Miscellany

import sys
import re
import bz2

def binary_to_int(string):
   x = len(string)
   number = 0
   for i in range(x):
      number += ord(string[i])*256**i
   return number
   
def binary_to_int_backwards(string):
   x = len(string)
   number = 0
   for i in range(x):
      number += ord(string[x-i-1])*256**i
   return number
   
   
def main():
   argv = sys.argv
   argc = len(argv)
   
   if argc != 2:
      print "Error! Correct usage is:\n\trch_ana.py <source>"
      
   source_file = argv[1]
   
   rch_file = open(source_file, 'rb')
   rch_bin = rch_file.read()
   rch_file.close()
   
   
   if not re.match("FR01", rch_bin[0:4]):
      print "error. not a valid rch file."
      return 0
      
   #header info
   version = binary_to_int(rch_bin[0x4:0x8])
   timestamp = binary_to_int(rch_bin[0x8:0xc])
   #end header info
   
   #chunk info
   chunk_offset = 0x1c
   
   while 1:
      file_name = rch_bin[chunk_offset+0x2:chunk_offset+0x29].rstrip("\x00")
      chunk_size = binary_to_int(rch_bin[chunk_offset+0x32:chunk_offset+0x35])
      crc = binary_to_int(rch_bin[chunk_offset+0x36:chunk_offset+0x39])
      algorithm = binary_to_int(rch_bin[chunk_offset+0x3A:chunk_offset+0x3D])
      chunk_data = rch_bin[chunk_offset+0x3E:chunk_offset +0x3E + chunk_size]
      
      print "filename:", file_name
      print "chunk_size:", chunk_size
      print "actual chunk size:", len(chunk_data)
      print "crc:",crc
      print "algorithm:", algorithm,"\n"
      
      # next we actually do the decompressing
      
      if algorithm == 1:
         # "Here we just XOR each byte with 0xFF"
         new_bin = ""
         new_file = open(file_name, 'wb')
         for i in range(chunk_size):
            next_char = chunk_data[i]
            next_char = chr(0xff^binary_to_int(next_char))
            new_bin += next_char
         new_file.write(new_bin)
         new_file.close()
      
      if algorithm == 2:
         new_bin = ""
         
         new_file = open(file_name, 'wb')
         # "We must use bzip2 algorithm"
         new_bin = ""
         new_bin = bz2.BZ2Decompressor().decompress(chunk_data)
         new_file.write(new_bin)
         new_file.close()
         
      
      if len(rch_bin) > chunk_offset +0x3E + chunk_size:
         chunk_offset = chunk_offset +0x3E + chunk_size
      else:
         if len(rch_bin) != chunk_offset + 0x3E + chunk_size:
            print "file size error"
         break
   
if __name__ == "__main__":
   main()