miscjj1.py

import struct
import os
import math
from array import array

def rle_decompress(data):
    ''' function to take some data compressed in
        Jazz Jackrabbit 1's Run Length Encoding
        encryption, decompress it, and return the result'''
    offset = 0
    ret = []
    while offset < len(data):
        byte = struct.unpack("B", data[offset])[0]
        if byte > 127:
            for i in range(0, byte - 128):
                ret.append(struct.unpack("B", data[offset+1])[0])
            offset += 2
        elif byte >= 1:
            for i in range(1, byte+1):
                ret.append(struct.unpack("B", data[offset+i])[0])
            offset += byte+1
        else:
            ret.append(struct.unpack("B", data[offset+1])[0])
            break

    return ret

class Jazzfile:
    '''A file containing naught but uncompressed and RLE-compressed blocks'''
    blocklengths = None

    def __init__(self, filename):
        ''' loads file contents into memory '''
        try:
            self.filecontents = open(filename, "rb")
        except:
            print("file %s could not be read!" % filename)
            os._exit(0)

        self.filesize = os.path.getsize(filename)
        self.filecontents = self.filecontents.read(self.filesize)

    def discover_blocklengths(self):
        self.blocklengths = array('i')
        for i in range(len(self.uncompresseds)-1):
            if self.uncompresseds[i]:
                self.blocklengths.append(self.uncompresseds[i])
            else:
                offset = sum(self.blocklengths) + len(self.blocklengths)
                self.blocklengths.append(struct.unpack("H", self.filecontents[offset:][:2])[0]+1)
        offset = sum(self.blocklengths) + len(self.blocklengths)
        self.blocklengths.append(len(self.filecontents[offset:]))

    def get_block_offset(self, blockid):
        if not self.blocklengths:
            self.discover_blocklengths()
        return sum(self.blocklengths[:blockid]) + len(self.blocklengths[:blockid])

    def get_block(self, blockid):
        offset = self.get_block_offset(blockid)
        if self.uncompresseds[blockid]:
            return self.filecontents[offset:offset+self.blocklengths[blockid]]
        else:
            return rle_decompress(self.filecontents[offset+2:])