126 lines
3.7 KiB
Python
Executable File
126 lines
3.7 KiB
Python
Executable File
#!/usr/bin/env python
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#
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# Copyright (C) 2013 The Android Open Source Project
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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#
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"""Block diff utility."""
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from __future__ import absolute_import
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from __future__ import print_function
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# pylint: disable=import-error
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import argparse
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import sys
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class BlockDiffError(Exception):
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pass
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def BlockDiff(block_size, file1, file2, name1, name2, max_length=-1):
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"""Performs a binary diff of two files by blocks.
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Args:
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block_size: the size of a block to diff by
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file1: first file object
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file2: second file object
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name1: name of first file (for error reporting)
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name2: name of second file (for error reporting)
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max_length: the maximum length to read/diff in bytes (optional)
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Returns:
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A list of (start, length) pairs representing block extents that differ
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between the two files.
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Raises:
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BlockDiffError if there were errors while diffing.
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"""
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if max_length < 0:
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max_length = sys.maxsize
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diff_list = []
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num_blocks = extent_start = extent_length = 0
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while max_length or extent_length:
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read_length = min(max_length, block_size)
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data1 = file1.read(read_length)
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data2 = file2.read(read_length)
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if len(data1) != len(data2):
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raise BlockDiffError('read %d bytes from %s but %d bytes from %s' %
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(len(data1), name1, len(data2), name2))
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if data1 != data2:
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# Data is different, mark it down.
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if extent_length:
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# Stretch the current diff extent.
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extent_length += 1
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else:
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# Start a new diff extent.
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extent_start = num_blocks
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extent_length = 1
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elif extent_length:
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# Record the previous extent.
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diff_list.append((extent_start, extent_length))
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extent_length = 0
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# Are we done reading?
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if not data1:
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break
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max_length -= len(data1)
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num_blocks += 1
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return diff_list
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def main(argv):
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# Parse command-line arguments.
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parser = argparse.ArgumentParser(
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description='Compare FILE1 and FILE2 by blocks.',
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formatter_class=argparse.ArgumentDefaultsHelpFormatter)
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parser.add_argument('-b', '--block-size', metavar='NUM', type=int,
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default=4096, help='the block size to use')
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parser.add_argument('-m', '--max-length', metavar='NUM', type=int, default=-1,
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help='maximum number of bytes to compare')
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parser.add_argument('file1', metavar='FILE1')
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parser.add_argument('file2', metavar='FILE2')
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args = parser.parse_args(argv[1:])
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# Perform the block diff.
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try:
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with open(args.file1) as file1:
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with open(args.file2) as file2:
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diff_list = BlockDiff(args.block_size, file1, file2,
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args.file1, args.file2, args.max_length)
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except BlockDiffError as e:
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print('Error: ' % e, file=sys.stderr)
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return 2
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# Print the diff, if such was found.
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if diff_list:
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total_diff_blocks = 0
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for extent_start, extent_length in diff_list:
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total_diff_blocks += extent_length
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print('%d->%d (%d)' %
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(extent_start, extent_start + extent_length, extent_length))
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print('total diff: %d blocks' % total_diff_blocks)
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return 1
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return 0
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if __name__ == '__main__':
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sys.exit(main(sys.argv))
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