checksums

#!/usr/bin/env python3

# Copyright (C) 2014 Matthew Turnbull. All rights reserved.
#
# Redistribution and use in source and binary forms, with or without 
# modification, are permitted provided that the following conditions are met:
#
#  1. Redistributions of source code must retain the above copyright notice, this 
#     list of conditions and the following disclaimer.
#  2. Redistributions in binary form must reproduce the above copyright notice, 
#     this list of conditions and the following disclaimer in the documentation 
#     and/or other materials provided with the distribution. 
#  3. Neither the name of Caligon Studios nor the names of its contributors may 
#     be used to endorse or promote products derived from this software without 
#     specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND 
# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 
# WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 
# DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE 
# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 
# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR 
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# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

import sys, re, zlib,  shutil, textwrap
from optparse import OptionParser, IndentedHelpFormatter
from os import path

version = """\
%prog 2020.05.03.00.16
Copyright (C) 2020 Matthew Turnbull. All rights reserved.
Use of this source code is governed by the 3-clause BSD License
that can be found in the %prog source.
"""

usage="Usage: %prog [options] FILES"

description = """\
%prog is a utility to verify the integrity of a file using a CRC32 checksum \
stored in the file name. A CRC32 checksum is an 8 character hexadecimal string. \
This is a common practice used by Anime sub releases.

When checking the checksum, the following file name formats are recognized:
  ...[checksum]...
  ...(checksum)...
  ..._checksum_...

When appending the checksum to the file name, the bracketed (first) format is used.\
"""

epilog = """
FILES is the list of files to preform the action on. This can be a single file, \
multiple files, or a glob if your shell supports it.

Examples:
  %prog -a report.txt image.png *.xml
  %prog -c *.mkv
  %prog video-\[1004456E\].3gp
"""

# Constants
rcsum = re.compile("((?<=\[)[a-fA-F0-9]{8}(?=\]))|((?<=\()[a-fA-F0-9]{8}(?=\)))|((?<=_)[a-fA-F0-9]{8}(?=_))")
c_null = ""
c_red = ""
c_green = ""

# GRRR... Keep newlines in the description text.
class IndentedHelpFormatterNL(IndentedHelpFormatter):
	def format_description(self, description):
		if not description:
			return description
		desc_width = self.width - self.current_indent
		indent = " "*self.current_indent
		bits = description.split("\n")
		formatted_bits = [
			textwrap.fill(bit,
				desc_width,
				initial_indent=indent,
				subsequent_indent=indent)
	                 for bit in bits]
		return "\n".join(formatted_bits) + "\n"
	format_epilog = format_description

# Generator to read the file in chunks
def chunked_read(file_object, chunk_size=1024):
	while True:
		data = file_object.read(chunk_size)
		if not data:
			break;
		yield data

# Caclulate file CRC32 or return None on failure
def crc32_checksum(filename):
	if not path.isfile(filename):
		return None

	with open(filename, "rb") as f:
		csum = 0
		for chunk in chunked_read(f, 4096):
			csum = zlib.crc32(chunk, csum)
		return "%.8X" % (csum & 0xFFFFFFFF)

	return None

# Make the replacement handler function for re.sub
def makeSubHandler(csum, hasMatch):
	def subHandler(match):
		msum = match.group(0)
		if msum.upper() == csum:
			return c_green + msum + c_null
		if not hasMatch:
			return c_red + msum + c_null
		return msum
	return subHandler

# Process the files listed on the command line
def main():
	# Handle command line
	parser = OptionParser(version=version, usage=usage, description=description,
		formatter=IndentedHelpFormatterNL())
	parser.epilog=parser.expand_prog_name(epilog)
	parser.add_option("-c", "--check", action="store_true", default=False,
		help="Compute the checksum and try to match it to the file name using one of the formats listed above.")
	parser.add_option("-a", "--append", action="store_true", default=False,
		help="Compute the checksum and append it to the the file name, just before the file extension.")
	parser.add_option("-v", "--verbose", action="store_true", default=False,
		help="Print extra information")
	(opts, args) = parser.parse_args()

	if opts.append and opts.check:
		parser.error("Options 'append' and 'check' are mutually exclusive")
	if not opts.append and not opts.check:
		opts.check = True
	if opts.append:
		opts.verbose = True

	for filename in args:
		if opts.verbose:
			print("Professing file: %s" % filename)

		csum = crc32_checksum(filename)
		if not csum:
			print("Unable to calculate checksum for file: %s" % filename)
			continue

		if opts.append:
			src = filename
			(root, ext) = path.splitext(src)
			dst = "%s[%s]%s" % (root, csum, ext)
			shutil.move(src, dst)
			print("Moved to: %s" % dst)

		elif opts.check:
			(fpath, fname) = path.split(filename)
			c_in = c_red
			hasMatch = False
			if fname.upper().find("[%s]" % csum) >= 0 \
			or fname.upper().find("(%s)" % csum) >= 0 \
			or fname.upper().find("_%s_" % csum) >= 0:
				c_in = c_green
				hasMatch = True

			c_fname = rcsum.sub(makeSubHandler(csum, hasMatch), fname)

			print("%s%s%s   %s" % (c_in, csum, c_null, c_fname))

		if opts.verbose:
			print("Done")

if __name__ == "__main__":
	main()