#!/usr/bin/env python3.8
# Copyright 2020 The Fuchsia Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

import argparse
import os
import struct
import sys


def main():
    parser = argparse.ArgumentParser(description='Turns a signed zbi into the original zbi')
    parser.add_argument('--input',
                        help='the signed zbi to process',
                        required=True)
    parser.add_argument('--output',
                        help='the resulting zbi',
                        required=True)
    args = parser.parse_args()

    with open(args.input, 'rb') as f:
        # The signature format adds 512 bytes at the beginning, and some other number at the end.
        f.seek(512)
        header = f.read(32)
        length = struct.unpack('<I', header[4:8])[0]
        rest = f.read(length)
        with open(args.output, 'wb') as g:
            g.write(header)
            g.write(rest)

    return 0


if __name__ == '__main__':
    sys.exit(main())