process rotate checks groupsize using dict lookup

Author: arekbulski

kaitaistruct.py

@@ -348,20 +348,14 @@ def process_xor_many(data, key):
         else:
             return bytes(a ^ b for a, b in zip(data, itertools.cycle(key)))
 
-    precomputed_rotations = {amount:[(i << amount) & 0xff | (i >> (-amount & 7)) for i in range(256)] for amount in range(9)}
+    precomputed_rotations = {(amount,1):[(i << amount) & 0xff | (i >> (-amount & 7)) for i in range(256)] for amount in range(9)}
 
     @staticmethod
     def process_rotate_left(data, amount, group_size):
-        if group_size != 1:
-            raise Exception(
-                "unable to rotate group of %d bytes yet" %
-                (group_size,)
-            )
-
         if amount == 0:
             return data
 
-        translate = KaitaiStream.precomputed_rotations[amount]
+        translate = KaitaiStream.precomputed_rotations[amount,group_size]
         if PY2:
             return bytes(bytearray(translate[a] for a in bytearray(data)))
         else: