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1#!/usr/bin/env python
2##
3## Copyright (c) 2016, Alliance for Open Media. All rights reserved
4##
5## This source code is subject to the terms of the BSD 2 Clause License and
6## the Alliance for Open Media Patent License 1.0. If the BSD 2 Clause License
7## was not distributed with this source code in the LICENSE file, you can
8## obtain it at www.aomedia.org/license/software. If the Alliance for Open
9## Media Patent License 1.0 was not distributed with this source code in the
10## PATENTS file, you can obtain it at www.aomedia.org/license/patent.
11##
12"""Calculates the "intersection" of two unified diffs.
13
14Given two diffs, A and B, it finds all hunks in B that had non-context lines
15in A and prints them to stdout. This is useful to determine the hunks in B that
16are relevant to A. The resulting file can be applied with patch(1) on top of A.
17"""
18
19__author__ = "jkoleszar@google.com"
20
21import sys
22
23import diff
24
25
26def FormatDiffHunks(hunks):
27    """Re-serialize a list of DiffHunks."""
28    r = []
29    last_header = None
30    for hunk in hunks:
31        this_header = hunk.header[0:2]
32        if last_header != this_header:
33            r.extend(hunk.header)
34            last_header = this_header
35        else:
36            r.extend(hunk.header[2])
37        r.extend(hunk.lines)
38        r.append("\n")
39    return "".join(r)
40
41
42def ZipHunks(rhs_hunks, lhs_hunks):
43    """Join two hunk lists on filename."""
44    for rhs_hunk in rhs_hunks:
45        rhs_file = rhs_hunk.right.filename.split("/")[1:]
46
47        for lhs_hunk in lhs_hunks:
48            lhs_file = lhs_hunk.left.filename.split("/")[1:]
49            if lhs_file != rhs_file:
50                continue
51            yield (rhs_hunk, lhs_hunk)
52
53
54def main():
55    old_hunks = [x for x in diff.ParseDiffHunks(open(sys.argv[1], "r"))]
56    new_hunks = [x for x in diff.ParseDiffHunks(open(sys.argv[2], "r"))]
57    out_hunks = []
58
59    # Join the right hand side of the older diff with the left hand side of the
60    # newer diff.
61    for old_hunk, new_hunk in ZipHunks(old_hunks, new_hunks):
62        if new_hunk in out_hunks:
63            continue
64        old_lines = old_hunk.right
65        new_lines = new_hunk.left
66
67        # Determine if this hunk overlaps any non-context line from the other
68        for i in old_lines.delta_line_nums:
69            if i in new_lines:
70                out_hunks.append(new_hunk)
71                break
72
73    if out_hunks:
74        print FormatDiffHunks(out_hunks)
75        sys.exit(1)
76
77if __name__ == "__main__":
78    main()
79