add E7 detection, refactor, add some comments
This commit is contained in:
4am
parent
cfadf05a96
commit
82352e50f9
316
moofimage.py
316
moofimage.py
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@ -10,12 +10,6 @@ import sys
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def myhex(b):
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return hex(b)[2:].rjust(2, "0").upper()
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class MoofDiskImage(wozardry.WozDiskImage):
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def __init__(self, iostream=None):
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wozardry.WozDiskImage.__init__(self, iostream)
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for i,t in zip(range(len(self.tracks)), self.tracks):
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self.tracks[i] = MoofTrack(t.raw_bytes, t.raw_count)
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class MoofTrack(wozardry.Track):
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def __init__(self, raw_bytes, raw_count):
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wozardry.Track.__init__(self, raw_bytes, raw_count)
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@ -26,30 +20,31 @@ class MoofTrack(wozardry.Track):
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while len(self.bits) > raw_count:
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self.bits.pop()
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def bit(self):
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b = self.bits[self.bit_index] and 1 or 0
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self.bit_index += 1
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if self.bit_index >= self.raw_count:
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self.bit_index = 0
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def rewind(self, bit_count=1):
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self.bit_index -= bit_count
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while self.bit_index < 0:
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self.bit_index += self.raw_count
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self.revolutions -= 1
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def forward(self, bit_count=1):
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self.bit_index += bit_count
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while self.bit_index >= self.raw_count:
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self.bit_index -= self.raw_count
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self.revolutions += 1
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def bit(self):
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b = self.bits[self.bit_index]
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self.forward()
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yield b
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def nibble(self):
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b = 0
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while b == 0:
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b = next(self.bit())
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n = 0x80
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while not next(self.bit()): pass
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n = 0b10000000
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for bit_index in range(6, -1, -1):
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b = next(self.bit())
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n += b << bit_index
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n |= b << bit_index
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yield n
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def rewind(self, bit_count=1):
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self.bit_index -= bit_count
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if self.bit_index < 0:
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self.bit_index = self.raw_count - 1
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self.revolutions -= 1
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def find(self, sequence):
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starting_revolutions = self.revolutions
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seen = [0] * len(sequence)
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@ -76,21 +71,23 @@ class MoofTrack(wozardry.Track):
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return False
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class MoofAddressField:
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def __init__(self, volume, track_id, sector_id, valid):
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def __init__(self, valid, volume, track_id, sector_id):
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self.valid = valid
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self.volume = volume
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self.track_id = track_id
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self.sector_id = sector_id
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class MoofDataField:
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def __init__(self, valid, sector_id, tags, data):
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self.valid = valid
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self.sector_id = sector_id
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self.tags = tags
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self.data = data
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class MoofBlock:
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def __init__(self, address_field, decoded, start_bit_index=None, end_bit_index=None):
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def __init__(self, address_field, data_field):
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self.address_field = address_field
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self.decoded = decoded
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self.start_bit_index = start_bit_index
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self.end_bit_index = end_bit_index
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def __getitem__(self, i):
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return self.decoded[i]
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self.data_field = data_field
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class MoofRWTS:
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kDefaultAddressPrologue16 = (0xD5, 0xAA, 0x96)
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@ -119,7 +116,7 @@ class MoofRWTS:
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self.data_prologue = data_prologue
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self.data_epilogue = data_epilogue
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self.nibble_translate_table = nibble_translate_table
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self.expected_sectors_per_track = dict(zip(range(0xA0), (i for i in range(0x0C,0x07,-1) for j in range(0x20))))
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self.sectors_per_track = dict(zip(range(0xA0), (i for i in range(0x0C,0x07,-1) for j in range(0x20))))
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def _(self, track):
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return self.nibble_translate_table[next(track.nibble())]
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@ -133,8 +130,9 @@ class MoofRWTS:
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h2 = self._(track)
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volume = self._(track)
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checksum = self._(track)
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valid = h0 ^ sector_id ^ h2 ^ volume == checksum
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track_id = (h0 << 1) | ((h2 & 0b00000001) << 7) | ((h2 & 0b00100000) >> 5)
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return MoofAddressField(volume, track_id, sector_id, h0 ^ sector_id ^ h2 ^ volume == checksum)
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return MoofAddressField(valid, volume, track_id, sector_id)
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def verify_nibbles_at_point(self, track, nibbles):
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found = []
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@ -192,8 +190,8 @@ class MoofRWTS:
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for n in nibble_groups))
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# decode 524 bytes (12 tag bytes + 512 data bytes)
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tag_bytes = [next(gcr_byte) for i in range(12)]
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decoded_bytes = [next(gcr_byte) for i in range(512)]
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tags = [next(gcr_byte) for i in range(12)]
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data = [next(gcr_byte) for i in range(512)]
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# validate checksums against last data field nibble and three epilogue nibbles
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valid = nibble_groups[-1][-1] == ((c1 & 0b11000000) >> 6) | ((c2 & 0b11000000) >> 4) | ((c3 & 0b11000000) >> 2)
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@ -201,88 +199,190 @@ class MoofRWTS:
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valid &= self._(track) == (c2 & 0b00111111)
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valid &= self._(track) == (c1 & 0b00111111)
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return valid, sector_id, tag_bytes, decoded_bytes
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return MoofDataField(valid, sector_id, tags, data)
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def verify_data_epilogue_at_point(self, track):
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return self.verify_nibbles_at_point(track, self.data_epilogue)
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def get_pace_key_at_point(rwts, track, bit_index):
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track.bit_index, bit_index = bit_index, track.bit_index
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key = []
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prologue = (0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xAB, 0xCD, 0xEF, 0xEF)
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if rwts.verify_nibbles_at_point(track, prologue):
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for i in range(4):
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next(track.nibble())
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for i in range(4):
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x = (next(track.nibble()) << 8) + next(track.nibble())
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x = x & 0x5555
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x = (x | (x >> 1)) & 0x3333
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x = (x | (x >> 2)) & 0x0f0f
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x = (x | (x >> 4)) & 0x00ff
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x = (x | (x >> 8)) & 0xffff
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key.append(x)
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key.reverse()
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track.bit_index, bit_index = bit_index, track.bit_index
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return "".join(map(myhex, key))
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class DefaultLogger:
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def warn(self, message, T=None, S=None, X=None, Y=None):
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if T: T = myhex(T)
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if S: S = myhex(S)
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message = message.format(**locals())
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sys.stderr.write(message)
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sys.stderr.write('\n')
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info=warn
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error=warn
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class MoofDiskImage(wozardry.WozDiskImage):
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kE7Bytestream = (0x2B, 0x00, 0x2B, 0xFD, 0x83, 0x6F, 0x20, 0xE2,
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0x8D, 0x99, 0x49, 0x44, 0x47, 0x82, 0xD9, 0x26,
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0xFB, 0xC6, 0x3, 0xF8)
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kPACEPrologue = (0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
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0xFF, 0xFF, 0xFF, 0xFF, 0xAB, 0xCD, 0xEF, 0xEF)
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def __init__(self, iostream=None, rwtsclass=MoofRWTS, loggerclass=DefaultLogger):
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wozardry.WozDiskImage.__init__(self, iostream)
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self.logger = loggerclass()
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self.rwts = rwtsclass()
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for i,t in zip(range(len(self.tracks)), self.tracks):
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self.tracks[i] = MoofTrack(t.raw_bytes, t.raw_count)
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self.parse()
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def get_pace_key_at_point(self, track, bit_index):
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# save bitstream position
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track.bit_index, bit_index = bit_index, track.bit_index
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key = []
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if self.rwts.verify_nibbles_at_point(track, self.kPACEPrologue):
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for i in range(4):
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next(track.nibble())
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for i in range(4):
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x = (next(track.nibble()) << 8) + next(track.nibble())
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x = x & 0x5555
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x = (x | (x >> 1)) & 0x3333
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x = (x | (x >> 2)) & 0x0f0f
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x = (x | (x >> 4)) & 0x00ff
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x = (x | (x >> 8)) & 0xffff
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key.append(x)
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key.reverse()
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# restore bitstream position
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track.bit_index, bit_index = bit_index, track.bit_index
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return "".join(map(myhex, key))
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def parse(self):
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self.blocks = []
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# only 400K and 800K disks supported at the moment
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if not self.info["disk_type"] in (1,2): return
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for track_index in self.tmap:
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if track_index == 0xFF: continue
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track = self.tracks[track_index]
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seen_sectors = []
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track_id = -1
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while self.rwts.find_address_prologue(track):
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address_field = self.rwts.address_field_at_point(track)
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# log if address field checksum doesn't match
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if not address_field.valid:
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self.logger.warn(
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'T{T},S{S} Address field checksum invalid',
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T=address_field.track_id,
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S=address_field.sector_id
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)
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continue
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# log if track ID is ridiculous
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if not (0x00 <= address_field.track_id <= 0x9F):
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self.logger.warn(
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'Address field track ID {T} invalid',
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T=address_field.track_id
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)
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continue
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# log if sector ID is ridiculous
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if not (0x00 <= address_field.sector_id < self.rwts.sectors_per_track[address_field.track_id]):
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self.logger.warn(
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'Address field sector ID {S} invalid',
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S=address_field.sector_id
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)
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continue
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# log if address field epilogue isn't next
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if not self.rwts.verify_address_epilogue_at_point(track):
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self.logger.warn(
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'T{T},S{S} Address field epilogue invalid',
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T=address_field.track_id,
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S=address_field.sector_id
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)
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continue
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# if we see duplicate sector IDs, assume we're done
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if address_field.sector_id in seen_sectors: break
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seen_sectors.append(address_field.sector_id)
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old_bit_index = track.bit_index
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if not self.rwts.find_data_prologue(track):
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# if we didn't find any data field prologue at all
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# before the next address field prologue, then check
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# if this is a specially formatted protection sector
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# from which we can extract some useful information
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decryption_key = self.get_pace_key_at_point(track, old_bit_index)
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if decryption_key:
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self.logger.info(
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'T{T},S{S} Found PACE protection, key={X}',
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T=address_field.track_id,
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S=address_field.sector_id,
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X=decryption_key
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)
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continue
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try:
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data_field = self.rwts.data_field_at_point(track)
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except KeyError:
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# log if GCR decoding failed
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self.logger.warn(
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'T{T},S{S} Data field contains invalid nibble',
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T=address_field.track_id,
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S=address_field.sector_id
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)
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continue
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# log if checksums didn't match after GCR decoding
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if not data_field.valid:
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self.logger.warn(
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'T{T},S{S} Data field checksums invalid',
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T=address_field.track_id,
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S=address_field.sector_id
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)
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continue
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# address and data fields are supposed to contain
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# matching sector IDs, so log if they don't match
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if address_field.sector_id != data_field.sector_id:
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self.logger.warn(
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'T{T},S{S} Address and data field sector IDs do not match',
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T=address_field.track_id,
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S=address_field.sector_id
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)
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continue
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# log if sector data contains E7 bitstream
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if (sum(data_field.data[:0x18E]) == 0) and (tuple(data_field.data[0x18F:0x1A3]) == self.kE7Bytestream):
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#print(data_field.data[0x18F:0x1A3])
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self.logger.warn(
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'T{T},S{S} Found E7 bitstream',
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T=address_field.track_id,
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S=address_field.sector_id
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)
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# log if data field epilogue isn't next
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if not self.rwts.verify_data_epilogue_at_point(track):
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self.logger.warn(
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'T{T},S{S} Data field epilogue invalid',
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T=address_field.track_id,
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S=address_field.sector_id
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)
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continue
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track_id = address_field.track_id
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self.blocks.append(MoofBlock(address_field, data_field))
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# move on if we didn't find any valid sectors
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if track_id == -1: continue
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# log if we didn't find enough sectors
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sector_count = len(seen_sectors)
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expected_count = self.rwts.sectors_per_track[track_id]
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if sector_count < expected_count:
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self.logger.warn(
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'T{T} Found {X} sectors (expected {Y})',
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T=track_id,
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X=sector_count,
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Y=expected_count
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)
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def driver(filename):
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with open(filename, 'rb') as f:
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mdisk = MoofDiskImage(f)
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if not mdisk.info["disk_type"] in (1,2):
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print("/!\ MFM disks not supported yet")
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return
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rwts = MoofRWTS()
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for track_index in mdisk.tmap:
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if track_index == 0xFF: continue
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track = mdisk.tracks[track_index]
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seen_sectors = []
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track_id = -1
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while True:
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if not rwts.find_address_prologue(track): break
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address_field = rwts.address_field_at_point(track)
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if not address_field.valid: continue
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if (address_field.track_id < 0) or (address_field.track_id > 0x9F):
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print(f'/!\ invalid track ID {myhex(address_field.track_id)}')
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continue
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if (address_field.sector_id < 0) or \
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(address_field.sector_id > rwts.expected_sectors_per_track[address_field.track_id]):
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print(f'/!\ invalid sector ID {myhex(address_field.sector_id)}')
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continue
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if not rwts.verify_address_epilogue_at_point(track):
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print(f'/!\ track {myhex(address_field.track_id)}, sector {myhex(address_field.sector_id)}: address epilogue does not match')
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continue
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if address_field.sector_id in seen_sectors: break
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seen_sectors.append(address_field.sector_id)
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old_bit_index = track.bit_index
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if not rwts.find_data_prologue(track):
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key = get_pace_key_at_point(rwts, track, old_bit_index)
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if key:
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print(f'/!\ track {myhex(address_field.track_id)}, sector {myhex(address_field.sector_id)}: found PACE decryption key {key}')
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continue
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try:
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valid, sector_id, tags, decoded_bytes = rwts.data_field_at_point(track)
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except KeyError:
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print(f'/!\ track {myhex(address_field.track_id)}, sector {myhex(address_field.sector_id)}: invalid nibble')
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continue
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if not valid:
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print(f'/!\ track {myhex(address_field.track_id)}, sector {myhex(address_field.sector_id)}: data checksums do not match')
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continue
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if valid:
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valid = address_field.sector_id == sector_id
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if not valid:
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print(f'/!\ track {myhex(address_field.track_id)}, sector {myhex(address_field.sector_id)}: address/data field sector IDs do not match')
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continue
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valid = rwts.verify_data_epilogue_at_point(track)
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if not valid:
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print(f'/!\ track {myhex(address_field.track_id)}, sector {myhex(address_field.sector_id)}: data epilogue does not match')
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continue
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if (track_id == -1) and (address_field.valid):
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track_id = address_field.track_id
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if track_id == -1: continue
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sector_count = len(seen_sectors)
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expected_count = rwts.expected_sectors_per_track[track_id]
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if sector_count < expected_count:
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print(f'/!\ track {myhex(track_id)} only has {sector_count} sectors (expected {expected_count})')
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if __name__ == '__main__':
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driver(sys.argv[1])
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