released by Keir Fraser <keir.xen@gmail.com>

7 #

8 # This is free and unencumbered software released into the public domain.

9 # See the file COPYING for more details, or visit <http://unlicense.org>.

10

11 import struct, sys

12

13 # Amiga bootblock checksum

14 def checksum(bb, sum=0):

15 while len(bb):

16 x, bb = struct.unpack(">L",bb[:4]), bb[4:]

17 sum += x[0]

18 if sum >= (1<<32):

19 sum -= (1<<32)-1

20 return sum

21

22 def main(argv):

23 bb_f = open(argv[1], "rb")

24 pl_f = open(argv[2], "rb")

25 out_f = open(argv[3], "wb")

26 bb_dat = bb_f.read()

27 pl_dat = pl_f.read()

28

29 # Construct bootblock header. We will splice in the checksum later.

30 header = struct.pack(">ccccLLLL",

31 'D', 'O', 'S', '\0', # Bootblock signature

32 0, # Checksum (placeholder)

33 880, # Root block

34 0x60060000, # BRA.B +6

35 (len(pl_dat) + 511) & ~511) # Payload length, padded

36

37

38 # Compute checksum over header, bootblock, and first 512 bytes of payload.

39 sum = checksum(pl_dat[:512], checksum(bb_dat, checksum(header)))

40 sum ^= 0xFFFFFFFF

41 # Splice the computed checksum into the header

42 header = header[:4] + struct.pack(">L", sum) + header[8:]

43 # Write out the header and bootblock code

44 out_f.write(header)

45 out_f.write(bb_dat)

46 # Pad bootblock to 512 bytes

47 for x in xrange((512-len(bb_dat)-len(header))/4):

48 out_f.write(struct.pack(">L", 0))

49 # Write the payload from sector 1 onwards

50 out_f.write(pl_dat)

51 # Pad the ADF image to 880kB

52 for x in xrange((901120-len(pl_dat)-512)/4):

53 out_f.write(struct.pack(">L", 0))

54

55 if __name__ == "__main__":

56 main(sys.argv)