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1 # bdiff.py - Python implementation of bdiff.c
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2 #
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3 # Copyright 2009 Matt Mackall <mpm@selenic.com> and others
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4 #
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5 # This software may be used and distributed according to the terms of the
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6 # GNU General Public License version 2, incorporated herein by reference.
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7
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8 import struct, difflib
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9
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10 def splitnewlines(text):
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11 '''like str.splitlines, but only split on newlines.'''
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12 lines = [l + '\n' for l in text.split('\n')]
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13 if lines:
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14 if lines[-1] == '\n':
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15 lines.pop()
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16 else:
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17 lines[-1] = lines[-1][:-1]
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18 return lines
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19
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20 def _normalizeblocks(a, b, blocks):
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21 prev = None
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22 for curr in blocks:
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23 if prev is None:
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24 prev = curr
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25 continue
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26 shift = 0
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27
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28 a1, b1, l1 = prev
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29 a1end = a1 + l1
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30 b1end = b1 + l1
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31
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32 a2, b2, l2 = curr
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33 a2end = a2 + l2
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34 b2end = b2 + l2
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35 if a1end == a2:
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36 while a1end+shift < a2end and a[a1end+shift] == b[b1end+shift]:
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37 shift += 1
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38 elif b1end == b2:
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39 while b1end+shift < b2end and a[a1end+shift] == b[b1end+shift]:
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40 shift += 1
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41 yield a1, b1, l1+shift
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42 prev = a2+shift, b2+shift, l2-shift
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43 yield prev
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44
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45 def bdiff(a, b):
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46 a = str(a).splitlines(True)
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47 b = str(b).splitlines(True)
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48
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49 if not a:
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50 s = "".join(b)
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51 return s and (struct.pack(">lll", 0, 0, len(s)) + s)
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52
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53 bin = []
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54 p = [0]
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55 for i in a: p.append(p[-1] + len(i))
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56
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57 d = difflib.SequenceMatcher(None, a, b).get_matching_blocks()
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58 d = _normalizeblocks(a, b, d)
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59 la = 0
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60 lb = 0
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61 for am, bm, size in d:
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62 s = "".join(b[lb:bm])
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63 if am > la or s:
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64 bin.append(struct.pack(">lll", p[la], p[am], len(s)) + s)
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65 la = am + size
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66 lb = bm + size
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67
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68 return "".join(bin)
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69
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70 def blocks(a, b):
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71 an = splitnewlines(a)
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72 bn = splitnewlines(b)
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73 d = difflib.SequenceMatcher(None, an, bn).get_matching_blocks()
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74 d = _normalizeblocks(an, bn, d)
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75 return [(i, i + n, j, j + n) for (i, j, n) in d]
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76
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