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      1 #!/usr/bin/env python
      2 ##  Copyright (c) 2012 The WebM project authors. All Rights Reserved.
      3 ##
      4 ##  Use of this source code is governed by a BSD-style license
      5 ##  that can be found in the LICENSE file in the root of the source
      6 ##  tree. An additional intellectual property rights grant can be found
      7 ##  in the file PATENTS.  All contributing project authors may
      8 ##  be found in the AUTHORS file in the root of the source tree.
      9 ##
     10 """Calculates the "intersection" of two unified diffs.
     11 
     12 Given two diffs, A and B, it finds all hunks in B that had non-context lines
     13 in A and prints them to stdout. This is useful to determine the hunks in B that
     14 are relevant to A. The resulting file can be applied with patch(1) on top of A.
     15 """
     16 
     17 __author__ = "jkoleszar (at] google.com"
     18 
     19 import sys
     20 
     21 import diff
     22 
     23 
     24 def FormatDiffHunks(hunks):
     25     """Re-serialize a list of DiffHunks."""
     26     r = []
     27     last_header = None
     28     for hunk in hunks:
     29         this_header = hunk.header[0:2]
     30         if last_header != this_header:
     31             r.extend(hunk.header)
     32             last_header = this_header
     33         else:
     34             r.extend(hunk.header[2])
     35         r.extend(hunk.lines)
     36         r.append("\n")
     37     return "".join(r)
     38 
     39 
     40 def ZipHunks(rhs_hunks, lhs_hunks):
     41     """Join two hunk lists on filename."""
     42     for rhs_hunk in rhs_hunks:
     43         rhs_file = rhs_hunk.right.filename.split("/")[1:]
     44 
     45         for lhs_hunk in lhs_hunks:
     46             lhs_file = lhs_hunk.left.filename.split("/")[1:]
     47             if lhs_file != rhs_file:
     48                 continue
     49             yield (rhs_hunk, lhs_hunk)
     50 
     51 
     52 def main():
     53     old_hunks = [x for x in diff.ParseDiffHunks(open(sys.argv[1], "r"))]
     54     new_hunks = [x for x in diff.ParseDiffHunks(open(sys.argv[2], "r"))]
     55     out_hunks = []
     56 
     57     # Join the right hand side of the older diff with the left hand side of the
     58     # newer diff.
     59     for old_hunk, new_hunk in ZipHunks(old_hunks, new_hunks):
     60         if new_hunk in out_hunks:
     61             continue
     62         old_lines = old_hunk.right
     63         new_lines = new_hunk.left
     64 
     65         # Determine if this hunk overlaps any non-context line from the other
     66         for i in old_lines.delta_line_nums:
     67             if i in new_lines:
     68                 out_hunks.append(new_hunk)
     69                 break
     70 
     71     if out_hunks:
     72         print FormatDiffHunks(out_hunks)
     73         sys.exit(1)
     74 
     75 if __name__ == "__main__":
     76     main()
     77