diff-match-patch/lua/diff_match_patch.lua at master · google/diff-match-patch · GitHub

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--[[

* Diff Match and Patch

* 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

-- ---------------------------------------------------------------------------

-- 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

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

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

pointer = pointer + 1

end

pointer = pointer + 1

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)

(

(#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

pointer = pointer + 1

end

if changes then

_diff_cleanupMerge(diffs)

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

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

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.

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

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

-- 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

-- 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

--[[

* 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

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

--[[

* 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)

View remainder of file in raw view

diff-match-patch/lua/diff_match_patch.lua at master · google/diff-match-patch · GitHub

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