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Jooyung Hand35952e2021-11-08 17:53:47 +09001#!/usr/bin/env python
2#
3# Copyright (C) 2021 The Android Open Source Project
4#
5# Licensed under the Apache License, Version 2.0 (the "License");
6# you may not use this file except in compliance with the License.
7# You may obtain a copy of the License at
8#
9# http://www.apache.org/licenses/LICENSE-2.0
10#
11# Unless required by applicable law or agreed to in writing, software
12# distributed under the License is distributed on an "AS IS" BASIS,
13# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14# See the License for the specific language governing permissions and
15# limitations under the License.
16"""replace_bytes is a command line tool to replace bytes in a file.
17
18Typical usage: replace_bytes target_file old_file new_file
19
20 replace bytes of old_file with bytes of new_file in target_file. old_file and new_file should be
21 the same size.
22
23"""
24import argparse
25import sys
26
27
28def ParseArgs(argv):
29 parser = argparse.ArgumentParser(description='Replace bytes')
30 parser.add_argument(
31 'target_file',
32 help='path to the target file.')
33 parser.add_argument(
34 'old_file',
35 help='path to the file containing old bytes')
36 parser.add_argument(
37 'new_file',
38 help='path to the file containing new bytes')
39 return parser.parse_args(argv)
40
41
42def ReplaceBytes(target_file, old_file, new_file):
43 # read old bytes
44 with open(old_file, 'rb') as f:
45 old_bytes = f.read()
46
47 # read new bytes
48 with open(new_file, 'rb') as f:
49 new_bytes = f.read()
50
51 assert len(old_bytes) == len(new_bytes), 'Pubkeys should be the same size. (%d != %d)' % (
52 len(old_bytes), len(new_bytes))
53
54 # replace bytes in target_file
55 with open(target_file, 'r+b') as f:
56 pos = f.read().find(old_bytes)
57 assert pos != -1, 'Pubkey not found'
58 f.seek(pos)
59 f.write(new_bytes)
60
61
62def main(argv):
63 try:
64 args = ParseArgs(argv)
65 ReplaceBytes(args.target_file, args.old_file, args.new_file)
66 except Exception as e:
67 print(e)
68 sys.exit(1)
69
70
71if __name__ == '__main__':
72 main(sys.argv[1:])