Come usare l'unpacker

import struct, os, sys, re

# For easy file reading and writing interactions
def readLong(fhandle):
    return struct.unpack('l', fhandle.read(4))[0]
def readShort(fhandle):
    return struct.unpack('h', fhandle.read(2))[0]
def readByte(fhandle):
    return struct.unpack('B', fhandle.read(1))[0]
def readBool(fhandle):
    val = fhandle.read(1)
    if val == "00":
        return False
    else:
        return True
    
def writeLong(fhandle, value):
    fhandle.write(struct.pack('l',value))
def writeShort(fhandle, value):
    fhandle.write(struct.pack('h',value))
def writeByte(fhandle, value):
    fhandle.write(struct.pack('B',value))
def writeBool(fhandle, value):
    if value:
        fhandle.write('\x01')
    else:
        fhandle.write('\x00')
        
def removeDir(path):
    # remove all files in a folder
    if not (os.path.isdir(path)):
        return True
    
    files = os.listdir(path)
    
    for x in files:
        fullpath=os.path.join(path, x)
        if os.path.isfile(fullpath):
            os.remove(fullpath)
        elif os.path.isdir(fullpath):
            removeDir(fullpath)
    os.rmdir(path)

def parseArgs(args):
    pack = packFile('demo1.pack','unpacked')
    
    # create argument tree
    argtree = []
    for arg in args[1:]:
        if arg.startswith('-'):
            argtree.append([arg,[]])
        else:
            argtree[-1][1].append(arg)
    
    # wander the tree, top level always has hyphenated arguments
    for arg in argtree:
        # case 1: list
        if arg[0] == '-l':
            if len(arg[1]) > 0:
                for file in arg[1]:
                    pack.printEyeCandy(str(file))
            else:
                pack.printEyeCandy('./list.txt')
        # case 2: unpack
        elif arg[0] == '-u':
            for file in arg[1]:
                if file == 'all':
                    for i in range(len(pack.files)):
                        pack.exportFile(i)
                else:
                    pack.exportFile(file)
        # case 3: unpack (regexp)
        elif arg[0] == '-ur':
            for file in arg[1]:
                pack.exportFile(file, True)
        # case 4: change pack
        elif arg[0] == '-p':
            for file in arg[1]:
                print()
                print('Changing pack to '+file)
                print()
                pack.newPack(file,pack.outputdir)
        # case 5: change output directory
        elif arg[0] == '-o':
            for file in arg[1]:
                print()
                print('Changing output directory to '+file)
                print()
                pack.changeOutputDir(file)
    

class packFile:
    def __init__(self, path='', outputdir=None):
        self.handle = None
        if outputdir:
            removeDir(outputdir)
        self.newPack(path,outputdir)
    
    def newPack(self,path,outputdir=None):
        # safely open new pack
        if self.handle:
            self.handle.close()
            self.handle = None
        self.files = []
        self.numFiles = 0
        self.arr = 0
        self.outputdir = outputdir
        self.defLength = 0
        self.path = path
        self.readPackDefinition()
    
    def changeOutputDir(self,path):
        self.outputdir = path
        if self.outputdir != None:
            removeDir(self.outputdir)
    
    def packOpen(self):
        if not self.handle:
            self.handle = open(self.path,"rb")
        return self.handle
            
    def packClose(self):
        self.handle.close()
        
    def readPackDefinition(self):     
        pack = self.packOpen()
        
        # skip empty bytes and stuff at the start
        pack.seek(16)
        self.defLength += 16

        # read number of files
        self.numFiles = readLong(pack)
        self.defLength += 4
        
        # read ??
        self.arr = readLong(pack)
        self.defLength += 4
        
        # store the offset of a certain file
        offset = 0
        # read file metadata
        for i in range(self.numFiles):
        
            # read length of file
            length = readLong(pack)
            self.defLength += 4
            
            # read file name
            char = ''
            filename = ''
            while char != b'\x00':
                char = pack.read(1)
                if (char != b'\x00'):
                    filename += char.decode()
                self.defLength += 1
            self.files.append((filename,length,offset))
            offset += length
            
    def exportFile(self, arg, regexp = False):
        try: 
            arg = int(arg)
            # option a: arg is an index
            list = [self.files[arg]]
        except:
            # option b: arg is a string
            if regexp:
                list = filter(lambda x: re.search(str(arg),x[0]),self.files)
            else:
                list = filter(lambda x: arg in x[0],self.files)
        for (path,length,offset) in list:
            print('Exporting '+path+', length: '+str(length)+', at offset: '+str(offset))
            
            # create output directory    
            dir = os.path.split(os.path.join(self.outputdir,path))[0]
            if not os.path.isdir(dir):
                os.makedirs(dir)
            output = open(os.path.join(self.outputdir,path),'wb')
            
            # open pack and go to offset
            pack = self.packOpen()
            pack.seek(self.defLength+offset)
            # copy content
            i = 0
            # read MB-sized chunks as long as possible
            j = length//(2**20)
            while i < j:
                output.write(pack.read(2**20))
                i+=1
            i = 0
            j = (length%(2**20))//(2**10)
            # read KB-sized chunks
            while i < j:
                output.write(pack.read(2**10))
                i+=1
            i = 0
            j = length%(2**10)
            # read byte-sized chunks
            while i < j:
                output.write(pack.read(1))
                i+=1
            output.close()
        return True
        
        
    
    def printEyeCandy(self, outfile):
        output = open(outfile,'w')
        for (path,length,offset) in self.files:
            output.write(str(path)+'\r\n')
        output.close()
        

# main
parseArgs(sys.argv)