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#!/usr/bin/env python3
import argparse
import functools
import os
import pathlib
import shutil
def revert(args):
bkup_path = args.file.with_suffix(args.file.suffix + args.backup_suffix)
if bkup_path.exists():
bkup_path.replace(args.file)
def corrupt(args):
revert(args)
if args.backup:
bkup_path = args.file.with_suffix(args.file.suffix
+ args.backup_suffix)
shutil.copy2(args.file, bkup_path)
with args.file.open('r+b', buffering=0) as f:
f.seek(args.offset)
f.write(args.value.to_bytes((args.value.bit_length() + 7)//8,
byteorder='big'))
int_parser = functools.partial(int, base=0)
parser = argparse.ArgumentParser(
description="Write a value into a file at an offset, making a backup.")
parser.add_argument("file", type=pathlib.Path,
help="File to corrupt")
parser.add_argument("--backup-suffix", default=os.extsep + "pristine",
metavar="SUFFIX",
help="suffix for uncorrupted copy of the file "
"[default: %(default)s]")
cmd_parser = parser.add_subparsers(dest='mode')
cmd_parser.add_parser(
'revert', aliases=['r', 're', 'rev'],
help='Revert the damage, restore backup').set_defaults(mode=revert)
damage = cmd_parser.add_parser(
'damage', aliases=['d', 'da', 'dam'],
help='Corrupt the file at the offset with the value')
damage.set_defaults(mode=corrupt)
damage.add_argument("offset", type=int_parser,
help="Offset into file in bytes")
damage.add_argument("value", type=int_parser,
help="Value to overwrite at OFFSET")
damage.add_argument("-b", "--backup",
action="store_true", default=True,
help="create a backup of the uncorrupted original"
" [default: %(default)s]")
damage.add_argument("--no-backup", dest='backup',
action="store_false",
help="do not create a backup of the uncorrupted original.")
args = parser.parse_args()
args.mode(args)
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