unknytt.py

#!/usr/bin/python

import struct
import os
import sys

def readheader(f):
    magic = f.read(2)
    if magic == '':
        raise EOFError
    if magic != 'NF':
        raise ValueError, "not a valid knytt stories file"
    nextchar = f.read(1)
    name = []
    while nextchar != '\0':
        name.append(nextchar)
        nextchar = f.read(1)
    name = ''.join(name)
    sizedata = f.read(4)
    (size,) = struct.unpack('<L', sizedata)
    return name, size

def extractfile(f, destdir='.'):
    try:
        name, size = readheader(f)
    except EOFError:
        return False

    outfilename = os.path.join(destdir, *name.split('\\'))

    print("Extracting %s (%s bytes).." % (name, size))

    outdir, dummy = os.path.split(outfilename)
    try:
        os.makedirs(outdir)
    except OSError:
        pass

    outfile = open(outfilename, 'wb')
    bytestowrite = size
    while bytestowrite > 0:
        data = f.read(min(bytestowrite, 4096))
        if data == '':
            raise EOFError, "file ended prematurely"
        outfile.write(data)
        bytestowrite -= len(data)

    return True

def unknytt(f, worlddir='.'):
    try:
        name, dummy = readheader(f)
    except EOFError:
        raise ValueError, "not a valid knytt stories file"

    print("Creating %s\\" % name)
    destdir = os.path.join(worlddir, name)
    os.mkdir(destdir)

    while extractfile(f, destdir):
        pass

    print("Everything is ok.")

if __name__ == '__main__':
    f = open(sys.argv[1], 'rb')
    unknytt(f)