Bitflip script written in Python with chunk reading function. Mainly used to de-anti-decompile Gamemaker fangames like MTO (Mysterytale Online).

bitflip.py

from os import fstat
from time import sleep

filename = "data.win"
new_filename = f"new_{filename}"
chunk_size = 1024

# Main progress
wf = open(new_filename, "wb")
with open(filename, "rb") as f:
    file_stats = fstat(f.fileno())
    file_size = file_stats.st_size
    c = 0

    while True:
        chunk = f.read(chunk_size)
        if not chunk:
            break

        c += chunk_size
        print(f"Bitflipping {filename}... {c}/{file_size}")

        binary = "".join(f"{byte:08b}" for byte in chunk)
        n_binary = "".join(map(lambda b: '0' if b == '1' else '1', [*binary]))
        new_binary = bytes(int(n_binary[i:i+8], 2) for i in range(0, len(n_binary), 8))
        wf.write(new_binary)
        sleep(0.01)

    f.close()

print(f"Bitflip done. Output saved to {new_filename}")