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/*
* Copyright 2008 Google Inc. All Rights Reserved.
* Copyright 2013-2014 Jan Krüger. All Rights Reserved.
* Author: fraser@google.com (Neil Fraser)
* Author: anteru@developer.shelter13.net (Matthaeus G. Chajdas)
* Author: jan@jandoe.de (Jan Krüger)
*
* 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.
*
* Diff Match and Patch
* http://code.google.com/p/google-diff-match-patch/
*/
module ddmp.diff;
import ddmp.util;
import std.array;
import std.conv;
import std.datetime : SysTime, Clock, UTC;
import std.exception : enforce;
import std.string : indexOf, endsWith, startsWith;
import std.uni;
import std.regex;
import std.algorithm : min, max;
import std.digest.sha;
import core.time;
Duration diffTimeout = 1.seconds;
int DIFF_EDIT_COST = 4;
/**
* Compute and return the source text (all equalities and deletions).
* @param diffs List of Diff objects.
* @return Source text.
*/
string diff_text1(Diff[] diffs) {
auto text = appender!string();
foreach ( d; diffs ) {
if (d.operation != Operation.INSERT) {
text.put(d.text);
}
}
return text.data();
}
/**
* Compute and return the destination text (all equalities and insertions).
* @param diffs List of Diff objects.
* @return Destination text.
*/
string diff_text2(Diff[] diffs) {
auto text = appender!string();
foreach ( d; diffs ) {
if (d.operation != Operation.DELETE) {
text.put(d.text);
}
}
return text.data();
}
/**
* Compute the Levenshtein distance; the number of inserted, deleted or
* substituted characters.
* @param diffs List of Diff objects.
* @return Number of changes.
*/
int levenshtein(Diff[] diffs) {
int levenshtein = 0;
int insertions = 0;
int deletions = 0;
foreach ( d ; diffs ) {
final switch (d.operation) {
case Operation.INSERT:
insertions += d.text.length;
break;
case Operation.DELETE:
deletions += d.text.length;
break;
case Operation.EQUAL:
// A deletion and an insertion is one substitution.
levenshtein += max(insertions, deletions);
insertions = 0;
deletions = 0;
break;
}
}
levenshtein += max(insertions, deletions);
return levenshtein;
}
/**
* 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 diffs Array of Diff objects.
* @return Delta text.
*/
string toDelta(in Diff[] diffs)
{
import std.range : walkLength;
import std.format : formattedWrite;
import std.uri : encode;
auto text = appender!string;
foreach (aDiff; diffs) {
final switch (aDiff.operation) {
case Operation.INSERT:
text.formattedWrite("+%s\t", encode(aDiff.text).replace("%20", " "));
break;
case Operation.DELETE:
text.formattedWrite("-%s\t", aDiff.text.walkLength);
break;
case Operation.EQUAL:
text.formattedWrite("=%s\t", aDiff.text.walkLength);
break;
}
}
string delta = text.data;
if (delta.length != 0) {
// Strip off trailing tab character.
delta = delta[0 .. $-1];
delta = unescapeForEncodeUriCompatibility(delta);
}
return delta;
}
/**
* Given the original text1, and an encoded string which describes the
* operations required to transform text1 into text2, comAdde the full diff.
* @param text1 Source string for the diff.
* @param delta Delta text.
* @return Array of Diff objects or null if invalid.
* @throws ArgumentException If invalid input.
*/
Diff[] fromDelta(string text1, string delta)
{
import std.algorithm;
import std.range;
import std.string : format;
import std.uri : decodeComponent;
auto diffs = appender!(Diff[]);
foreach (token; delta.splitter("\t")) {
if (token.length == 0) {
// Blank tokens are ok (from a trailing \t).
continue;
}
// Each token begins with a one character parameter which specifies the
// operation of this token (delete, insert, equality).
string param = token[1 .. $];
switch (token[0]) {
case '+':
// decode would change all "+" to " "
param = param.replace("+", "%2b");
param = decodeComponent(param);
//} catch (UnsupportedEncodingException e) {
// // Not likely on modern system.
// throw new Error("This system does not support UTF-8.", e);
//} catch (IllegalArgumentException e) {
// // Malformed URI sequence.
// throw new IllegalArgumentException(
// "Illegal escape in diff_fromDelta: " + param, e);
//}
diffs ~= Diff(Operation.INSERT, param);
break;
case '-': // Fall through.
case '=':
int n;
try {
n = param.to!int;
} catch (ConvException e) {
throw new Exception("Invalid number in diff_fromDelta: " ~ param);
}
enforce (n >= 0, "Negative number in diff_fromDelta: " ~ param);
string text;
enforce (n <= text1.walkLength, "Delta length larger than source text length.");
text = text1.takeExactly(n).array.to!string;
text1.popFrontN(n);
if (token[0] == '=') {
diffs ~= Diff(Operation.EQUAL, text);
} else {
diffs ~= Diff(Operation.DELETE, text);
}
break;
default:
// Anything else is an error.
throw new Exception(
"Invalid diff operation in diff_fromDelta: " ~ token[0]);
}
}
if (text1.length > 0)
throw new Exception("Delta length smaller than source text length.");
return diffs.data;
}
struct LinesToCharsResult {
string text1;
string text2;
string[] uniqueStrings;
bool opEquals()(auto ref const LinesToCharsResult other) const {
return text1 == other.text1 &&
text2 == other.text2 &&
uniqueStrings == other.uniqueStrings;
}
}
LinesToCharsResult linesToChars(string text1, string text2)
{
size_t[string] lineHash;
LinesToCharsResult res;
res.uniqueStrings = [""];
res.text1 = linesToCharsMunge(text1, res.uniqueStrings, lineHash);
res.text2 = linesToCharsMunge(text2, res.uniqueStrings, lineHash);
return res;
}
string linesToCharsMunge(string text, ref string[] lines, ref size_t[string] linehash)
{
sizediff_t lineStart = 0;
sizediff_t lineEnd = -1;
string line;
auto chars = appender!string();
while( lineEnd+1 < text.length ){
lineEnd = text.indexOfAlt("\n", lineStart);
if( lineEnd == -1 ) lineEnd = text.length - 1;
line = text[lineStart..lineEnd + 1];
lineStart = lineEnd + 1;
if (auto pv = line in linehash) {
chars ~= cast(dchar)*pv;
} else {
lines ~= line;
linehash[line] = lines.length - 1;
chars ~= cast(dchar)(lines.length -1);
}
}
return chars.data();
}
void charsToLines(Diff[] diffs, string[] lineArray)
{
foreach (ref d; diffs) {
auto str = appender!string();
foreach (dchar ch; d.text)
str.put(lineArray[ch]);
d.text = str.data();
}
}
size_t commonPrefix(string text1, string text2)
{
auto n = min(text1.length, text2.length);
foreach (i; 0 .. n)
if (text1[i] != text2[i])
return i;
return n;
}
size_t commonSuffix(string text1, string text2)
{
auto n = min(text1.length, text2.length);
foreach (i; 1 .. n+1)
if (text1[$-i] != text2[$-i])
return i-1;
return n;
}
/**
* Determine if the suffix of one string is the prefix of another.
* @param text1 First string.
* @param text2 Second string.
* @return The number of characters common to the end of the first
* string and the start of the second string.
*/
size_t commonOverlap(string text1, string text2) {
// Cache the text lengths to prevent multiple calls.
auto text1_length = text1.length;
auto text2_length = text2.length;
// Eliminate the null case.
if (text1_length == 0 || text2_length == 0) return 0;
// Truncate the longer string.
if (text1_length > text2_length) {
text1 = text1[$ - text2_length .. $];
} else if (text1_length < text2_length) {
text2 = text2[0 .. text1_length];
}
auto text_length = min(text1_length, text2_length);
// Quick check for the worst case.
if (text1 == text2) {
return text_length;
}
// Start by looking for a single character match
// and increase length until no match is found.
// Performance analysis: http://neil.fraser.name/news/2010/11/04/
int best = 0;
int length = 1;
while (true) {
string pattern = text1[text_length - length .. $];
auto found = text2.indexOf(pattern);
if (found == -1) {
return best;
}
length += found;
if (found == 0 || text1[text_length - length .. $] == text2[0 .. length]) {
best = length;
length++;
}
}
}
/**-
* The data structure representing a diff is a List of Diff objects:
* {Diff(Operation.DELETE, "Hello"), Diff(Operation.INSERT, "Goodbye"),
* Diff(Operation.EQUAL, " world.")}
* which means: delete "Hello", add "Goodbye" and keep " world."
*/
enum Operation {
DELETE,
INSERT,
EQUAL
}
/**
* Struct representing one diff operation.
*/
struct Diff {
Operation operation;
string text;
this(Operation operation, string text)
{
this.operation = operation;
this.text = text;
}
string toString()
{
//string prettyText = text.replace('\n', '\u00b6');
string op;
final switch(operation) {
case Operation.DELETE:
op = "DELETE"; break;
case Operation.INSERT:
op = "INSERT"; break;
case Operation.EQUAL:
op = "EQUAL"; break;
}
return "Diff(" ~ op ~ ",\"" ~ text ~ "\")";
}
bool opEquals(const Diff other) const
{
return operation == other.operation && text == other.text;
}
}
/**
* Find the differences between two texts.
* Run a faster, slightly less optimal diff.
* This method allows the 'checklines' of diff_main() to be optional.
* Most of the time checklines is wanted, so default to true.
* @param text1 Old string to be diffed.
* @param text2 New string to be diffed.
* @return List of Diff objects.
*/
Diff[] diff_main(string text1, string text2)
{
return diff_main(text1, text2, true);
}
/**
* Find the differences between two texts.
* @param text1 Old string to be diffed.
* @param text2 New string to be diffed.
* @param checklines Speedup flag. If false, then don't run a
* line-level diff first to identify the changed areas.
* If true, then run a faster slightly less optimal diff.
* @return List of Diff objects.
*/
Diff[] diff_main(string text1, string text2, bool checklines)
{
// Set a deadline by which time the diff must be complete.
SysTime deadline;
if (diffTimeout <= 0.seconds) {
deadline = SysTime.max;
} else {
deadline = Clock.currTime(UTC()) + diffTimeout;
}
return diff_main(text1, text2, checklines, deadline);
}
/**
* Find the differences between two texts. Simplifies the problem by
* stripping any common prefix or suffix off the texts before diffing.
* @param text1 Old string to be diffed.
* @param text2 New string to be diffed.
* @param checklines Speedup flag. If false, then don't run a
* line-level diff first to identify the changed areas.
* If true, then run a faster slightly less optimal diff.
* @param deadline Time when the diff should be complete by. Used
* internally for recursive calls. Users should set DiffTimeout
* instead.
* @return List of Diff objects.
*/
Diff[] diff_main(string text1, string text2, bool checklines, SysTime deadline)
{
Diff[] diffs;
if( text1 == text2 ){
if( text1.length != 0 ) diffs ~= Diff(Operation.EQUAL, text1);
return diffs;
}
auto pos = commonPrefix(text1, text2);
auto prefix = text1[0 .. pos];
text1 = text1[pos .. $];
text2 = text2[pos .. $];
pos = commonSuffix(text1, text2);
auto suffix = text1[$ - pos .. $];
text1 = text1[0 .. $ - pos];
text2 = text2[0 .. $ - pos];
// Compute the diff on the middle block.
diffs = computeDiffs(text1, text2, checklines, deadline);
// Restore the prefix and suffix.
if( prefix.length != 0 ) {
diffs.insert(0, [Diff(Operation.EQUAL, prefix)]);
}
if( suffix.length != 0 ) {
diffs ~= Diff(Operation.EQUAL, suffix);
}
cleanupMerge(diffs);
return diffs;
}
struct HalfMatch {
string prefix1;
string suffix1;
string suffix2;
string prefix2;
string commonMiddle;
bool opEquals()(auto ref const HalfMatch other) const {
return prefix1 == other.prefix1 &&
suffix1 == other.suffix1 &&
prefix2 == other.prefix2 &&
suffix2 == other.suffix2;
}
}
/*
* Do the two texts share a Substring which is at least half the length of
* the longer text?
* This speedup can produce non-minimal diffs.
* @param text1 First string.
* @param text2 Second string.
* @return Five element String array, containing the prefix of text1, the
* suffix of text1, the prefix of text2, the suffix of text2 and the
* common middle. Or null if there was no match.
*/
bool halfMatch(string text1, string text2, out HalfMatch halfmatch){
if (diffTimeout <= 0.seconds) {
// Don't risk returning a non-optimal diff if we have unlimited time.
return false;
}
string longtext = text1.length > text2.length ? text1 : text2;
string shorttext = text1.length > text2.length ? text2 : text1;
if( longtext.length < 4 || shorttext.length * 2 < longtext.length ) return false; //pointless
HalfMatch hm1;
HalfMatch hm2;
auto is_hm1 = halfMatchI(longtext, shorttext, (longtext.length + 3) / 4, hm1);
auto is_hm2 = halfMatchI(longtext, shorttext, (longtext.length + 1) / 2, hm2);
HalfMatch hm;
if( !is_hm1 && !is_hm2 ){
return false;
} else if( !is_hm2 ){
hm = hm1;
} else if( !is_hm1 ){
hm = hm2;
} else {
hm = hm1.commonMiddle.length > hm2.commonMiddle.length ? hm1 : hm2;
}
if( text1.length > text2.length ) {
halfmatch = hm;
return true;
}
halfmatch.prefix1 = hm.prefix2;
halfmatch.suffix1 = hm.suffix2;
halfmatch.prefix2 = hm.prefix1;
halfmatch.suffix2 = hm.suffix1;
halfmatch.commonMiddle = hm.commonMiddle;
return true;
}
bool halfMatchI(string longtext, string shorttext, sizediff_t i, out HalfMatch hm){
auto seed = longtext.substr(i, longtext.length / 4);
sizediff_t j = -1;
string best_common;
string best_longtext_a;
string best_longtext_b;
string best_shorttext_a;
string best_shorttext_b;
while( j < cast(sizediff_t)shorttext.length && ( j = shorttext.indexOfAlt(seed, j + 1)) != -1 ){
auto prefixLen = commonPrefix(longtext[i .. $], shorttext[j .. $]);
auto suffixLen = commonSuffix(longtext[0 .. i], shorttext[0 .. j]);
if( best_common.length < suffixLen + prefixLen ) {
best_common = shorttext.substr(j - suffixLen, suffixLen) ~ shorttext.substr(j, prefixLen);
best_longtext_a = longtext[0 .. i - suffixLen];
best_longtext_b = longtext[i + prefixLen .. $];
best_shorttext_a = shorttext[0 .. j - suffixLen];
best_shorttext_b = shorttext[j + prefixLen .. $];
}
}
if( best_common.length * 2 >= longtext.length ) {
hm.prefix1 = best_longtext_a;
hm.suffix1 = best_longtext_b;
hm.prefix2 = best_shorttext_a;
hm.suffix2 = best_shorttext_b;
hm.commonMiddle = best_common;
return true;
} else {
return false;
}
}
/**
* Find the differences between two texts. Assumes that the texts do not
* have any common prefix or suffix.
* @param text1 Old string to be diffed.
* @param text2 New string to be diffed.
* @param checklines Speedup flag. If false, then don't run a
* line-level diff first to identify the changed areas.
* If true, then run a faster slightly less optimal diff.
* @param deadline Time when the diff should be complete by.
* @return List of Diff objects.
*/
Diff[] computeDiffs(string text1, string text2, bool checklines, SysTime deadline)
{
Diff[] diffs;
if( text1.length == 0 ){
diffs ~= Diff(Operation.INSERT, text2);
return diffs;
}
if( text2.length == 0 ){
diffs ~= Diff(Operation.DELETE, text1);
return diffs;
}
auto longtext = text1.length > text2.length ? text1 : text2;
auto shorttext = text1.length > text2.length ? text2 : text1;
auto i = longtext.indexOf(shorttext);
if( i != -1 ){
Operation op = (text1.length > text2.length) ? Operation.DELETE : Operation.INSERT;
diffs ~= Diff(op, longtext[0 .. i]);
diffs ~= Diff(Operation.EQUAL, shorttext);
diffs ~= Diff(op, longtext[i + shorttext.length .. $]);
return diffs;
}
if( shorttext.length == 1 ){
diffs ~= Diff(Operation.DELETE, text1);
diffs ~= Diff(Operation.INSERT, text2);
return diffs;
}
HalfMatch hm;
auto is_hm = halfMatch(text1, text2, hm);
if( is_hm ){
auto diffs_a = diff_main(hm.prefix1, hm.prefix2, checklines, deadline);
auto diffs_b = diff_main(hm.suffix1, hm.suffix2, checklines, deadline);
diffs = diffs_a;
diffs ~= Diff(Operation.EQUAL, hm.commonMiddle);
diffs ~= diffs_b;
return diffs;
}
if( checklines && text1.length > 100 && text2.length > 100 ){
return diff_lineMode(text1, text2, deadline);
}
return bisect(text1, text2, deadline);
}
Diff[] diff_lineMode(string text1, string text2, SysTime deadline)
{
auto b = linesToChars(text1, text2);
auto diffs = diff_main(b.text1, b.text2, false, deadline);
charsToLines(diffs, b.uniqueStrings);
cleanupSemantic(diffs);
diffs ~= Diff(Operation.EQUAL, "");
auto pointer = 0;
auto count_delete = 0;
auto count_insert = 0;
string text_delete;
string text_insert;
while( pointer < diffs.length ){
final switch( diffs[pointer].operation ) {
case Operation.INSERT:
count_insert++;
text_insert ~= diffs[pointer].text;
break;
case Operation.DELETE:
count_delete++;
text_delete ~= diffs[pointer].text;
break;
case Operation.EQUAL:
if( count_delete >= 1 && count_insert >= 1 ){
diffs.remove(pointer - count_delete - count_insert,
count_delete + count_insert);
pointer = pointer - count_delete - count_insert;
auto a = diff_main(text_delete, text_insert, false, deadline);
diffs.insert(pointer, a);
pointer += a.length;
}
count_insert = 0;
count_delete = 0;
text_delete = "";
text_insert = "";
break;
}
pointer++;
}
diffs.remove(diffs.length - 1);
return diffs;
}
Diff[] bisect(string text1, string text2, SysTime deadline)
{
auto text1_len = text1.length;
auto text2_len = text2.length;
auto max_d = (text1_len + text2_len + 1) / 2;
auto v_offset = max_d;
auto v_len = 2 * max_d;
sizediff_t[] v1;
sizediff_t[] v2;
for( auto x = 0; x < v_len; x++ ){
v1 ~= -1;
v2 ~= -1;
}
v1[v_offset + 1] = 0;
v2[v_offset + 1] = 0;
auto delta = text1_len - text2_len;
bool front = (delta % 2 != 0);
auto k1start = 0;
auto k1end = 0;
auto k2start = 0;
auto k2end = 0;
for( auto d = 0; d < max_d; d++ ){
// Bail out if deadline is reached.
if (Clock.currTime(UTC()) > deadline) {
break;
}
for( auto k1 = -d + k1start; k1 <= d - k1end; k1 += 2 ){
auto k1_offset = v_offset + k1;
sizediff_t x1;
if( k1 == -d || k1 != d && v1[k1_offset - 1] < v1[k1_offset + 1] ) {
x1 = v1[k1_offset + 1];
} else {
x1 = v1[k1_offset - 1] + 1;
}
auto y1 = x1 - k1;
while( x1 < text1_len && y1 < text2_len && text1[x1] == text2[y1] ){
x1++;
y1++;
}
v1[k1_offset] = x1;
if( x1 > text1_len) {
k1end += 2;
} else if( y1 > text2_len ){
k1start += 2;
} else if( front ){
auto k2_offset = v_offset + delta - k1;
if( k2_offset >= 0 && k2_offset < v_len && v2[k2_offset] != -1) {
auto x2 = text1_len - v2[k2_offset];
if( x1 >= x2 ) return bisectSplit(text1, text2, x1, y1, deadline);
}
}
}
for( auto k2 = -d + k2start; k2 <= d - k2end; k2 += 2) {
auto k2_offset = v_offset + k2;
sizediff_t x2;
if (k2 == -d || k2 != d && v2[k2_offset - 1] < v2[k2_offset + 1]) {
x2 = v2[k2_offset + 1];
} else {
x2 = v2[k2_offset - 1] + 1;
}
auto y2 = x2 - k2;
while( x2 < text1_len && y2 < text2_len
&& text1[text1_len - x2 - 1]
== text2[text2_len - y2 - 1] ){
x2++;
y2++;
}
v2[k2_offset] = x2;
if (x2 > text1_len) {
// Ran off the left of the graph.
k2end += 2;
} else if (y2 > text2_len) {
// Ran off the top of the graph.
k2start += 2;
} else if (!front) {
auto k1_offset = v_offset + delta - k2;
if (k1_offset >= 0 && k1_offset < v_len && v1[k1_offset] != -1) {
auto x1 = v1[k1_offset];
auto y1 = v_offset + x1 - k1_offset;
// Mirror x2 onto top-left coordinate system.
x2 = text1_len - v2[k2_offset];
if (x1 >= x2) {
// Overlap detected.
return bisectSplit(text1, text2, x1, y1, deadline);
}
}
}
}
}
Diff[] diffs;
diffs ~= Diff(Operation.DELETE, text1);
diffs ~= Diff(Operation.INSERT, text2);
return diffs;
}
Diff[] bisectSplit(string text1, string text2, sizediff_t x, sizediff_t y, SysTime deadline)
{
auto text1a = text1[0 .. x];
auto text2a = text2[0 .. y];
auto text1b = text1[x .. $];
auto text2b = text2[y .. $];
Diff[] diffs = diff_main(text1a, text2a, false, deadline);
Diff[] diffsb = diff_main(text1b, text2b, false, deadline);
diffs ~= diffsb;
return diffs;
}
void cleanupSemantic(ref Diff[] diffs)
{
bool changes = false;
size_t[] equalities;
string last_equality = null;
size_t pointer = 0;
size_t length_insertions1 = 0;
size_t length_deletions1 = 0;
size_t length_insertions2 = 0;
size_t length_deletions2 = 0;
while( pointer < diffs.length) {
if( diffs[pointer].operation == Operation.EQUAL ){
equalities ~= pointer;
length_insertions1 = length_insertions2;
length_deletions1 = length_deletions2;
length_insertions2 = 0;
length_deletions2 = 0;
last_equality = diffs[pointer].text;
} else {
if( diffs[pointer].operation == Operation.INSERT ){
length_insertions2 += diffs[pointer].text.length;
} else {
length_deletions2 += diffs[pointer].text.length;
}
if( last_equality !is null &&
(last_equality.length <= max(length_insertions1, length_deletions1))
&& (last_equality.length <= max(length_insertions2, length_deletions2)))
{
// Duplicate record.
diffs.insert(equalities[$-1], [Diff(Operation.DELETE, last_equality)]);
diffs[equalities[$-1]+1] = Diff(Operation.INSERT, diffs[equalities[$-1]+1].text);
// Throw away the equality we just deleted.
equalities.length--;
if (equalities.length > 0) {
// Throw away the previous equality (it needs to be reevaluated).
equalities.length--;
}
equalities.assumeSafeAppend();
pointer = equalities.length > 0 ? equalities[$-1] : -1;
length_insertions1 = 0;
length_deletions1 = 0;
length_insertions2 = 0;
length_deletions2 = 0;
last_equality = null;
changes = true;
}
}
pointer++;
}
if( changes ) {
cleanupMerge(diffs);
}
cleanupSemanticLossless(diffs);
// Find any overlaps between deletions and insertions.
// e.g: <del>abcxxx</del><ins>xxxdef</ins>
// -> <del>abc</del>xxx<ins>def</ins>
// e.g: <del>xxxabc</del><ins>defxxx</ins>
// -> <ins>def</ins>xxx<del>abc</del>
// Only extract an overlap if it is as big as the edit ahead or behind it.
pointer = 1;
while( pointer < diffs.length ){
if( diffs[pointer - 1].operation == Operation.DELETE &&
diffs[pointer].operation == Operation.INSERT) {
auto deletion = diffs[pointer - 1].text;
auto insertion = diffs[pointer].text;
auto overlap_len1 = commonOverlap(deletion, insertion);
auto overlap_len2 = commonOverlap(insertion, deletion);
if( overlap_len1 >= overlap_len2 ){
if( overlap_len1 * 2 >= deletion.length ||
overlap_len1 * 2 >= insertion.length) {
//Overlap found.
//Insert an equality and trim the surrounding edits.
diffs.insert(pointer, [Diff(Operation.EQUAL, insertion[0 .. overlap_len1])]);
diffs[pointer - 1].text = deletion[0 .. $ - overlap_len1];
diffs[pointer + 1].text = insertion[overlap_len1 .. $];
pointer++;
}
} else {
if( overlap_len2 * 2 >= deletion.length ||
overlap_len2 * 2 >= insertion.length) {
diffs.insert(pointer, [Diff(Operation.EQUAL, deletion[0 .. overlap_len2])]);
diffs[pointer - 1].operation = Operation.INSERT;
diffs[pointer - 1].text = insertion[0 .. $ - overlap_len2];
diffs[pointer + 1].operation = Operation.DELETE;
diffs[pointer + 1].text = deletion[overlap_len2 .. $];
pointer++;
}
}
pointer++;
}
pointer++;
}
}
/**
* Look for single edits surrounded on both sides by equalities
* which can be shifted sideways to align the edit to a word boundary.
* e.g: The c<ins>at c</ins>ame. -> The <ins>cat </ins>came.
* @param diffs List of Diff objects.
*/
void cleanupSemanticLossless(ref Diff[] diffs)
{
auto pointer = 1;
// Intentionally ignore the first and last element (don't need checking).
while( pointer < cast(sizediff_t)(diffs.length) - 1 ){
if( diffs[pointer-1].operation == Operation.EQUAL &&
diffs[pointer+1].operation == Operation.EQUAL) {
// This is a single edit surrounded by equalities.
auto equality1 = diffs[pointer-1].text;
auto edit = diffs[pointer].text;
auto equality2 = diffs[pointer+1].text;
// First, shift the edit as far left as possible
auto commonOffset = commonSuffix(equality1, edit);
if( commonOffset > 0 ){
auto commonString = edit[$ - commonOffset .. $];
equality1 = equality1[0 .. $ - commonOffset];
edit = commonString ~ edit[0 .. $ - commonOffset];
equality2 = commonString ~ equality2;
}
// Second, step character by character right,
// looking for the best fit.
auto best_equality1 = equality1;
auto best_edit = edit;
auto best_equality2 = equality2;
auto best_score = cleanupSemanticScore(equality1, edit) + cleanupSemanticScore(edit, equality2);
while( edit.length != 0 && equality2.length != 0 && edit[0] == equality2[0]){
equality1 ~= edit[0];
edit = edit[1 .. $] ~ equality2[0];
equality2 = equality2[1 .. $];
auto score = cleanupSemanticScore(equality1, edit) + cleanupSemanticScore(edit, equality2);
// The >= encourages trailing rather than leading whitespace on
// edits.
if (score >= best_score) {
best_score = score;
best_equality1 = equality1;
best_edit = edit;
best_equality2 = equality2;
}
}
if( diffs[pointer-1].text != best_equality1 ){
// We have an improvement, save it back to the diff.
if( best_equality1.length != 0) {
diffs[pointer-1].text = best_equality1;
} else {
diffs.remove(pointer - 1);
pointer--;
}
diffs[pointer].text = best_edit;
if( best_equality2.length != 0 ){
diffs[pointer+1].text = best_equality2;
} else {
diffs.remove(pointer + 1);
pointer--;
}
}
}
pointer++;
}
}
/**
* Reorder and merge like edit sections. Merge equalities.
* Any edit section can move as sizediff_t as it doesn't cross an equality.
* @param diffs List of Diff objects.
*/
void cleanupMerge(ref Diff[] diffs) {
diffs ~= Diff(Operation.EQUAL, "");
size_t pointer = 0;
size_t count_delete = 0;
size_t count_insert = 0;
string text_delete;
string text_insert;
while(pointer < diffs.length) {
final switch(diffs[pointer].operation){
case Operation.INSERT:
count_insert++;
text_insert ~= diffs[pointer].text;
pointer++;
break;
case Operation.DELETE:
count_delete++;
text_delete ~= diffs[pointer].text;
pointer++;
break;
case Operation.EQUAL:
// Upon reaching an equality, check for prior redundancies.
if (count_delete + count_insert > 1) {
if (count_delete != 0 && count_insert != 0) {
// Factor out any common prefixies.
if (auto commonlength = commonPrefix(text_insert, text_delete)) {
if (pointer > count_delete + count_insert &&
diffs[pointer - count_delete - count_insert - 1].operation
== Operation.EQUAL)
{
diffs[pointer - count_delete - count_insert - 1].text
~= text_insert[0 .. commonlength];
} else {
diffs.insert(0, [Diff(Operation.EQUAL, text_insert[0 .. commonlength])]);
pointer++;
}
text_insert = text_insert[commonlength .. $];
text_delete = text_delete[commonlength .. $];
}
// Factor out any common suffixies.
if (auto commonlength = commonSuffix(text_insert, text_delete)) {
diffs[pointer].text = text_insert[$ - commonlength .. $] ~ diffs[pointer].text;
text_insert = text_insert[0 .. $ - commonlength];
text_delete = text_delete[0 .. $ - commonlength];
}
}
// Delete the offending records and add the merged ones.
if (count_delete == 0) {
diffs.splice(pointer - count_insert, count_delete + count_insert, [Diff(Operation.INSERT, text_insert)]);
} else if (count_insert == 0) {
diffs.splice(pointer - count_delete, count_delete + count_insert, [Diff(Operation.DELETE, text_delete)]);
} else {
diffs.splice(pointer - count_delete - count_insert, count_delete + count_insert, [Diff(Operation.DELETE, text_delete), Diff(Operation.INSERT, text_insert)]);
}
pointer = pointer - count_delete - count_insert +
(count_delete != 0 ? 1 : 0) + (count_insert != 0 ? 1 : 0) + 1;
} else if( pointer != 0 && diffs[pointer-1].operation == Operation.EQUAL ){
diffs[pointer - 1].text ~= diffs[pointer].text;
diffs.remove(pointer);
} else {
pointer++;
}
count_insert = 0;
count_delete = 0;
text_delete = "";
text_insert = "";
break;
}
}
if( diffs[$-1].text.length == 0){
diffs.length--;
}
bool changes = false;
pointer = 1;
while( pointer + 1 < diffs.length ) {
if( diffs[pointer - 1].operation == Operation.EQUAL &&
diffs[pointer + 1].operation == Operation.EQUAL)
{
if( diffs[pointer].text.endsWith(diffs[pointer - 1].text)) {
diffs[pointer].text = diffs[pointer - 1].text ~ diffs[pointer].text[0 .. $ - diffs[pointer - 1].text.length];
diffs[pointer + 1].text = diffs[pointer - 1].text ~ diffs[pointer + 1].text;
diffs.splice(pointer - 1, 1);
changes = true;
} else if( diffs[pointer].text.startsWith(diffs[pointer + 1].text)) {
diffs[pointer - 1].text ~= diffs[pointer + 1].text;
diffs[pointer].text =
diffs[pointer].text[diffs[pointer + 1].text.length .. $]
~ diffs[pointer + 1].text;
diffs.splice(pointer + 1, 1);
changes = true;
}
}
pointer++;
}
if( changes ) cleanupMerge(diffs);
}
/**
* Given two strings, comAdde a score representing whether the internal
* boundary falls on logical boundaries.
* Scores range from 6 (best) to 0 (worst).
* @param one First string.
* @param two Second string.
* @return The score.
*/
int cleanupSemanticScore(string one, string two)
{
if( one.length == 0 || two.length == 0) return 6; //Edges are the best
auto char1 = one[$-1];
auto char2 = two[0];
auto nonAlphaNumeric1 = !(isAlpha(char1) || isNumber(char1));
auto nonAlphaNumeric2 = !(isAlpha(char2) || isNumber(char2));
auto whitespace1 = nonAlphaNumeric1 && isWhite(char1);
auto whitespace2 = nonAlphaNumeric2 && isWhite(char2);
auto lineBreak1 = whitespace1 && isControl(char1);
auto lineBreak2 = whitespace2 && isControl(char2);
auto blankLine1 = lineBreak1 && match(one, `\n\r?\n\Z`);
auto blankLine2 = lineBreak2 && match(two, `\A\r?\n\r?\n`);
if (blankLine1 || blankLine2) return 5;
else if (lineBreak1 || lineBreak2) return 4;
else if (nonAlphaNumeric1 && !whitespace1 && whitespace2) return 3;
else if (whitespace1 || whitespace2) return 2;
else if (nonAlphaNumeric1 || nonAlphaNumeric2) return 1;
return 0;
}
/**
* Reduce the number of edits by eliminating operationally trivial
* equalities.
* @param diffs List of Diff objects.
*/
void cleanupEfficiency(ref Diff[] diffs) {
bool changes = false;
size_t[] equalities;
string lastequality;
size_t pointer = 0;
auto pre_ins = false;
auto pre_del = false;
auto post_ins = false;
auto post_del = false;
while( pointer < diffs.length ){
if( diffs[pointer].operation == Operation.EQUAL ){
if( diffs[pointer].text.length < DIFF_EDIT_COST && (post_ins || post_del)) {
equalities ~= pointer;
pre_ins = post_ins;
pre_del = post_del;
lastequality = diffs[pointer].text;
} else {
equalities.length = 0;
equalities.assumeSafeAppend;
lastequality = "";
}
post_ins = false;
post_del = false;
} else {
if( diffs[pointer].operation == Operation.DELETE ){
post_del = true;
} else {
post_ins = true;
}
if( lastequality.length != 0
&& (
(pre_ins && pre_del && post_ins && post_del)
|| ((lastequality.length < DIFF_EDIT_COST / 2)
&& ((pre_ins ? 1 : 0) + (pre_del ? 1 : 0) + (post_ins ? 1 : 0) + (post_del ? 1 : 0)) == 3)
)
)
{
diffs.insert(equalities[$-1], [Diff(Operation.DELETE, lastequality)]);
diffs[equalities[$-1] + 1].operation = Operation.INSERT;
equalities.length--;
equalities.assumeSafeAppend;
lastequality = "";
if( pre_ins && pre_del ){
post_ins = true;
post_del = true;
equalities.length = 0;
equalities.assumeSafeAppend;
} else {
if( equalities.length > 0 ) {
equalities.length--;
equalities.assumeSafeAppend;
}
pointer = equalities.length > 0 ? equalities[$-1] : -1;
post_ins = false;
post_del = false;
}
changes = true;
}
}
pointer++;
}
if( changes ){
cleanupMerge(diffs);
}
}
/**
* loc is a location in text1, comAdde and return the equivalent location in
* text2.
* e.g. "The cat" vs "The big cat", 1->1, 5->8
* @param diffs List of Diff objects.
* @param loc Location within text1.
* @return Location within text2.
*/
sizediff_t xIndex(Diff[] diffs, sizediff_t loc){
auto chars1 = 0;
auto chars2 = 0;
auto last_chars1 = 0;
auto last_chars2 = 0;
Diff lastDiff;
foreach ( diff; diffs) {
if (diff.operation != Operation.INSERT) {
// Equality or deletion.
chars1 += diff.text.length;
}
if (diff.operation != Operation.DELETE) {
// Equality or insertion.
chars2 += diff.text.length;
}
if (chars1 > loc) {
// Overshot the location.
lastDiff = diff;
break;
}
last_chars1 = chars1;
last_chars2 = chars2;
}
if (lastDiff.operation == Operation.DELETE) {
// The location was deleted.
return last_chars2;
}
// Add the remaining character length.
return last_chars2 + (loc - last_chars1);
}
/**
* Unescape selected chars for compatability with JavaScript's encodeURI.
* In speed critical applications this could be dropped since the
* receiving application will certainly decode these fine.
* Note that this function is case-sensitive. Thus "%3F" would not be
* unescaped. But this is ok because it is only called with the output of
* HttpUtility.UrlEncode which returns lowercase hex.
*
* Example: "%3f" -> "?", "%24" -> "$", etc.
*
* @param str The string to escape.
* @return The escaped string.
*/
public static string unescapeForEncodeUriCompatibility(string str)
{
// FIXME: this is ridiculously inefficient
return str.replace("%21", "!").replace("%7e", "~")
.replace("%27", "'").replace("%28", "(").replace("%29", ")")
.replace("%3b", ";").replace("%2f", "/").replace("%3f", "?")
.replace("%3a", ":").replace("%40", "@").replace("%26", "&")
.replace("%3d", "=").replace("%2b", "+").replace("%24", "$")
.replace("%2c", ",").replace("%23", "#");
}