quick and dirty python script to check how much of the original data is left if a partition or a image is formatted using ext4. Hint: it's none ;)

ext4check.py

#!/usr/bin/python

"""
quick test to check how much of the original data is left if a partition or a
image is formatted using ext4.
"""

from __future__ import print_function
import os
import sys
import subprocess

magic = "\xF5\xF6\xF7\xF8"
magicstr = magic * (512/4)
size = 512 * 1024 * 1024
imgfile = "./test.img"

print("[+] creating test image at {}".format(imgfile))

with open(imgfile, "wb") as f:
    print("[+] writing pattern \"{}\" to image".format(repr(magic)))
    written = 0
    while written < size:
        f.write(magicstr)
        written += len(magicstr)

print("[+] calling mkfs.ext4")

print(subprocess.check_output(["mkfs.ext4", "-F", imgfile],
                              stderr=sys.stderr))

print("[+] reading data an searching for pattern")

fsize = os.stat(imgfile).st_size
bs = len(magicstr) * 100
blocks = fsize / bs
curblock = 0
count = 0

with open(imgfile, "rb") as f:
    while f.tell() < fsize:
        s = f.read(bs)
        count += s.count(magic)
        if curblock % 17 == 0:  # this is pretty random, just for less output 
            print(("[+] block {} of {}, byte {} of {} \n" +
                  "currently magic was found {} times")
                  .format(curblock, blocks, f.tell(), fsize, count))
        curblock += 1

print("[+] found magic pattern {} times".format(count))