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Ivan Zakrevsky committed e40a996

upgraded diff_match_patch

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Files changed (12)

versioning/diff_match_patch.py

-#!/usr/bin/python
-
-"""Diff Match and Patch
-
-Copyright 2006 Google Inc.
-http://code.google.com/p/google-diff-match-patch/
-
-Licensed under the Apache License, Version 2.0 (the "License");
-you may not use this file except in compliance with the License.
-You may obtain a copy of the License at
-
-  http://www.apache.org/licenses/LICENSE-2.0
-
-Unless required by applicable law or agreed to in writing, software
-distributed under the License is distributed on an "AS IS" BASIS,
-WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-See the License for the specific language governing permissions and
-limitations under the License.
-"""
-
-"""Functions for diff, match and patch.
-
-Computes the difference between two texts to create a patch.
-Applies the patch onto another text, allowing for errors.
-"""
-
-__author__ = 'fraser@google.com (Neil Fraser)'
-
-import math
-import time
-import urllib
-import re
-
-class diff_match_patch:
-  """Class containing the diff, match and patch methods.
-
-  Also contains the behaviour settings.
-  """
-
-  def __init__(self):
-    """Inits a diff_match_patch object with default settings.
-    Redefine these in your program to override the defaults.
-    """
-
-    # Number of seconds to map a diff before giving up (0 for infinity).
-    self.Diff_Timeout = 1.0
-    # Cost of an empty edit operation in terms of edit characters.
-    self.Diff_EditCost = 4
-    # The size beyond which the double-ended diff activates.
-    # Double-ending is twice as fast, but less accurate.
-    self.Diff_DualThreshold = 32
-    # At what point is no match declared (0.0 = perfection, 1.0 = very loose).
-    self.Match_Threshold = 0.5
-    # How far to search for a match (0 = exact location, 1000+ = broad match).
-    # A match this many characters away from the expected location will add
-    # 1.0 to the score (0.0 is a perfect match).
-    self.Match_Distance = 1000
-    # Chunk size for context length.
-    self.Patch_Margin = 4
-
-    # How many bits in a number?
-    # Python has no maximum, thus to disable patch splitting set to 0.
-    # However to avoid long patches in certain pathological cases, use 32.
-    # Multiple short patches (using native ints) are much faster than long ones.
-    self.Match_MaxBits = 32
-
-  #  DIFF FUNCTIONS
-
-  # The data structure representing a diff is an array of tuples:
-  # [(DIFF_DELETE, "Hello"), (DIFF_INSERT, "Goodbye"), (DIFF_EQUAL, " world.")]
-  # which means: delete "Hello", add "Goodbye" and keep " world."
-  DIFF_DELETE = -1
-  DIFF_INSERT = 1
-  DIFF_EQUAL = 0
-
-  def diff_main(self, text1, text2, checklines=True):
-    """Find the differences between two texts.  Simplifies the problem by
-      stripping any common prefix or suffix off the texts before diffing.
-
-    Args:
-      text1: Old string to be diffed.
-      text2: New string to be diffed.
-      checklines: Optional speedup flag.  If present and false, then don't run
-        a line-level diff first to identify the changed areas.
-        Defaults to true, which does a faster, slightly less optimal diff.
-
-    Returns:
-      Array of changes.
-    """
-
-    # Check for equality (speedup)
-    if text1 == text2:
-      return [(self.DIFF_EQUAL, text1)]
-
-    # Trim off common prefix (speedup)
-    commonlength = self.diff_commonPrefix(text1, text2)
-    commonprefix = text1[:commonlength]
-    text1 = text1[commonlength:]
-    text2 = text2[commonlength:]
-
-    # Trim off common suffix (speedup)
-    commonlength = self.diff_commonSuffix(text1, text2)
-    if commonlength == 0:
-      commonsuffix = ''
-    else:
-      commonsuffix = text1[-commonlength:]
-      text1 = text1[:-commonlength]
-      text2 = text2[:-commonlength]
-
-    # Compute the diff on the middle block
-    diffs = self.diff_compute(text1, text2, checklines)
-
-    # Restore the prefix and suffix
-    if commonprefix:
-      diffs[:0] = [(self.DIFF_EQUAL, commonprefix)]
-    if commonsuffix:
-      diffs.append((self.DIFF_EQUAL, commonsuffix))
-    self.diff_cleanupMerge(diffs)
-    return diffs
-
-  def diff_compute(self, text1, text2, checklines):
-    """Find the differences between two texts.  Assumes that the texts do not
-      have any common prefix or suffix.
-
-    Args:
-      text1: Old string to be diffed.
-      text2: New string to be diffed.
-      checklines: Speedup flag.  If false, then don't run a line-level diff
-        first to identify the changed areas.
-        If true, then run a faster, slightly less optimal diff.
-
-    Returns:
-      Array of changes.
-    """
-    if not text1:
-      # Just add some text (speedup)
-      return [(self.DIFF_INSERT, text2)]
-
-    if not text2:
-      # Just delete some text (speedup)
-      return [(self.DIFF_DELETE, text1)]
-
-    if len(text1) > len(text2):
-      (longtext, shorttext) = (text1, text2)
-    else:
-      (shorttext, longtext) = (text1, text2)
-    i = longtext.find(shorttext)
-    if i != -1:
-      # Shorter text is inside the longer text (speedup)
-      diffs = [(self.DIFF_INSERT, longtext[:i]), (self.DIFF_EQUAL, shorttext),
-               (self.DIFF_INSERT, longtext[i + len(shorttext):])]
-      # Swap insertions for deletions if diff is reversed.
-      if len(text1) > len(text2):
-        diffs[0] = (self.DIFF_DELETE, diffs[0][1])
-        diffs[2] = (self.DIFF_DELETE, diffs[2][1])
-      return diffs
-    longtext = shorttext = None  # Garbage collect
-
-    # Check to see if the problem can be split in two.
-    hm = self.diff_halfMatch(text1, text2)
-    if hm:
-      # A half-match was found, sort out the return data.
-      (text1_a, text1_b, text2_a, text2_b, mid_common) = hm
-      # Send both pairs off for separate processing.
-      diffs_a = self.diff_main(text1_a, text2_a, checklines)
-      diffs_b = self.diff_main(text1_b, text2_b, checklines)
-      # Merge the results.
-      return diffs_a + [(self.DIFF_EQUAL, mid_common)] + diffs_b
-
-    # Perform a real diff.
-    if checklines and (len(text1) < 100 or len(text2) < 100):
-      checklines = False  # Too trivial for the overhead.
-    if checklines:
-      # Scan the text on a line-by-line basis first.
-      (text1, text2, linearray) = self.diff_linesToChars(text1, text2)
-
-    diffs = self.diff_map(text1, text2)
-    if not diffs:  # No acceptable result.
-      diffs = [(self.DIFF_DELETE, text1), (self.DIFF_INSERT, text2)]
-    if checklines:
-      # Convert the diff back to original text.
-      self.diff_charsToLines(diffs, linearray)
-      # Eliminate freak matches (e.g. blank lines)
-      self.diff_cleanupSemantic(diffs)
-
-      # Rediff any replacement blocks, this time character-by-character.
-      # Add a dummy entry at the end.
-      diffs.append((self.DIFF_EQUAL, ''))
-      pointer = 0
-      count_delete = 0
-      count_insert = 0
-      text_delete = ''
-      text_insert = ''
-      while pointer < len(diffs):
-        if diffs[pointer][0] == self.DIFF_INSERT:
-          count_insert += 1
-          text_insert += diffs[pointer][1]
-        elif diffs[pointer][0] == self.DIFF_DELETE:
-          count_delete += 1
-          text_delete += diffs[pointer][1]
-        elif diffs[pointer][0] == self.DIFF_EQUAL:
-          # Upon reaching an equality, check for prior redundancies.
-          if count_delete >= 1 and count_insert >= 1:
-            # Delete the offending records and add the merged ones.
-            a = self.diff_main(text_delete, text_insert, False)
-            diffs[pointer - count_delete - count_insert : pointer] = a
-            pointer = pointer - count_delete - count_insert + len(a)
-          count_insert = 0
-          count_delete = 0
-          text_delete = ''
-          text_insert = ''
-
-        pointer += 1
-
-      diffs.pop()  # Remove the dummy entry at the end.
-    return diffs
-
-  def diff_linesToChars(self, text1, text2):
-    """Split two texts into an array of strings.  Reduce the texts to a string
-    of hashes where each Unicode character represents one line.
-
-    Args:
-      text1: First string.
-      text2: Second string.
-
-    Returns:
-      Three element tuple, containing the encoded text1, the encoded text2 and
-      the array of unique strings.  The zeroth element of the array of unique
-      strings is intentionally blank.
-    """
-    lineArray = []  # e.g. lineArray[4] == "Hello\n"
-    lineHash = {}   # e.g. lineHash["Hello\n"] == 4
-
-    # "\x00" is a valid character, but various debuggers don't like it.
-    # So we'll insert a junk entry to avoid generating a null character.
-    lineArray.append('')
-
-    def diff_linesToCharsMunge(text):
-      """Split a text into an array of strings.  Reduce the texts to a string
-      of hashes where each Unicode character represents one line.
-      Modifies linearray and linehash through being a closure.
-
-      Args:
-        text: String to encode.
-
-      Returns:
-        Encoded string.
-      """
-      chars = []
-      # Walk the text, pulling out a substring for each line.
-      # text.split('\n') would would temporarily double our memory footprint.
-      # Modifying text would create many large strings to garbage collect.
-      lineStart = 0
-      lineEnd = -1
-      while lineEnd < len(text) - 1:
-        lineEnd = text.find('\n', lineStart)
-        if lineEnd == -1:
-          lineEnd = len(text) - 1
-        line = text[lineStart:lineEnd + 1]
-        lineStart = lineEnd + 1
-
-        if line in lineHash:
-          chars.append(unichr(lineHash[line]))
-        else:
-          lineArray.append(line)
-          lineHash[line] = len(lineArray) - 1
-          chars.append(unichr(len(lineArray) - 1))
-      return "".join(chars)
-
-    chars1 = diff_linesToCharsMunge(text1)
-    chars2 = diff_linesToCharsMunge(text2)
-    return (chars1, chars2, lineArray)
-
-  def diff_charsToLines(self, diffs, lineArray):
-    """Rehydrate the text in a diff from a string of line hashes to real lines
-    of text.
-
-    Args:
-      diffs: Array of diff tuples.
-      lineArray: Array of unique strings.
-    """
-    for x in xrange(len(diffs)):
-      text = []
-      for char in diffs[x][1]:
-        text.append(lineArray[ord(char)])
-      diffs[x] = (diffs[x][0], "".join(text))
-
-  def diff_map(self, text1, text2):
-    """Explore the intersection points between the two texts.
-
-    Args:
-      text1: Old string to be diffed.
-      text2: New string to be diffed.
-
-    Returns:
-      Array of diff tuples or None if no diff available.
-    """
-
-    # Unlike in most languages, Python counts time in seconds.
-    s_end = time.time() + self.Diff_Timeout  # Don't run for too long.
-    max_d = len(text1) + len(text2) - 1
-    doubleEnd = self.Diff_DualThreshold * 2 < max_d
-    v_map1 = []
-    v_map2 = []
-    v1 = {}
-    v2 = {}
-    v1[1] = 0
-    v2[1] = 0
-    footsteps = {}
-    done = False
-    # If the total number of characters is odd, then the front path will
-    # collide with the reverse path.
-    front = (len(text1) + len(text2)) % 2
-    for d in xrange(max_d):
-      # Bail out if timeout reached.
-      if self.Diff_Timeout > 0 and time.time() > s_end:
-        return None
-
-      # Walk the front path one step.
-      v_map1.append({})
-      for k in xrange(-d, d + 1, 2):
-        if k == -d or k != d and v1[k - 1] < v1[k + 1]:
-          x = v1[k + 1]
-        else:
-          x = v1[k - 1] + 1
-        y = x - k
-        if doubleEnd:
-          footstep = (x, y)
-          if front and footstep in footsteps:
-            done = True
-          if not front:
-            footsteps[footstep] = d
-
-        while (not done and x < len(text1) and y < len(text2) and
-               text1[x] == text2[y]):
-          x += 1
-          y += 1
-          if doubleEnd:
-            footstep = (x, y)
-            if front and footstep in footsteps:
-              done = True
-            if not front:
-              footsteps[footstep] = d
-
-        v1[k] = x
-        v_map1[d][(x, y)] = True
-        if x == len(text1) and y == len(text2):
-          # Reached the end in single-path mode.
-          return self.diff_path1(v_map1, text1, text2)
-        elif done:
-          # Front path ran over reverse path.
-          v_map2 = v_map2[:footsteps[footstep] + 1]
-          a = self.diff_path1(v_map1, text1[:x], text2[:y])
-          b = self.diff_path2(v_map2, text1[x:], text2[y:])
-          return a + b
-
-      if doubleEnd:
-        # Walk the reverse path one step.
-        v_map2.append({})
-        for k in xrange(-d, d + 1, 2):
-          if k == -d or k != d and v2[k - 1] < v2[k + 1]:
-            x = v2[k + 1]
-          else:
-            x = v2[k - 1] + 1
-          y = x - k
-          footstep = (len(text1) - x, len(text2) - y)
-          if not front and footstep in footsteps:
-            done = True
-          if front:
-            footsteps[footstep] = d
-          while (not done and x < len(text1) and y < len(text2) and
-                 text1[-x - 1] == text2[-y - 1]):
-            x += 1
-            y += 1
-            footstep = (len(text1) - x, len(text2) - y)
-            if not front and footstep in footsteps:
-              done = True
-            if front:
-              footsteps[footstep] = d
-
-          v2[k] = x
-          v_map2[d][(x, y)] = True
-          if done:
-            # Reverse path ran over front path.
-            v_map1 = v_map1[:footsteps[footstep] + 1]
-            a = self.diff_path1(v_map1, text1[:len(text1) - x],
-                                text2[:len(text2) - y])
-            b = self.diff_path2(v_map2, text1[len(text1) - x:],
-                                text2[len(text2) - y:])
-            return a + b
-
-    # Number of diffs equals number of characters, no commonality at all.
-    return None
-
-  def diff_path1(self, v_map, text1, text2):
-    """Work from the middle back to the start to determine the path.
-
-    Args:
-      v_map: Array of paths.
-      text1: Old string fragment to be diffed.
-      text2: New string fragment to be diffed.
-
-    Returns:
-      Array of diff tuples.
-    """
-    path = []
-    x = len(text1)
-    y = len(text2)
-    last_op = None
-    for d in xrange(len(v_map) - 2, -1, -1):
-      while True:
-        if (x - 1, y) in v_map[d]:
-          x -= 1
-          if last_op == self.DIFF_DELETE:
-            path[0] = (self.DIFF_DELETE, text1[x] + path[0][1])
-          else:
-            path[:0] = [(self.DIFF_DELETE, text1[x])]
-          last_op = self.DIFF_DELETE
-          break
-        elif (x, y - 1) in v_map[d]:
-          y -= 1
-          if last_op == self.DIFF_INSERT:
-            path[0] = (self.DIFF_INSERT, text2[y] + path[0][1])
-          else:
-            path[:0] = [(self.DIFF_INSERT, text2[y])]
-          last_op = self.DIFF_INSERT
-          break
-        else:
-          x -= 1
-          y -= 1
-          assert text1[x] == text2[y], ("No diagonal.  " +
-              "Can't happen. (diff_path1)")
-          if last_op == self.DIFF_EQUAL:
-            path[0] = (self.DIFF_EQUAL, text1[x] + path[0][1])
-          else:
-            path[:0] = [(self.DIFF_EQUAL, text1[x])]
-          last_op = self.DIFF_EQUAL
-    return path
-
-  def diff_path2(self, v_map, text1, text2):
-    """Work from the middle back to the end to determine the path.
-
-    Args:
-      v_map: Array of paths.
-      text1: Old string fragment to be diffed.
-      text2: New string fragment to be diffed.
-
-    Returns:
-      Array of diff tuples.
-    """
-    path = []
-    x = len(text1)
-    y = len(text2)
-    last_op = None
-    for d in xrange(len(v_map) - 2, -1, -1):
-      while True:
-        if (x - 1, y) in v_map[d]:
-          x -= 1
-          if last_op == self.DIFF_DELETE:
-            path[-1] = (self.DIFF_DELETE, path[-1][1] + text1[-x - 1])
-          else:
-            path.append((self.DIFF_DELETE, text1[-x - 1]))
-          last_op = self.DIFF_DELETE
-          break
-        elif (x, y - 1) in v_map[d]:
-          y -= 1
-          if last_op == self.DIFF_INSERT:
-            path[-1] = (self.DIFF_INSERT, path[-1][1] + text2[-y - 1])
-          else:
-            path.append((self.DIFF_INSERT, text2[-y - 1]))
-          last_op = self.DIFF_INSERT
-          break
-        else:
-          x -= 1
-          y -= 1
-          assert text1[-x - 1] == text2[-y - 1], ("No diagonal.  " +
-              "Can't happen. (diff_path2)")
-          if last_op == self.DIFF_EQUAL:
-            path[-1] = (self.DIFF_EQUAL, path[-1][1] + text1[-x - 1])
-          else:
-            path.append((self.DIFF_EQUAL, text1[-x - 1]))
-          last_op = self.DIFF_EQUAL
-    return path
-
-  def diff_commonPrefix(self, text1, text2):
-    """Determine the common prefix of two strings.
-
-    Args:
-      text1: First string.
-      text2: Second string.
-
-    Returns:
-      The number of characters common to the start of each string.
-    """
-    # Quick check for common null cases.
-    if not text1 or not text2 or text1[0] != text2[0]:
-      return 0
-    # Binary search.
-    # Performance analysis: http://neil.fraser.name/news/2007/10/09/
-    pointermin = 0
-    pointermax = min(len(text1), len(text2))
-    pointermid = pointermax
-    pointerstart = 0
-    while pointermin < pointermid:
-      if text1[pointerstart:pointermid] == text2[pointerstart:pointermid]:
-        pointermin = pointermid
-        pointerstart = pointermin
-      else:
-        pointermax = pointermid
-      pointermid = int((pointermax - pointermin) / 2 + pointermin)
-    return pointermid
-
-  def diff_commonSuffix(self, text1, text2):
-    """Determine the common suffix of two strings.
-
-    Args:
-      text1: First string.
-      text2: Second string.
-
-    Returns:
-      The number of characters common to the end of each string.
-    """
-    # Quick check for common null cases.
-    if not text1 or not text2 or text1[-1] != text2[-1]:
-      return 0
-    # Binary search.
-    # Performance analysis: http://neil.fraser.name/news/2007/10/09/
-    pointermin = 0
-    pointermax = min(len(text1), len(text2))
-    pointermid = pointermax
-    pointerend = 0
-    while pointermin < pointermid:
-      if (text1[-pointermid:len(text1) - pointerend] ==
-          text2[-pointermid:len(text2) - pointerend]):
-        pointermin = pointermid
-        pointerend = pointermin
-      else:
-        pointermax = pointermid
-      pointermid = int((pointermax - pointermin) / 2 + pointermin)
-    return pointermid
-
-  def diff_halfMatch(self, text1, text2):
-    """Do the two texts share a substring which is at least half the length of
-    the longer text?
-
-    Args:
-      text1: First string.
-      text2: Second string.
-
-    Returns:
-      Five element Array, containing the prefix of text1, the suffix of text1,
-      the prefix of text2, the suffix of text2 and the common middle.  Or None
-      if there was no match.
-    """
-    if len(text1) > len(text2):
-      (longtext, shorttext) = (text1, text2)
-    else:
-      (shorttext, longtext) = (text1, text2)
-    if len(longtext) < 10 or len(shorttext) < 1:
-      return None  # Pointless.
-
-    def diff_halfMatchI(longtext, shorttext, i):
-      """Does a substring of shorttext exist within longtext such that the
-      substring is at least half the length of longtext?
-      Closure, but does not reference any external variables.
-
-      Args:
-        longtext: Longer string.
-        shorttext: Shorter string.
-        i: Start index of quarter length substring within longtext.
-
-      Returns:
-        Five element Array, containing the prefix of longtext, the suffix of
-        longtext, the prefix of shorttext, the suffix of shorttext and the
-        common middle.  Or None if there was no match.
-      """
-      seed = longtext[i:i + len(longtext) / 4]
-      best_common = ''
-      j = shorttext.find(seed)
-      while j != -1:
-        prefixLength = self.diff_commonPrefix(longtext[i:], shorttext[j:])
-        suffixLength = self.diff_commonSuffix(longtext[:i], shorttext[:j])
-        if len(best_common) < suffixLength + prefixLength:
-          best_common = (shorttext[j - suffixLength:j] +
-              shorttext[j:j + prefixLength])
-          best_longtext_a = longtext[:i - suffixLength]
-          best_longtext_b = longtext[i + prefixLength:]
-          best_shorttext_a = shorttext[:j - suffixLength]
-          best_shorttext_b = shorttext[j + prefixLength:]
-        j = shorttext.find(seed, j + 1)
-
-      if len(best_common) >= len(longtext) / 2:
-        return (best_longtext_a, best_longtext_b,
-                best_shorttext_a, best_shorttext_b, best_common)
-      else:
-        return None
-
-    # First check if the second quarter is the seed for a half-match.
-    hm1 = diff_halfMatchI(longtext, shorttext, (len(longtext) + 3) / 4)
-    # Check again based on the third quarter.
-    hm2 = diff_halfMatchI(longtext, shorttext, (len(longtext) + 1) / 2)
-    if not hm1 and not hm2:
-      return None
-    elif not hm2:
-      hm = hm1
-    elif not hm1:
-      hm = hm2
-    else:
-      # Both matched.  Select the longest.
-      if len(hm1[4]) > len(hm2[4]):
-        hm = hm1
-      else:
-        hm = hm2
-
-    # A half-match was found, sort out the return data.
-    if len(text1) > len(text2):
-      (text1_a, text1_b, text2_a, text2_b, mid_common) = hm
-    else:
-      (text2_a, text2_b, text1_a, text1_b, mid_common) = hm
-    return (text1_a, text1_b, text2_a, text2_b, mid_common)
-
-  def diff_cleanupSemantic(self, diffs):
-    """Reduce the number of edits by eliminating semantically trivial
-    equalities.
-
-    Args:
-      diffs: Array of diff tuples.
-    """
-    changes = False
-    equalities = []  # Stack of indices where equalities are found.
-    lastequality = None  # Always equal to equalities[-1][1]
-    pointer = 0  # Index of current position.
-    length_changes1 = 0  # Number of chars that changed prior to the equality.
-    length_changes2 = 0  # Number of chars that changed after the equality.
-    while pointer < len(diffs):
-      if diffs[pointer][0] == self.DIFF_EQUAL:  # equality found
-        equalities.append(pointer)
-        length_changes1 = length_changes2
-        length_changes2 = 0
-        lastequality = diffs[pointer][1]
-      else:  # an insertion or deletion
-        length_changes2 += len(diffs[pointer][1])
-        if (lastequality != None and (len(lastequality) <= length_changes1) and
-            (len(lastequality) <= length_changes2)):
-          # Duplicate record
-          diffs.insert(equalities[-1], (self.DIFF_DELETE, lastequality))
-          # Change second copy to insert.
-          diffs[equalities[-1] + 1] = (self.DIFF_INSERT,
-              diffs[equalities[-1] + 1][1])
-          # Throw away the equality we just deleted.
-          equalities.pop()
-          # Throw away the previous equality (it needs to be reevaluated).
-          if len(equalities) != 0:
-            equalities.pop()
-          if len(equalities):
-            pointer = equalities[-1]
-          else:
-            pointer = -1
-          length_changes1 = 0  # Reset the counters.
-          length_changes2 = 0
-          lastequality = None
-          changes = True
-      pointer += 1
-
-    if changes:
-      self.diff_cleanupMerge(diffs)
-
-    self.diff_cleanupSemanticLossless(diffs)
-
-  def diff_cleanupSemanticLossless(self, diffs):
-    """Look for single edits surrounded on both sides by equalities
-    which can be shifted sideways to align the edit to a word boundary.
-    e.g: The c<ins>at c</ins>ame. -> The <ins>cat </ins>came.
-
-    Args:
-      diffs: Array of diff tuples.
-    """
-
-    def diff_cleanupSemanticScore(one, two):
-      """Given two strings, compute a score representing whether the
-      internal boundary falls on logical boundaries.
-      Scores range from 5 (best) to 0 (worst).
-      Closure, but does not reference any external variables.
-
-      Args:
-        one: First string.
-        two: Second string.
-
-      Returns:
-        The score.
-      """
-      if not one or not two:
-        # Edges are the best.
-        return 5
-
-      # Each port of this function behaves slightly differently due to
-      # subtle differences in each language's definition of things like
-      # 'whitespace'.  Since this function's purpose is largely cosmetic,
-      # the choice has been made to use each language's native features
-      # rather than force total conformity.
-      score = 0
-      # One point for non-alphanumeric.
-      if not one[-1].isalnum() or not two[0].isalnum():
-        score += 1
-        # Two points for whitespace.
-        if one[-1].isspace() or two[0].isspace():
-          score += 1
-          # Three points for line breaks.
-          if (one[-1] == "\r" or one[-1] == "\n" or
-              two[0] == "\r" or two[0] == "\n"):
-            score += 1
-            # Four points for blank lines.
-            if (re.search("\\n\\r?\\n$", one) or
-                re.match("^\\r?\\n\\r?\\n", two)):
-              score += 1
-      return score
-
-    pointer = 1
-    # Intentionally ignore the first and last element (don't need checking).
-    while pointer < len(diffs) - 1:
-      if (diffs[pointer - 1][0] == self.DIFF_EQUAL and
-          diffs[pointer + 1][0] == self.DIFF_EQUAL):
-        # This is a single edit surrounded by equalities.
-        equality1 = diffs[pointer - 1][1]
-        edit = diffs[pointer][1]
-        equality2 = diffs[pointer + 1][1]
-
-        # First, shift the edit as far left as possible.
-        commonOffset = self.diff_commonSuffix(equality1, edit)
-        if commonOffset:
-          commonString = edit[-commonOffset:]
-          equality1 = equality1[:-commonOffset]
-          edit = commonString + edit[:-commonOffset]
-          equality2 = commonString + equality2
-
-        # Second, step character by character right, looking for the best fit.
-        bestEquality1 = equality1
-        bestEdit = edit
-        bestEquality2 = equality2
-        bestScore = (diff_cleanupSemanticScore(equality1, edit) +
-            diff_cleanupSemanticScore(edit, equality2))
-        while edit and equality2 and edit[0] == equality2[0]:
-          equality1 += edit[0]
-          edit = edit[1:] + equality2[0]
-          equality2 = equality2[1:]
-          score = (diff_cleanupSemanticScore(equality1, edit) +
-              diff_cleanupSemanticScore(edit, equality2))
-          # The >= encourages trailing rather than leading whitespace on edits.
-          if score >= bestScore:
-            bestScore = score
-            bestEquality1 = equality1
-            bestEdit = edit
-            bestEquality2 = equality2
-
-        if diffs[pointer - 1][1] != bestEquality1:
-          # We have an improvement, save it back to the diff.
-          if bestEquality1:
-            diffs[pointer - 1] = (diffs[pointer - 1][0], bestEquality1)
-          else:
-            del diffs[pointer - 1]
-            pointer -= 1
-          diffs[pointer] = (diffs[pointer][0], bestEdit)
-          if bestEquality2:
-            diffs[pointer + 1] = (diffs[pointer + 1][0], bestEquality2)
-          else:
-            del diffs[pointer + 1]
-            pointer -= 1
-      pointer += 1
-
-  def diff_cleanupEfficiency(self, diffs):
-    """Reduce the number of edits by eliminating operationally trivial
-    equalities.
-
-    Args:
-      diffs: Array of diff tuples.
-    """
-    changes = False
-    equalities = []  # Stack of indices where equalities are found.
-    lastequality = ''  # Always equal to equalities[-1][1]
-    pointer = 0  # Index of current position.
-    pre_ins = False  # Is there an insertion operation before the last equality.
-    pre_del = False  # Is there a deletion operation before the last equality.
-    post_ins = False  # Is there an insertion operation after the last equality.
-    post_del = False  # Is there a deletion operation after the last equality.
-    while pointer < len(diffs):
-      if diffs[pointer][0] == self.DIFF_EQUAL:  # equality found
-        if (len(diffs[pointer][1]) < self.Diff_EditCost and
-            (post_ins or post_del)):
-          # Candidate found.
-          equalities.append(pointer)
-          pre_ins = post_ins
-          pre_del = post_del
-          lastequality = diffs[pointer][1]
-        else:
-          # Not a candidate, and can never become one.
-          equalities = []
-          lastequality = ''
-
-        post_ins = post_del = False
-      else:  # an insertion or deletion
-        if diffs[pointer][0] == self.DIFF_DELETE:
-          post_del = True
-        else:
-          post_ins = True
-
-        # Five types to be split:
-        # <ins>A</ins><del>B</del>XY<ins>C</ins><del>D</del>
-        # <ins>A</ins>X<ins>C</ins><del>D</del>
-        # <ins>A</ins><del>B</del>X<ins>C</ins>
-        # <ins>A</del>X<ins>C</ins><del>D</del>
-        # <ins>A</ins><del>B</del>X<del>C</del>
-
-        if lastequality and ((pre_ins and pre_del and post_ins and post_del) or
-                             ((len(lastequality) < self.Diff_EditCost / 2) and
-                              (pre_ins + pre_del + post_ins + post_del) == 3)):
-          # Duplicate record
-          diffs.insert(equalities[-1], (self.DIFF_DELETE, lastequality))
-          # Change second copy to insert.
-          diffs[equalities[-1] + 1] = (self.DIFF_INSERT,
-              diffs[equalities[-1] + 1][1])
-          equalities.pop()  # Throw away the equality we just deleted
-          lastequality = ''
-          if pre_ins and pre_del:
-            # No changes made which could affect previous entry, keep going.
-            post_ins = post_del = True
-            equalities = []
-          else:
-            if len(equalities):
-              equalities.pop()  # Throw away the previous equality
-            if len(equalities):
-              pointer = equalities[-1]
-            else:
-              pointer = -1
-            post_ins = post_del = False
-          changes = True
-      pointer += 1
-
-    if changes:
-      self.diff_cleanupMerge(diffs)
-
-  def diff_cleanupMerge(self, diffs):
-    """Reorder and merge like edit sections.  Merge equalities.
-    Any edit section can move as long as it doesn't cross an equality.
-
-    Args:
-      diffs: Array of diff tuples.
-    """
-    diffs.append((self.DIFF_EQUAL, ''))  # Add a dummy entry at the end.
-    pointer = 0
-    count_delete = 0
-    count_insert = 0
-    text_delete = ''
-    text_insert = ''
-    while pointer < len(diffs):
-      if diffs[pointer][0] == self.DIFF_INSERT:
-        count_insert += 1
-        text_insert += diffs[pointer][1]
-        pointer += 1
-      elif diffs[pointer][0] == self.DIFF_DELETE:
-        count_delete += 1
-        text_delete += diffs[pointer][1]
-        pointer += 1
-      elif diffs[pointer][0] == self.DIFF_EQUAL:
-        # Upon reaching an equality, check for prior redundancies.
-        if count_delete != 0 or count_insert != 0:
-          if count_delete != 0 and count_insert != 0:
-            # Factor out any common prefixies.
-            commonlength = self.diff_commonPrefix(text_insert, text_delete)
-            if commonlength != 0:
-              x = pointer - count_delete - count_insert - 1
-              if x >= 0 and diffs[x][0] == self.DIFF_EQUAL:
-                diffs[x] = (diffs[x][0], diffs[x][1] +
-                            text_insert[:commonlength])
-              else:
-                diffs.insert(0, (self.DIFF_EQUAL, text_insert[:commonlength]))
-                pointer += 1
-              text_insert = text_insert[commonlength:]
-              text_delete = text_delete[commonlength:]
-            # Factor out any common suffixies.
-            commonlength = self.diff_commonSuffix(text_insert, text_delete)
-            if commonlength != 0:
-              diffs[pointer] = (diffs[pointer][0], text_insert[-commonlength:] +
-                  diffs[pointer][1])
-              text_insert = text_insert[:-commonlength]
-              text_delete = text_delete[:-commonlength]
-          # Delete the offending records and add the merged ones.
-          if count_delete == 0:
-            diffs[pointer - count_insert : pointer] = [
-                (self.DIFF_INSERT, text_insert)]
-          elif count_insert == 0:
-            diffs[pointer - count_delete : pointer] = [
-                (self.DIFF_DELETE, text_delete)]
-          else:
-            diffs[pointer - count_delete - count_insert : pointer] = [
-                (self.DIFF_DELETE, text_delete),
-                (self.DIFF_INSERT, text_insert)]
-          pointer = pointer - count_delete - count_insert + 1
-          if count_delete != 0:
-            pointer += 1
-          if count_insert != 0:
-            pointer += 1
-        elif pointer != 0 and diffs[pointer - 1][0] == self.DIFF_EQUAL:
-          # Merge this equality with the previous one.
-          diffs[pointer - 1] = (diffs[pointer - 1][0],
-                                diffs[pointer - 1][1] + diffs[pointer][1])
-          del diffs[pointer]
-        else:
-          pointer += 1
-
-        count_insert = 0
-        count_delete = 0
-        text_delete = ''
-        text_insert = ''
-
-    if diffs[-1][1] == '':
-      diffs.pop()  # Remove the dummy entry at the end.
-
-    # Second pass: look for single edits surrounded on both sides by equalities
-    # which can be shifted sideways to eliminate an equality.
-    # e.g: A<ins>BA</ins>C -> <ins>AB</ins>AC
-    changes = False
-    pointer = 1
-    # Intentionally ignore the first and last element (don't need checking).
-    while pointer < len(diffs) - 1:
-      if (diffs[pointer - 1][0] == self.DIFF_EQUAL and
-          diffs[pointer + 1][0] == self.DIFF_EQUAL):
-        # This is a single edit surrounded by equalities.
-        if diffs[pointer][1].endswith(diffs[pointer - 1][1]):
-          # Shift the edit over the previous equality.
-          diffs[pointer] = (diffs[pointer][0],
-              diffs[pointer - 1][1] +
-              diffs[pointer][1][:-len(diffs[pointer - 1][1])])
-          diffs[pointer + 1] = (diffs[pointer + 1][0],
-                                diffs[pointer - 1][1] + diffs[pointer + 1][1])
-          del diffs[pointer - 1]
-          changes = True
-        elif diffs[pointer][1].startswith(diffs[pointer + 1][1]):
-          # Shift the edit over the next equality.
-          diffs[pointer - 1] = (diffs[pointer - 1][0],
-                                diffs[pointer - 1][1] + diffs[pointer + 1][1])
-          diffs[pointer] = (diffs[pointer][0],
-              diffs[pointer][1][len(diffs[pointer + 1][1]):] +
-              diffs[pointer + 1][1])
-          del diffs[pointer + 1]
-          changes = True
-      pointer += 1
-
-    # If shifts were made, the diff needs reordering and another shift sweep.
-    if changes:
-      self.diff_cleanupMerge(diffs)
-
-  def diff_xIndex(self, diffs, loc):
-    """loc is a location in text1, compute and return the equivalent location
-    in text2.  e.g. "The cat" vs "The big cat", 1->1, 5->8
-
-    Args:
-      diffs: Array of diff tuples.
-      loc: Location within text1.
-
-    Returns:
-      Location within text2.
-    """
-    chars1 = 0
-    chars2 = 0
-    last_chars1 = 0
-    last_chars2 = 0
-    for x in xrange(len(diffs)):
-      (op, text) = diffs[x]
-      if op != self.DIFF_INSERT:  # Equality or deletion.
-        chars1 += len(text)
-      if op != self.DIFF_DELETE:  # Equality or insertion.
-        chars2 += len(text)
-      if chars1 > loc:  # Overshot the location.
-        break
-      last_chars1 = chars1
-      last_chars2 = chars2
-
-    if len(diffs) != x and diffs[x][0] == self.DIFF_DELETE:
-      # The location was deleted.
-      return last_chars2
-    # Add the remaining len(character).
-    return last_chars2 + (loc - last_chars1)
-
-  def diff_prettyHtml(self, diffs):
-    """Convert a diff array into a pretty HTML report.
-
-    Args:
-      diffs: Array of diff tuples.
-
-    Returns:
-      HTML representation.
-    """
-    html = []
-    i = 0
-    for (op, data) in diffs:
-      text = (data.replace("&", "&amp;").replace("<", "&lt;")
-                 .replace(">", "&gt;").replace("\n", "&para;<BR>"))
-      if op == self.DIFF_INSERT:
-        html.append("<INS STYLE=\"background:#E6FFE6;\" TITLE=\"i=%i\">%s</INS>"
-            % (i, text))
-      elif op == self.DIFF_DELETE:
-        html.append("<DEL STYLE=\"background:#FFE6E6;\" TITLE=\"i=%i\">%s</DEL>"
-            % (i, text))
-      elif op == self.DIFF_EQUAL:
-        html.append("<SPAN TITLE=\"i=%i\">%s</SPAN>" % (i, text))
-      if op != self.DIFF_DELETE:
-        i += len(data)
-    return "".join(html)
-
-  def diff_text1(self, diffs):
-    """Compute and return the source text (all equalities and deletions).
-
-    Args:
-      diffs: Array of diff tuples.
-
-    Returns:
-      Source text.
-    """
-    text = []
-    for (op, data) in diffs:
-      if op != self.DIFF_INSERT:
-        text.append(data)
-    return "".join(text)
-
-  def diff_text2(self, diffs):
-    """Compute and return the destination text (all equalities and insertions).
-
-    Args:
-      diffs: Array of diff tuples.
-
-    Returns:
-      Destination text.
-    """
-    text = []
-    for (op, data) in diffs:
-      if op != self.DIFF_DELETE:
-        text.append(data)
-    return "".join(text)
-
-  def diff_levenshtein(self, diffs):
-    """Compute the Levenshtein distance; the number of inserted, deleted or
-    substituted characters.
-
-    Args:
-      diffs: Array of diff tuples.
-
-    Returns:
-      Number of changes.
-    """
-    levenshtein = 0
-    insertions = 0
-    deletions = 0
-    for (op, data) in diffs:
-      if op == self.DIFF_INSERT:
-        insertions += len(data)
-      elif op == self.DIFF_DELETE:
-        deletions += len(data)
-      elif op == self.DIFF_EQUAL:
-        # A deletion and an insertion is one substitution.
-        levenshtein += max(insertions, deletions)
-        insertions = 0
-        deletions = 0
-    levenshtein += max(insertions, deletions)
-    return levenshtein
-
-  def diff_toDelta(self, diffs):
-    """Crush the diff into an encoded string which describes the operations
-    required to transform text1 into text2.
-    E.g. =3\t-2\t+ing  -> Keep 3 chars, delete 2 chars, insert 'ing'.
-    Operations are tab-separated.  Inserted text is escaped using %xx notation.
-
-    Args:
-      diffs: Array of diff tuples.
-
-    Returns:
-      Delta text.
-    """
-    text = []
-    for (op, data) in diffs:
-      if op == self.DIFF_INSERT:
-        # High ascii will raise UnicodeDecodeError.  Use Unicode instead.
-        data = data.encode("utf-8")
-        text.append("+" + urllib.quote(data, "!~*'();/?:@&=+$,# "))
-      elif op == self.DIFF_DELETE:
-        text.append("-%d" % len(data))
-      elif op == self.DIFF_EQUAL:
-        text.append("=%d" % len(data))
-    return "\t".join(text)
-
-  def diff_fromDelta(self, text1, delta):
-    """Given the original text1, and an encoded string which describes the
-    operations required to transform text1 into text2, compute the full diff.
-
-    Args:
-      text1: Source string for the diff.
-      delta: Delta text.
-
-    Returns:
-      Array of diff tuples.
-
-    Raises:
-      ValueError: If invalid input.
-    """
-    if type(delta) == unicode:
-      # Deltas should be composed of a subset of ascii chars, Unicode not
-      # required.  If this encode raises UnicodeEncodeError, delta is invalid.
-      delta = delta.encode("ascii")
-    diffs = []
-    pointer = 0  # Cursor in text1
-    tokens = delta.split("\t")
-    for token in tokens:
-      if token == "":
-        # Blank tokens are ok (from a trailing \t).
-        continue
-      # Each token begins with a one character parameter which specifies the
-      # operation of this token (delete, insert, equality).
-      param = token[1:]
-      if token[0] == "+":
-        param = urllib.unquote(param).decode("utf-8")
-        diffs.append((self.DIFF_INSERT, param))
-      elif token[0] == "-" or token[0] == "=":
-        try:
-          n = int(param)
-        except ValueError:
-          raise ValueError, "Invalid number in diff_fromDelta: " + param
-        if n < 0:
-          raise ValueError, "Negative number in diff_fromDelta: " + param
-        text = text1[pointer : pointer + n]
-        pointer += n
-        if token[0] == "=":
-          diffs.append((self.DIFF_EQUAL, text))
-        else:
-          diffs.append((self.DIFF_DELETE, text))
-      else:
-        # Anything else is an error.
-        raise ValueError, ("Invalid diff operation in diff_fromDelta: " +
-            token[0])
-    if pointer != len(text1):
-      raise ValueError, (
-          "Delta length (%d) does not equal source text length (%d)." %
-         (pointer, len(text1)))
-    return diffs
-
-  #  MATCH FUNCTIONS
-
-  def match_main(self, text, pattern, loc):
-    """Locate the best instance of 'pattern' in 'text' near 'loc'.
-
-    Args:
-      text: The text to search.
-      pattern: The pattern to search for.
-      loc: The location to search around.
-
-    Returns:
-      Best match index or -1.
-    """
-    loc = max(0, min(loc, len(text)))
-    if text == pattern:
-      # Shortcut (potentially not guaranteed by the algorithm)
-      return 0
-    elif not text:
-      # Nothing to match.
-      return -1
-    elif text[loc:loc + len(pattern)] == pattern:
-      # Perfect match at the perfect spot!  (Includes case of null pattern)
-      return loc
-    else:
-      # Do a fuzzy compare.
-      match = self.match_bitap(text, pattern, loc)
-      return match
-
-  def match_bitap(self, text, pattern, loc):
-    """Locate the best instance of 'pattern' in 'text' near 'loc' using the
-    Bitap algorithm.
-
-    Args:
-      text: The text to search.
-      pattern: The pattern to search for.
-      loc: The location to search around.
-
-    Returns:
-      Best match index or -1.
-    """
-    # Python doesn't have a maxint limit, so ignore this check.
-    #if self.Match_MaxBits != 0 and len(pattern) > self.Match_MaxBits:
-    #  raise ValueError("Pattern too long for this application.")
-
-    # Initialise the alphabet.
-    s = self.match_alphabet(pattern)
-
-    def match_bitapScore(e, x):
-      """Compute and return the score for a match with e errors and x location.
-      Accesses loc and pattern through being a closure.
-
-      Args:
-        e: Number of errors in match.
-        x: Location of match.
-
-      Returns:
-        Overall score for match (0.0 = good, 1.0 = bad).
-      """
-      accuracy = float(e) / len(pattern)
-      proximity = abs(loc - x)
-      if not self.Match_Distance:
-        # Dodge divide by zero error.
-        return proximity and 1.0 or accuracy
-      return accuracy + proximity / float(self.Match_Distance)
-
-    # Highest score beyond which we give up.
-    score_threshold = self.Match_Threshold
-    # Is there a nearby exact match? (speedup)
-    best_loc = text.find(pattern, loc)
-    if best_loc != -1:
-      score_threshold = min(match_bitapScore(0, best_loc), score_threshold)
-    # What about in the other direction? (speedup)
-    best_loc = text.rfind(pattern, loc + len(pattern))
-    if best_loc != -1:
-      score_threshold = min(match_bitapScore(0, best_loc), score_threshold)
-
-    # Initialise the bit arrays.
-    matchmask = 1 << (len(pattern) - 1)
-    best_loc = -1
-
-    bin_max = len(pattern) + len(text)
-    # Empty initialization added to appease pychecker.
-    last_rd = None
-    for d in xrange(len(pattern)):
-      # Scan for the best match each iteration allows for one more error.
-      # Run a binary search to determine how far from 'loc' we can stray at
-      # this error level.
-      bin_min = 0
-      bin_mid = bin_max
-      while bin_min < bin_mid:
-        if match_bitapScore(d, loc + bin_mid) <= score_threshold:
-          bin_min = bin_mid
-        else:
-          bin_max = bin_mid
-        bin_mid = (bin_max - bin_min) / 2 + bin_min
-
-      # Use the result from this iteration as the maximum for the next.
-      bin_max = bin_mid
-      start = max(1, loc - bin_mid + 1)
-      finish = min(loc + bin_mid, len(text)) + len(pattern)
-
-      rd = range(finish + 1)
-      rd.append((1 << d) - 1)
-      for j in xrange(finish, start - 1, -1):
-        if len(text) <= j - 1:
-          # Out of range.
-          charMatch = 0
-        else:
-          charMatch = s.get(text[j - 1], 0)
-        if d == 0:  # First pass: exact match.
-          rd[j] = ((rd[j + 1] << 1) | 1) & charMatch
-        else:  # Subsequent passes: fuzzy match.
-          rd[j] = ((rd[j + 1] << 1) | 1) & charMatch | (
-              ((last_rd[j + 1] | last_rd[j]) << 1) | 1) | last_rd[j + 1]
-        if rd[j] & matchmask:
-          score = match_bitapScore(d, j - 1)
-          # This match will almost certainly be better than any existing match.
-          # But check anyway.
-          if score <= score_threshold:
-            # Told you so.
-            score_threshold = score
-            best_loc = j - 1
-            if best_loc > loc:
-              # When passing loc, don't exceed our current distance from loc.
-              start = max(1, 2 * loc - best_loc)
-            else:
-              # Already passed loc, downhill from here on in.
-              break
-      # No hope for a (better) match at greater error levels.
-      if match_bitapScore(d + 1, loc) > score_threshold:
-        break
-      last_rd = rd
-    return best_loc
-
-  def match_alphabet(self, pattern):
-    """Initialise the alphabet for the Bitap algorithm.
-
-    Args:
-      pattern: The text to encode.
-
-    Returns:
-      Hash of character locations.
-    """
-    s = {}
-    for char in pattern:
-      s[char] = 0
-    for i in xrange(len(pattern)):
-      s[pattern[i]] |= 1 << (len(pattern) - i - 1)
-    return s
-
-  #  PATCH FUNCTIONS
-
-  def patch_addContext(self, patch, text):
-    """Increase the context until it is unique,
-    but don't let the pattern expand beyond Match_MaxBits.
-
-    Args:
-      patch: The patch to grow.
-      text: Source text.
-    """
-    pattern = text[patch.start2 : patch.start2 + patch.length1]
-    padding = 0
-    while (text.find(pattern) != text.rfind(pattern) and (self.Match_MaxBits ==
-        0 or len(pattern) < self.Match_MaxBits - self.Patch_Margin -
-        self.Patch_Margin)):
-      padding += self.Patch_Margin
-      pattern = text[max(0, patch.start2 - padding) :
-                     min(len(text), patch.start2 + patch.length1 + padding)]
-
-    # Add one chunk for good luck.
-    padding += self.Patch_Margin
-    # Add the prefix.
-    prefix = text[max(0, patch.start2 - padding) : patch.start2]
-    if prefix:
-      patch.diffs[:0] = [(self.DIFF_EQUAL, prefix)]
-    # Add the suffix.
-    suffix = text[patch.start2 + patch.length1 :
-                  min(len(text), patch.start2 + patch.length1 + padding)]
-    if suffix:
-      patch.diffs.append((self.DIFF_EQUAL, suffix))
-
-    # Roll back the start points.
-    patch.start1 -= len(prefix)
-    patch.start2 -= len(prefix)
-    # Extend lengths.
-    patch.length1 += len(prefix) + len(suffix)
-    patch.length2 += len(prefix) + len(suffix)
-
-  def patch_make(self, a, b=None, c=None):
-    """Compute a list of patches to turn text1 into text2.
-    Use diffs if provided, otherwise compute it ourselves.
-    There are four ways to call this function, depending on what data is
-    available to the caller:
-    Method 1:
-    a = text1, b = text2
-    Method 2:
-    a = diffs
-    Method 3 (optimal):
-    a = text1, b = diffs
-    Method 4 (deprecated, use method 3):
-    a = text1, b = text2, c = diffs
-
-    Args:
-      a: text1 (methods 1,3,4) or Array of diff tuples for text1 to
-          text2 (method 2).
-      b: text2 (methods 1,4) or Array of diff tuples for text1 to
-          text2 (method 3) or undefined (method 2).
-      c: Array of diff tuples for text1 to text2 (method 4) or
-          undefined (methods 1,2,3).
-
-    Returns:
-      Array of patch objects.
-    """
-    text1 = None
-    diffs = None
-    # Note that texts may arrive as 'str' or 'unicode'.
-    if isinstance(a, basestring) and isinstance(b, basestring) and c is None:
-      # Method 1: text1, text2
-      # Compute diffs from text1 and text2.
-      text1 = a
-      diffs = self.diff_main(text1, b, True)
-      if len(diffs) > 2:
-        self.diff_cleanupSemantic(diffs)
-        self.diff_cleanupEfficiency(diffs)
-    elif isinstance(a, list) and b is None and c is None:
-      # Method 2: diffs
-      # Compute text1 from diffs.
-      diffs = a
-      text1 = self.diff_text1(diffs)
-    elif isinstance(a, basestring) and isinstance(b, list) and c is None:
-      # Method 3: text1, diffs
-      text1 = a
-      diffs = b
-    elif (isinstance(a, basestring) and isinstance(b, basestring) and
-          isinstance(c, list)):
-      # Method 4: text1, text2, diffs
-      # text2 is not used.
-      text1 = a
-      diffs = c
-    else:
-      raise ValueError("Unknown call format to patch_make.")
-
-    if not diffs:
-      return []  # Get rid of the None case.
-    patches = []
-    patch = patch_obj()
-    char_count1 = 0  # Number of characters into the text1 string.
-    char_count2 = 0  # Number of characters into the text2 string.
-    prepatch_text = text1  # Recreate the patches to determine context info.
-    postpatch_text = text1
-    for x in xrange(len(diffs)):
-      (diff_type, diff_text) = diffs[x]
-      if len(patch.diffs) == 0 and diff_type != self.DIFF_EQUAL:
-        # A new patch starts here.
-        patch.start1 = char_count1
-        patch.start2 = char_count2
-      if diff_type == self.DIFF_INSERT:
-        # Insertion
-        patch.diffs.append(diffs[x])
-        patch.length2 += len(diff_text)
-        postpatch_text = (postpatch_text[:char_count2] + diff_text +
-                          postpatch_text[char_count2:])
-      elif diff_type == self.DIFF_DELETE:
-        # Deletion.
-        patch.length1 += len(diff_text)
-        patch.diffs.append(diffs[x])
-        postpatch_text = (postpatch_text[:char_count2] +
-                          postpatch_text[char_count2 + len(diff_text):])
-      elif (diff_type == self.DIFF_EQUAL and
-            len(diff_text) <= 2 * self.Patch_Margin and
-            len(patch.diffs) != 0 and len(diffs) != x + 1):
-        # Small equality inside a patch.
-        patch.diffs.append(diffs[x])
-        patch.length1 += len(diff_text)
-        patch.length2 += len(diff_text)
-
-      if (diff_type == self.DIFF_EQUAL and
-          len(diff_text) >= 2 * self.Patch_Margin):
-        # Time for a new patch.
-        if len(patch.diffs) != 0:
-          self.patch_addContext(patch, prepatch_text)
-          patches.append(patch)
-          patch = patch_obj()
-          # Unlike Unidiff, our patch lists have a rolling context.
-          # http://code.google.com/p/google-diff-match-patch/wiki/Unidiff
-          # Update prepatch text & pos to reflect the application of the
-          # just completed patch.
-          prepatch_text = postpatch_text
-          char_count1 = char_count2
-
-      # Update the current character count.
-      if diff_type != self.DIFF_INSERT:
-        char_count1 += len(diff_text)
-      if diff_type != self.DIFF_DELETE:
-        char_count2 += len(diff_text)
-
-    # Pick up the leftover patch if not empty.
-    if len(patch.diffs) != 0:
-      self.patch_addContext(patch, prepatch_text)
-      patches.append(patch)
-    return patches
-
-  def patch_deepCopy(self, patches):
-    """Given an array of patches, return another array that is identical.
-
-    Args:
-      patches: Array of patch objects.
-
-    Returns:
-      Array of patch objects.
-    """
-    patchesCopy = []
-    for patch in patches:
-      patchCopy = patch_obj()
-      # No need to deep copy the tuples since they are immutable.
-      patchCopy.diffs = patch.diffs[:]
-      patchCopy.start1 = patch.start1
-      patchCopy.start2 = patch.start2
-      patchCopy.length1 = patch.length1
-      patchCopy.length2 = patch.length2
-      patchesCopy.append(patchCopy)
-    return patchesCopy
-
-  def patch_apply(self, patches, text):
-    """Merge a set of patches onto the text.  Return a patched text, as well
-    as a list of true/false values indicating which patches were applied.
-
-    Args:
-      patches: Array of patch objects.
-      text: Old text.
-
-    Returns:
-      Two element Array, containing the new text and an array of boolean values.
-    """
-    if not patches:
-      return (text, [])
-
-    # Deep copy the patches so that no changes are made to originals.
-    patches = self.patch_deepCopy(patches)
-
-    nullPadding = self.patch_addPadding(patches)
-    text = nullPadding + text + nullPadding
-    self.patch_splitMax(patches)
-
-    # delta keeps track of the offset between the expected and actual location
-    # of the previous patch.  If there are patches expected at positions 10 and
-    # 20, but the first patch was found at 12, delta is 2 and the second patch
-    # has an effective expected position of 22.
-    delta = 0
-    results = []
-    for patch in patches:
-      expected_loc = patch.start2 + delta
-      text1 = self.diff_text1(patch.diffs)
-      start_loc = self.match_main(text, text1, expected_loc)
-      if start_loc == -1:
-        # No match found.  :(
-        results.append(False)
-      else:
-        # Found a match.  :)
-        results.append(True)
-        delta = start_loc - expected_loc
-        text2 = text[start_loc : start_loc + len(text1)]
-        if text1 == text2:
-          # Perfect match, just shove the replacement text in.
-          text = (text[:start_loc] + self.diff_text2(patch.diffs) +
-                      text[start_loc + len(text1):])
-        else:
-          # Imperfect match.
-          # Run a diff to get a framework of equivalent indicies.
-          diffs = self.diff_main(text1, text2, False)
-          self.diff_cleanupSemanticLossless(diffs)
-          index1 = 0
-          for (op, data) in patch.diffs:
-            if op != self.DIFF_EQUAL:
-              index2 = self.diff_xIndex(diffs, index1)
-            if op == self.DIFF_INSERT:  # Insertion
-              text = text[:start_loc + index2] + data + text[start_loc +
-                                                             index2:]
-            elif op == self.DIFF_DELETE:  # Deletion
-              text = text[:start_loc + index2] + text[start_loc +
-                  self.diff_xIndex(diffs, index1 + len(data)):]
-            if op != self.DIFF_DELETE:
-              index1 += len(data)
-    # Strip the padding off.
-    text = text[len(nullPadding):-len(nullPadding)]
-    return (text, results)
-
-  def patch_addPadding(self, patches):
-    """Add some padding on text start and end so that edges can match
-    something.
-
-    Args:
-      patches: Array of patch objects.
-
-    Returns:
-      The padding string added to each side.
-    """
-    nullPadding = ""
-    for x in xrange(self.Patch_Margin):
-      nullPadding += chr(x)
-
-    # Bump all the patches forward.
-    for patch in patches:
-      patch.start1 += len(nullPadding)
-      patch.start2 += len(nullPadding)
-
-    # Add some padding on start of first diff.
-    patch = patches[0]
-    diffs = patch.diffs
-    if not diffs or diffs[0][0] != self.DIFF_EQUAL:
-      # Add nullPadding equality.
-      diffs.insert(0, (self.DIFF_EQUAL, nullPadding))
-      patch.start1 -= len(nullPadding)  # Should be 0.
-      patch.start2 -= len(nullPadding)  # Should be 0.
-      patch.length1 += len(nullPadding)
-      patch.length2 += len(nullPadding)
-    elif len(nullPadding) > len(diffs[0][1]):
-      # Grow first equality.
-      extraLength = len(nullPadding) - len(diffs[0][1])
-      newText = nullPadding[len(diffs[0][1]):] + diffs[0][1]
-      diffs[0] = (diffs[0][0], newText)
-      patch.start1 -= extraLength
-      patch.start2 -= extraLength
-      patch.length1 += extraLength
-      patch.length2 += extraLength
-
-    # Add some padding on end of last diff.
-    patch = patches[-1]
-    diffs = patch.diffs
-    if not diffs or diffs[-1][0] != self.DIFF_EQUAL:
-      # Add nullPadding equality.
-      diffs.append((self.DIFF_EQUAL, nullPadding))
-      patch.length1 += len(nullPadding)
-      patch.length2 += len(nullPadding)
-    elif len(nullPadding) > len(diffs[-1][1]):
-      # Grow last equality.
-      extraLength = len(nullPadding) - len(diffs[-1][1])
-      newText = diffs[-1][1] + nullPadding[:extraLength]
-      diffs[-1] = (diffs[-1][0], newText)
-      patch.length1 += extraLength
-      patch.length2 += extraLength
-
-    return nullPadding
-
-  def patch_splitMax(self, patches):
-    """Look through the patches and break up any which are longer than the
-    maximum limit of the match algorithm.
-
-    Args:
-      patches: Array of patch objects.
-    """
-    if self.Match_MaxBits == 0:
-      return
-    for x in xrange(len(patches)):
-      if patches[x].length1 > self.Match_MaxBits:
-        bigpatch = patches[x]
-        # Remove the big old patch.
-        del patches[x]
-        x -= 1
-        patch_size = self.Match_MaxBits
-        start1 = bigpatch.start1
-        start2 = bigpatch.start2
-        precontext = ''
-        while len(bigpatch.diffs) != 0:
-          # Create one of several smaller patches.
-          patch = patch_obj()
-          empty = True
-          patch.start1 = start1 - len(precontext)
-          patch.start2 = start2 - len(precontext)
-          if precontext:
-            patch.length1 = patch.length2 = len(precontext)
-            patch.diffs.append((self.DIFF_EQUAL, precontext))
-
-          while (len(bigpatch.diffs) != 0 and
-                 patch.length1 < patch_size - self.Patch_Margin):
-            (diff_type, diff_text) = bigpatch.diffs[0]
-            if diff_type == self.DIFF_INSERT:
-              # Insertions are harmless.
-              patch.length2 += len(diff_text)
-              start2 += len(diff_text)
-              patch.diffs.append(bigpatch.diffs.pop(0))
-              empty = False
-            else:
-              # Deletion or equality.  Only take as much as we can stomach.
-              diff_text = diff_text[:patch_size - patch.length1 -
-                                    self.Patch_Margin]
-              patch.length1 += len(diff_text)
-              start1 += len(diff_text)
-              if diff_type == self.DIFF_EQUAL:
-                patch.length2 += len(diff_text)
-                start2 += len(diff_text)
-              else:
-                empty = False
-
-              patch.diffs.append((diff_type, diff_text))
-              if diff_text == bigpatch.diffs[0][1]:
-                del bigpatch.diffs[0]
-              else:
-                bigpatch.diffs[0] = (bigpatch.diffs[0][0],
-                                     bigpatch.diffs[0][1][len(diff_text):])
-
-          # Compute the head context for the next patch.
-          precontext = self.diff_text2(patch.diffs)
-          precontext = precontext[-self.Patch_Margin:]
-          # Append the end context for this patch.
-          postcontext = self.diff_text1(bigpatch.diffs)[:self.Patch_Margin]
-          if postcontext:
-            patch.length1 += len(postcontext)
-            patch.length2 += len(postcontext)
-            if len(patch.diffs) != 0 and patch.diffs[-1][0] == self.DIFF_EQUAL:
-              patch.diffs[-1] = (self.DIFF_EQUAL, patch.diffs[-1][1] +
-                                 postcontext)
-            else:
-              patch.diffs.append((self.DIFF_EQUAL, postcontext))
-
-          if not empty:
-            x += 1
-            patches.insert(x, patch)
-
-  def patch_toText(self, patches):
-    """Take a list of patches and return a textual representation.
-
-    Args:
-      patches: Array of patch objects.
-
-    Returns:
-      Text representation of patches.
-    """
-    text = []
-    for patch in patches:
-      text.append(str(patch))
-    return "".join(text)
-
-  def patch_fromText(self, textline):
-    """Parse a textual representation of patches and return a list of patch
-    objects.
-
-    Args:
-      textline: Text representation of patches.
-
-    Returns:
-      Array of patch objects.
-
-    Raises:
-      ValueError: If invalid input.
-    """
-    if type(textline) == unicode:
-      # Patches should be composed of a subset of ascii chars, Unicode not
-      # required.  If this encode raises UnicodeEncodeError, patch is invalid.
-      textline = textline.encode("ascii")
-    patches = []
-    if not textline:
-      return patches
-    text = textline.split('\n')
-    while len(text) != 0:
-      m = re.match("^@@ -(\d+),?(\d*) \+(\d+),?(\d*) @@$", text[0])
-      if not m:
-        raise ValueError, "Invalid patch string: " + text[0]
-      patch = patch_obj()
-      patches.append(patch)
-      patch.start1 = int(m.group(1))
-      if m.group(2) == '':
-        patch.start1 -= 1
-        patch.length1 = 1
-      elif m.group(2) == '0':
-        patch.length1 = 0
-      else:
-        patch.start1 -= 1
-        patch.length1 = int(m.group(2))
-
-      patch.start2 = int(m.group(3))
-      if m.group(4) == '':
-        patch.start2 -= 1
-        patch.length2 = 1
-      elif m.group(4) == '0':
-        patch.length2 = 0
-      else:
-        patch.start2 -= 1
-        patch.length2 = int(m.group(4))
-
-      del text[0]
-
-      while len(text) != 0:
-        if text[0]:
-          sign = text[0][0]
-        else:
-          sign = ''
-        line = urllib.unquote(text[0][1:])
-        line = line.decode("utf-8")
-        if sign == '+':
-          # Insertion.
-          patch.diffs.append((self.DIFF_INSERT, line))
-        elif sign == '-':
-          # Deletion.
-          patch.diffs.append((self.DIFF_DELETE, line))
-        elif sign == ' ':
-          # Minor equality.
-          patch.diffs.append((self.DIFF_EQUAL, line))
-        elif sign == '@':
-          # Start of next patch.
-          break
-        elif sign == '':
-          # Blank line?  Whatever.
-          pass
-        else:
-          # WTF?
-          raise ValueError, "Invalid patch mode: '%s'\n%s" % (sign, line)
-        del text[0]
-    return patches
-
-
-class patch_obj:
-  """Class representing one patch operation.
-  """
-
-  def __init__(self):
-    """Initializes with an empty list of diffs.
-    """
-    self.diffs = []
-    self.start1 = None
-    self.start2 = None
-    self.length1 = 0
-    self.length2 = 0
-
-  def __str__(self):
-    """Emmulate GNU diff's format.
-    Header: @@ -382,8 +481,9 @@
-    Indicies are printed as 1-based, not 0-based.
-
-    Returns:
-      The GNU diff string.
-    """
-    if self.length1 == 0:
-      coords1 = str(self.start1) + ",0"
-    elif self.length1 == 1:
-      coords1 = str(self.start1 + 1)
-    else:
-      coords1 = str(self.start1 + 1) + "," + str(self.length1)
-    if self.length2 == 0:
-      coords2 = str(self.start2) + ",0"
-    elif self.length2 == 1:
-      coords2 = str(self.start2 + 1)
-    else:
-      coords2 = str(self.start2 + 1) + "," + str(self.length2)
-    text = ["@@ -", coords1, " +", coords2, " @@\n"]
-    # Escape the body of the patch with %xx notation.
-    for (op, data) in self.diffs:
-      if op == diff_match_patch.DIFF_INSERT:
-        text.append("+")
-      elif op == diff_match_patch.DIFF_DELETE:
-        text.append("-")
-      elif op == diff_match_patch.DIFF_EQUAL:
-        text.append(" ")
-      # High ascii will raise UnicodeDecodeError.  Use Unicode instead.
-      data = data.encode("utf-8")
-      text.append(urllib.quote(data, "!~*'();/?:@&=+$,# ") + "\n")
-    return "".join(text)

versioning/utils.py

 from __future__ import absolute_import, unicode_literals
+import sys
 from difflib import SequenceMatcher
 from django.utils.encoding import force_unicode
 
 #from django.utils.encoding import smart_unicode
 # Google Diff Match Patch library
 # http://code.google.com/p/google-diff-match-patch
-from .diff_match_patch import diff_match_patch
+if sys.version_info > (3, ):
+    from .vendor.diff_match_patch.python3.diff_match_patch import diff_match_patch
+else:
+    from .vendor.diff_match_patch.python2.diff_match_patch import diff_match_patch
 
 from versioning import _registry
 

versioning/vendor/__init__.py

Empty file added.

versioning/vendor/diff_match_patch/COPYING

+
+                                 Apache License
+                           Version 2.0, January 2004
+                        http://www.apache.org/licenses/
+
+   TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+
+   1. Definitions.
+
+      "License" shall mean the terms and conditions for use, reproduction,
+      and distribution as defined by Sections 1 through 9 of this document.
+
+      "Licensor" shall mean the copyright owner or entity authorized by
+      the copyright owner that is granting the License.
+
+      "Legal Entity" shall mean the union of the acting entity and all
+      other entities that control, are controlled by, or are under common
+      control with that entity. For the purposes of this definition,
+      "control" means (i) the power, direct or indirect, to cause the
+      direction or management of such entity, whether by contract or
+      otherwise, or (ii) ownership of fifty percent (50%) or more of the
+      outstanding shares, or (iii) beneficial ownership of such entity.
+
+      "You" (or "Your") shall mean an individual or Legal Entity
+      exercising permissions granted by this License.
+
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+      including but not limited to software source code, documentation
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+
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+      transformation or translation of a Source form, including but
+      not limited to compiled object code, generated documentation,
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+
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+      the original version of the Work and any modifications or additions
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+      communication on electronic mailing lists, source code control systems,
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+
+      (a) You must give any other recipients of the Work or
+          Derivative Works a copy of this License; and
+
+      (b) You must cause any modified files to carry prominent notices
+          stating that You changed the files; and
+
+      (c) You must retain, in the Source form of any Derivative Works
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versioning/vendor/diff_match_patch/README.txt

+Diff, Match and Patch Library
+http://code.google.com/p/google-diff-match-patch/
+Neil Fraser
+
+This library is currently available in seven different ports, all using the same API.
+Every version includes a full set of unit tests.
+
+C++:
+* Ported by Mike Slemmer.
+* Currently requires the Qt library.
+
+C#:
+* Ported by Matthaeus G. Chajdas.
+
+Dart:
+* The Dart language is still growing and evolving, so this port is only as
+  stable as the underlying language.
+
+Java:
+* Included is both the source and a Maven package.
+
+JavaScript:
+* diff_match_patch_uncompressed.js is the human-readable version.
+  Users of node.js should 'require' this uncompressed version since the
+  compressed version is not guaranteed to work outside of a web browser.
+* diff_match_patch.js has been compressed using Google's internal JavaScript compressor.
+  Non-Google hackers who wish to recompress the source can use:
+  http://dean.edwards.name/packer/
+
+Lua:
+* Ported by Duncan Cross.