diff-match: python3/code fixes for backport code

rhodecode/lib/diff_match_patch.py

@@ -1,1919 +1,2031 b''
-
-
-
 """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__ = '[e-mail] (Neil Fraser)'
+__author__ = "[e-mail] (Neil Fraser)"
 
 import math
 import re
 import sys
 import time
 import urllib.request, urllib.parse, urllib.error
 
 
 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
-    # 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
-    # When deleting a large block of text (over ~64 characters), how close do
-    # the contents have to be to match the expected contents. (0.0 = perfection,
-    # 1.0 = very loose).  Note that Match_Threshold controls how closely the
-    # end points of a delete need to match.
-    self.Patch_DeleteThreshold = 0.5
-    # Chunk size for context length.
-    self.Patch_Margin = 4
-
-    # The number of bits in an int.
-    # 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, deadline=None):
-    """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.
-      deadline: Optional time when the diff should be complete by.  Used
-        internally for recursive calls.  Users should set DiffTimeout instead.
-
-    Returns:
-      Array of changes.
-    """
-    # Set a deadline by which time the diff must be complete.
-    if deadline is None:
-      # Unlike in most languages, Python counts time in seconds.
-      if self.Diff_Timeout <= 0:
-        deadline = sys.maxint
-      else:
-        deadline = time.time() + self.Diff_Timeout
-
-    # Check for null inputs.
-    if text1 is None or text2 is None:
-      raise ValueError("Null inputs. (diff_main)")
-
-    # Check for equality (speedup).
-    if text1 == text2:
-      if text1:
-        return [(self.DIFF_EQUAL, text1)]
-      return []
-
-    # 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, deadline)
-
-    # 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, deadline):
-    """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.
-      deadline: Time when the diff should be complete by.
-
-    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
-
-    if len(shorttext) == 1:
-      # Single character string.
-      # After the previous speedup, the character can't be an equality.
-      return [(self.DIFF_DELETE, text1), (self.DIFF_INSERT, text2)]
-
-    # 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, deadline)
-      diffs_b = self.diff_main(text1_b, text2_b, checklines, deadline)
-      # Merge the results.
-      return diffs_a + [(self.DIFF_EQUAL, mid_common)] + diffs_b
-
-    if checklines and len(text1) > 100 and len(text2) > 100:
-      return self.diff_lineMode(text1, text2, deadline)
-
-    return self.diff_bisect(text1, text2, deadline)
-
-  def diff_lineMode(self, text1, text2, deadline):
-    """Do a quick line-level diff on both strings, then rediff the parts for
-      greater accuracy.
-      This speedup can produce non-minimal diffs.
-
-    Args:
-      text1: Old string to be diffed.
-      text2: New string to be diffed.
-      deadline: Time when the diff should be complete by.
-
-    Returns:
-      Array of changes.
-    """
-
-    # Scan the text on a line-by-line basis first.
-    (text1, text2, linearray) = self.diff_linesToChars(text1, text2)
-
-    diffs = self.diff_main(text1, text2, False, deadline)
-
-    # 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, deadline)
-          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_bisect(self, text1, text2, deadline):
-    """Find the 'middle snake' of a diff, split the problem in two
-      and return the recursively constructed diff.
-      See Myers 1986 paper: An O(ND) Difference Algorithm and Its Variations.
-
-    Args:
-      text1: Old string to be diffed.
-      text2: New string to be diffed.
-      deadline: Time at which to bail if not yet complete.
-
-    Returns:
-      Array of diff tuples.
-    """
-
-    # Cache the text lengths to prevent multiple calls.
-    text1_length = len(text1)
-    text2_length = len(text2)
-    max_d = (text1_length + text2_length + 1) // 2
-    v_offset = max_d
-    v_length = 2 * max_d
-    v1 = [-1] * v_length
-    v1[v_offset + 1] = 0
-    v2 = v1[:]
-    delta = text1_length - text2_length
-    # If the total number of characters is odd, then the front path will
-    # collide with the reverse path.
-    front = (delta % 2 != 0)
-    # Offsets for start and end of k loop.
-    # Prevents mapping of space beyond the grid.
-    k1start = 0
-    k1end = 0
-    k2start = 0
-    k2end = 0
-    for d in range(max_d):
-      # Bail out if deadline is reached.
-      if time.time() > deadline:
-        break
-
-      # Walk the front path one step.
-      for k1 in range(-d + k1start, d + 1 - k1end, 2):
-        k1_offset = v_offset + k1
-        if k1 == -d or (k1 != d and
-            v1[k1_offset - 1] < v1[k1_offset + 1]):
-          x1 = v1[k1_offset + 1]
-        else:
-          x1 = v1[k1_offset - 1] + 1
-        y1 = x1 - k1
-        while (x1 < text1_length and y1 < text2_length and
-               text1[x1] == text2[y1]):
-          x1 += 1
-          y1 += 1
-        v1[k1_offset] = x1
-        if x1 > text1_length:
-          # Ran off the right of the graph.
-          k1end += 2
-        elif y1 > text2_length:
-          # Ran off the bottom of the graph.
-          k1start += 2
-        elif front:
-          k2_offset = v_offset + delta - k1
-          if k2_offset >= 0 and k2_offset < v_length and v2[k2_offset] != -1:
-            # Mirror x2 onto top-left coordinate system.
-            x2 = text1_length - v2[k2_offset]
-            if x1 >= x2:
-              # Overlap detected.
-              return self.diff_bisectSplit(text1, text2, x1, y1, deadline)
-
-      # Walk the reverse path one step.
-      for k2 in range(-d + k2start, d + 1 - k2end, 2):
-        k2_offset = v_offset + k2
-        if k2 == -d or (k2 != d and
-            v2[k2_offset - 1] < v2[k2_offset + 1]):
-          x2 = v2[k2_offset + 1]
-        else:
-          x2 = v2[k2_offset - 1] + 1
-        y2 = x2 - k2
-        while (x2 < text1_length and y2 < text2_length and
-               text1[-x2 - 1] == text2[-y2 - 1]):
-          x2 += 1
-          y2 += 1
-        v2[k2_offset] = x2
-        if x2 > text1_length:
-          # Ran off the left of the graph.
-          k2end += 2
-        elif y2 > text2_length:
-          # Ran off the top of the graph.
-          k2start += 2
-        elif not front:
-          k1_offset = v_offset + delta - k2
-          if k1_offset >= 0 and k1_offset < v_length and v1[k1_offset] != -1:
-            x1 = v1[k1_offset]
-            y1 = v_offset + x1 - k1_offset
-            # Mirror x2 onto top-left coordinate system.
-            x2 = text1_length - x2
-            if x1 >= x2:
-              # Overlap detected.
-              return self.diff_bisectSplit(text1, text2, x1, y1, deadline)
-
-    # Diff took too long and hit the deadline or
-    # number of diffs equals number of characters, no commonality at all.
-    return [(self.DIFF_DELETE, text1), (self.DIFF_INSERT, text2)]
-
-  def diff_bisectSplit(self, text1, text2, x, y, deadline):
-    """Given the location of the 'middle snake', split the diff in two parts
-    and recurse.
-
-    Args:
-      text1: Old string to be diffed.
-      text2: New string to be diffed.
-      x: Index of split point in text1.
-      y: Index of split point in text2.
-      deadline: Time at which to bail if not yet complete.
-
-    Returns:
-      Array of diff tuples.
-    """
-    text1a = text1[:x]
-    text2a = text2[:y]
-    text1b = text1[x:]
-    text2b = text2[y:]
-
-    # Compute both diffs serially.
-    diffs = self.diff_main(text1a, text2a, False, deadline)
-    diffsb = self.diff_main(text1b, text2b, False, deadline)
-
-    return diffs + diffsb
-
-  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.
+    """Class containing the diff, match and patch methods.
 
-    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 range(len(diffs)):
-      text = []
-      for char in diffs[x][1]:
-        text.append(lineArray[ord(char)])
-      diffs[x] = (diffs[x][0], "".join(text))
-
-  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 = (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 = (pointermax - pointermin) // 2 + pointermin
-    return pointermid
-
-  def diff_commonOverlap(self, text1, text2):
-    """Determine if the suffix of one string is the prefix of another.
-
-    Args:
-      text1 First string.
-      text2 Second string.
-
-    Returns:
-      The number of characters common to the end of the first
-      string and the start of the second string.
-    """
-    # Cache the text lengths to prevent multiple calls.
-    text1_length = len(text1)
-    text2_length = len(text2)
-    # Eliminate the null case.
-    if text1_length == 0 or text2_length == 0:
-      return 0
-    # Truncate the longer string.
-    if text1_length > text2_length:
-      text1 = text1[-text2_length:]
-    elif text1_length < text2_length:
-      text2 = text2[:text1_length]
-    text_length = min(text1_length, text2_length)
-    # Quick check for the worst case.
-    if text1 == text2:
-      return text_length
-
-    # Start by looking for a single character match
-    # and increase length until no match is found.
-    # Performance analysis: http://neil.fraser.name/news/2010/11/04/
-    best = 0
-    length = 1
-    while True:
-      pattern = text1[-length:]
-      found = text2.find(pattern)
-      if found == -1:
-        return best
-      length += found
-      if found == 0 or text1[-length:] == text2[:length]:
-        best = length
-        length += 1
-
-  def diff_halfMatch(self, text1, text2):
-    """Do the two texts share a substring which is at least half the length of
-    the longer text?
-    This speedup can produce non-minimal diffs.
-
-    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 self.Diff_Timeout <= 0:
-      # Don't risk returning a non-optimal diff if we have unlimited time.
-      return None
-    if len(text1) > len(text2):
-      (longtext, shorttext) = (text1, text2)
-    else:
-      (shorttext, longtext) = (text1, text2)
-    if len(longtext) < 4 or len(shorttext) * 2 < len(longtext):
-      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) * 2 >= len(longtext):
-        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 diffs[equalities[-1]][1]
-    pointer = 0  # Index of current position.
-    # Number of chars that changed prior to the equality.
-    length_insertions1, length_deletions1 = 0, 0
-    # Number of chars that changed after the equality.
-    length_insertions2, length_deletions2 = 0, 0
-    while pointer < len(diffs):
-      if diffs[pointer][0] == self.DIFF_EQUAL:  # Equality found.
-        equalities.append(pointer)
-        length_insertions1, length_insertions2 = length_insertions2, 0
-        length_deletions1, length_deletions2 = length_deletions2, 0
-        lastequality = diffs[pointer][1]
-      else:  # An insertion or deletion.
-        if diffs[pointer][0] == self.DIFF_INSERT:
-          length_insertions2 += len(diffs[pointer][1])
-        else:
-          length_deletions2 += len(diffs[pointer][1])
-        # Eliminate an equality that is smaller or equal to the edits on both
-        # sides of it.
-        if (lastequality and (len(lastequality) <=
-            max(length_insertions1, length_deletions1)) and
-            (len(lastequality) <= max(length_insertions2, length_deletions2))):
-          # 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):
-            equalities.pop()
-          if len(equalities):
-            pointer = equalities[-1]
-          else:
-            pointer = -1
-          # Reset the counters.
-          length_insertions1, length_deletions1 = 0, 0
-          length_insertions2, length_deletions2 = 0, 0
-          lastequality = None
-          changes = True
-      pointer += 1
-
-    # Normalize the diff.
-    if changes:
-      self.diff_cleanupMerge(diffs)
-    self.diff_cleanupSemanticLossless(diffs)
-
-    # Find any overlaps between deletions and insertions.
-    # e.g: <del>abcxxx</del><ins>xxxdef</ins>
-    #   -> <del>abc</del>xxx<ins>def</ins>
-    # e.g: <del>xxxabc</del><ins>defxxx</ins>
-    #   -> <ins>def</ins>xxx<del>abc</del>
-    # Only extract an overlap if it is as big as the edit ahead or behind it.
-    pointer = 1
-    while pointer < len(diffs):
-      if (diffs[pointer - 1][0] == self.DIFF_DELETE and
-          diffs[pointer][0] == self.DIFF_INSERT):
-        deletion = diffs[pointer - 1][1]
-        insertion = diffs[pointer][1]
-        overlap_length1 = self.diff_commonOverlap(deletion, insertion)
-        overlap_length2 = self.diff_commonOverlap(insertion, deletion)
-        if overlap_length1 >= overlap_length2:
-          if (overlap_length1 >= len(deletion) / 2.0 or
-              overlap_length1 >= len(insertion) / 2.0):
-            # Overlap found.  Insert an equality and trim the surrounding edits.
-            diffs.insert(pointer, (self.DIFF_EQUAL,
-                                   insertion[:overlap_length1]))
-            diffs[pointer - 1] = (self.DIFF_DELETE,
-                                  deletion[:len(deletion) - overlap_length1])
-            diffs[pointer + 1] = (self.DIFF_INSERT,
-                                  insertion[overlap_length1:])
-            pointer += 1
-        else:
-          if (overlap_length2 >= len(deletion) / 2.0 or
-              overlap_length2 >= len(insertion) / 2.0):
-            # Reverse overlap found.
-            # Insert an equality and swap and trim the surrounding edits.
-            diffs.insert(pointer, (self.DIFF_EQUAL, deletion[:overlap_length2]))
-            diffs[pointer - 1] = (self.DIFF_INSERT,
-                                  insertion[:len(insertion) - overlap_length2])
-            diffs[pointer + 1] = (self.DIFF_DELETE, deletion[overlap_length2:])
-            pointer += 1
-        pointer += 1
-      pointer += 1
-
-  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.
+    Also contains the behaviour settings.
     """
 
-    def diff_cleanupSemanticScore(one, two):
-      """Given two strings, compute a score representing whether the
-      internal boundary falls on logical boundaries.
-      Scores range from 6 (best) to 0 (worst).
-      Closure, but does not reference any external variables.
+    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
+        # 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
+        # When deleting a large block of text (over ~64 characters), how close do
+        # the contents have to be to match the expected contents. (0.0 = perfection,
+        # 1.0 = very loose).  Note that Match_Threshold controls how closely the
+        # end points of a delete need to match.
+        self.Patch_DeleteThreshold = 0.5
+        # Chunk size for context length.
+        self.Patch_Margin = 4
+
+        # The number of bits in an int.
+        # 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
 
-      Args:
-        one: First string.
-        two: Second string.
+    # 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, deadline=None):
+        """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.
+          deadline: Optional time when the diff should be complete by.  Used
+            internally for recursive calls.  Users should set DiffTimeout instead.
+
+        Returns:
+          Array of changes.
+        """
+        # Set a deadline by which time the diff must be complete.
+        if deadline is None:
+            # Unlike in most languages, Python counts time in seconds.
+            if self.Diff_Timeout <= 0:
+                deadline = sys.maxsize
+            else:
+                deadline = time.time() + self.Diff_Timeout
+
+        # Check for null inputs.
+        if text1 is None or text2 is None:
+            raise ValueError("Null inputs. (diff_main)")
 
-      Returns:
-        The score.
-      """
-      if not one or not two:
-        # Edges are the best.
-        return 6
+        # Check for equality (speedup).
+        if text1 == text2:
+            if text1:
+                return [(self.DIFF_EQUAL, text1)]
+            return []
+
+        # 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, deadline)
+
+        # 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, deadline):
+        """Find the differences between two texts.  Assumes that the texts do not
+          have any common prefix or suffix.
 
-      # 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.
-      char1 = one[-1]
-      char2 = two[0]
-      nonAlphaNumeric1 = not char1.isalnum()
-      nonAlphaNumeric2 = not char2.isalnum()
-      whitespace1 = nonAlphaNumeric1 and char1.isspace()
-      whitespace2 = nonAlphaNumeric2 and char2.isspace()
-      lineBreak1 = whitespace1 and (char1 == "\r" or char1 == "\n")
-      lineBreak2 = whitespace2 and (char2 == "\r" or char2 == "\n")
-      blankLine1 = lineBreak1 and self.BLANKLINEEND.search(one)
-      blankLine2 = lineBreak2 and self.BLANKLINESTART.match(two)
+        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.
+          deadline: Time when the diff should be complete by.
+
+        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
 
-      if blankLine1 or blankLine2:
-        # Five points for blank lines.
-        return 5
-      elif lineBreak1 or lineBreak2:
-        # Four points for line breaks.
-        return 4
-      elif nonAlphaNumeric1 and not whitespace1 and whitespace2:
-        # Three points for end of sentences.
-        return 3
-      elif whitespace1 or whitespace2:
-        # Two points for whitespace.
-        return 2
-      elif nonAlphaNumeric1 or nonAlphaNumeric2:
-        # One point for non-alphanumeric.
-        return 1
-      return 0
+        if len(shorttext) == 1:
+            # Single character string.
+            # After the previous speedup, the character can't be an equality.
+            return [(self.DIFF_DELETE, text1), (self.DIFF_INSERT, text2)]
+
+        # 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, deadline)
+            diffs_b = self.diff_main(text1_b, text2_b, checklines, deadline)
+            # Merge the results.
+            return diffs_a + [(self.DIFF_EQUAL, mid_common)] + diffs_b
+
+        if checklines and len(text1) > 100 and len(text2) > 100:
+            return self.diff_lineMode(text1, text2, deadline)
+
+        return self.diff_bisect(text1, text2, deadline)
+
+    def diff_lineMode(self, text1, text2, deadline):
+        """Do a quick line-level diff on both strings, then rediff the parts for
+          greater accuracy.
+          This speedup can produce non-minimal diffs.
+
+        Args:
+          text1: Old string to be diffed.
+          text2: New string to be diffed.
+          deadline: Time when the diff should be complete by.
+
+        Returns:
+          Array of changes.
+        """
 
-    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]
+        # Scan the text on a line-by-line basis first.
+        (text1, text2, linearray) = self.diff_linesToChars(text1, text2)
+
+        diffs = self.diff_main(text1, text2, False, deadline)
+
+        # 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, deadline)
+                    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 = ""
 
-        # 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
+            pointer += 1
+
+        diffs.pop()  # Remove the dummy entry at the end.
+
+        return diffs
+
+    def diff_bisect(self, text1, text2, deadline):
+        """Find the 'middle snake' of a diff, split the problem in two
+          and return the recursively constructed diff.
+          See Myers 1986 paper: An O(ND) Difference Algorithm and Its Variations.
+
+        Args:
+          text1: Old string to be diffed.
+          text2: New string to be diffed.
+          deadline: Time at which to bail if not yet complete.
+
+        Returns:
+          Array of diff tuples.
+        """
 
-        # 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
+        # Cache the text lengths to prevent multiple calls.
+        text1_length = len(text1)
+        text2_length = len(text2)
+        max_d = (text1_length + text2_length + 1) // 2
+        v_offset = max_d
+        v_length = 2 * max_d
+        v1 = [-1] * v_length
+        v1[v_offset + 1] = 0
+        v2 = v1[:]
+        delta = text1_length - text2_length
+        # If the total number of characters is odd, then the front path will
+        # collide with the reverse path.
+        front = delta % 2 != 0
+        # Offsets for start and end of k loop.
+        # Prevents mapping of space beyond the grid.
+        k1start = 0
+        k1end = 0
+        k2start = 0
+        k2end = 0
+        for d in range(max_d):
+            # Bail out if deadline is reached.
+            if time.time() > deadline:
+                break
+
+            # Walk the front path one step.
+            for k1 in range(-d + k1start, d + 1 - k1end, 2):
+                k1_offset = v_offset + k1
+                if k1 == -d or (k1 != d and v1[k1_offset - 1] < v1[k1_offset + 1]):
+                    x1 = v1[k1_offset + 1]
+                else:
+                    x1 = v1[k1_offset - 1] + 1
+                y1 = x1 - k1
+                while (
+                    x1 < text1_length and y1 < text2_length and text1[x1] == text2[y1]
+                ):
+                    x1 += 1
+                    y1 += 1
+                v1[k1_offset] = x1
+                if x1 > text1_length:
+                    # Ran off the right of the graph.
+                    k1end += 2
+                elif y1 > text2_length:
+                    # Ran off the bottom of the graph.
+                    k1start += 2
+                elif front:
+                    k2_offset = v_offset + delta - k1
+                    if k2_offset >= 0 and k2_offset < v_length and v2[k2_offset] != -1:
+                        # Mirror x2 onto top-left coordinate system.
+                        x2 = text1_length - v2[k2_offset]
+                        if x1 >= x2:
+                            # Overlap detected.
+                            return self.diff_bisectSplit(text1, text2, x1, y1, deadline)
 
-        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
+            # Walk the reverse path one step.
+            for k2 in range(-d + k2start, d + 1 - k2end, 2):
+                k2_offset = v_offset + k2
+                if k2 == -d or (k2 != d and v2[k2_offset - 1] < v2[k2_offset + 1]):
+                    x2 = v2[k2_offset + 1]
+                else:
+                    x2 = v2[k2_offset - 1] + 1
+                y2 = x2 - k2
+                while (
+                    x2 < text1_length
+                    and y2 < text2_length
+                    and text1[-x2 - 1] == text2[-y2 - 1]
+                ):
+                    x2 += 1
+                    y2 += 1
+                v2[k2_offset] = x2
+                if x2 > text1_length:
+                    # Ran off the left of the graph.
+                    k2end += 2
+                elif y2 > text2_length:
+                    # Ran off the top of the graph.
+                    k2start += 2
+                elif not front:
+                    k1_offset = v_offset + delta - k2
+                    if k1_offset >= 0 and k1_offset < v_length and v1[k1_offset] != -1:
+                        x1 = v1[k1_offset]
+                        y1 = v_offset + x1 - k1_offset
+                        # Mirror x2 onto top-left coordinate system.
+                        x2 = text1_length - x2
+                        if x1 >= x2:
+                            # Overlap detected.
+                            return self.diff_bisectSplit(text1, text2, x1, y1, deadline)
+
+        # Diff took too long and hit the deadline or
+        # number of diffs equals number of characters, no commonality at all.
+        return [(self.DIFF_DELETE, text1), (self.DIFF_INSERT, text2)]
+
+    def diff_bisectSplit(self, text1, text2, x, y, deadline):
+        """Given the location of the 'middle snake', split the diff in two parts
+        and recurse.
+
+        Args:
+          text1: Old string to be diffed.
+          text2: New string to be diffed.
+          x: Index of split point in text1.
+          y: Index of split point in text2.
+          deadline: Time at which to bail if not yet complete.
+
+        Returns:
+          Array of diff tuples.
+        """
+        text1a = text1[:x]
+        text2a = text2[:y]
+        text1b = text1[x:]
+        text2b = text2[y:]
+
+        # Compute both diffs serially.
+        diffs = self.diff_main(text1a, text2a, False, deadline)
+        diffsb = self.diff_main(text1b, text2b, False, deadline)
 
-  # Define some regex patterns for matching boundaries.
-  BLANKLINEEND = re.compile(r"\n\r?\n$");
-  BLANKLINESTART = re.compile(r"^\r?\n\r?\n");
+        return diffs + diffsb
+
+    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(chr(lineHash[line]))
+                else:
+                    lineArray.append(line)
+                    lineHash[line] = len(lineArray) - 1
+                    chars.append(chr(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.
 
-  def diff_cleanupEfficiency(self, diffs):
-    """Reduce the number of edits by eliminating operationally trivial
-    equalities.
+        Args:
+          diffs: Array of diff tuples.
+          lineArray: Array of unique strings.
+        """
+        for x in range(len(diffs)):
+            text = []
+            for char in diffs[x][1]:
+                text.append(lineArray[ord(char)])
+            diffs[x] = (diffs[x][0], "".join(text))
+
+    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 = (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.
 
-    Args:
-      diffs: Array of diff tuples.
-    """
-    changes = False
-    equalities = []  # Stack of indices where equalities are found.
-    lastequality = None  # Always equal to diffs[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]
+        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 = (pointermax - pointermin) // 2 + pointermin
+        return pointermid
+
+    def diff_commonOverlap(self, text1, text2):
+        """Determine if the suffix of one string is the prefix of another.
+
+        Args:
+          text1 First string.
+          text2 Second string.
+
+        Returns:
+          The number of characters common to the end of the first
+          string and the start of the second string.
+        """
+        # Cache the text lengths to prevent multiple calls.
+        text1_length = len(text1)
+        text2_length = len(text2)
+        # Eliminate the null case.
+        if text1_length == 0 or text2_length == 0:
+            return 0
+        # Truncate the longer string.
+        if text1_length > text2_length:
+            text1 = text1[-text2_length:]
+        elif text1_length < text2_length:
+            text2 = text2[:text1_length]
+        text_length = min(text1_length, text2_length)
+        # Quick check for the worst case.
+        if text1 == text2:
+            return text_length
+
+        # Start by looking for a single character match
+        # and increase length until no match is found.
+        # Performance analysis: http://neil.fraser.name/news/2010/11/04/
+        best = 0
+        length = 1
+        while True:
+            pattern = text1[-length:]
+            found = text2.find(pattern)
+            if found == -1:
+                return best
+            length += found
+            if found == 0 or text1[-length:] == text2[:length]:
+                best = length
+                length += 1
+
+    def diff_halfMatch(self, text1, text2):
+        """Do the two texts share a substring which is at least half the length of
+        the longer text?
+        This speedup can produce non-minimal diffs.
+
+        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 self.Diff_Timeout <= 0:
+            # Don't risk returning a non-optimal diff if we have unlimited time.
+            return None
+        if len(text1) > len(text2):
+            (longtext, shorttext) = (text1, text2)
         else:
-          # Not a candidate, and can never become one.
-          equalities = []
-          lastequality = None
+            (shorttext, longtext) = (text1, text2)
+        if len(longtext) < 4 or len(shorttext) * 2 < len(longtext):
+            return None  # Pointless.
 
-        post_ins = post_del = False
-      else:  # An insertion or deletion.
-        if diffs[pointer][0] == self.DIFF_DELETE:
-          post_del = True
-        else:
-          post_ins = True
+        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.
 
-        # 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>
+            Args:
+              longtext: Longer string.
+              shorttext: Shorter string.
+              i: Start index of quarter length substring within longtext.
 
-        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 = None
-          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.
+            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)
 
-    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 + count_insert > 1:
-          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]))
+            if len(best_common) * 2 >= len(longtext):
+                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 diffs[equalities[-1]][1]
+        pointer = 0  # Index of current position.
+        # Number of chars that changed prior to the equality.
+        length_insertions1, length_deletions1 = 0, 0
+        # Number of chars that changed after the equality.
+        length_insertions2, length_deletions2 = 0, 0
+        while pointer < len(diffs):
+            if diffs[pointer][0] == self.DIFF_EQUAL:  # Equality found.
+                equalities.append(pointer)
+                length_insertions1, length_insertions2 = length_insertions2, 0
+                length_deletions1, length_deletions2 = length_deletions2, 0
+                lastequality = diffs[pointer][1]
+            else:  # An insertion or deletion.
+                if diffs[pointer][0] == self.DIFF_INSERT:
+                    length_insertions2 += len(diffs[pointer][1])
+                else:
+                    length_deletions2 += len(diffs[pointer][1])
+                # Eliminate an equality that is smaller or equal to the edits on both
+                # sides of it.
+                if (
+                    lastequality
+                    and (
+                        len(lastequality) <= max(length_insertions1, length_deletions1)
+                    )
+                    and (
+                        len(lastequality) <= max(length_insertions2, length_deletions2)
+                    )
+                ):
+                    # 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):
+                        equalities.pop()
+                    if len(equalities):
+                        pointer = equalities[-1]
+                    else:
+                        pointer = -1
+                    # Reset the counters.
+                    length_insertions1, length_deletions1 = 0, 0
+                    length_insertions2, length_deletions2 = 0, 0
+                    lastequality = None
+                    changes = True
+            pointer += 1
+
+        # Normalize the diff.
+        if changes:
+            self.diff_cleanupMerge(diffs)
+        self.diff_cleanupSemanticLossless(diffs)
+
+        # Find any overlaps between deletions and insertions.
+        # e.g: <del>abcxxx</del><ins>xxxdef</ins>
+        #   -> <del>abc</del>xxx<ins>def</ins>
+        # e.g: <del>xxxabc</del><ins>defxxx</ins>
+        #   -> <ins>def</ins>xxx<del>abc</del>
+        # Only extract an overlap if it is as big as the edit ahead or behind it.
+        pointer = 1
+        while pointer < len(diffs):
+            if (
+                diffs[pointer - 1][0] == self.DIFF_DELETE
+                and diffs[pointer][0] == self.DIFF_INSERT
+            ):
+                deletion = diffs[pointer - 1][1]
+                insertion = diffs[pointer][1]
+                overlap_length1 = self.diff_commonOverlap(deletion, insertion)
+                overlap_length2 = self.diff_commonOverlap(insertion, deletion)
+                if overlap_length1 >= overlap_length2:
+                    if (
+                        overlap_length1 >= len(deletion) / 2.0
+                        or overlap_length1 >= len(insertion) / 2.0
+                    ):
+                        # Overlap found.  Insert an equality and trim the surrounding edits.
+                        diffs.insert(
+                            pointer, (self.DIFF_EQUAL, insertion[:overlap_length1])
+                        )
+                        diffs[pointer - 1] = (
+                            self.DIFF_DELETE,
+                            deletion[: len(deletion) - overlap_length1],
+                        )
+                        diffs[pointer + 1] = (
+                            self.DIFF_INSERT,
+                            insertion[overlap_length1:],
+                        )
+                        pointer += 1
+                else:
+                    if (
+                        overlap_length2 >= len(deletion) / 2.0
+                        or overlap_length2 >= len(insertion) / 2.0
+                    ):
+                        # Reverse overlap found.
+                        # Insert an equality and swap and trim the surrounding edits.
+                        diffs.insert(
+                            pointer, (self.DIFF_EQUAL, deletion[:overlap_length2])
+                        )
+                        diffs[pointer - 1] = (
+                            self.DIFF_INSERT,
+                            insertion[: len(insertion) - overlap_length2],
+                        )
+                        diffs[pointer + 1] = (
+                            self.DIFF_DELETE,
+                            deletion[overlap_length2:],
+                        )
+                        pointer += 1
                 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
+
+    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 6 (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 6
+
+            # 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.
+            char1 = one[-1]
+            char2 = two[0]
+            nonAlphaNumeric1 = not char1.isalnum()
+            nonAlphaNumeric2 = not char2.isalnum()
+            whitespace1 = nonAlphaNumeric1 and char1.isspace()
+            whitespace2 = nonAlphaNumeric2 and char2.isspace()
+            lineBreak1 = whitespace1 and (char1 == "\r" or char1 == "\n")
+            lineBreak2 = whitespace2 and (char2 == "\r" or char2 == "\n")
+            blankLine1 = lineBreak1 and self.BLANKLINEEND.search(one)
+            blankLine2 = lineBreak2 and self.BLANKLINESTART.match(two)
+
+            if blankLine1 or blankLine2:
+                # Five points for blank lines.
+                return 5
+            elif lineBreak1 or lineBreak2:
+                # Four points for line breaks.
+                return 4
+            elif nonAlphaNumeric1 and not whitespace1 and whitespace2:
+                # Three points for end of sentences.
+                return 3
+            elif whitespace1 or whitespace2:
+                # Two points for whitespace.
+                return 2
+            elif nonAlphaNumeric1 or nonAlphaNumeric2:
+                # One point for non-alphanumeric.
+                return 1
+            return 0
 
-        count_insert = 0
-        count_delete = 0
-        text_delete = ''
-        text_insert = ''
+        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]
 
-    if diffs[-1][1] == '':
-      diffs.pop()  # Remove the dummy entry at the end.
+                # 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 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
+                # 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
+
+    # Define some regex patterns for matching boundaries.
+    BLANKLINEEND = re.compile(r"\n\r?\n$")
+    BLANKLINESTART = re.compile(r"^\r?\n\r?\n")
+
+    def diff_cleanupEfficiency(self, diffs):
+        """Reduce the number of edits by eliminating operationally trivial
+        equalities.
 
-    # If shifts were made, the diff needs reordering and another shift sweep.
-    if changes:
-      self.diff_cleanupMerge(diffs)
+        Args:
+          diffs: Array of diff tuples.
+        """
+        changes = False
+        equalities = []  # Stack of indices where equalities are found.
+        lastequality = None  # Always equal to diffs[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 = None
 
-  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.
+                post_ins = post_del = False
+            else:  # An insertion or deletion.
+                if diffs[pointer][0] == self.DIFF_DELETE:
+                    post_del = True
+                else:
+                    post_ins = True
 
-    Returns:
-      Location within text2.
-    """
-    chars1 = 0
-    chars2 = 0
-    last_chars1 = 0
-    last_chars2 = 0
-    for x in range(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
+                # 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 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)
+                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 = None
+                    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
 
-  def diff_prettyHtml(self, diffs):
-    """Convert a diff array into a pretty HTML report.
+        if changes:
+            self.diff_cleanupMerge(diffs)
 
-    Args:
-      diffs: Array of diff tuples.
+    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.
 
-    Returns:
-      HTML representation.
-    """
-    html = []
-    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;\">%s</ins>" % text)
-      elif op == self.DIFF_DELETE:
-        html.append("<del style=\"background:#ffe6e6;\">%s</del>" % text)
-      elif op == self.DIFF_EQUAL:
-        html.append("<span>%s</span>" % text)
-    return "".join(html)
+        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 + count_insert > 1:
+                    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
 
-  def diff_text1(self, diffs):
-    """Compute and return the source text (all equalities and deletions).
-
-    Args:
-      diffs: Array of diff tuples.
+                count_insert = 0
+                count_delete = 0
+                text_delete = ""
+                text_insert = ""
 
-    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).
+        if diffs[-1][1] == "":
+            diffs.pop()  # Remove the dummy entry at the end.
 
-    Args:
-      diffs: Array of diff tuples.
+        # 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
 
-    Returns:
-      Destination text.
-    """
-    text = []
-    for (op, data) in diffs:
-      if op != self.DIFF_DELETE:
-        text.append(data)
-    return "".join(text)
+        # 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.
 
-  def diff_levenshtein(self, diffs):
-    """Compute the Levenshtein distance; the number of inserted, deleted or
-    substituted characters.
+        Returns:
+          Location within text2.
+        """
+        chars1 = 0
+        chars2 = 0
+        last_chars1 = 0
+        last_chars2 = 0
+        for x in range(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
 
-    Args:
-      diffs: Array of diff tuples.
+        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 = []
+        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;">%s</ins>' % text)
+            elif op == self.DIFF_DELETE:
+                html.append('<del style="background:#ffe6e6;">%s</del>' % text)
+            elif op == self.DIFF_EQUAL:
+                html.append("<span>%s</span>" % text)
+        return "".join(html)
+
+    def diff_text1(self, diffs):
+        """Compute and return the source text (all equalities and deletions).
 
-    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)
+        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
-    levenshtein += max(insertions, deletions)
-    return levenshtein
+        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.
+    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.
+        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.parse.quote(data, "!~*'();/?:@&=+$,# "))
-      elif op == self.DIFF_DELETE:
-        text.append("-%d" % len(data))
-      elif op == self.DIFF_EQUAL:
-        text.append("=%d" % len(data))
-    return "\t".join(text)
+        Returns:
+          Delta text.
+        """
+        text = []
+        for op, data in diffs:
+            if op == self.DIFF_INSERT:
+                # High ascii will raise UnicodeDecodeError.  Use Unicode instead.
+                data = data.encode("utf-8")
+                text.append("+" + urllib.parse.quote(data, "!~*'();/?:@&=+$,# "))
+            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.
+    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.
+        Args:
+          text1: Source string for the diff.
+          delta: Delta text.
 
-    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.parse.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
+        Returns:
+          Array of diff tuples.
 
-  #  MATCH FUNCTIONS
+        Raises:
+          ValueError: If invalid input.
+        """
+        if type(delta) == str:
+            # 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.parse.unquote(param)
+                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
 
-  def match_main(self, text, pattern, loc):
-    """Locate the best instance of 'pattern' in 'text' near 'loc'.
+    #  MATCH FUNCTIONS
 
-    Args:
-      text: The text to search.
-      pattern: The pattern to search for.
-      loc: The location to search around.
+    def match_main(self, text, pattern, loc):
+        """Locate the best instance of 'pattern' in 'text' near 'loc'.
 
-    Returns:
-      Best match index or -1.
-    """
-    # Check for null inputs.
-    if text is None or pattern is None:
-      raise ValueError("Null inputs. (match_main)")
+        Args:
+          text: The text to search.
+          pattern: The pattern to search for.
+          loc: The location to search around.
+
+        Returns:
+          Best match index or -1.
+        """
+        # Check for null inputs.
+        if text is None or pattern is None:
+            raise ValueError("Null inputs. (match_main)")
 
-    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
+        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.
+    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.
+        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.")
+        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)
+        # 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.
+        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.
+            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))
+            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)
+        # 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
+        # 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 range(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
+        bin_max = len(pattern) + len(text)
+        # Empty initialization added to appease pychecker.
+        last_rd = None
+        for d in range(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)
+            # 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 = [0] * (finish + 2)
-      rd[finish + 1] = (1 << d) - 1
-      for j in range(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
+            rd = [0] * (finish + 2)
+            rd[finish + 1] = (1 << d) - 1
+            for j in range(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.
+    def match_alphabet(self, pattern):
+        """Initialise the alphabet for the Bitap algorithm.
 
-    Args:
-      pattern: The text to encode.
+        Args:
+          pattern: The text to encode.
 
-    Returns:
-      Hash of character locations.
-    """
-    s = {}
-    for char in pattern:
-      s[char] = 0
-    for i in range(len(pattern)):
-      s[pattern[i]] |= 1 << (len(pattern) - i - 1)
-    return s
+        Returns:
+          Hash of character locations.
+        """
+        s = {}
+        for char in pattern:
+            s[char] = 0
+        for i in range(len(pattern)):
+            s[pattern[i]] |= 1 << (len(pattern) - i - 1)
+        return s
 
-  #  PATCH FUNCTIONS
+    #  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.
+    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.
-    """
-    if len(text) == 0:
-      return
-    pattern = text[patch.start2 : patch.start2 + patch.length1]
-    padding = 0
+        Args:
+          patch: The patch to grow.
+          text: Source text.
+        """
+        if len(text) == 0:
+            return
+        pattern = text[patch.start2 : patch.start2 + patch.length1]
+        padding = 0
 
-    # Look for the first and last matches of pattern in text.  If two different
-    # matches are found, increase the pattern length.
-    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) :
-                     patch.start2 + patch.length1 + padding]
-    # Add one chunk for good luck.
-    padding += self.Patch_Margin
+        # Look for the first and last matches of pattern in text.  If two different
+        # matches are found, increase the pattern length.
+        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) : 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 :
-                  patch.start2 + patch.length1 + padding]
-    if suffix:
-      patch.diffs.append((self.DIFF_EQUAL, suffix))
+        # 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 : 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)
+        # 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
+    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).
+        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, str) and isinstance(b, str) 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, str) and isinstance(b, list) and c is None:
-      # Method 3: text1, diffs
-      text1 = a
-      diffs = b
-    elif (isinstance(a, str) and isinstance(b, str) 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.")
+        Returns:
+          Array of Patch objects.
+        """
+        text1 = None
+        diffs = None
+        # Note that texts may arrive as 'str' or 'unicode'.
+        if isinstance(a, str) and isinstance(b, str) 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, str) and isinstance(b, list) and c is None:
+            # Method 3: text1, diffs
+            text1 = a
+            diffs = b
+        elif isinstance(a, str) and isinstance(b, str) 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 range(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 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 range(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
+            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)
+            # 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
+        # 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.
+    def patch_deepCopy(self, patches):
+        """Given an array of patches, return another array that is identical.
 
-    Args:
-      patches: Array of Patch objects.
+        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
+        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.
+    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.
+        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, [])
+        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)
+        # 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)
+        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)
-      end_loc = -1
-      if len(text1) > self.Match_MaxBits:
-        # patch_splitMax will only provide an oversized pattern in the case of
-        # a monster delete.
-        start_loc = self.match_main(text, text1[:self.Match_MaxBits],
-                                    expected_loc)
-        if start_loc != -1:
-          end_loc = self.match_main(text, text1[-self.Match_MaxBits:],
-              expected_loc + len(text1) - self.Match_MaxBits)
-          if end_loc == -1 or start_loc >= end_loc:
-            # Can't find valid trailing context.  Drop this patch.
-            start_loc = -1
-      else:
-        start_loc = self.match_main(text, text1, expected_loc)
-      if start_loc == -1:
-        # No match found.  :(
-        results.append(False)
-        # Subtract the delta for this failed patch from subsequent patches.
-        delta -= patch.length2 - patch.length1
-      else:
-        # Found a match.  :)
-        results.append(True)
-        delta = start_loc - expected_loc
-        if end_loc == -1:
-          text2 = text[start_loc : start_loc + len(text1)]
-        else:
-          text2 = text[start_loc : end_loc + self.Match_MaxBits]
-        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 indices.
-          diffs = self.diff_main(text1, text2, False)
-          if (len(text1) > self.Match_MaxBits and
-              self.diff_levenshtein(diffs) / float(len(text1)) >
-              self.Patch_DeleteThreshold):
-            # The end points match, but the content is unacceptably bad.
-            results[-1] = False
-          else:
-            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)
+        # 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)
+            end_loc = -1
+            if len(text1) > self.Match_MaxBits:
+                # patch_splitMax will only provide an oversized pattern in the case of
+                # a monster delete.
+                start_loc = self.match_main(
+                    text, text1[: self.Match_MaxBits], expected_loc
+                )
+                if start_loc != -1:
+                    end_loc = self.match_main(
+                        text,
+                        text1[-self.Match_MaxBits :],
+                        expected_loc + len(text1) - self.Match_MaxBits,
+                    )
+                    if end_loc == -1 or start_loc >= end_loc:
+                        # Can't find valid trailing context.  Drop this patch.
+                        start_loc = -1
+            else:
+                start_loc = self.match_main(text, text1, expected_loc)
+            if start_loc == -1:
+                # No match found.  :(
+                results.append(False)
+                # Subtract the delta for this failed patch from subsequent patches.
+                delta -= patch.length2 - patch.length1
+            else:
+                # Found a match.  :)
+                results.append(True)
+                delta = start_loc - expected_loc
+                if end_loc == -1:
+                    text2 = text[start_loc : start_loc + len(text1)]
+                else:
+                    text2 = text[start_loc : end_loc + self.Match_MaxBits]
+                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 indices.
+                    diffs = self.diff_main(text1, text2, False)
+                    if (
+                        len(text1) > self.Match_MaxBits
+                        and self.diff_levenshtein(diffs) / float(len(text1))
+                        > self.Patch_DeleteThreshold
+                    ):
+                        # The end points match, but the content is unacceptably bad.
+                        results[-1] = False
+                    else:
+                        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.  Intended to be called only from within patch_apply.
+    def patch_addPadding(self, patches):
+        """Add some padding on text start and end so that edges can match
+        something.  Intended to be called only from within patch_apply.
 
-    Args:
-      patches: Array of Patch objects.
+        Args:
+          patches: Array of Patch objects.
 
-    Returns:
-      The padding string added to each side.
-    """
-    paddingLength = self.Patch_Margin
-    nullPadding = ""
-    for x in range(1, paddingLength + 1):
-      nullPadding += chr(x)
+        Returns:
+          The padding string added to each side.
+        """
+        paddingLength = self.Patch_Margin
+        nullPadding = ""
+        for x in range(1, paddingLength + 1):
+            nullPadding += chr(x)
 
-    # Bump all the patches forward.
-    for patch in patches:
-      patch.start1 += paddingLength
-      patch.start2 += paddingLength
+        # Bump all the patches forward.
+        for patch in patches:
+            patch.start1 += paddingLength
+            patch.start2 += paddingLength
 
-    # 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 -= paddingLength  # Should be 0.
-      patch.start2 -= paddingLength  # Should be 0.
-      patch.length1 += paddingLength
-      patch.length2 += paddingLength
-    elif paddingLength > len(diffs[0][1]):
-      # Grow first equality.
-      extraLength = paddingLength - 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 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 -= paddingLength  # Should be 0.
+            patch.start2 -= paddingLength  # Should be 0.
+            patch.length1 += paddingLength
+            patch.length2 += paddingLength
+        elif paddingLength > len(diffs[0][1]):
+            # Grow first equality.
+            extraLength = paddingLength - 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 += paddingLength
-      patch.length2 += paddingLength
-    elif paddingLength > len(diffs[-1][1]):
-      # Grow last equality.
-      extraLength = paddingLength - len(diffs[-1][1])
-      newText = diffs[-1][1] + nullPadding[:extraLength]
-      diffs[-1] = (diffs[-1][0], newText)
-      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 += paddingLength
+            patch.length2 += paddingLength
+        elif paddingLength > len(diffs[-1][1]):
+            # Grow last equality.
+            extraLength = paddingLength - len(diffs[-1][1])
+            newText = diffs[-1][1] + nullPadding[:extraLength]
+            diffs[-1] = (diffs[-1][0], newText)
+            patch.length1 += extraLength
+            patch.length2 += extraLength
 
-    return nullPadding
+        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.
-    Intended to be called only from within patch_apply.
+    def patch_splitMax(self, patches):
+        """Look through the patches and break up any which are longer than the
+        maximum limit of the match algorithm.
+        Intended to be called only from within patch_apply.
 
-    Args:
-      patches: Array of Patch objects.
-    """
-    patch_size = self.Match_MaxBits
-    if patch_size == 0:
-      # Python has the option of not splitting strings due to its ability
-      # to handle integers of arbitrary precision.
-      return
-    for x in range(len(patches)):
-      if patches[x].length1 <= patch_size:
-        continue
-      bigpatch = patches[x]
-      # Remove the big old patch.
-      del patches[x]
-      x -= 1
-      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))
+        Args:
+          patches: Array of Patch objects.
+        """
+        patch_size = self.Match_MaxBits
+        if patch_size == 0:
+            # Python has the option of not splitting strings due to its ability
+            # to handle integers of arbitrary precision.
+            return
+        for x in range(len(patches)):
+            if patches[x].length1 <= patch_size:
+                continue
+            bigpatch = patches[x]
+            # Remove the big old patch.
+            del patches[x]
+            x -= 1
+            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
-          elif (diff_type == self.DIFF_DELETE and len(patch.diffs) == 1 and
-              patch.diffs[0][0] == self.DIFF_EQUAL and
-              len(diff_text) > 2 * patch_size):
-            # This is a large deletion.  Let it pass in one chunk.
-            patch.length1 += len(diff_text)
-            start1 += len(diff_text)
-            empty = False
-            patch.diffs.append((diff_type, diff_text))
-            del bigpatch.diffs[0]
-          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
+                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
+                    elif (
+                        diff_type == self.DIFF_DELETE
+                        and len(patch.diffs) == 1
+                        and patch.diffs[0][0] == self.DIFF_EQUAL
+                        and len(diff_text) > 2 * patch_size
+                    ):
+                        # This is a large deletion.  Let it pass in one chunk.
+                        patch.length1 += len(diff_text)
+                        start1 += len(diff_text)
+                        empty = False
+                        patch.diffs.append((diff_type, diff_text))
+                        del bigpatch.diffs[0]
+                    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):])
+                        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))
+                # 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.
+                if not empty:
+                    x += 1
+                    patches.insert(x, patch)
 
-    Args:
-      patches: Array of Patch objects.
+    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)
+        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.
+    def patch_fromText(self, textline):
+        """Parse a textual representation of patches and return a list of patch
+        objects.
 
-    Args:
-      textline: Text representation of patches.
+        Args:
+          textline: Text representation of patches.
 
-    Returns:
-      Array of Patch objects.
+        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*) @@$", text[0])
-      if not m:
-        raise ValueError("Invalid patch string: " + text[0])
-      patch = patch_obj()
-      patches.append(patch)
-      patch.start1 = int(m.group(1))
-      if m.group(2) == '':
-        patch.start1 -= 1
-        patch.length1 = 1
-      elif m.group(2) == '0':
-        patch.length1 = 0
-      else:
-        patch.start1 -= 1
-        patch.length1 = int(m.group(2))
+        Raises:
+          ValueError: If invalid input.
+        """
+        if type(textline) == unicode:
+            # Patches should be composed of a subset of ascii chars, Unicode not
+            # required.  If this encode raises UnicodeEncodeError, patch is invalid.
+            textline = textline.encode("ascii")
+        patches = []
+        if not textline:
+            return patches
+        text = textline.split("\n")
+        while len(text) != 0:
+            m = re.match("^@@ -(\d+),?(\d*) \+(\d+),?(\d*) @@$", 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))
+            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]
+            del text[0]
 
-      while len(text) != 0:
-        if text[0]:
-          sign = text[0][0]
-        else:
-          sign = ''
-        line = urllib.parse.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
+            while len(text) != 0:
+                if text[0]:
+                    sign = text[0][0]
+                else:
+                    sign = ""
+                line = urllib.parse.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.
-  """
+    """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 __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.
+    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.parse.quote(data, "!~*'();/?:@&=+$,# ") + "\n")
-    return "".join(text)
  No newline at end of file
+        Returns:
+          The GNU diff string.
+        """
+        if self.length1 == 0:
+            coords1 = str(self.start1) + ",0"
+        elif self.length1 == 1:
+            coords1 = str(self.start1 + 1)
+        else:
+            coords1 = str(self.start1 + 1) + "," + str(self.length1)
+        if self.length2 == 0:
+            coords2 = str(self.start2) + ",0"
+        elif self.length2 == 1:
+            coords2 = str(self.start2 + 1)
+        else:
+            coords2 = str(self.start2 + 1) + "," + str(self.length2)
+        text = ["@@ -", coords1, " +", coords2, " @@\n"]
+        # Escape the body of the patch with %xx notation.
+        for op, data in self.diffs:
+            if op == diff_match_patch.DIFF_INSERT:
+                text.append("+")
+            elif op == diff_match_patch.DIFF_DELETE:
+                text.append("-")
+            elif op == diff_match_patch.DIFF_EQUAL:
+                text.append(" ")
+            # High ascii will raise UnicodeDecodeError.  Use Unicode instead.
+            data = data.encode("utf-8")
+            text.append(urllib.parse.quote(data, "!~*'();/?:@&=+$,# ") + "\n")
+        return "".join(text)