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Mini Shell
Mini Shell
#!/usr/bin/env python3
__license__ = 'GPL v3'
__copyright__ = '2011, Kovid Goyal <kovid@kovidgoyal.net>'
__docformat__ = 'restructuredtext en'
'''
Decompress MOBI files compressed with the Huff/cdic algorithm. Code thanks to darkninja
and igorsk.
'''
import struct
from calibre.ebooks.mobi import MobiError
class Reader:
def __init__(self):
self.q = struct.Struct(b'>Q').unpack_from
def load_huff(self, huff):
if huff[0:8] != b'HUFF\x00\x00\x00\x18':
raise MobiError('Invalid HUFF header')
off1, off2 = struct.unpack_from(b'>LL', huff, 8)
def dict1_unpack(v):
codelen, term, maxcode = v&0x1f, v&0x80, v>>8
assert codelen != 0
if codelen <= 8:
assert term
maxcode = ((maxcode + 1) << (32 - codelen)) - 1
return (codelen, term, maxcode)
self.dict1 = tuple(map(dict1_unpack, struct.unpack_from(b'>256L', huff, off1)))
dict2 = struct.unpack_from(b'>64L', huff, off2)
self.mincode, self.maxcode = (), ()
for codelen, mincode in enumerate((0,) + dict2[0::2]):
self.mincode += (mincode << (32 - codelen), )
for codelen, maxcode in enumerate((0,) + dict2[1::2]):
self.maxcode += (((maxcode + 1) << (32 - codelen)) - 1, )
self.dictionary = []
def load_cdic(self, cdic):
if cdic[0:8] != b'CDIC\x00\x00\x00\x10':
raise MobiError('Invalid CDIC header')
phrases, bits = struct.unpack_from(b'>LL', cdic, 8)
n = min(1<<bits, phrases-len(self.dictionary))
h = struct.Struct(b'>H').unpack_from
def getslice(off):
blen, = h(cdic, 16+off)
slice = cdic[18+off:18+off+(blen&0x7fff)]
return (slice, blen&0x8000)
self.dictionary += map(getslice, struct.unpack_from(b'>%dH' % n, cdic, 16))
def unpack(self, data):
q = self.q
bitsleft = len(data) * 8
data += b'\x00\x00\x00\x00\x00\x00\x00\x00'
pos = 0
x, = q(data, pos)
n = 32
s = []
while True:
if n <= 0:
pos += 4
x, = q(data, pos)
n += 32
code = (x >> n) & ((1 << 32) - 1)
codelen, term, maxcode = self.dict1[code >> 24]
if not term:
while code < self.mincode[codelen]:
codelen += 1
maxcode = self.maxcode[codelen]
n -= codelen
bitsleft -= codelen
if bitsleft < 0:
break
r = (maxcode - code) >> (32 - codelen)
slice_, flag = self.dictionary[r]
if not flag:
self.dictionary[r] = None
slice_ = self.unpack(slice_)
self.dictionary[r] = (slice_, 1)
s.append(slice_)
return b''.join(s)
class HuffReader:
def __init__(self, huffs):
self.reader = Reader()
self.reader.load_huff(huffs[0])
for cdic in huffs[1:]:
self.reader.load_cdic(cdic)
def unpack(self, section):
return self.reader.unpack(section)
Zerion Mini Shell 1.0