Binary diff + yEnc encoding

gistfile1.txt

% ./usenetpatch.py --help
usage: usenetpatch.py [-h] {diff,patch} ...

positional arguments:
  {diff,patch}  mode
    diff        diff mode
    patch       patch mode

optional arguments:
  -h, --help    show this help message and exit

% md5sum a.png
2c953dc7ba29ecd119f05bd97d4ef584  a.png

% md5sum b.png 
c1576f1ee3b7ea5569707bd4e732fc9c  b.png

% ./usenetpatch.py diff a.png b.png c.patch
Writing 365666 bytes to c.patch - crc32: 9d30f5cb

% ./usenetpatch.py patch a.png c.patch c.png
Writing 370128 bytes to c.png

% md5sum c.png 
c1576f1ee3b7ea5569707bd4e732fc9c  c.png

usenetpatch.py

#!/usr/bin/python3 

import os
import io
import yenc
import bsdiff4
import argparse

# define 'diff' method
def diff(file_1, file_2):
    file_1 = bytes(open(file_1, 'rb').read())
    file_2 = bytes(open(file_2, 'rb').read())
    diff = io.BytesIO(bsdiff4.diff(file_1, file_2))
    patch = io.BytesIO()
    size, crc = yenc.encode(diff, patch)
    patch.seek(0)
    return patch, size, crc

# define 'patch' method
def patch(file_1, file_2, crc=None):
    file_1 = bytes(open(file_1, 'rb').read())
    patch = io.BytesIO()
    yenc.decode(open(args.patch, 'rb'), patch, crc_in=crc)
    patch.seek(0)
    patch = bytes(patch.read())
    file_2 = bsdiff4.patch(file_1, patch)
    return file_2, len(file_2)

# initialize argument parser
parser = argparse.ArgumentParser()
# initialize 'mode' argument parser
subparsers = parser.add_subparsers(dest='mode', help='mode')
# initialize 'diff' mode parser
diff_parser = subparsers.add_parser('diff', help='diff mode')
diff_parser.add_argument('file_1', help='original file')
diff_parser.add_argument('file_2', help='modified file')
diff_parser.add_argument('patch', help='patch file')
# initialize 'patch' mode parser
patch_parser = subparsers.add_parser('patch', help='patch mode')
patch_parser.add_argument('file_1', help='original file')
patch_parser.add_argument('patch', help='patch file')
patch_parser.add_argument('file_2', help='modified file')
patch_parser.add_argument('--crc', help='crc checksum')
# parse arguments
args = parser.parse_args()

# perform 'diff' method
if args.mode == 'diff':
    patch, size, crc = diff(args.file_1, args.file_2)
    with open(args.patch, 'wb') as f:
        f.write(patch.read())
    print("Writing %s bytes to %s - crc32: %s" % (size, args.patch, crc))

# perform 'patch' method
elif args.mode == 'patch':
    diff, size = patch(args.file_1, args.patch, args.crc)
    with open(args.file_2, 'wb') as f:
        f.write(diff)
    print("Writing %s bytes to %s" % (size, args.file_2))