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Copy pathdiff_match_patch.lua
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2184 lines (2047 loc) · 71.8 KB
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--[[
* Diff Match and Patch
* Copyright 2018 The diff-match-patch Authors.
* https://github.com/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' -- <https://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 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 = {
['&'] = '&', ['<'] = '<', ['>'] = '>', ['\n'] = '¶<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 (strsub(text1, x1, x1) == strsub(text2, y1, 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 (strsub(text1, -x2, -x2) == strsub(text2, -y2, -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: https://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: https://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: https://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)
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