Gensokyo Tower Defense extraction

import os
import sys

#Constants taken from insani tools.
LITTLE_ENDIAN = 1
BIG_ENDIAN = -1

BYTE_LENGTH = 1
SHORT_LENGTH = 2
INT_LENGTH = 4
LONG_LENGTH = 8

ERROR_NONE = 0
ERROR_WARNING = 1
ERROR_ABORT = 2

def readbytes(infile, bytecount, key=-1):
    ret = infile.read(bytecount)

    if (key != -1):
        mask = int('FF' * bytecount, 16)
        value = converttoint(ret, bytecount)
        value = (value - key)&mask
        value = (~value)&mask

        ret = convertfromint(value, bytecount)

    return ret

def converttoint(bytes, size=INT_LENGTH, endian=LITTLE_ENDIAN):
    result = 0
    for i in xrange(size):
        temp=long(ord(bytes[i]))
        if endian == LITTLE_ENDIAN :
            result |= (temp << (8*i))
        elif endian == BIG_ENDIAN :
            result = (result << 8) | temp
        else :
                raise Exception('converttoint: Unknown endian specification')

        return result

def convertfromint(value, size=INT_LENGTH, endian=LITTLE_ENDIAN):
    result = ""
    for i in xrange(size):
        if endian == LITTLE_ENDIAN :
            #result |= (temp << (8*i))
            temp = (value >> (8*i)) & 0x00FF
        elif endian == BIG_ENDIAN :
            #result = (result << 8) | temp
            temp = (value >> (8*(size-i-1))) & 0x00FF
        else :
                raise Exception('convertfromint: Unknown endian specification')
            result += chr(temp)

        return result

#program

files = sys.argv[1:]
for filename in files:
    infile = open(filename, 'rb')

    print "Reading file", filename

    #Header:
    #4 bytes for the decryption key, 4 bytes for the number of files in the archive, then 8 bytes of I have no idea.

    #Decryption:
    #The first byte (padded to 4) is the decryption key. This game uses subtraction/addition and binary NOT.
        #To decrypt, convert the value to an int (this is done either on a 4 byte block or a single byte),
        #subtract the key (values roll over, e.g. 5 - 10 = 251 on single byte)
        #NOT the result (251 becomes 4)
    #Then this process is reversed on encryption: NOT the value, add the key.
    #Presumably any arbitrary key can be used when rebuilding the archive. Maybe even 0 (you still need to NOT it).
    #The encryption applies to everything but the files and the key itself. File entries and the last 12 bytes of header are encrypted.

    decryptkey = converttoint(readbytes(infile, 4))

    filecount = converttoint(readbytes(infile, 4, decryptkey))
    print "Expecting", filecount, "files. Decryption key is " + ("%02X" % decryptkey)

    #Almost certainly 2 4 byte ints. One might be a CRC. I can't be arsed to confirm this.
    unk = readbytes(infile, 8, decryptkey)

    #Each file entry is
    #4 bytes    2C bytes    4 bytes     4 bytes     4 bytes     4 bytes
    #Filename len   Filename    Filesize    Filestart   unk     unk

    #Total of x40 bytes per entry.
    #Filename is encrypted one byte at a time. Everything else is 4 bytes at a time.

    entries = []

    for i in xrange(filecount):
        entry = {}
        namelen = converttoint(readbytes(infile, 4, decryptkey))
        nameraw = ""
        for i in xrange(0x2C):
            #Need to do this one byte at a time. Or write a separate function.
            nameraw += readbytes(infile, 1, decryptkey)
        entry['name'] = nameraw[0:namelen]
        entry['filesize'] = converttoint(readbytes(infile, 4, decryptkey))
        entry['filestart'] = converttoint(readbytes(infile, 4, decryptkey))
        entry['unk1'] = converttoint(readbytes(infile, 4, decryptkey))      #Neither of these is a CRC.
        entry['unk2'] = converttoint(readbytes(infile, 4, decryptkey))      #

        entries.append(entry)


    #print "Current position is now %d / %X" % (infile.tell(), infile.tell())

    #for entry in entries:
    #   for i in entry:
    #       print i + ":", entry[i]
    #   print ""

    #sys.exit(0)

    dirname = filename[0:filename.find(".")]
    if not os.path.isdir(dirname):
        os.mkdir(dirname)

    i = 0
    for entry in entries:
        filename = entry['name'].strip(" \n\t\x00")

        dirsegment, filesegment = os.path.split(filename)
        #filename = os.path.join(dirsegment, ("%03d_" % i) + filesegment)       #Can be done to enforce correct order on repacking
        if (not os.path.isdir(os.path.join(dirname, dirsegment))):
            os.makedirs(os.path.join(dirname, dirsegment))

        infile.seek(entry['filestart'])
        data = readbytes(infile, entry['filesize'])
        outfile = open(os.path.join(dirname, filename), 'wb')
        outfile.write(data)
        outfile.close()

        print "Created file %s of size %08X from position %08X" % (filename, entry['filesize'], entry['filestart'])
        #print "Unks are %08X and %08X" % (entry['unk1'], entry['unk2'])

        i += 1

    infile.close()