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141 lines
4.3 KiB
Python
141 lines
4.3 KiB
Python
#!/usr/bin/env python3
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import sys
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import argparse
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import os.path
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import itertools
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PATCH_EXT = ".1337"
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CRLF = b"\x0d\x0a"
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HEADER_FORMAT = b">%s"
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LINE_FORMAT = CRLF + b"%016X:%02X->%02X"
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OFFSET_ADJUSTMENT = 0xC00
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class ByteDiffException(Exception):
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""" Base class for all exceptions """
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pass
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class LengthMismatchException(ByteDiffException):
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""" Throwed when length of input sequences do not match """
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pass
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class DiffLimitException(ByteDiffException):
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""" Throwed when difference limit hit """
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pass
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def check_positive_int(value):
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value = int(value)
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if value <= 0:
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raise argparse.ArgumentTypeError(
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"%s is an invalid positive number value" % value)
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return value
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def parse_args():
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parser = argparse.ArgumentParser(
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description="Make .1337 patch file from original and patched files")
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parser.add_argument("orig_file",
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metavar="ORIG_FILE",
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help="original file")
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parser.add_argument("patched_file",
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metavar="PATCHED_FILE",
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help="patched file")
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parser.add_argument("output_file",
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metavar="OUTPUT_FILE",
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nargs='?',
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help="filename for patch output. Default: basename of "
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"original filename with .1337 extension")
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parser.add_argument("-f", "--header-filename",
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metavar="FILENAME",
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help="filename specified in resulting patch header. "
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"Default: basename of original filename.")
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parser.add_argument("-l", "--limit",
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help="stop after number of differences",
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type=check_positive_int)
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args = parser.parse_args()
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return args
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def feed_chunks(f, chunk_size=4096):
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""" Reads file-like object with chunks having up to `chunk_size` length """
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while True:
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buf = f.read(chunk_size)
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if not buf:
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break
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yield buf
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def zip_files_bytes(left, right):
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""" Iterate over two files, returning pair of bytes.
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Throw LengthMismatch if file sizes is uneven. """
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class EndMarker(object):
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pass
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end_marker = EndMarker()
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left_iter = itertools.chain.from_iterable(
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feed_chunks(left))
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right_iter = itertools.chain.from_iterable(
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feed_chunks(right))
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for a, b in itertools.zip_longest(left_iter,
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right_iter,
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fillvalue=end_marker):
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if a is end_marker or b is end_marker:
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raise LengthMismatchException("Length of input files inequal.")
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yield a, b
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def diff(left, right, limit=None):
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offset = 0
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diff_count = 0
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for a, b in zip_files_bytes(left, right):
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if a != b:
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diff_count += 1
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if limit is not None and diff_count > limit:
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raise DiffLimitException()
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yield offset, a, b
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offset += 1
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def compose_diff_file(orig, patched, output, header, *,
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limit=None, offset_adjustment=True):
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output.write(HEADER_FORMAT % (header.encode('latin-1'),))
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adj = OFFSET_ADJUSTMENT if offset_adjustment else 0
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for offset, a, b in diff(orig, patched, limit):
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output.write(LINE_FORMAT % (offset + adj, a, b))
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def main():
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args = parse_args()
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output_filename = args.output_file
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if not output_filename:
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orig_bname = os.path.basename(args.orig_file)
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before, _, after = orig_bname.rpartition('.')
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orig_bname_noext = before if before else after
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output_filename = orig_bname_noext + PATCH_EXT
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header_filename = args.header_filename
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if not header_filename:
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header_filename = os.path.basename(args.orig_file)
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with open(args.orig_file, 'rb') as orig,\
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open(args.patched_file, 'rb') as patched,\
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open(output_filename, 'wb') as output:
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try:
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compose_diff_file(orig, patched, output, header_filename,
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limit=args.limit)
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except LengthMismatchException:
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print("Input files have inequal length. Aborting...",
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file=sys.stderr)
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except DiffLimitException:
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print("Differences limit hit. Aborting...",
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file=sys.stderr)
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if __name__ == '__main__':
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main()
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