diff_match_patch.lua - google-diff-match-patch - Diff, Match and Patch libraries for Plain Text

Source path: svn/ trunk/ lua/ diff_match_patch.lua

‹r102

r103

--[[
* Diff Match and Patch
*
* Copyright 2006 Google Inc.
* http://code.google.com/p/google-diff-match-patch/
*
* Based on the JavaScript implementation by Neil Fraser.
* Ported to Lua by Duncan Cross.
*
* 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.
--]]

--[[
-- Lua 5.1 and earlier requires the external BitOp library.
-- This library is built-in from Lua 5.2 and later as 'bit32'.
require 'bit'   -- <http://bitop.luajit.org/>
local band, bor, lshift
    = bit.band, bit.bor, bit.lshift
--]]

local band, bor, lshift
    = bit32.band, bit32.bor, bit32.lshift
local type, setmetatable, ipairs, select
    = type, setmetatable, ipairs, select
local unpack, tonumber, error
    = unpack, tonumber, error
local strsub, strbyte, strchar, gmatch, gsub
    = string.sub, string.byte, string.char, string.gmatch, string.gsub
local strmatch, strfind, strformat
    = string.match, string.find, string.format
local tinsert, tremove, tconcat
    = table.insert, table.remove, table.concat
local max, min, floor, ceil, abs
    = math.max, math.min, math.floor, math.ceil, math.abs
local clock = os.clock


-- Utility functions.

local percentEncode_pattern = '[^A-Za-z0-9%-=;\',./~!@#$%&*%(%)_%+ %?]'
local function percentEncode_replace(v)
  return strformat('%%%02X', strbyte(v))
end

local function tsplice(t, idx, deletions, ...)
  local insertions = select('#', ...)
  for i = 1, deletions do
    tremove(t, idx)
  end
  for i = insertions, 1, -1 do
    -- do not remove parentheses around select
    tinsert(t, idx, (select(i, ...)))
  end
end

local function strelement(str, i)
  return strsub(str, i, i)
end

local function indexOf(a, b, start)
  if (#b == 0) then
    return nil
  end
  return strfind(a, b, start, true)
end

local htmlEncode_pattern = '[&<>\n]'
local htmlEncode_replace = {
  ['&'] = '&amp;', ['<'] = '&lt;', ['>'] = '&gt;', ['\n'] = '&para;<br>'
}

-- Public API Functions
-- (Exported at the end of the script)

local diff_main,
      diff_cleanupSemantic,
      diff_cleanupEfficiency,
      diff_levenshtein,
      diff_prettyHtml

local match_main

local patch_make,
      patch_toText,
      patch_fromText,
      patch_apply

--[[
* 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.'
--]]
local DIFF_DELETE = -1
local DIFF_INSERT = 1
local DIFF_EQUAL = 0

-- Number of seconds to map a diff before giving up (0 for infinity).
local Diff_Timeout = 1.0
-- Cost of an empty edit operation in terms of edit characters.
local Diff_EditCost = 4
-- At what point is no match declared (0.0 = perfection, 1.0 = very loose).
local 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).
local 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.
local Patch_DeleteThreshold = 0.5
-- Chunk size for context length.
local Patch_Margin = 4
-- The number of bits in an int.
local Match_MaxBits = 32

function settings(new)
  if new then
    Diff_Timeout = new.Diff_Timeout or Diff_Timeout
    Diff_EditCost = new.Diff_EditCost or Diff_EditCost
    Match_Threshold = new.Match_Threshold or Match_Threshold
    Match_Distance = new.Match_Distance or Match_Distance
    Patch_DeleteThreshold = new.Patch_DeleteThreshold or Patch_DeleteThreshold
    Patch_Margin = new.Patch_Margin or Patch_Margin
    Match_MaxBits = new.Match_MaxBits or Match_MaxBits
  else
    return {
      Diff_Timeout = Diff_Timeout;
      Diff_EditCost = Diff_EditCost;
      Match_Threshold = Match_Threshold;
      Match_Distance = Match_Distance;
      Patch_DeleteThreshold = Patch_DeleteThreshold;
      Patch_Margin = Patch_Margin;
      Match_MaxBits = Match_MaxBits;
    }
  end
end

-- ---------------------------------------------------------------------------
--  DIFF API
-- ---------------------------------------------------------------------------

-- The private diff functions
local _diff_compute,
      _diff_bisect,
      _diff_halfMatchI,
      _diff_halfMatch,
      _diff_cleanupSemanticScore,
      _diff_cleanupSemanticLossless,
      _diff_cleanupMerge,
      _diff_commonPrefix,
      _diff_commonSuffix,
      _diff_commonOverlap,
      _diff_xIndex,
      _diff_text1,
      _diff_text2,
      _diff_toDelta,
      _diff_fromDelta

--[[
* Find the differences between two texts.  Simplifies the problem by stripping
* any common prefix or suffix off the texts before diffing.
* @param {string} text1 Old string to be diffed.
* @param {string} text2 New string to be diffed.
* @param {boolean} opt_checklines Has no effect in Lua.
* @param {number} opt_deadline Optional time when the diff should be complete
*     by.  Used internally for recursive calls.  Users should set DiffTimeout
*     instead.
* @return {Array.<Array.<number|string>>} Array of diff tuples.
--]]
function diff_main(text1, text2, opt_checklines, opt_deadline)
  -- Set a deadline by which time the diff must be complete.
  if opt_deadline == nil then
    if Diff_Timeout <= 0 then
      opt_deadline = 2 ^ 31
    else
      opt_deadline = clock() + Diff_Timeout
    end
  end
  local deadline = opt_deadline

  -- Check for null inputs.
  if text1 == nil or text1 == nil then
    error('Null inputs. (diff_main)')
  end

  -- Check for equality (speedup).
  if text1 == text2 then
    if #text1 > 0 then
      return {{DIFF_EQUAL, text1}}
    end
    return {}
  end

  -- LUANOTE: Due to the lack of Unicode support, Lua is incapable of
  -- implementing the line-mode speedup.
  local checklines = false

  -- Trim off common prefix (speedup).
  local commonlength = _diff_commonPrefix(text1, text2)
  local commonprefix
  if commonlength > 0 then
    commonprefix = strsub(text1, 1, commonlength)
    text1 = strsub(text1, commonlength + 1)
    text2 = strsub(text2, commonlength + 1)
  end

  -- Trim off common suffix (speedup).
  commonlength = _diff_commonSuffix(text1, text2)
  local commonsuffix
  if commonlength > 0 then
    commonsuffix = strsub(text1, -commonlength)
    text1 = strsub(text1, 1, -commonlength - 1)
    text2 = strsub(text2, 1, -commonlength - 1)
  end

  -- Compute the diff on the middle block.
  local diffs = _diff_compute(text1, text2, checklines, deadline)

  -- Restore the prefix and suffix.
  if commonprefix then
    tinsert(diffs, 1, {DIFF_EQUAL, commonprefix})
  end
  if commonsuffix then
    diffs[#diffs + 1] = {DIFF_EQUAL, commonsuffix}
  end

  _diff_cleanupMerge(diffs)
  return diffs
end

--[[
* Reduce the number of edits by eliminating semantically trivial equalities.
* @param {Array.<Array.<number|string>>} diffs Array of diff tuples.
--]]
function diff_cleanupSemantic(diffs)
  local changes = false
  local equalities = {}  -- Stack of indices where equalities are found.
  local equalitiesLength = 0  -- Keeping our own length var is faster.
  local lastequality = nil
  -- Always equal to diffs[equalities[equalitiesLength]][2]
  local pointer = 1  -- Index of current position.
  -- Number of characters that changed prior to the equality.
  local length_insertions1 = 0
  local length_deletions1 = 0
  -- Number of characters that changed after the equality.
  local length_insertions2 = 0
  local length_deletions2 = 0

  while diffs[pointer] do
    if diffs[pointer][1] == DIFF_EQUAL then  -- Equality found.
      equalitiesLength = equalitiesLength + 1
      equalities[equalitiesLength] = pointer
      length_insertions1 = length_insertions2
      length_deletions1 = length_deletions2
      length_insertions2 = 0
      length_deletions2 = 0
      lastequality = diffs[pointer][2]
    else  -- An insertion or deletion.
      if diffs[pointer][1] == DIFF_INSERT then
        length_insertions2 = length_insertions2 + #(diffs[pointer][2])
      else
        length_deletions2 = length_deletions2 + #(diffs[pointer][2])
      end
      -- Eliminate an equality that is smaller or equal to the edits on both
      -- sides of it.
      if lastequality
          and (#lastequality <= max(length_insertions1, length_deletions1))
          and (#lastequality <= max(length_insertions2, length_deletions2)) then
        -- Duplicate record.
        tinsert(diffs, equalities[equalitiesLength],
         {DIFF_DELETE, lastequality})
        -- Change second copy to insert.
        diffs[equalities[equalitiesLength] + 1][1] = DIFF_INSERT
        -- Throw away the equality we just deleted.
        equalitiesLength = equalitiesLength - 1
        -- Throw away the previous equality (it needs to be reevaluated).
        equalitiesLength = equalitiesLength - 1
        pointer = (equalitiesLength > 0) and equalities[equalitiesLength] or 0
        length_insertions1, length_deletions1 = 0, 0  -- Reset the counters.
        length_insertions2, length_deletions2 = 0, 0
        lastequality = nil
        changes = true
      end
    end
    pointer = pointer + 1
  end

  -- Normalize the diff.
  if changes then
    _diff_cleanupMerge(diffs)
  end
  _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 = 2
  while diffs[pointer] do
    if (diffs[pointer - 1][1] == DIFF_DELETE and
        diffs[pointer][1] == DIFF_INSERT) then
      local deletion = diffs[pointer - 1][2]
      local insertion = diffs[pointer][2]
      local overlap_length1 = _diff_commonOverlap(deletion, insertion)
      local overlap_length2 = _diff_commonOverlap(insertion, deletion)
      if (overlap_length1 >= overlap_length2) then
        if (overlap_length1 >= #deletion / 2 or
            overlap_length1 >= #insertion / 2) then
          -- Overlap found.  Insert an equality and trim the surrounding edits.
          tinsert(diffs, pointer,
              {DIFF_EQUAL, strsub(insertion, 1, overlap_length1)})
          diffs[pointer - 1][2] =
              strsub(deletion, 1, #deletion - overlap_length1)
          diffs[pointer + 1][2] = strsub(insertion, overlap_length1 + 1)
          pointer = pointer + 1
        end
      else
        if (overlap_length2 >= #deletion / 2 or
            overlap_length2 >= #insertion / 2) then
          -- Reverse overlap found.
          -- Insert an equality and swap and trim the surrounding edits.
          tinsert(diffs, pointer,
              {DIFF_EQUAL, strsub(deletion, 1, overlap_length2)})
          diffs[pointer - 1] = {DIFF_INSERT,
              strsub(insertion, 1, #insertion - overlap_length2)}
          diffs[pointer + 1] = {DIFF_DELETE,
              strsub(deletion, overlap_length2 + 1)}
          pointer = pointer + 1
        end
      end
      pointer = pointer + 1
    end
    pointer = pointer + 1
  end
end

--[[
* Reduce the number of edits by eliminating operationally trivial equalities.
* @param {Array.<Array.<number|string>>} diffs Array of diff tuples.
--]]
function diff_cleanupEfficiency(diffs)
  local changes = false
  -- Stack of indices where equalities are found.
  local equalities = {}
  -- Keeping our own length var is faster.
  local equalitiesLength = 0
  -- Always equal to diffs[equalities[equalitiesLength]][2]
  local lastequality = nil
  -- Index of current position.
  local pointer = 1

  -- The following four are really booleans but are stored as numbers because
  -- they are used at one point like this:
  --
  -- (pre_ins + pre_del + post_ins + post_del) == 3
  --
  -- ...i.e. checking that 3 of them are true and 1 of them is false.

  -- Is there an insertion operation before the last equality.
  local pre_ins = 0
  -- Is there a deletion operation before the last equality.
  local pre_del = 0
  -- Is there an insertion operation after the last equality.
  local post_ins = 0
  -- Is there a deletion operation after the last equality.
  local post_del = 0

  while diffs[pointer] do
    if diffs[pointer][1] == DIFF_EQUAL then  -- Equality found.
      local diffText = diffs[pointer][2]
      if (#diffText < Diff_EditCost) and (post_ins == 1 or post_del == 1) then
        -- Candidate found.
        equalitiesLength = equalitiesLength + 1
        equalities[equalitiesLength] = pointer
        pre_ins, pre_del = post_ins, post_del
        lastequality = diffText
      else
        -- Not a candidate, and can never become one.
        equalitiesLength = 0
        lastequality = nil
      end
      post_ins, post_del = 0, 0
    else  -- An insertion or deletion.
      if diffs[pointer][1] == DIFF_DELETE then
        post_del = 1
      else
        post_ins = 1
      end
      --[[
      * Five types to be split:
      * <ins>A</ins><del>B</del>XY<ins>C</ins><del>D</del>
      * <ins>A</ins>X<ins>C</ins><del>D</del>
      * <ins>A</ins><del>B</del>X<ins>C</ins>
      * <ins>A</del>X<ins>C</ins><del>D</del>
      * <ins>A</ins><del>B</del>X<del>C</del>
      --]]
      if lastequality and (
          (pre_ins+pre_del+post_ins+post_del == 4)
          or
          (
            (#lastequality < Diff_EditCost / 2)
            and
            (pre_ins+pre_del+post_ins+post_del == 3)
          )) then
        -- Duplicate record.
        tinsert(diffs, equalities[equalitiesLength],
            {DIFF_DELETE, lastequality})
        -- Change second copy to insert.
        diffs[equalities[equalitiesLength] + 1][1] = DIFF_INSERT
        -- Throw away the equality we just deleted.
        equalitiesLength = equalitiesLength - 1
        lastequality = nil
        if (pre_ins == 1) and (pre_del == 1) then
          -- No changes made which could affect previous entry, keep going.
          post_ins, post_del = 1, 1
          equalitiesLength = 0
        else
          -- Throw away the previous equality.
          equalitiesLength = equalitiesLength - 1
          pointer = (equalitiesLength > 0) and equalities[equalitiesLength] or 0
          post_ins, post_del = 0, 0
        end
        changes = true
      end
    end
    pointer = pointer + 1
  end

  if changes then
    _diff_cleanupMerge(diffs)
  end
end

--[[
* Compute the Levenshtein distance; the number of inserted, deleted or
* substituted characters.
* @param {Array.<Array.<number|string>>} diffs Array of diff tuples.
* @return {number} Number of changes.
--]]
function diff_levenshtein(diffs)
  local levenshtein = 0
  local insertions, deletions = 0, 0
  for x, diff in ipairs(diffs) do
    local op, data = diff[1], diff[2]
    if (op == DIFF_INSERT) then
      insertions = insertions + #data
    elseif (op == DIFF_DELETE) then
      deletions = deletions + #data
    elseif (op == DIFF_EQUAL) then
      -- A deletion and an insertion is one substitution.
      levenshtein = levenshtein + max(insertions, deletions)
      insertions = 0
      deletions = 0
    end
  end
  levenshtein = levenshtein + max(insertions, deletions)
  return levenshtein
end

--[[
* Convert a diff array into a pretty HTML report.
* @param {Array.<Array.<number|string>>} diffs Array of diff tuples.
* @return {string} HTML representation.
--]]
function diff_prettyHtml(diffs)
  local html = {}
  for x, diff in ipairs(diffs) do
    local op = diff[1]   -- Operation (insert, delete, equal)
    local data = diff[2]  -- Text of change.
    local text = gsub(data, htmlEncode_pattern, htmlEncode_replace)
    if op == DIFF_INSERT then
      html[x] = '<ins style="background:#e6ffe6;">' .. text .. '</ins>'
    elseif op == DIFF_DELETE then
      html[x] = '<del style="background:#ffe6e6;">' .. text .. '</del>'
    elseif op == DIFF_EQUAL then
      html[x] = '<span>' .. text .. '</span>'
    end
  end
  return tconcat(html)
end

-- ---------------------------------------------------------------------------
-- UNOFFICIAL/PRIVATE DIFF FUNCTIONS
-- ---------------------------------------------------------------------------

--[[
* Find the differences between two texts.  Assumes that the texts do not
* have any common prefix or suffix.
* @param {string} text1 Old string to be diffed.
* @param {string} text2 New string to be diffed.
* @param {boolean} checklines Has no effect in Lua.
* @param {number} deadline Time when the diff should be complete by.
* @return {Array.<Array.<number|string>>} Array of diff tuples.
* @private
--]]
function _diff_compute(text1, text2, checklines, deadline)
  if #text1 == 0 then
    -- Just add some text (speedup).
    return {{DIFF_INSERT, text2}}
  end

  if #text2 == 0 then
    -- Just delete some text (speedup).
    return {{DIFF_DELETE, text1}}
  end

  local diffs

  local longtext = (#text1 > #text2) and text1 or text2
  local shorttext = (#text1 > #text2) and text2 or text1
  local i = indexOf(longtext, shorttext)

  if i ~= nil then
    -- Shorter text is inside the longer text (speedup).
    diffs = {
      {DIFF_INSERT, strsub(longtext, 1, i - 1)},
      {DIFF_EQUAL, shorttext},
      {DIFF_INSERT, strsub(longtext, i + #shorttext)}
    }
    -- Swap insertions for deletions if diff is reversed.
    if #text1 > #text2 then
      diffs[1][1], diffs[3][1] = DIFF_DELETE, DIFF_DELETE
    end
    return diffs
  end

  if #shorttext == 1 then
    -- Single character string.
    -- After the previous speedup, the character can't be an equality.
    return {{DIFF_DELETE, text1}, {DIFF_INSERT, text2}}
  end

  -- Check to see if the problem can be split in two.
  do
    local
     text1_a, text1_b,
     text2_a, text2_b,
     mid_common        = _diff_halfMatch(text1, text2)

    if text1_a then
      -- A half-match was found, sort out the return data.
      -- Send both pairs off for separate processing.
      local diffs_a = diff_main(text1_a, text2_a, checklines, deadline)
      local diffs_b = diff_main(text1_b, text2_b, checklines, deadline)
      -- Merge the results.
      local diffs_a_len = #diffs_a
      diffs = diffs_a
      diffs[diffs_a_len + 1] = {DIFF_EQUAL, mid_common}
      for i, b_diff in ipairs(diffs_b) do
        diffs[diffs_a_len + 1 + i] = b_diff
      end
      return diffs
    end
  end

  return _diff_bisect(text1, text2, deadline)
end

--[[
* 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.
* @param {string} text1 Old string to be diffed.
* @param {string} text2 New string to be diffed.
* @param {number} deadline Time at which to bail if not yet complete.
* @return {Array.<Array.<number|string>>} Array of diff tuples.
* @private
--]]
function _diff_bisect(text1, text2, deadline)
  -- Cache the text lengths to prevent multiple calls.
  local text1_length = #text1
  local text2_length = #text2
  local _sub, _element
  local max_d = ceil((text1_length + text2_length) / 2)
  local v_offset = max_d
  local v_length = 2 * max_d
  local v1 = {}
  local v2 = {}
  -- Setting all elements to -1 is faster in Lua than mixing integers and nil.
  for x = 0, v_length - 1 do
    v1[x] = -1
    v2[x] = -1
  end
  v1[v_offset + 1] = 0
  v2[v_offset + 1] = 0
  local delta = text1_length - text2_length
  -- If the total number of characters is odd, then
  -- the front path will collide with the reverse path.
  local front = (delta % 2 ~= 0)
  -- Offsets for start and end of k loop.
  -- Prevents mapping of space beyond the grid.
  local k1start = 0
  local k1end = 0
  local k2start = 0
  local k2end = 0
  for d = 0, max_d - 1 do
    -- Bail out if deadline is reached.
    if clock() > deadline then
      break
    end

    -- Walk the front path one step.
    for k1 = -d + k1start, d - k1end, 2 do
      local k1_offset = v_offset + k1
      local x1
      if (k1 == -d) or ((k1 ~= d) and
          (v1[k1_offset - 1] < v1[k1_offset + 1])) then
        x1 = v1[k1_offset + 1]
      else
        x1 = v1[k1_offset - 1] + 1
      end
      local y1 = x1 - k1
      while (x1 <= text1_length) and (y1 <= text2_length)
          and (strelement(text1, x1) == strelement(text2, y1)) do
        x1 = x1 + 1
        y1 = y1 + 1
      end
      v1[k1_offset] = x1
      if x1 > text1_length + 1 then
        -- Ran off the right of the graph.
        k1end = k1end + 2
      elseif y1 > text2_length + 1 then
        -- Ran off the bottom of the graph.
        k1start = k1start + 2
      elseif front then
        local k2_offset = v_offset + delta - k1
        if k2_offset >= 0 and k2_offset < v_length and v2[k2_offset] ~= -1 then
          -- Mirror x2 onto top-left coordinate system.
          local x2 = text1_length - v2[k2_offset] + 1
          if x1 > x2 then
            -- Overlap detected.
            return _diff_bisectSplit(text1, text2, x1, y1, deadline)
          end
        end
      end
    end

    -- Walk the reverse path one step.
    for k2 = -d + k2start, d - k2end, 2 do
      local k2_offset = v_offset + k2
      local x2
      if (k2 == -d) or ((k2 ~= d) and
          (v2[k2_offset - 1] < v2[k2_offset + 1])) then
        x2 = v2[k2_offset + 1]
      else
        x2 = v2[k2_offset - 1] + 1
      end
      local y2 = x2 - k2
      while (x2 <= text1_length) and (y2 <= text2_length)
          and (strelement(text1, -x2) == strelement(text2, -y2)) do
        x2 = x2 + 1
        y2 = y2 + 1
      end
      v2[k2_offset] = x2
      if x2 > text1_length + 1 then
        -- Ran off the left of the graph.
        k2end = k2end + 2
      elseif y2 > text2_length + 1 then
        -- Ran off the top of the graph.
        k2start = k2start + 2
      elseif not front then
        local k1_offset = v_offset + delta - k2
        if k1_offset >= 0 and k1_offset < v_length and v1[k1_offset] ~= -1 then
          local x1 = v1[k1_offset]
          local y1 = v_offset + x1 - k1_offset
          -- Mirror x2 onto top-left coordinate system.
          x2 = text1_length - x2 + 1
          if x1 > x2 then
            -- Overlap detected.
            return _diff_bisectSplit(text1, text2, x1, y1, deadline)
          end
        end
      end
    end
  end
  -- Diff took too long and hit the deadline or
  -- number of diffs equals number of characters, no commonality at all.
  return {{DIFF_DELETE, text1}, {DIFF_INSERT, text2}}
end

--[[
 * Given the location of the 'middle snake', split the diff in two parts
 * and recurse.
 * @param {string} text1 Old string to be diffed.
 * @param {string} text2 New string to be diffed.
 * @param {number} x Index of split point in text1.
 * @param {number} y Index of split point in text2.
 * @param {number} deadline Time at which to bail if not yet complete.
 * @return {Array.<Array.<number|string>>} Array of diff tuples.
 * @private
--]]
function _diff_bisectSplit(text1, text2, x, y, deadline)
  local text1a = strsub(text1, 1, x - 1)
  local text2a = strsub(text2, 1, y - 1)
  local text1b = strsub(text1, x)
  local text2b = strsub(text2, y)

  -- Compute both diffs serially.
  local diffs = diff_main(text1a, text2a, false, deadline)
  local diffsb = diff_main(text1b, text2b, false, deadline)

  local diffs_len = #diffs
  for i, v in ipairs(diffsb) do
    diffs[diffs_len + i] = v
  end
  return diffs
end

--[[
* Determine the common prefix of two strings.
* @param {string} text1 First string.
* @param {string} text2 Second string.
* @return {number} The number of characters common to the start of each
*    string.
--]]
function _diff_commonPrefix(text1, text2)
  -- Quick check for common null cases.
  if (#text1 == 0) or (#text2 == 0) or (strbyte(text1, 1) ~= strbyte(text2, 1))
      then
    return 0
  end
  -- Binary search.
  -- Performance analysis: http://neil.fraser.name/news/2007/10/09/
  local pointermin = 1
  local pointermax = min(#text1, #text2)
  local pointermid = pointermax
  local pointerstart = 1
  while (pointermin < pointermid) do
    if (strsub(text1, pointerstart, pointermid)
        == strsub(text2, pointerstart, pointermid)) then
      pointermin = pointermid
      pointerstart = pointermin
    else
      pointermax = pointermid
    end
    pointermid = floor(pointermin + (pointermax - pointermin) / 2)
  end
  return pointermid
end

--[[
* Determine the common suffix of two strings.
* @param {string} text1 First string.
* @param {string} text2 Second string.
* @return {number} The number of characters common to the end of each string.
--]]
function _diff_commonSuffix(text1, text2)
  -- Quick check for common null cases.
  if (#text1 == 0) or (#text2 == 0)
      or (strbyte(text1, -1) ~= strbyte(text2, -1)) then
    return 0
  end
  -- Binary search.
  -- Performance analysis: http://neil.fraser.name/news/2007/10/09/
  local pointermin = 1
  local pointermax = min(#text1, #text2)
  local pointermid = pointermax
  local pointerend = 1
  while (pointermin < pointermid) do
    if (strsub(text1, -pointermid, -pointerend)
        == strsub(text2, -pointermid, -pointerend)) then
      pointermin = pointermid
      pointerend = pointermin
    else
      pointermax = pointermid
    end
    pointermid = floor(pointermin + (pointermax - pointermin) / 2)
  end
  return pointermid
end

--[[
* Determine if the suffix of one string is the prefix of another.
* @param {string} text1 First string.
* @param {string} text2 Second string.
* @return {number} The number of characters common to the end of the first
*     string and the start of the second string.
* @private
--]]
function _diff_commonOverlap(text1, text2)
  -- Cache the text lengths to prevent multiple calls.
  local text1_length = #text1
  local text2_length = #text2
  -- Eliminate the null case.
  if text1_length == 0 or text2_length == 0 then
    return 0
  end
  -- Truncate the longer string.
  if text1_length > text2_length then
    text1 = strsub(text1, text1_length - text2_length + 1)
  elseif text1_length < text2_length then
    text2 = strsub(text2, 1, text1_length)
  end
  local text_length = min(text1_length, text2_length)
  -- Quick check for the worst case.
  if text1 == text2 then
    return text_length
  end

  -- 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/
  local best = 0
  local length = 1
  while true do
    local pattern = strsub(text1, text_length - length + 1)
    local found = strfind(text2, pattern, 1, true)
    if found == nil then
      return best
    end
    length = length + found - 1
    if found == 1 or strsub(text1, text_length - length + 1) ==
                     strsub(text2, 1, length) then
      best = length
      length = length + 1
    end
  end
end

--[[
* Does a substring of shorttext exist within longtext such that the substring
* is at least half the length of longtext?
* This speedup can produce non-minimal diffs.
* Closure, but does not reference any external variables.
* @param {string} longtext Longer string.
* @param {string} shorttext Shorter string.
* @param {number} i Start index of quarter length substring within longtext.
* @return {?Array.<string>} 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 nil if there was no match.
* @private
--]]
function _diff_halfMatchI(longtext, shorttext, i)
  -- Start with a 1/4 length substring at position i as a seed.
  local seed = strsub(longtext, i, i + floor(#longtext / 4))
  local j = 0  -- LUANOTE: do not change to 1, was originally -1
  local best_common = ''
  local best_longtext_a, best_longtext_b, best_shorttext_a, best_shorttext_b
  while true do
    j = indexOf(shorttext, seed, j + 1)
    if (j == nil) then
      break
    end
    local prefixLength = _diff_commonPrefix(strsub(longtext, i),
        strsub(shorttext, j))
    local suffixLength = _diff_commonSuffix(strsub(longtext, 1, i - 1),
        strsub(shorttext, 1, j - 1))
    if #best_common < suffixLength + prefixLength then
      best_common = strsub(shorttext, j - suffixLength, j - 1)
          .. strsub(shorttext, j, j + prefixLength - 1)
      best_longtext_a = strsub(longtext, 1, i - suffixLength - 1)
      best_longtext_b = strsub(longtext, i + prefixLength)
      best_shorttext_a = strsub(shorttext, 1, j - suffixLength - 1)
      best_shorttext_b = strsub(shorttext, j + prefixLength)
    end
  end
  if #best_common * 2 >= #longtext then
    return {best_longtext_a, best_longtext_b,
            best_shorttext_a, best_shorttext_b, best_common}
  else
    return nil
  end
end

--[[
* Do the two texts share a substring which is at least half the length of the
* longer text?
* @param {string} text1 First string.
* @param {string} text2 Second string.
* @return {?Array.<string>} 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 nil if there was no match.
* @private
--]]
function _diff_halfMatch(text1, text2)
  if Diff_Timeout <= 0 then
    -- Don't risk returning a non-optimal diff if we have unlimited time.
    return nil
  end
  local longtext = (#text1 > #text2) and text1 or text2
  local shorttext = (#text1 > #text2) and text2 or text1
  if (#longtext < 4) or (#shorttext * 2 < #longtext) then
    return nil  -- Pointless.
  end

  -- First check if the second quarter is the seed for a half-match.
  local hm1 = _diff_halfMatchI(longtext, shorttext, ceil(#longtext / 4))
  -- Check again based on the third quarter.
  local hm2 = _diff_halfMatchI(longtext, shorttext, ceil(#longtext / 2))
  local hm
  if not hm1 and not hm2 then
    return nil
  elseif not hm2 then
    hm = hm1
  elseif not hm1 then
    hm = hm2
  else
    -- Both matched.  Select the longest.
    hm = (#hm1[5] > #hm2[5]) and hm1 or hm2
  end

  -- A half-match was found, sort out the return data.
  local text1_a, text1_b, text2_a, text2_b
  if (#text1 > #text2) then
    text1_a, text1_b = hm[1], hm[2]
    text2_a, text2_b = hm[3], hm[4]
  else
    text2_a, text2_b = hm[1], hm[2]
    text1_a, text1_b = hm[3], hm[4]
  end
  local mid_common = hm[5]
  return text1_a, text1_b, text2_a, text2_b, mid_common
end

--[[
* Given two strings, compute a score representing whether the internal
* boundary falls on logical boundaries.
* Scores range from 6 (best) to 0 (worst).
* @param {string} one First string.
* @param {string} two Second string.
* @return {number} The score.
* @private
--]]
function _diff_cleanupSemanticScore(one, two)
  if (#one == 0) or (#two == 0) then
    -- Edges are the best.
    return 6
  end

  -- 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.
  local char1 = strsub(one, -1)
  local char2 = strsub(two, 1, 1)
  local nonAlphaNumeric1 = strmatch(char1, '%W')
  local nonAlphaNumeric2 = strmatch(char2, '%W')
  local whitespace1 = nonAlphaNumeric1 and strmatch(char1, '%s')
  local whitespace2 = nonAlphaNumeric2 and strmatch(char2, '%s')
  local lineBreak1 = whitespace1 and strmatch(char1, '%c')
  local lineBreak2 = whitespace2 and strmatch(char2, '%c')
  local blankLine1 = lineBreak1 and strmatch(one, '\n\r?\n$')
  local blankLine2 = lineBreak2 and strmatch(two, '^\r?\n\r?\n')

  if blankLine1 or blankLine2 then
    -- Five points for blank lines.
    return 5
  elseif lineBreak1 or lineBreak2 then
    -- Four points for line breaks.
    return 4
  elseif nonAlphaNumeric1 and not whitespace1 and whitespace2 then
    -- Three points for end of sentences.
    return 3
  elseif whitespace1 or whitespace2 then
    -- Two points for whitespace.
    return 2
  elseif nonAlphaNumeric1 or nonAlphaNumeric2 then
    -- One point for non-alphanumeric.
    return 1
  end
  return 0
end

--[[
* 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.
* @param {Array.<Array.<number|string>>} diffs Array of diff tuples.
--]]
function _diff_cleanupSemanticLossless(diffs)
  local pointer = 2
  -- Intentionally ignore the first and last element (don't need checking).
  while diffs[pointer + 1] do
    local prevDiff, nextDiff = diffs[pointer - 1], diffs[pointer + 1]
    if (prevDiff[1] == DIFF_EQUAL) and (nextDiff[1] == DIFF_EQUAL) then
      -- This is a single edit surrounded by equalities.
      local diff = diffs[pointer]

      local equality1 = prevDiff[2]
      local edit = diff[2]
      local equality2 = nextDiff[2]

      -- First, shift the edit as far left as possible.
      local commonOffset = _diff_commonSuffix(equality1, edit)
      if commonOffset > 0 then
        local commonString = strsub(edit, -commonOffset)
        equality1 = strsub(equality1, 1, -commonOffset - 1)
        edit = commonString .. strsub(edit, 1, -commonOffset - 1)
        equality2 = commonString .. equality2
      end

      -- Second, step character by character right, looking for the best fit.
      local bestEquality1 = equality1
      local bestEdit = edit
      local bestEquality2 = equality2
      local bestScore = _diff_cleanupSemanticScore(equality1, edit)
          + _diff_cleanupSemanticScore(edit, equality2)

      while strbyte(edit, 1) == strbyte(equality2, 1) do
        equality1 = equality1 .. strsub(edit, 1, 1)
        edit = strsub(edit, 2) .. strsub(equality2, 1, 1)
        equality2 = strsub(equality2, 2)
        local score = _diff_cleanupSemanticScore(equality1, edit)
            + _diff_cleanupSemanticScore(edit, equality2)
        -- The >= encourages trailing rather than leading whitespace on edits.
        if score >= bestScore then
          bestScore = score
          bestEquality1 = equality1
          bestEdit = edit
          bestEquality2 = equality2
        end
      end
      if prevDiff[2] ~= bestEquality1 then
        -- We have an improvement, save it back to the diff.
        if #bestEquality1 > 0 then
          diffs[pointer - 1][2] = bestEquality1
        else
          tremove(diffs, pointer - 1)
          pointer = pointer - 1
        end
        diffs[pointer][2] = bestEdit
        if #bestEquality2 > 0 then
          diffs[pointer + 1][2] = bestEquality2
        else
          tremove(diffs, pointer + 1, 1)
          pointer = pointer - 1
        end
      end
    end
    pointer = pointer + 1
  end
end

--[[
* Reorder and merge like edit sections.  Merge equalities.
* Any edit section can move as long as it doesn't cross an equality.
* @param {Array.<Array.<number|string>>} diffs Array of diff tuples.
--]]
function _diff_cleanupMerge(diffs)
  diffs[#diffs + 1] = {DIFF_EQUAL, ''}  -- Add a dummy entry at the end.
  local pointer = 1
  local count_delete, count_insert = 0, 0
  local text_delete, text_insert = '', ''
  local commonlength
  while diffs[pointer] do
    local diff_type = diffs[pointer][1]
    if diff_type == DIFF_INSERT then
      count_insert = count_insert + 1
      text_insert = text_insert .. diffs[pointer][2]
      pointer = pointer + 1
    elseif diff_type == DIFF_DELETE then
      count_delete = count_delete + 1
      text_delete = text_delete .. diffs[pointer][2]
      pointer = pointer + 1
    elseif diff_type == DIFF_EQUAL then
      -- Upon reaching an equality, check for prior redundancies.
      if count_delete + count_insert > 1 then
        if (count_delete > 0) and (count_insert > 0) then
          -- Factor out any common prefixies.
          commonlength = _diff_commonPrefix(text_insert, text_delete)
          if commonlength > 0 then
            local back_pointer = pointer - count_delete - count_insert
            if (back_pointer > 1) and (diffs[back_pointer - 1][1] == DIFF_EQUAL)
                then
              diffs[back_pointer - 1][2] = diffs[back_pointer - 1][2]
                  .. strsub(text_insert, 1, commonlength)
            else
              tinsert(diffs, 1,
                  {DIFF_EQUAL, strsub(text_insert, 1, commonlength)})
              pointer = pointer + 1
            end
            text_insert = strsub(text_insert, commonlength + 1)
            text_delete = strsub(text_delete, commonlength + 1)
          end
          -- Factor out any common suffixies.
          commonlength = _diff_commonSuffix(text_insert, text_delete)
          if commonlength ~= 0 then
            diffs[pointer][2] =
            strsub(text_insert, -commonlength) .. diffs[pointer][2]
            text_insert = strsub(text_insert, 1, -commonlength - 1)
            text_delete = strsub(text_delete, 1, -commonlength - 1)
          end
        end
        -- Delete the offending records and add the merged ones.
        if count_delete == 0 then
          tsplice(diffs, pointer - count_insert,
          count_insert, {DIFF_INSERT, text_insert})
        elseif count_insert == 0 then
          tsplice(diffs, pointer - count_delete,
          count_delete, {DIFF_DELETE, text_delete})
        else
          tsplice(diffs, pointer - count_delete - count_insert,
          count_delete + count_insert,
          {DIFF_DELETE, text_delete}, {DIFF_INSERT, text_insert})
        end
        pointer = pointer - count_delete - count_insert
            + (count_delete>0 and 1 or 0) + (count_insert>0 and 1 or 0) + 1
      elseif (pointer > 1) and (diffs[pointer - 1][1] == DIFF_EQUAL) then
        -- Merge this equality with the previous one.
        diffs[pointer - 1][2] = diffs[pointer - 1][2] .. diffs[pointer][2]
        tremove(diffs, pointer)
      else
        pointer = pointer + 1
      end
      count_insert, count_delete = 0, 0
      text_delete, text_insert = '', ''
    end
  end
  if diffs[#diffs][2] == '' then
    diffs[#diffs] = nil  -- Remove the dummy entry at the end.
  end

  -- Second pass: look for single edits surrounded on both sides by equalities
  -- which can be shifted sideways to eliminate an equality.
  -- e.g: A<ins>BA</ins>C -> <ins>AB</ins>AC
  local changes = false
  pointer = 2
  -- Intentionally ignore the first and last element (don't need checking).
  while pointer < #diffs do
    local prevDiff, nextDiff = diffs[pointer - 1], diffs[pointer + 1]
    if (prevDiff[1] == DIFF_EQUAL) and (nextDiff[1] == DIFF_EQUAL) then
      -- This is a single edit surrounded by equalities.
      local diff = diffs[pointer]
      local currentText = diff[2]
      local prevText = prevDiff[2]
      local nextText = nextDiff[2]
      if strsub(currentText, -#prevText) == prevText then
        -- Shift the edit over the previous equality.
        diff[2] = prevText .. strsub(currentText, 1, -#prevText - 1)
        nextDiff[2] = prevText .. nextDiff[2]
        tremove(diffs, pointer - 1)
        changes = true
      elseif strsub(currentText, 1, #nextText) == nextText then
        -- Shift the edit over the next equality.
        prevDiff[2] = prevText .. nextText
        diff[2] = strsub(currentText, #nextText + 1) .. nextText
        tremove(diffs, pointer + 1)
        changes = true
      end
    end
    pointer = pointer + 1
  end
  -- If shifts were made, the diff needs reordering and another shift sweep.
  if changes then
    -- LUANOTE: no return value, but necessary to use 'return' to get
    -- tail calls.
    return _diff_cleanupMerge(diffs)
  end
end

--[[
* 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
* @param {Array.<Array.<number|string>>} diffs Array of diff tuples.
* @param {number} loc Location within text1.
* @return {number} Location within text2.
--]]
function _diff_xIndex(diffs, loc)
  local chars1 = 1
  local chars2 = 1
  local last_chars1 = 1
  local last_chars2 = 1
  local x
  for _x, diff in ipairs(diffs) do
    x = _x
    if diff[1] ~= DIFF_INSERT then   -- Equality or deletion.
      chars1 = chars1 + #diff[2]
    end
    if diff[1] ~= DIFF_DELETE then   -- Equality or insertion.
      chars2 = chars2 + #diff[2]
    end
    if chars1 > loc then   -- Overshot the location.
      break
    end
    last_chars1 = chars1
    last_chars2 = chars2
  end
  -- Was the location deleted?
  if diffs[x + 1] and (diffs[x][1] == DIFF_DELETE) then
    return last_chars2
  end
  -- Add the remaining character length.
  return last_chars2 + (loc - last_chars1)
end

--[[
* Compute and return the source text (all equalities and deletions).
* @param {Array.<Array.<number|string>>} diffs Array of diff tuples.
* @return {string} Source text.
--]]
function _diff_text1(diffs)
  local text = {}
  for x, diff in ipairs(diffs) do
    if diff[1] ~= DIFF_INSERT then
      text[#text + 1] = diff[2]
    end
  end
  return tconcat(text)
end

--[[
* Compute and return the destination text (all equalities and insertions).
* @param {Array.<Array.<number|string>>} diffs Array of diff tuples.
* @return {string} Destination text.
--]]
function _diff_text2(diffs)
  local text = {}
  for x, diff in ipairs(diffs) do
    if diff[1] ~= DIFF_DELETE then
      text[#text + 1] = diff[2]
    end
  end
  return tconcat(text)
end

--[[
* 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.
* @param {Array.<Array.<number|string>>} diffs Array of diff tuples.
* @return {string} Delta text.
--]]
function _diff_toDelta(diffs)
  local text = {}
  for x, diff in ipairs(diffs) do
    local op, data = diff[1], diff[2]
    if op == DIFF_INSERT then
      text[x] = '+' .. gsub(data, percentEncode_pattern, percentEncode_replace)
    elseif op == DIFF_DELETE then
      text[x] = '-' .. #data
    elseif op == DIFF_EQUAL then
      text[x] = '=' .. #data
    end
  end
  return tconcat(text, '\t')
end

--[[
* Given the original text1, and an encoded string which describes the
* operations required to transform text1 into text2, compute the full diff.
* @param {string} text1 Source string for the diff.
* @param {string} delta Delta text.
* @return {Array.<Array.<number|string>>} Array of diff tuples.
* @throws {Errorend If invalid input.
--]]
function _diff_fromDelta(text1, delta)
  local diffs = {}
  local diffsLength = 0  -- Keeping our own length var is faster
  local pointer = 1  -- Cursor in text1
  for token in gmatch(delta, '[^\t]+') do
    -- Each token begins with a one character parameter which specifies the
    -- operation of this token (delete, insert, equality).
    local tokenchar, param = strsub(token, 1, 1), strsub(token, 2)
    if (tokenchar == '+') then
      local invalidDecode = false
      local decoded = gsub(param, '%%(.?.?)',
          function(c)
            local n = tonumber(c, 16)
            if (#c ~= 2) or (n == nil) then
              invalidDecode = true
              return ''
            end
            return strchar(n)
          end)
      if invalidDecode then
        -- Malformed URI sequence.
        error('Illegal escape in _diff_fromDelta: ' .. param)
      end
      diffsLength = diffsLength + 1
      diffs[diffsLength] = {DIFF_INSERT, decoded}
    elseif (tokenchar == '-') or (tokenchar == '=') then
      local n = tonumber(param)
      if (n == nil) or (n < 0) then
        error('Invalid number in _diff_fromDelta: ' .. param)
      end
      local text = strsub(text1, pointer, pointer + n - 1)
      pointer = pointer + n
      if (tokenchar == '=') then
        diffsLength = diffsLength + 1
        diffs[diffsLength] = {DIFF_EQUAL, text}
      else
        diffsLength = diffsLength + 1
        diffs[diffsLength] = {DIFF_DELETE, text}
      end
    else
      error('Invalid diff operation in _diff_fromDelta: ' .. token)
    end
  end
  if (pointer ~= #text1 + 1) then
    error('Delta length (' .. (pointer - 1)
        .. ') does not equal source text length (' .. #text1 .. ').')
  end
  return diffs
end

-- ---------------------------------------------------------------------------
--  MATCH API
-- ---------------------------------------------------------------------------

local _match_bitap, _match_alphabet

--[[
* Locate the best instance of 'pattern' in 'text' near 'loc'.
* @param {string} text The text to search.
* @param {string} pattern The pattern to search for.
* @param {number} loc The location to search around.
* @return {number} Best match index or -1.
--]]
function match_main(text, pattern, loc)
  -- Check for null inputs.
  if text == nil or pattern == nil or loc == nil then
    error('Null inputs. (match_main)')
  end

  if text == pattern then
    -- Shortcut (potentially not guaranteed by the algorithm)
    return 1
  elseif #text == 0 then
    -- Nothing to match.
    return -1
  end
  loc = max(1, min(loc, #text))
  if strsub(text, loc, loc + #pattern - 1) == pattern then
    -- Perfect match at the perfect spot!  (Includes case of null pattern)
    return loc
  else
    -- Do a fuzzy compare.
    return _match_bitap(text, pattern, loc)
  end
end

-- ---------------------------------------------------------------------------
-- UNOFFICIAL/PRIVATE MATCH FUNCTIONS
-- ---------------------------------------------------------------------------

--[[
* Initialise the alphabet for the Bitap algorithm.
* @param {string} pattern The text to encode.
* @return {Object} Hash of character locations.
* @private
--]]
function _match_alphabet(pattern)
  local s = {}
  local i = 0
  for c in gmatch(pattern, '.') do
    s[c] = bor(s[c] or 0, lshift(1, #pattern - i - 1))
    i = i + 1
  end
  return s
end

--[[
* Locate the best instance of 'pattern' in 'text' near 'loc' using the
* Bitap algorithm.
* @param {string} text The text to search.
* @param {string} pattern The pattern to search for.
* @param {number} loc The location to search around.
* @return {number} Best match index or -1.
* @private
--]]
function _match_bitap(text, pattern, loc)
  if #pattern > Match_MaxBits then
    error('Pattern too long.')
  end

  -- Initialise the alphabet.
  local s = _match_alphabet(pattern)

  --[[
  * Compute and return the score for a match with e errors and x location.
  * Accesses loc and pattern through being a closure.
  * @param {number} e Number of errors in match.
  * @param {number} x Location of match.
  * @return {number} Overall score for match (0.0 = good, 1.0 = bad).
  * @private
  --]]
  local function _match_bitapScore(e, x)
    local accuracy = e / #pattern
    local proximity = abs(loc - x)
    if (Match_Distance == 0) then
      -- Dodge divide by zero error.
      return (proximity == 0) and 1 or accuracy
    end
    return accuracy + (proximity / Match_Distance)
  end

  -- Highest score beyond which we give up.
  local score_threshold = Match_Threshold
  -- Is there a nearby exact match? (speedup)
  local best_loc = indexOf(text, pattern, loc)
  if best_loc then
    score_threshold = min(_match_bitapScore(0, best_loc), score_threshold)
    -- LUANOTE: Ideally we'd also check from the other direction, but Lua
    -- doesn't have an efficent lastIndexOf function.
  end

  -- Initialise the bit arrays.
  local matchmask = lshift(1, #pattern - 1)
  best_loc = -1

  local bin_min, bin_mid
  local bin_max = #pattern + #text
  local last_rd
  for d = 0, #pattern - 1, 1 do
    -- 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) do
      if (_match_bitapScore(d, loc + bin_mid) <= score_threshold) then
        bin_min = bin_mid
      else
        bin_max = bin_mid
      end
      bin_mid = floor(bin_min + (bin_max - bin_min) / 2)
    end
    -- Use the result from this iteration as the maximum for the next.
    bin_max = bin_mid
    local start = max(1, loc - bin_mid + 1)
    local finish = min(loc + bin_mid, #text) + #pattern

    local rd = {}
    for j = start, finish do
      rd[j] = 0
    end
    rd[finish + 1] = lshift(1, d) - 1
    for j = finish, start, -1 do
      local charMatch = s[strsub(text, j - 1, j - 1)] or 0
      if (d == 0) then  -- First pass: exact match.
        rd[j] = band(bor((rd[j + 1] * 2), 1), charMatch)
      else
        -- Subsequent passes: fuzzy match.
        -- Functions instead of operators make this hella messy.
        rd[j] = bor(
                band(
                  bor(
                    lshift(rd[j + 1], 1),
                    1
                  ),
                  charMatch
                ),
                bor(
                  bor(
                    lshift(bor(last_rd[j + 1], last_rd[j]), 1),
                    1
                  ),
                  last_rd[j + 1]
                )
              )
      end
      if (band(rd[j], matchmask) ~= 0) then
        local score = _match_bitapScore(d, j - 1)
        -- This match will almost certainly be better than any existing match.
        -- But check anyway.
        if (score <= score_threshold) then
          -- Told you so.
          score_threshold = score
          best_loc = j - 1
          if (best_loc > loc) then
            -- When passing loc, don't exceed our current distance from loc.
            start = max(1, loc * 2 - best_loc)
          else
            -- Already passed loc, downhill from here on in.
            break
          end
        end
      end
    end
    -- No hope for a (better) match at greater error levels.
    if (_match_bitapScore(d + 1, loc) > score_threshold) then
      break
    end
    last_rd = rd
  end
  return best_loc
end

-- -----------------------------------------------------------------------------
-- PATCH API
-- -----------------------------------------------------------------------------

local _patch_addContext,
      _patch_deepCopy,
      _patch_addPadding,
      _patch_splitMax,
      _patch_appendText,
      _new_patch_obj

--[[
* 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
*
* @param {string|Array.<Array.<number|string>>} a text1 (methods 1,3,4) or
* Array of diff tuples for text1 to text2 (method 2).
* @param {string|Array.<Array.<number|string>>} opt_b text2 (methods 1,4) or
* Array of diff tuples for text1 to text2 (method 3) or undefined (method 2).
* @param {string|Array.<Array.<number|string>>} opt_c Array of diff tuples for
* text1 to text2 (method 4) or undefined (methods 1,2,3).
* @return {Array.<_new_patch_obj>} Array of patch objects.
--]]
function patch_make(a, opt_b, opt_c)
  local text1, diffs
  local type_a, type_b, type_c = type(a), type(opt_b), type(opt_c)
  if (type_a == 'string') and (type_b == 'string') and (type_c == 'nil') then
    -- Method 1: text1, text2
    -- Compute diffs from text1 and text2.
    text1 = a
    diffs = diff_main(text1, opt_b, true)
    if (#diffs > 2) then
      diff_cleanupSemantic(diffs)
      diff_cleanupEfficiency(diffs)
    end
  elseif (type_a == 'table') and (type_b == 'nil') and (type_c == 'nil') then
    -- Method 2: diffs
    -- Compute text1 from diffs.
    diffs = a
    text1 = _diff_text1(diffs)
  elseif (type_a == 'string') and (type_b == 'table') and (type_c == 'nil') then
    -- Method 3: text1, diffs
    text1 = a
    diffs = opt_b
  elseif (type_a == 'string') and (type_b == 'string') and (type_c == 'table')
      then
    -- Method 4: text1, text2, diffs
    -- text2 is not used.
    text1 = a
    diffs = opt_c
  else
    error('Unknown call format to patch_make.')
  end

  if (diffs[1] == nil) then
    return {}  -- Get rid of the null case.
  end

  local patches = {}
  local patch = _new_patch_obj()
  local patchDiffLength = 0  -- Keeping our own length var is faster.
  local char_count1 = 0  -- Number of characters into the text1 string.
  local char_count2 = 0  -- Number of characters into the text2 string.
  -- Start with text1 (prepatch_text) and apply the diffs until we arrive at
  -- text2 (postpatch_text).  We recreate the patches one by one to determine
  -- context info.
  local prepatch_text, postpatch_text = text1, text1
  for x, diff in ipairs(diffs) do
    local diff_type, diff_text = diff[1], diff[2]

    if (patchDiffLength == 0) and (diff_type ~= DIFF_EQUAL) then
      -- A new patch starts here.
      patch.start1 = char_count1 + 1
      patch.start2 = char_count2 + 1
    end

    if (diff_type == DIFF_INSERT) then
      patchDiffLength = patchDiffLength + 1
      patch.diffs[patchDiffLength] = diff
      patch.length2 = patch.length2 + #diff_text
      postpatch_text = strsub(postpatch_text, 1, char_count2)
          .. diff_text .. strsub(postpatch_text, char_count2 + 1)
    elseif (diff_type == DIFF_DELETE) then
      patch.length1 = patch.length1 + #diff_text
      patchDiffLength = patchDiffLength + 1
      patch.diffs[patchDiffLength] = diff
      postpatch_text = strsub(postpatch_text, 1, char_count2)
          .. strsub(postpatch_text, char_count2 + #diff_text + 1)
    elseif (diff_type == DIFF_EQUAL) then
      if (#diff_text <= Patch_Margin * 2)
          and (patchDiffLength ~= 0) and (#diffs ~= x) then
        -- Small equality inside a patch.
        patchDiffLength = patchDiffLength + 1
        patch.diffs[patchDiffLength] = diff
        patch.length1 = patch.length1 + #diff_text
        patch.length2 = patch.length2 + #diff_text
      elseif (#diff_text >= Patch_Margin * 2) then
        -- Time for a new patch.
        if (patchDiffLength ~= 0) then
          _patch_addContext(patch, prepatch_text)
          patches[#patches + 1] = patch
          patch = _new_patch_obj()
          patchDiffLength = 0
          -- 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
        end
      end
    end

    -- Update the current character count.
    if (diff_type ~= DIFF_INSERT) then
      char_count1 = char_count1 + #diff_text
    end
    if (diff_type ~= DIFF_DELETE) then
      char_count2 = char_count2 + #diff_text
    end
  end

  -- Pick up the leftover patch if not empty.
  if (patchDiffLength > 0) then
    _patch_addContext(patch, prepatch_text)
    patches[#patches + 1] = patch
  end

  return patches
end

--[[
* 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.
* @param {Array.<_new_patch_obj>} patches Array of patch objects.
* @param {string} text Old text.
* @return {Array.<string|Array.<boolean>>} Two return values, the
*     new text and an array of boolean values.
--]]
function patch_apply(patches, text)
  if patches[1] == nil then
    return text, {}
  end

  -- Deep copy the patches so that no changes are made to originals.
  patches = _patch_deepCopy(patches)

  local nullPadding = _patch_addPadding(patches)
  text = nullPadding .. text .. nullPadding

  _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.
  local delta = 0
  local results = {}
  for x, patch in ipairs(patches) do
    local expected_loc = patch.start2 + delta
    local text1 = _diff_text1(patch.diffs)
    local start_loc
    local end_loc = -1
    if #text1 > Match_MaxBits then
      -- _patch_splitMax will only provide an oversized pattern in
      -- the case of a monster delete.
      start_loc = match_main(text,
          strsub(text1, 1, Match_MaxBits), expected_loc)
      if start_loc ~= -1 then
        end_loc = match_main(text, strsub(text1, -Match_MaxBits),
            expected_loc + #text1 - Match_MaxBits)
        if end_loc == -1 or start_loc >= end_loc then
          -- Can't find valid trailing context.  Drop this patch.
          start_loc = -1
        end
      end
    else
      start_loc = match_main(text, text1, expected_loc)
    end
    if start_loc == -1 then
      -- No match found.  :(
      results[x] = false
      -- Subtract the delta for this failed patch from subsequent patches.
      delta = delta - patch.length2 - patch.length1
    else
      -- Found a match.  :)
      results[x] = true
      delta = start_loc - expected_loc
      local text2
      if end_loc == -1 then
        text2 = strsub(text, start_loc, start_loc + #text1 - 1)
      else
        text2 = strsub(text, start_loc, end_loc + Match_MaxBits - 1)
      end
      if text1 == text2 then
        -- Perfect match, just shove the replacement text in.
        text = strsub(text, 1, start_loc - 1) .. _diff_text2(patch.diffs)
            .. strsub(text, start_loc + #text1)
      else
        -- Imperfect match.  Run a diff to get a framework of equivalent
        -- indices.
        local diffs = diff_main(text1, text2, false)
        if (#text1 > Match_MaxBits)
            and (diff_levenshtein(diffs) / #text1 > Patch_DeleteThreshold) then
          -- The end points match, but the content is unacceptably bad.
          results[x] = false
        else
          _diff_cleanupSemanticLossless(diffs)
          local index1 = 1
          local index2
          for y, mod in ipairs(patch.diffs) do
            if mod[1] ~= DIFF_EQUAL then
              index2 = _diff_xIndex(diffs, index1)
            end
            if mod[1] == DIFF_INSERT then
              text = strsub(text, 1, start_loc + index2 - 2)
                  .. mod[2] .. strsub(text, start_loc + index2 - 1)
            elseif mod[1] == DIFF_DELETE then
              text = strsub(text, 1, start_loc + index2 - 2) .. strsub(text,
                  start_loc + _diff_xIndex(diffs, index1 + #mod[2] - 1))
            end
            if mod[1] ~= DIFF_DELETE then
              index1 = index1 + #mod[2]
            end
          end
        end
      end
    end
  end
  -- Strip the padding off.
  text = strsub(text, #nullPadding + 1, -#nullPadding - 1)
  return text, results
end

--[[
* Take a list of patches and return a textual representation.
* @param {Array.<_new_patch_obj>} patches Array of patch objects.
* @return {string} Text representation of patches.
--]]
function patch_toText(patches)
  local text = {}
  for x, patch in ipairs(patches) do
    _patch_appendText(patch, text)
  end
  return tconcat(text)
end

--[[
* Parse a textual representation of patches and return a list of patch objects.
* @param {string} textline Text representation of patches.
* @return {Array.<_new_patch_obj>} Array of patch objects.
* @throws {Error} If invalid input.
--]]
function patch_fromText(textline)
  local patches = {}
  if (#textline == 0) then
    return patches
  end
  local text = {}
  for line in gmatch(textline, '([^\n]*)') do
    text[#text + 1] = line
  end
  local textPointer = 1
  while (textPointer <= #text) do
    local start1, length1, start2, length2
     = strmatch(text[textPointer], '^@@ %-(%d+),?(%d*) %+(%d+),?(%d*) @@$')
    if (start1 == nil) then
      error('Invalid patch string: "' .. text[textPointer] .. '"')
    end
    local patch = _new_patch_obj()
    patches[#patches + 1] = patch

    start1 = tonumber(start1)
    length1 = tonumber(length1) or 1
    if (length1 == 0) then
      start1 = start1 + 1
    end
    patch.start1 = start1
    patch.length1 = length1

    start2 = tonumber(start2)
    length2 = tonumber(length2) or 1
    if (length2 == 0) then
      start2 = start2 + 1
    end
    patch.start2 = start2
    patch.length2 = length2

    textPointer = textPointer + 1

    while true do
      local line = text[textPointer]
      if (line == nil) then
        break
      end
      local sign; sign, line = strsub(line, 1, 1), strsub(line, 2)

      local invalidDecode = false
      local decoded = gsub(line, '%%(.?.?)',
          function(c)
            local n = tonumber(c, 16)
            if (#c ~= 2) or (n == nil) then
              invalidDecode = true
              return ''
            end
            return strchar(n)
          end)
      if invalidDecode then
        -- Malformed URI sequence.
        error('Illegal escape in patch_fromText: ' .. line)
      end

      line = decoded

      if (sign == '-') then
        -- Deletion.
        patch.diffs[#patch.diffs + 1] = {DIFF_DELETE, line}
      elseif (sign == '+') then
        -- Insertion.
        patch.diffs[#patch.diffs + 1] = {DIFF_INSERT, line}
      elseif (sign == ' ') then
        -- Minor equality.
        patch.diffs[#patch.diffs + 1] = {DIFF_EQUAL, line}
      elseif (sign == '@') then
        -- Start of next patch.
        break
      elseif (sign == '') then
        -- Blank line?  Whatever.
      else
        -- WTF?
        error('Invalid patch mode "' .. sign .. '" in: ' .. line)
      end
      textPointer = textPointer + 1
    end
  end
  return patches
end

-- ---------------------------------------------------------------------------
-- UNOFFICIAL/PRIVATE PATCH FUNCTIONS
-- ---------------------------------------------------------------------------

local patch_meta = {
  __tostring = function(patch)
    local buf = {}
    _patch_appendText(patch, buf)
    return tconcat(buf)
  end
}

--[[
* Class representing one patch operation.
* @constructor
--]]
function _new_patch_obj()
  return setmetatable({
    --[[ @type {Array.<Array.<number|string>>} ]]
    diffs = {};
    --[[ @type {?number} ]]
    start1 = 1;  -- nil;
    --[[ @type {?number} ]]
    start2 = 1;  -- nil;
    --[[ @type {number} ]]
    length1 = 0;
    --[[ @type {number} ]]
    length2 = 0;
  }, patch_meta)
end

--[[
* Increase the context until it is unique,
* but don't let the pattern expand beyond Match_MaxBits.
* @param {_new_patch_obj} patch The patch to grow.
* @param {string} text Source text.
* @private
--]]
function _patch_addContext(patch, text)
  if (#text == 0) then
    return
  end
  local pattern = strsub(text, patch.start2, patch.start2 + patch.length1 - 1)
  local padding = 0

  -- LUANOTE: Lua's lack of a lastIndexOf function results in slightly
  -- different logic here than in other language ports.
  -- Look for the first two matches of pattern in text.  If two are found,
  -- increase the pattern length.
  local firstMatch = indexOf(text, pattern)
  local secondMatch = nil
  if (firstMatch ~= nil) then
    secondMatch = indexOf(text, pattern, firstMatch + 1)
  end
  while (#pattern == 0 or secondMatch ~= nil)
      and (#pattern < Match_MaxBits - Patch_Margin - Patch_Margin) do
    padding = padding + Patch_Margin
    pattern = strsub(text, max(1, patch.start2 - padding),
    patch.start2 + patch.length1 - 1 + padding)
    firstMatch = indexOf(text, pattern)
    if (firstMatch ~= nil) then
      secondMatch = indexOf(text, pattern, firstMatch + 1)
    else
      secondMatch = nil
    end
  end
  -- Add one chunk for good luck.
  padding = padding + Patch_Margin

  -- Add the prefix.
  local prefix = strsub(text, max(1, patch.start2 - padding), patch.start2 - 1)
  if (#prefix > 0) then
    tinsert(patch.diffs, 1, {DIFF_EQUAL, prefix})
  end
  -- Add the suffix.
  local suffix = strsub(text, patch.start2 + patch.length1,
  patch.start2 + patch.length1 - 1 + padding)
  if (#suffix > 0) then
    patch.diffs[#patch.diffs + 1] = {DIFF_EQUAL, suffix}
  end

  -- Roll back the start points.
  patch.start1 = patch.start1 - #prefix
  patch.start2 = patch.start2 - #prefix
  -- Extend the lengths.
  patch.length1 = patch.length1 + #prefix + #suffix
  patch.length2 = patch.length2 + #prefix + #suffix
end

--[[
* Given an array of patches, return another array that is identical.
* @param {Array.<_new_patch_obj>} patches Array of patch objects.
* @return {Array.<_new_patch_obj>} Array of patch objects.
--]]
function _patch_deepCopy(patches)
  local patchesCopy = {}
  for x, patch in ipairs(patches) do
    local patchCopy = _new_patch_obj()
    local diffsCopy = {}
    for i, diff in ipairs(patch.diffs) do
      diffsCopy[i] = {diff[1], diff[2]}
    end
    patchCopy.diffs = diffsCopy
    patchCopy.start1 = patch.start1
    patchCopy.start2 = patch.start2
    patchCopy.length1 = patch.length1
    patchCopy.length2 = patch.length2
    patchesCopy[x] = patchCopy
  end
  return patchesCopy
end

--[[
* Add some padding on text start and end so that edges can match something.
* Intended to be called only from within patch_apply.
* @param {Array.<_new_patch_obj>} patches Array of patch objects.
* @return {string} The padding string added to each side.
--]]
function _patch_addPadding(patches)
  local paddingLength = Patch_Margin
  local nullPadding = ''
  for x = 1, paddingLength do
    nullPadding = nullPadding .. strchar(x)
  end

  -- Bump all the patches forward.
  for x, patch in ipairs(patches) do
    patch.start1 = patch.start1 + paddingLength
    patch.start2 = patch.start2 + paddingLength
  end

  -- Add some padding on start of first diff.
  local patch = patches[1]
  local diffs = patch.diffs
  local firstDiff = diffs[1]
  if (firstDiff == nil) or (firstDiff[1] ~= DIFF_EQUAL) then
    -- Add nullPadding equality.
    tinsert(diffs, 1, {DIFF_EQUAL, nullPadding})
    patch.start1 = patch.start1 - paddingLength  -- Should be 0.
    patch.start2 = patch.start2 - paddingLength  -- Should be 0.
    patch.length1 = patch.length1 + paddingLength
    patch.length2 = patch.length2 + paddingLength
  elseif (paddingLength > #firstDiff[2]) then
    -- Grow first equality.
    local extraLength = paddingLength - #firstDiff[2]
    firstDiff[2] = strsub(nullPadding, #firstDiff[2] + 1) .. firstDiff[2]
    patch.start1 = patch.start1 - extraLength
    patch.start2 = patch.start2 - extraLength
    patch.length1 = patch.length1 + extraLength
    patch.length2 = patch.length2 + extraLength
  end

  -- Add some padding on end of last diff.
  patch = patches[#patches]
  diffs = patch.diffs
  local lastDiff = diffs[#diffs]
  if (lastDiff == nil) or (lastDiff[1] ~= DIFF_EQUAL) then
    -- Add nullPadding equality.
    diffs[#diffs + 1] = {DIFF_EQUAL, nullPadding}
    patch.length1 = patch.length1 + paddingLength
    patch.length2 = patch.length2 + paddingLength
  elseif (paddingLength > #lastDiff[2]) then
    -- Grow last equality.
    local extraLength = paddingLength - #lastDiff[2]
    lastDiff[2] = lastDiff[2] .. strsub(nullPadding, 1, extraLength)
    patch.length1 = patch.length1 + extraLength
    patch.length2 = patch.length2 + extraLength
  end

  return nullPadding
end

--[[
* 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.
* @param {Array.<_new_patch_obj>} patches Array of patch objects.
--]]
function _patch_splitMax(patches)
  local patch_size = Match_MaxBits
  local x = 1
  while true do
    local patch = patches[x]
    if patch == nil then
      return
    end
    if patch.length1 > patch_size then
      local bigpatch = patch
      -- Remove the big old patch.
      tremove(patches, x)
      x = x - 1
      local start1 = bigpatch.start1
      local start2 = bigpatch.start2
      local precontext = ''
      while bigpatch.diffs[1] do
        -- Create one of several smaller patches.
        local patch = _new_patch_obj()
        local empty = true
        patch.start1 = start1 - #precontext
        patch.start2 = start2 - #precontext
        if precontext ~= '' then
          patch.length1, patch.length2 = #precontext, #precontext
          patch.diffs[#patch.diffs + 1] = {DIFF_EQUAL, precontext}
        end
        while bigpatch.diffs[1] and (patch.length1 < patch_size-Patch_Margin) do
          local diff_type = bigpatch.diffs[1][1]
          local diff_text = bigpatch.diffs[1][2]
          if (diff_type == DIFF_INSERT) then
            -- Insertions are harmless.
            patch.length2 = patch.length2 + #diff_text
            start2 = start2 + #diff_text
            patch.diffs[#(patch.diffs) + 1] = bigpatch.diffs[1]
            tremove(bigpatch.diffs, 1)
            empty = false
          elseif (diff_type == DIFF_DELETE) and (#patch.diffs == 1)
           and (patch.diffs[1][1] == DIFF_EQUAL)
           and (#diff_text > 2 * patch_size) then
            -- This is a large deletion.  Let it pass in one chunk.
            patch.length1 = patch.length1 + #diff_text
            start1 = start1 + #diff_text
            empty = false
            patch.diffs[#patch.diffs + 1] = {diff_type, diff_text}
            tremove(bigpatch.diffs, 1)
          else
            -- Deletion or equality.
            -- Only take as much as we can stomach.
            diff_text = strsub(diff_text, 1,
            patch_size - patch.length1 - Patch_Margin)
            patch.length1 = patch.length1 + #diff_text
            start1 = start1 + #diff_text
            if (diff_type == DIFF_EQUAL) then
              patch.length2 = patch.length2 + #diff_text
              start2 = start2 + #diff_text
            else
              empty = false
            end
            patch.diffs[#patch.diffs + 1] = {diff_type, diff_text}
            if (diff_text == bigpatch.diffs[1][2]) then
              tremove(bigpatch.diffs, 1)
            else
              bigpatch.diffs[1][2]
                  = strsub(bigpatch.diffs[1][2], #diff_text + 1)
            end
          end
        end
        -- Compute the head context for the next patch.
        precontext = _diff_text2(patch.diffs)
        precontext = strsub(precontext, -Patch_Margin)
        -- Append the end context for this patch.
        local postcontext = strsub(_diff_text1(bigpatch.diffs), 1, Patch_Margin)
        if postcontext ~= '' then
          patch.length1 = patch.length1 + #postcontext
          patch.length2 = patch.length2 + #postcontext
          if patch.diffs[1]
              and (patch.diffs[#patch.diffs][1] == DIFF_EQUAL) then
            patch.diffs[#patch.diffs][2] = patch.diffs[#patch.diffs][2]
                .. postcontext
          else
            patch.diffs[#patch.diffs + 1] = {DIFF_EQUAL, postcontext}
          end
        end
        if not empty then
          x = x + 1
          tinsert(patches, x, patch)
        end
      end
    end
    x = x + 1
  end
end

--[[
* Emulate GNU diff's format.
* Header: @@ -382,8 +481,9 @@
* @return {string} The GNU diff string.
--]]
function _patch_appendText(patch, text)
  local coords1, coords2
  local length1, length2 = patch.length1, patch.length2
  local start1, start2 = patch.start1, patch.start2
  local diffs = patch.diffs

  if length1 == 1 then
    coords1 = start1
  else
    coords1 = ((length1 == 0) and (start1 - 1) or start1) .. ',' .. length1
  end

  if length2 == 1 then
    coords2 = start2
  else
    coords2 = ((length2 == 0) and (start2 - 1) or start2) .. ',' .. length2
  end
  text[#text + 1] = '@@ -' .. coords1 .. ' +' .. coords2 .. ' @@\n'

  local op
  -- Escape the body of the patch with %xx notation.
  for x, diff in ipairs(patch.diffs) do
    local diff_type = diff[1]
    if diff_type == DIFF_INSERT then
      op = '+'
    elseif diff_type == DIFF_DELETE then
      op = '-'
    elseif diff_type == DIFF_EQUAL then
      op = ' '
    end
    text[#text + 1] = op
        .. gsub(diffs[x][2], percentEncode_pattern, percentEncode_replace)
        .. '\n'
  end

  return text
end

-- Expose the API
local _M = {}

_M.DIFF_DELETE = DIFF_DELETE
_M.DIFF_INSERT = DIFF_INSERT
_M.DIFF_EQUAL = DIFF_EQUAL

_M.diff_main = diff_main
_M.diff_cleanupSemantic = diff_cleanupSemantic
_M.diff_cleanupEfficiency = diff_cleanupEfficiency
_M.diff_levenshtein = diff_levenshtein
_M.diff_prettyHtml = diff_prettyHtml

_M.match_main = match_main

_M.patch_make = patch_make
_M.patch_toText = patch_toText
_M.patch_fromText = patch_fromText
_M.patch_apply = patch_apply

-- Expose some non-API functions as well, for testing purposes etc.
_M.diff_commonPrefix = _diff_commonPrefix
_M.diff_commonSuffix = _diff_commonSuffix
_M.diff_commonOverlap = _diff_commonOverlap
_M.diff_halfMatch = _diff_halfMatch
_M.diff_bisect = _diff_bisect
_M.diff_cleanupMerge = _diff_cleanupMerge
_M.diff_cleanupSemanticLossless = _diff_cleanupSemanticLossless
_M.diff_text1 = _diff_text1
_M.diff_text2 = _diff_text2
_M.diff_toDelta = _diff_toDelta
_M.diff_fromDelta = _diff_fromDelta
_M.diff_xIndex = _diff_xIndex
_M.match_alphabet = _match_alphabet
_M.match_bitap = _match_bitap
_M.new_patch_obj = _new_patch_obj
_M.patch_addContext = _patch_addContext
_M.patch_splitMax = _patch_splitMax
_M.patch_addPadding = _patch_addPadding
_M.settings = settings

return _M

Show details Hide details

Change log

r103 by neil.fraser on Jan 11, 2012 Diff

Removing long/shorttext scoping or
dereferencing in all languages.
Modifying Lua's module structure to work
consistently.

Go to:

Project members, sign in to write a code review

Older revisions

r102 by neil.fraser on Jan 6, 2012 Diff

Adding complete Dart port of Diff
Match Patch.
Also misc cleanup of other versions
(no functional changes).

r101 by neil.fraser on Dec 22, 2011 Diff

Code cleanup:
  Updating from Lua 5.1 to 5.2.
  Removing all checklines code from
Lua due to lack of Unicode support.
  Fix warnings in latest version of
...

r100 by neil.fraser on Nov 17, 2011 Diff

Improve diff sliding algorithm to
encourage lining up and the end of
sentences.
This fixes  Issue 60 .

All revisions of this file

File info

Size: 73869 bytes, 2197 lines

View raw file