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#!/usr/bin/env python3
#
# bit_op.py -- Performs bitwise operations on files
#
# Copyright (c) 2014 Samuel Lidén Borell <samuel@kodafritt.se>
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.
#
def bit_op(op, a, b):
"""Performs a bitwise operation ('|' or '&'). It is performed
in-place on the byte-string a, which is extended if necessary."""
initval = 0xFF if op == '&' else 0x00
if len(b) > len(a):
#a += bytearray(len(b) - len(a))
a.extend([initval for i in range(len(b) - len(a))])
if op == '|':
for i in range(len(a)):
a[i] |= b[i]
elif op == '&':
for i in range(len(a)):
a[i] &= b[i]
elif op == '^':
for i in range(len(a)):
a[i] ^= b[i]
if __name__ == '__main__':
import argparse, sys
ap = argparse.ArgumentParser(description='Performs a bitwise operation on multiple files and outputs the result')
ap.add_argument('files', metavar='FILE', type=argparse.FileType('rb', 0), nargs='+',
help='filenames of files to use as operands')
group = ap.add_mutually_exclusive_group(required=True)
group.add_argument('-a', '--and', dest='op', action='store_const', const='&',
help='use bitwise AND operation (0101 & 0011 = 0001)')
group.add_argument('-o', '--or', dest='op', action='store_const', const='|',
help='use bitwise OR operation (0101 & 0011 = 0111)')
group.add_argument('-x', '--xor', dest='op', action='store_const', const='^',
help='use bitwise XOR operation (0101 & 0011 = 0110)')
args = ap.parse_args()
data = bytearray(0)
for f in args.files:
filedata = bytearray(f.read())
f.close()
bit_op(args.op, data, filedata)
sys.stdout.buffer.write(data)
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