Binary patcher

patcher.py

from io import BytesIO

class Patch():
    def __init__(self, offset: int, original: str, new: str):
        self.offset = offset
        self.original = bytes.fromhex(original)
        self.new = bytes.fromhex(new)

    def __str__(self):
        return f"[\"{self.original.hex()}\" -> \"{self.new.hex()}\" (at {self.offset})]"

def apply_patches(data: bytes, patches: list[Patch]):
    f = BytesIO(data)

    for patch in patches:
        f.seek(patch.offset)

        data = f.read(len(patch.original))
        if data != patch.original:
            raise Exception(f"Failed to apply a patch: {patch}")

        f.seek(patch.offset)
        f.write(patch.new)

    f.seek(0)
    return f.read()