/usr/lib/python2.7/dist-packages/pdfminer/lzw.py is in python-pdfminer 20140328+dfsg-1.
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 | #!/usr/bin/env python
import sys
try:
from cStringIO import StringIO
except ImportError:
from StringIO import StringIO
class CorruptDataError(Exception):
pass
## LZWDecoder
##
class LZWDecoder(object):
debug = 0
def __init__(self, fp):
self.fp = fp
self.buff = 0
self.bpos = 8
self.nbits = 9
self.table = None
self.prevbuf = None
return
def readbits(self, bits):
v = 0
while 1:
# the number of remaining bits we can get from the current buffer.
r = 8-self.bpos
if bits <= r:
# |-----8-bits-----|
# |-bpos-|-bits-| |
# | |----r----|
v = (v << bits) | ((self.buff >> (r-bits)) & ((1 << bits)-1))
self.bpos += bits
break
else:
# |-----8-bits-----|
# |-bpos-|---bits----...
# | |----r----|
v = (v << r) | (self.buff & ((1 << r)-1))
bits -= r
x = self.fp.read(1)
if not x:
raise EOFError
self.buff = ord(x)
self.bpos = 0
return v
def feed(self, code):
x = ''
if code == 256:
self.table = [chr(c) for c in xrange(256)] # 0-255
self.table.append(None) # 256
self.table.append(None) # 257
self.prevbuf = ''
self.nbits = 9
elif code == 257:
pass
elif not self.prevbuf:
x = self.prevbuf = self.table[code]
else:
if code < len(self.table):
x = self.table[code]
self.table.append(self.prevbuf+x[:1])
elif code == len(self.table):
self.table.append(self.prevbuf+self.prevbuf[:1])
x = self.table[code]
else:
raise CorruptDataError
l = len(self.table)
if l == 511:
self.nbits = 10
elif l == 1023:
self.nbits = 11
elif l == 2047:
self.nbits = 12
self.prevbuf = x
return x
def run(self):
while 1:
try:
code = self.readbits(self.nbits)
except EOFError:
break
try:
x = self.feed(code)
except CorruptDataError:
# just ignore corrupt data and stop yielding there
break
yield x
if self.debug:
print >>sys.stderr, ('nbits=%d, code=%d, output=%r, table=%r' %
(self.nbits, code, x, self.table[258:]))
return
# lzwdecode
def lzwdecode(data):
"""
>>> lzwdecode('\x80\x0b\x60\x50\x22\x0c\x0c\x85\x01')
'\x2d\x2d\x2d\x2d\x2d\x41\x2d\x2d\x2d\x42'
"""
fp = StringIO(data)
return ''.join(LZWDecoder(fp).run())
if __name__ == '__main__':
import doctest
doctest.testmod()
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