lz77.py

import struct

class LZS11(object):
	def __init__(self):
		self.magic = 0x11
		self.decomp_size = 0
		self.curr_size = 0
		self.compressed = True
		self.outdata = []
	def Decompress11LZS( self , filein ):
		offset = 0
		# check that file is < 2GB
		#print "length of file: 0x%x" % len(filein)
		assert len(filein) < ( 0x4000 * 0x4000 * 2 )
		self.magic = struct.unpack('<B', filein[0:1])[0]
		#print "magic = 0x%x" % self.magic
		assert self.magic == 0x11
		self.decomp_size = struct.unpack('<I', filein[offset:offset+4])[0] >> 8
		offset += 4
		assert self.decomp_size <= 0x200000
		if ( self.decomp_size == 0 ):
			self.decomp_size = struct.unpack('<I', filein[offset:offset+4])[0]
			offset += 4
		assert self.decomp_size <= 0x200000 << 8

		#print "Decompressing 0x%x. (outsize: 0x%x)" % (len(filein), self.decomp_size)
		self.outdata = [0 for x in xrange(self.decomp_size)]

		while self.curr_size < self.decomp_size and offset < len(filein):
			flags = struct.unpack('<B', filein[offset:offset+1])[0]
			offset += 1

			for i in xrange( 8 ):
				x = 7 - i
				if self.curr_size >= self.decomp_size:
					break
				if (flags & (1 << x)) > 0:
					first = struct.unpack('<B', filein[offset:offset+1])[0]
					offset += 1
					second = struct.unpack('<B', filein[offset:offset+1])[0]
					offset += 1

					if first < 0x20:
						third = struct.unpack('<B', filein[offset:offset+1])[0]
						offset += 1

						if first >= 0x10:
							fourth = struct.unpack('<B', filein[offset:offset+1])[0]
							offset += 1

							pos = (((third & 0xF) << 8) | fourth) + 1
							copylen = ((second << 4) | ((first & 0xF) << 12) | (third >> 4)) + 273
						else:
							pos = (((second & 0xF) << 8) | third) + 1
							copylen = (((first & 0xF) << 4) | (second >> 4)) + 17
					else:
						pos = (((first & 0xF) << 8) | second) + 1
						copylen = (first >> 4) + 1

					for y in xrange( copylen ):
						self.outdata[self.curr_size + y] = self.outdata[self.curr_size - pos + y]

					self.curr_size += copylen
				else:

					self.outdata[self.curr_size] = struct.unpack('<B', filein[offset:offset+1])[0]
					offset += 1
					self.curr_size += 1

				if offset >= len(filein) or self.curr_size >= self.decomp_size:
					break
		return self.outdata