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diff_match_patch.cpp
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/*
* Diff Match and Patch
* Copyright 2018 The diff-match-patch Authors.
* https://github.com/google/diff-match-patch
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include <algorithm>
#include <limits>
// Code known to compile and run with Qt 4.3 through Qt 4.7.
#include <QtCore>
#include <time.h>
#include "diff_match_patch.h"
//////////////////////////
//
// Diff Class
//
//////////////////////////
/**
* Constructor. Initializes the diff with the provided values.
* @param operation One of INSERT, DELETE or EQUAL
* @param text The text being applied
*/
Diff::Diff(Operation _operation, const QString &_text) :
operation(_operation), text(_text) {
// Construct a diff with the specified operation and text.
}
Diff::Diff() {
}
QString Diff::strOperation(Operation op) {
switch (op) {
case INSERT:
return "INSERT";
case DELETE:
return "DELETE";
case EQUAL:
return "EQUAL";
}
throw "Invalid operation.";
}
/**
* Display a human-readable version of this Diff.
* @return text version
*/
QString Diff::toString() const {
QString prettyText = text;
// Replace linebreaks with Pilcrow signs.
prettyText.replace('\n', L'\u00b6');
return QString("Diff(") + strOperation(operation) + QString(",\"")
+ prettyText + QString("\")");
}
/**
* Is this Diff equivalent to another Diff?
* @param d Another Diff to compare against
* @return true or false
*/
bool Diff::operator==(const Diff &d) const {
return (d.operation == this->operation) && (d.text == this->text);
}
bool Diff::operator!=(const Diff &d) const {
return !(operator == (d));
}
/////////////////////////////////////////////
//
// Patch Class
//
/////////////////////////////////////////////
/**
* Constructor. Initializes with an empty list of diffs.
*/
Patch::Patch() :
start1(0), start2(0),
length1(0), length2(0) {
}
bool Patch::isNull() const {
if (start1 == 0 && start2 == 0 && length1 == 0 && length2 == 0
&& diffs.size() == 0) {
return true;
}
return false;
}
/**
* Emulate GNU diff's format.
* Header: @@ -382,8 +481,9 @@
* Indices are printed as 1-based, not 0-based.
* @return The GNU diff string
*/
QString Patch::toString() {
QString coords1, coords2;
if (length1 == 0) {
coords1 = QString::number(start1) + QString(",0");
} else if (length1 == 1) {
coords1 = QString::number(start1 + 1);
} else {
coords1 = QString::number(start1 + 1) + QString(",")
+ QString::number(length1);
}
if (length2 == 0) {
coords2 = QString::number(start2) + QString(",0");
} else if (length2 == 1) {
coords2 = QString::number(start2 + 1);
} else {
coords2 = QString::number(start2 + 1) + QString(",")
+ QString::number(length2);
}
QString text;
text = QString("@@ -") + coords1 + QString(" +") + coords2
+ QString(" @@\n");
// Escape the body of the patch with %xx notation.
foreach (Diff aDiff, diffs) {
switch (aDiff.operation) {
case INSERT:
text += QString('+');
break;
case DELETE:
text += QString('-');
break;
case EQUAL:
text += QString(' ');
break;
}
text += QString(QUrl::toPercentEncoding(aDiff.text, " !~*'();/?:@&=+$,#"))
+ QString("\n");
}
return text;
}
/////////////////////////////////////////////
//
// diff_match_patch Class
//
/////////////////////////////////////////////
diff_match_patch::diff_match_patch() :
Diff_Timeout(1.0f),
Diff_EditCost(4),
Match_Threshold(0.5f),
Match_Distance(1000),
Patch_DeleteThreshold(0.5f),
Patch_Margin(4),
Match_MaxBits(32) {
}
QList<Diff> diff_match_patch::diff_main(const QString &text1,
const QString &text2) {
return diff_main(text1, text2, true);
}
QList<Diff> diff_match_patch::diff_main(const QString &text1,
const QString &text2, bool checklines) {
// Set a deadline by which time the diff must be complete.
clock_t deadline;
if (Diff_Timeout <= 0) {
deadline = std::numeric_limits<clock_t>::max();
} else {
deadline = clock() + (clock_t)(Diff_Timeout * CLOCKS_PER_SEC);
}
return diff_main(text1, text2, checklines, deadline);
}
QList<Diff> diff_match_patch::diff_main(const QString &text1,
const QString &text2, bool checklines, clock_t deadline) {
// Check for null inputs.
if (text1.isNull() || text2.isNull()) {
throw "Null inputs. (diff_main)";
}
// Check for equality (speedup).
QList<Diff> diffs;
if (text1 == text2) {
if (!text1.isEmpty()) {
diffs.append(Diff(EQUAL, text1));
}
return diffs;
}
// Trim off common prefix (speedup).
int commonlength = diff_commonPrefix(text1, text2);
const QString &commonprefix = text1.left(commonlength);
QString textChopped1 = text1.mid(commonlength);
QString textChopped2 = text2.mid(commonlength);
// Trim off common suffix (speedup).
commonlength = diff_commonSuffix(textChopped1, textChopped2);
const QString &commonsuffix = textChopped1.right(commonlength);
textChopped1 = textChopped1.left(textChopped1.length() - commonlength);
textChopped2 = textChopped2.left(textChopped2.length() - commonlength);
// Compute the diff on the middle block.
diffs = diff_compute(textChopped1, textChopped2, checklines, deadline);
// Restore the prefix and suffix.
if (!commonprefix.isEmpty()) {
diffs.prepend(Diff(EQUAL, commonprefix));
}
if (!commonsuffix.isEmpty()) {
diffs.append(Diff(EQUAL, commonsuffix));
}
diff_cleanupMerge(diffs);
return diffs;
}
QList<Diff> diff_match_patch::diff_compute(QString text1, QString text2,
bool checklines, clock_t deadline) {
QList<Diff> diffs;
if (text1.isEmpty()) {
// Just add some text (speedup).
diffs.append(Diff(INSERT, text2));
return diffs;
}
if (text2.isEmpty()) {
// Just delete some text (speedup).
diffs.append(Diff(DELETE, text1));
return diffs;
}
{
const QString longtext = text1.length() > text2.length() ? text1 : text2;
const QString shorttext = text1.length() > text2.length() ? text2 : text1;
const int i = longtext.indexOf(shorttext);
if (i != -1) {
// Shorter text is inside the longer text (speedup).
const Operation op = (text1.length() > text2.length()) ? DELETE : INSERT;
diffs.append(Diff(op, longtext.left(i)));
diffs.append(Diff(EQUAL, shorttext));
diffs.append(Diff(op, safeMid(longtext, i + shorttext.length())));
return diffs;
}
if (shorttext.length() == 1) {
// Single character string.
// After the previous speedup, the character can't be an equality.
diffs.append(Diff(DELETE, text1));
diffs.append(Diff(INSERT, text2));
return diffs;
}
// Garbage collect longtext and shorttext by scoping out.
}
// Check to see if the problem can be split in two.
const QStringList hm = diff_halfMatch(text1, text2);
if (hm.count() > 0) {
// A half-match was found, sort out the return data.
const QString text1_a = hm[0];
const QString text1_b = hm[1];
const QString text2_a = hm[2];
const QString text2_b = hm[3];
const QString mid_common = hm[4];
// Send both pairs off for separate processing.
const QList<Diff> diffs_a = diff_main(text1_a, text2_a,
checklines, deadline);
const QList<Diff> diffs_b = diff_main(text1_b, text2_b,
checklines, deadline);
// Merge the results.
diffs = diffs_a;
diffs.append(Diff(EQUAL, mid_common));
diffs += diffs_b;
return diffs;
}
// Perform a real diff.
if (checklines && text1.length() > 100 && text2.length() > 100) {
return diff_lineMode(text1, text2, deadline);
}
return diff_bisect(text1, text2, deadline);
}
QList<Diff> diff_match_patch::diff_lineMode(QString text1, QString text2,
clock_t deadline) {
// Scan the text on a line-by-line basis first.
const QList<QVariant> b = diff_linesToChars(text1, text2);
text1 = b[0].toString();
text2 = b[1].toString();
QStringList linearray = b[2].toStringList();
QList<Diff> diffs = diff_main(text1, text2, false, deadline);
// Convert the diff back to original text.
diff_charsToLines(diffs, linearray);
// Eliminate freak matches (e.g. blank lines)
diff_cleanupSemantic(diffs);
// Rediff any replacement blocks, this time character-by-character.
// Add a dummy entry at the end.
diffs.append(Diff(EQUAL, ""));
int count_delete = 0;
int count_insert = 0;
QString text_delete = "";
QString text_insert = "";
QMutableListIterator<Diff> pointer(diffs);
Diff *thisDiff = pointer.hasNext() ? &pointer.next() : NULL;
while (thisDiff != NULL) {
switch (thisDiff->operation) {
case INSERT:
count_insert++;
text_insert += thisDiff->text;
break;
case DELETE:
count_delete++;
text_delete += thisDiff->text;
break;
case EQUAL:
// Upon reaching an equality, check for prior redundancies.
if (count_delete >= 1 && count_insert >= 1) {
// Delete the offending records and add the merged ones.
pointer.previous();
for (int j = 0; j < count_delete + count_insert; j++) {
pointer.previous();
pointer.remove();
}
foreach(Diff newDiff,
diff_main(text_delete, text_insert, false, deadline)) {
pointer.insert(newDiff);
}
}
count_insert = 0;
count_delete = 0;
text_delete = "";
text_insert = "";
break;
}
thisDiff = pointer.hasNext() ? &pointer.next() : NULL;
}
diffs.removeLast(); // Remove the dummy entry at the end.
return diffs;
}
QList<Diff> diff_match_patch::diff_bisect(const QString &text1,
const QString &text2, clock_t deadline) {
// Cache the text lengths to prevent multiple calls.
const int text1_length = text1.length();
const int text2_length = text2.length();
const int max_d = (text1_length + text2_length + 1) / 2;
const int v_offset = max_d;
const int v_length = 2 * max_d;
int *v1 = new int[v_length];
int *v2 = new int[v_length];
for (int x = 0; x < v_length; x++) {
v1[x] = -1;
v2[x] = -1;
}
v1[v_offset + 1] = 0;
v2[v_offset + 1] = 0;
const int delta = text1_length - text2_length;
// If the total number of characters is odd, then the front path will
// collide with the reverse path.
const bool front = (delta % 2 != 0);
// Offsets for start and end of k loop.
// Prevents mapping of space beyond the grid.
int k1start = 0;
int k1end = 0;
int k2start = 0;
int k2end = 0;
for (int d = 0; d < max_d; d++) {
// Bail out if deadline is reached.
if (clock() > deadline) {
break;
}
// Walk the front path one step.
for (int k1 = -d + k1start; k1 <= d - k1end; k1 += 2) {
const int k1_offset = v_offset + k1;
int 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;
}
int y1 = x1 - k1;
while (x1 < text1_length && y1 < text2_length
&& text1[x1] == text2[y1]) {
x1++;
y1++;
}
v1[k1_offset] = x1;
if (x1 > text1_length) {
// Ran off the right of the graph.
k1end += 2;
} else if (y1 > text2_length) {
// Ran off the bottom of the graph.
k1start += 2;
} else if (front) {
int k2_offset = v_offset + delta - k1;
if (k2_offset >= 0 && k2_offset < v_length && v2[k2_offset] != -1) {
// Mirror x2 onto top-left coordinate system.
int x2 = text1_length - v2[k2_offset];
if (x1 >= x2) {
// Overlap detected.
delete [] v1;
delete [] v2;
return diff_bisectSplit(text1, text2, x1, y1, deadline);
}
}
}
}
// Walk the reverse path one step.
for (int k2 = -d + k2start; k2 <= d - k2end; k2 += 2) {
const int k2_offset = v_offset + k2;
int 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;
}
int y2 = x2 - k2;
while (x2 < text1_length && y2 < text2_length
&& text1[text1_length - x2 - 1] == text2[text2_length - y2 - 1]) {
x2++;
y2++;
}
v2[k2_offset] = x2;
if (x2 > text1_length) {
// Ran off the left of the graph.
k2end += 2;
} else if (y2 > text2_length) {
// Ran off the top of the graph.
k2start += 2;
} else if (!front) {
int k1_offset = v_offset + delta - k2;
if (k1_offset >= 0 && k1_offset < v_length && v1[k1_offset] != -1) {
int x1 = v1[k1_offset];
int y1 = v_offset + x1 - k1_offset;
// Mirror x2 onto top-left coordinate system.
x2 = text1_length - x2;
if (x1 >= x2) {
// Overlap detected.
delete [] v1;
delete [] v2;
return diff_bisectSplit(text1, text2, x1, y1, deadline);
}
}
}
}
}
delete [] v1;
delete [] v2;
// Diff took too long and hit the deadline or
// number of diffs equals number of characters, no commonality at all.
QList<Diff> diffs;
diffs.append(Diff(DELETE, text1));
diffs.append(Diff(INSERT, text2));
return diffs;
}
QList<Diff> diff_match_patch::diff_bisectSplit(const QString &text1,
const QString &text2, int x, int y, clock_t deadline) {
QString text1a = text1.left(x);
QString text2a = text2.left(y);
QString text1b = safeMid(text1, x);
QString text2b = safeMid(text2, y);
// Compute both diffs serially.
QList<Diff> diffs = diff_main(text1a, text2a, false, deadline);
QList<Diff> diffsb = diff_main(text1b, text2b, false, deadline);
return diffs + diffsb;
}
QList<QVariant> diff_match_patch::diff_linesToChars(const QString &text1,
const QString &text2) {
QStringList lineArray;
QMap<QString, int> lineHash;
// e.g. linearray[4] == "Hello\n"
// e.g. linehash.get("Hello\n") == 4
// "\x00" is a valid character, but various debuggers don't like it.
// So we'll insert a junk entry to avoid generating a null character.
lineArray.append("");
const QString chars1 = diff_linesToCharsMunge(text1, lineArray, lineHash);
const QString chars2 = diff_linesToCharsMunge(text2, lineArray, lineHash);
QList<QVariant> listRet;
listRet.append(QVariant::fromValue(chars1));
listRet.append(QVariant::fromValue(chars2));
listRet.append(QVariant::fromValue(lineArray));
return listRet;
}
QString diff_match_patch::diff_linesToCharsMunge(const QString &text,
QStringList &lineArray,
QMap<QString, int> &lineHash) {
int lineStart = 0;
int lineEnd = -1;
QString line;
QString chars;
// Walk the text, pulling out a substring for each line.
// text.split('\n') would would temporarily double our memory footprint.
// Modifying text would create many large strings to garbage collect.
while (lineEnd < text.length() - 1) {
lineEnd = text.indexOf('\n', lineStart);
if (lineEnd == -1) {
lineEnd = text.length() - 1;
}
line = safeMid(text, lineStart, lineEnd + 1 - lineStart);
lineStart = lineEnd + 1;
if (lineHash.contains(line)) {
chars += QChar(static_cast<ushort>(lineHash.value(line)));
} else {
lineArray.append(line);
lineHash.insert(line, lineArray.size() - 1);
chars += QChar(static_cast<ushort>(lineArray.size() - 1));
}
}
return chars;
}
void diff_match_patch::diff_charsToLines(QList<Diff> &diffs,
const QStringList &lineArray) {
// Qt has no mutable foreach construct.
QMutableListIterator<Diff> i(diffs);
while (i.hasNext()) {
Diff &diff = i.next();
QString text;
for (int y = 0; y < diff.text.length(); y++) {
text += lineArray.value(static_cast<ushort>(diff.text[y].unicode()));
}
diff.text = text;
}
}
int diff_match_patch::diff_commonPrefix(const QString &text1,
const QString &text2) {
// Performance analysis: http://neil.fraser.name/news/2007/10/09/
const int n = std::min(text1.length(), text2.length());
for (int i = 0; i < n; i++) {
if (text1[i] != text2[i]) {
return i;
}
}
return n;
}
int diff_match_patch::diff_commonSuffix(const QString &text1,
const QString &text2) {
// Performance analysis: http://neil.fraser.name/news/2007/10/09/
const int text1_length = text1.length();
const int text2_length = text2.length();
const int n = std::min(text1_length, text2_length);
for (int i = 1; i <= n; i++) {
if (text1[text1_length - i] != text2[text2_length - i]) {
return i - 1;
}
}
return n;
}
int diff_match_patch::diff_commonOverlap(const QString &text1,
const QString &text2) {
// Cache the text lengths to prevent multiple calls.
const int text1_length = text1.length();
const int text2_length = text2.length();
// Eliminate the null case.
if (text1_length == 0 || text2_length == 0) {
return 0;
}
// Truncate the longer string.
QString text1_trunc = text1;
QString text2_trunc = text2;
if (text1_length > text2_length) {
text1_trunc = text1.right(text2_length);
} else if (text1_length < text2_length) {
text2_trunc = text2.left(text1_length);
}
const int text_length = std::min(text1_length, text2_length);
// Quick check for the worst case.
if (text1_trunc == text2_trunc) {
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) {
QString pattern = text1_trunc.right(length);
int found = text2_trunc.indexOf(pattern);
if (found == -1) {
return best;
}
length += found;
if (found == 0 || text1_trunc.right(length) == text2_trunc.left(length)) {
best = length;
length++;
}
}
}
QStringList diff_match_patch::diff_halfMatch(const QString &text1,
const QString &text2) {
if (Diff_Timeout <= 0) {
// Don't risk returning a non-optimal diff if we have unlimited time.
return QStringList();
}
const QString longtext = text1.length() > text2.length() ? text1 : text2;
const QString shorttext = text1.length() > text2.length() ? text2 : text1;
if (longtext.length() < 4 || shorttext.length() * 2 < longtext.length()) {
return QStringList(); // Pointless.
}
// First check if the second quarter is the seed for a half-match.
const QStringList hm1 = diff_halfMatchI(longtext, shorttext,
(longtext.length() + 3) / 4);
// Check again based on the third quarter.
const QStringList hm2 = diff_halfMatchI(longtext, shorttext,
(longtext.length() + 1) / 2);
QStringList hm;
if (hm1.isEmpty() && hm2.isEmpty()) {
return QStringList();
} else if (hm2.isEmpty()) {
hm = hm1;
} else if (hm1.isEmpty()) {
hm = hm2;
} else {
// Both matched. Select the longest.
hm = hm1[4].length() > hm2[4].length() ? hm1 : hm2;
}
// A half-match was found, sort out the return data.
if (text1.length() > text2.length()) {
return hm;
} else {
QStringList listRet;
listRet << hm[2] << hm[3] << hm[0] << hm[1] << hm[4];
return listRet;
}
}
QStringList diff_match_patch::diff_halfMatchI(const QString &longtext,
const QString &shorttext,
int i) {
// Start with a 1/4 length substring at position i as a seed.
const QString seed = safeMid(longtext, i, longtext.length() / 4);
int j = -1;
QString best_common;
QString best_longtext_a, best_longtext_b;
QString best_shorttext_a, best_shorttext_b;
while ((j = shorttext.indexOf(seed, j + 1)) != -1) {
const int prefixLength = diff_commonPrefix(safeMid(longtext, i),
safeMid(shorttext, j));
const int suffixLength = diff_commonSuffix(longtext.left(i),
shorttext.left(j));
if (best_common.length() < suffixLength + prefixLength) {
best_common = safeMid(shorttext, j - suffixLength, suffixLength)
+ safeMid(shorttext, j, prefixLength);
best_longtext_a = longtext.left(i - suffixLength);
best_longtext_b = safeMid(longtext, i + prefixLength);
best_shorttext_a = shorttext.left(j - suffixLength);
best_shorttext_b = safeMid(shorttext, j + prefixLength);
}
}
if (best_common.length() * 2 >= longtext.length()) {
QStringList listRet;
listRet << best_longtext_a << best_longtext_b << best_shorttext_a
<< best_shorttext_b << best_common;
return listRet;
} else {
return QStringList();
}
}
void diff_match_patch::diff_cleanupSemantic(QList<Diff> &diffs) {
if (diffs.isEmpty()) {
return;
}
bool changes = false;
QStack<Diff> equalities; // Stack of equalities.
QString lastequality; // Always equal to equalities.lastElement().text
QMutableListIterator<Diff> pointer(diffs);
// Number of characters that changed prior to the equality.
int length_insertions1 = 0;
int length_deletions1 = 0;
// Number of characters that changed after the equality.
int length_insertions2 = 0;
int length_deletions2 = 0;
Diff *thisDiff = pointer.hasNext() ? &pointer.next() : NULL;
while (thisDiff != NULL) {
if (thisDiff->operation == EQUAL) {
// Equality found.
equalities.push(*thisDiff);
length_insertions1 = length_insertions2;
length_deletions1 = length_deletions2;
length_insertions2 = 0;
length_deletions2 = 0;
lastequality = thisDiff->text;
} else {
// An insertion or deletion.
if (thisDiff->operation == INSERT) {
length_insertions2 += thisDiff->text.length();
} else {
length_deletions2 += thisDiff->text.length();
}
// Eliminate an equality that is smaller or equal to the edits on both
// sides of it.
if (!lastequality.isNull()
&& (lastequality.length()
<= std::max(length_insertions1, length_deletions1))
&& (lastequality.length()
<= std::max(length_insertions2, length_deletions2))) {
// printf("Splitting: '%s'\n", qPrintable(lastequality));
// Walk back to offending equality.
while (*thisDiff != equalities.top()) {
thisDiff = &pointer.previous();
}
pointer.next();
// Replace equality with a delete.
pointer.setValue(Diff(DELETE, lastequality));
// Insert a corresponding an insert.
pointer.insert(Diff(INSERT, lastequality));
equalities.pop(); // Throw away the equality we just deleted.
if (!equalities.isEmpty()) {
// Throw away the previous equality (it needs to be reevaluated).
equalities.pop();
}
if (equalities.isEmpty()) {
// There are no previous equalities, walk back to the start.
while (pointer.hasPrevious()) {
pointer.previous();
}
} else {
// There is a safe equality we can fall back to.
thisDiff = &equalities.top();
while (*thisDiff != pointer.previous()) {
// Intentionally empty loop.
}
}
length_insertions1 = 0; // Reset the counters.
length_deletions1 = 0;
length_insertions2 = 0;
length_deletions2 = 0;
lastequality = QString();
changes = true;
}
}
thisDiff = pointer.hasNext() ? &pointer.next() : NULL;
}
// Normalize the diff.
if (changes) {
diff_cleanupMerge(diffs);
}
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.toFront();
Diff *prevDiff = NULL;
thisDiff = NULL;
if (pointer.hasNext()) {
prevDiff = &pointer.next();
if (pointer.hasNext()) {
thisDiff = &pointer.next();
}
}
while (thisDiff != NULL) {
if (prevDiff->operation == DELETE &&
thisDiff->operation == INSERT) {
QString deletion = prevDiff->text;
QString insertion = thisDiff->text;
int overlap_length1 = diff_commonOverlap(deletion, insertion);
int overlap_length2 = diff_commonOverlap(insertion, deletion);
if (overlap_length1 >= overlap_length2) {
if (overlap_length1 >= deletion.length() / 2.0 ||
overlap_length1 >= insertion.length() / 2.0) {
// Overlap found. Insert an equality and trim the surrounding edits.
pointer.previous();
pointer.insert(Diff(EQUAL, insertion.left(overlap_length1)));
prevDiff->text =
deletion.left(deletion.length() - overlap_length1);
thisDiff->text = safeMid(insertion, overlap_length1);
// pointer.insert inserts the element before the cursor, so there is
// no need to step past the new element.
}
} else {
if (overlap_length2 >= deletion.length() / 2.0 ||
overlap_length2 >= insertion.length() / 2.0) {
// Reverse overlap found.
// Insert an equality and swap and trim the surrounding edits.
pointer.previous();
pointer.insert(Diff(EQUAL, deletion.left(overlap_length2)));
prevDiff->operation = INSERT;
prevDiff->text =
insertion.left(insertion.length() - overlap_length2);
thisDiff->operation = DELETE;
thisDiff->text = safeMid(deletion, overlap_length2);
// pointer.insert inserts the element before the cursor, so there is
// no need to step past the new element.
}
}
thisDiff = pointer.hasNext() ? &pointer.next() : NULL;
}
prevDiff = thisDiff;
thisDiff = pointer.hasNext() ? &pointer.next() : NULL;
}
}
void diff_match_patch::diff_cleanupSemanticLossless(QList<Diff> &diffs) {
QString equality1, edit, equality2;
QString commonString;
int commonOffset;
int score, bestScore;
QString bestEquality1, bestEdit, bestEquality2;
// Create a new iterator at the start.
QMutableListIterator<Diff> pointer(diffs);
Diff *prevDiff = pointer.hasNext() ? &pointer.next() : NULL;
Diff *thisDiff = pointer.hasNext() ? &pointer.next() : NULL;
Diff *nextDiff = pointer.hasNext() ? &pointer.next() : NULL;
// Intentionally ignore the first and last element (don't need checking).
while (nextDiff != NULL) {
if (prevDiff->operation == EQUAL &&
nextDiff->operation == EQUAL) {
// This is a single edit surrounded by equalities.
equality1 = prevDiff->text;
edit = thisDiff->text;
equality2 = nextDiff->text;
// First, shift the edit as far left as possible.
commonOffset = diff_commonSuffix(equality1, edit);
if (commonOffset != 0) {
commonString = safeMid(edit, edit.length() - commonOffset);
equality1 = equality1.left(equality1.length() - commonOffset);
edit = commonString + edit.left(edit.length() - commonOffset);
equality2 = commonString + equality2;
}
// Second, step character by character right, looking for the best fit.
bestEquality1 = equality1;
bestEdit = edit;
bestEquality2 = equality2;
bestScore = diff_cleanupSemanticScore(equality1, edit)
+ diff_cleanupSemanticScore(edit, equality2);
while (!edit.isEmpty() && !equality2.isEmpty()
&& edit[0] == equality2[0]) {
equality1 += edit[0];
edit = safeMid(edit, 1) + equality2[0];
equality2 = safeMid(equality2, 1);
score = diff_cleanupSemanticScore(equality1, edit)
+ diff_cleanupSemanticScore(edit, equality2);
// The >= encourages trailing rather than leading whitespace on edits.
if (score >= bestScore) {
bestScore = score;
bestEquality1 = equality1;
bestEdit = edit;
bestEquality2 = equality2;
}
}
if (prevDiff->text != bestEquality1) {
// We have an improvement, save it back to the diff.
if (!bestEquality1.isEmpty()) {
prevDiff->text = bestEquality1;
} else {
pointer.previous(); // Walk past nextDiff.
pointer.previous(); // Walk past thisDiff.
pointer.previous(); // Walk past prevDiff.
pointer.remove(); // Delete prevDiff.
pointer.next(); // Walk past thisDiff.
pointer.next(); // Walk past nextDiff.
}
thisDiff->text = bestEdit;
if (!bestEquality2.isEmpty()) {
nextDiff->text = bestEquality2;
} else {
pointer.remove(); // Delete nextDiff.
nextDiff = thisDiff;
thisDiff = prevDiff;
}
}
}
prevDiff = thisDiff;
thisDiff = nextDiff;
nextDiff = pointer.hasNext() ? &pointer.next() : NULL;
}
}
int diff_match_patch::diff_cleanupSemanticScore(const QString &one,
const QString &two) {
if (one.isEmpty() || two.isEmpty()) {
// Edges are the best.
return 6;
}
// Each port of this function behaves slightly differently due to
// subtle differences in each language's definition of things like
// 'whitespace'. Since this function's purpose is largely cosmetic,
// the choice has been made to use each language's native features
// rather than force total conformity.
QChar char1 = one[one.length() - 1];
QChar char2 = two[0];
bool nonAlphaNumeric1 = !char1.isLetterOrNumber();
bool nonAlphaNumeric2 = !char2.isLetterOrNumber();
bool whitespace1 = nonAlphaNumeric1 && char1.isSpace();
bool whitespace2 = nonAlphaNumeric2 && char2.isSpace();
bool lineBreak1 = whitespace1 && char1.category() == QChar::Other_Control;
bool lineBreak2 = whitespace2 && char2.category() == QChar::Other_Control;
bool blankLine1 = lineBreak1 && BLANKLINEEND.indexIn(one) != -1;
bool blankLine2 = lineBreak2 && BLANKLINESTART.indexIn(two) != -1;
if (blankLine1 || blankLine2) {
// Five points for blank lines.
return 5;
} else if (lineBreak1 || lineBreak2) {
// Four points for line breaks.
return 4;
} else if (nonAlphaNumeric1 && !whitespace1 && whitespace2) {
// Three points for end of sentences.
return 3;
} else if (whitespace1 || whitespace2) {
// Two points for whitespace.
return 2;
} else if (nonAlphaNumeric1 || nonAlphaNumeric2) {
// One point for non-alphanumeric.
return 1;
}
return 0;
}
// Define some regex patterns for matching boundaries.
QRegExp diff_match_patch::BLANKLINEEND = QRegExp("\\n\\r?\\n$");
QRegExp diff_match_patch::BLANKLINESTART = QRegExp("^\\r?\\n\\r?\\n");
void diff_match_patch::diff_cleanupEfficiency(QList<Diff> &diffs) {
if (diffs.isEmpty()) {
return;
}
bool changes = false;
QStack<Diff> equalities; // Stack of equalities.
QString lastequality; // Always equal to equalities.lastElement().text
QMutableListIterator<Diff> pointer(diffs);
// Is there an insertion operation before the last equality.
bool pre_ins = false;
// Is there a deletion operation before the last equality.
bool pre_del = false;
// Is there an insertion operation after the last equality.
bool post_ins = false;
// Is there a deletion operation after the last equality.
bool post_del = false;