hacks/dump-imessages/iphone-dataprotection/python_scripts/util/lzss.py

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"""
/**************************************************************
LZSS.C -- A Data Compression Program
***************************************************************
4/6/1989 Haruhiko Okumura
Use, distribute, and modify this program freely.
Please send me your improved versions.
PC-VAN SCIENCE
NIFTY-Serve PAF01022
CompuServe 74050,1022
**************************************************************/
/*
* lzss.c - Package for decompressing lzss compressed objects
*
* Copyright (c) 2003 Apple Computer, Inc.
*
* DRI: Josh de Cesare
*/
"""
from array import array
import struct
N = 4096
F = 18
THRESHOLD = 2
NIL = N
def decompress_lzss(str):
if str[:8] !="complzss":
print "decompress_lzss: complzss magic missing"
return
decompsize = struct.unpack(">L", str[12:16])[0]
text_buf = array("B", " "*(N + F - 1))
src = array("B", str[0x180:])
srclen = len(src)
dst = array("B", " "*decompsize)
r = N - F
srcidx, dstidx, flags, c = 0, 0, 0, 0
while True:
flags >>= 1
if ((flags & 0x100) == 0):
if (srcidx >= srclen):
break
c = src[srcidx]; srcidx += 1
flags = c | 0xFF00;
if (flags & 1):
if (srcidx >= srclen):
break
c = src[srcidx]; srcidx += 1
dst[dstidx] = c; dstidx += 1
text_buf[r] = c; r += 1
r &= (N - 1);
else:
if (srcidx >= srclen):
break
i = src[srcidx]; srcidx += 1
if (srcidx >= srclen):
break
j = src[srcidx]; srcidx += 1
i |= ((j & 0xF0) << 4)
j = (j & 0x0F) + THRESHOLD
for k in xrange(j+1):
c = text_buf[(i + k) & (N - 1)]
dst[dstidx] = c; dstidx += 1
text_buf[r] = c; r += 1
r &= (N - 1)
return dst.tostring()