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The Slimmed Down LOCKSS Daemon Core
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/*
* $Id$
*/
/*
Copyright (c) 2013 Board of Trustees of Leland Stanford Jr. University,
all rights reserved.
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
STANFORD UNIVERSITY BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
Except as contained in this notice, the name of Stanford University shall not
be used in advertising or otherwise to promote the sale, use or other dealings
in this Software without prior written authorization from Stanford University.
*/
/*
* This file is substantially unmodified from:
*
* Copyright (c) 2000-2003 Sun Microsystems. All Rights Reserved.
*
/*
* Diff Match and Patch
*
* Copyright 2006 Google Inc.
* http://code.google.com/p/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.
*/
package org.lockss.util;
import java.io.UnsupportedEncodingException;
import java.net.URLEncoder;
import java.net.URLDecoder;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.ListIterator;
import java.util.Map;
import java.util.Stack;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
/*
* Functions for diff, match and patch.
* Computes the difference between two texts to create a patch.
* Applies the patch onto another text, allowing for errors.
*
* @author [email protected] (Neil Fraser)
*/
/**
* Class containing the diff, match and patch methods.
* Also contains the behaviour settings.
*/
public class DiffMatchPatch {
// Defaults.
// Set these on your DiffMatchPatch instance to override the defaults.
/**
* Number of seconds to map a diff before giving up (0 for infinity).
*/
public float Diff_Timeout = 1.0f;
/**
* Cost of an empty edit operation in terms of edit characters.
*/
public short Diff_EditCost = 4;
/**
* At what point is no match declared (0.0 = perfection, 1.0 = very loose).
*/
public float Match_Threshold = 0.5f;
/**
* 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).
*/
public int 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.
*/
public float Patch_DeleteThreshold = 0.5f;
/**
* Chunk size for context length.
*/
public short Patch_Margin = 4;
/**
* The number of bits in an int.
*/
private short Match_MaxBits = 32;
/**
* Internal class for returning results from diff_linesToChars().
* Other less paranoid languages just use a three-element array.
*/
protected static class LinesToCharsResult {
protected String chars1;
protected String chars2;
protected List lineArray;
protected LinesToCharsResult(String chars1, String chars2,
List lineArray) {
this.chars1 = chars1;
this.chars2 = chars2;
this.lineArray = lineArray;
}
}
// DIFF FUNCTIONS
/**
* The data structure representing a diff is a Linked 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."
*/
public enum Operation {
DELETE, INSERT, EQUAL
}
/**
* 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 Linked List of Diff objects.
*/
public LinkedList 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 Linked List of Diff objects.
*/
public LinkedList diff_main(String text1, String text2,
boolean checklines) {
// Set a deadline by which time the diff must be complete.
long deadline;
if (Diff_Timeout <= 0) {
deadline = Long.MAX_VALUE;
} else {
deadline = System.currentTimeMillis() + (long) (Diff_Timeout * 1000);
}
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 Linked List of Diff objects.
*/
private LinkedList diff_main(String text1, String text2,
boolean checklines, long deadline) {
// Check for null inputs.
if (text1 == null || text2 == null) {
throw new IllegalArgumentException("Null inputs. (diff_main)");
}
// Check for equality (speedup).
LinkedList diffs;
if (text1.equals(text2)) {
diffs = new LinkedList();
if (text1.length() != 0) {
diffs.add(new Diff(Operation.EQUAL, text1));
}
return diffs;
}
// Trim off common prefix (speedup).
int commonlength = diff_commonPrefix(text1, text2);
String commonprefix = text1.substring(0, commonlength);
text1 = text1.substring(commonlength);
text2 = text2.substring(commonlength);
// Trim off common suffix (speedup).
commonlength = diff_commonSuffix(text1, text2);
String commonsuffix = text1.substring(text1.length() - commonlength);
text1 = text1.substring(0, text1.length() - commonlength);
text2 = text2.substring(0, text2.length() - commonlength);
// Compute the diff on the middle block.
diffs = diff_compute(text1, text2, checklines, deadline);
// Restore the prefix and suffix.
if (commonprefix.length() != 0) {
diffs.addFirst(new Diff(Operation.EQUAL, commonprefix));
}
if (commonsuffix.length() != 0) {
diffs.addLast(new Diff(Operation.EQUAL, commonsuffix));
}
diff_cleanupMerge(diffs);
return diffs;
}
/**
* 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 Linked List of Diff objects.
*/
private LinkedList diff_compute(String text1, String text2,
boolean checklines, long deadline) {
LinkedList diffs = new LinkedList();
if (text1.length() == 0) {
// Just add some text (speedup).
diffs.add(new Diff(Operation.INSERT, text2));
return diffs;
}
if (text2.length() == 0) {
// Just delete some text (speedup).
diffs.add(new Diff(Operation.DELETE, text1));
return diffs;
}
String longtext = text1.length() > text2.length() ? text1 : text2;
String shorttext = text1.length() > text2.length() ? text2 : text1;
int i = longtext.indexOf(shorttext);
if (i != -1) {
// Shorter text is inside the longer text (speedup).
Operation op = (text1.length() > text2.length()) ?
Operation.DELETE : Operation.INSERT;
diffs.add(new Diff(op, longtext.substring(0, i)));
diffs.add(new Diff(Operation.EQUAL, shorttext));
diffs.add(new Diff(op, longtext.substring(i + shorttext.length())));
return diffs;
}
if (shorttext.length() == 1) {
// Single character string.
// After the previous speedup, the character can't be an equality.
diffs.add(new Diff(Operation.DELETE, text1));
diffs.add(new Diff(Operation.INSERT, text2));
return diffs;
}
// Check to see if the problem can be split in two.
String[] hm = diff_halfMatch(text1, text2);
if (hm != null) {
// A half-match was found, sort out the return data.
String text1_a = hm[0];
String text1_b = hm[1];
String text2_a = hm[2];
String text2_b = hm[3];
String mid_common = hm[4];
// Send both pairs off for separate processing.
LinkedList diffs_a = diff_main(text1_a, text2_a,
checklines, deadline);
LinkedList diffs_b = diff_main(text1_b, text2_b,
checklines, deadline);
// Merge the results.
diffs = diffs_a;
diffs.add(new Diff(Operation.EQUAL, mid_common));
diffs.addAll(diffs_b);
return diffs;
}
if (checklines && text1.length() > 100 && text2.length() > 100) {
return diff_lineMode(text1, text2, deadline);
}
return diff_bisect(text1, text2, deadline);
}
/**
* Do a quick line-level diff on both strings, then rediff the parts for
* greater accuracy.
* This speedup can produce non-minimal diffs.
* @param text1 Old string to be diffed.
* @param text2 New string to be diffed.
* @param deadline Time when the diff should be complete by.
* @return Linked List of Diff objects.
*/
private LinkedList diff_lineMode(String text1, String text2,
long deadline) {
// Scan the text on a line-by-line basis first.
LinesToCharsResult b = diff_linesToChars(text1, text2);
text1 = b.chars1;
text2 = b.chars2;
List linearray = b.lineArray;
LinkedList 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.add(new Diff(Operation.EQUAL, ""));
int count_delete = 0;
int count_insert = 0;
String text_delete = "";
String text_insert = "";
ListIterator pointer = diffs.listIterator();
Diff thisDiff = pointer.next();
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();
}
for (Diff newDiff : diff_main(text_delete, text_insert, false,
deadline)) {
pointer.add(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;
}
/**
* 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 text1 Old string to be diffed.
* @param text2 New string to be diffed.
* @param deadline Time at which to bail if not yet complete.
* @return LinkedList of Diff objects.
*/
protected LinkedList diff_bisect(String text1, String text2,
long deadline) {
// Cache the text lengths to prevent multiple calls.
int text1_length = text1.length();
int text2_length = text2.length();
int max_d = (text1_length + text2_length + 1) / 2;
int v_offset = max_d;
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;
int delta = text1_length - text2_length;
// If the total number of characters is odd, then the front path will
// collide with the reverse path.
boolean 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 (System.currentTimeMillis() > deadline) {
break;
}
// Walk the front path one step.
for (int k1 = -d + k1start; k1 <= d - k1end; k1 += 2) {
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.charAt(x1) == text2.charAt(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.
return diff_bisectSplit(text1, text2, x1, y1, deadline);
}
}
}
}
// Walk the reverse path one step.
for (int k2 = -d + k2start; k2 <= d - k2end; k2 += 2) {
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.charAt(text1_length - x2 - 1)
== text2.charAt(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.
return diff_bisectSplit(text1, text2, x1, y1, deadline);
}
}
}
}
}
// Diff took too long and hit the deadline or
// number of diffs equals number of characters, no commonality at all.
LinkedList diffs = new LinkedList();
diffs.add(new Diff(Operation.DELETE, text1));
diffs.add(new Diff(Operation.INSERT, text2));
return diffs;
}
/**
* Given the location of the 'middle snake', split the diff in two parts
* and recurse.
* @param text1 Old string to be diffed.
* @param text2 New string to be diffed.
* @param x Index of split point in text1.
* @param y Index of split point in text2.
* @param deadline Time at which to bail if not yet complete.
* @return LinkedList of Diff objects.
*/
private LinkedList diff_bisectSplit(String text1, String text2,
int x, int y, long deadline) {
String text1a = text1.substring(0, x);
String text2a = text2.substring(0, y);
String text1b = text1.substring(x);
String text2b = text2.substring(y);
// Compute both diffs serially.
LinkedList diffs = diff_main(text1a, text2a, false, deadline);
LinkedList diffsb = diff_main(text1b, text2b, false, deadline);
diffs.addAll(diffsb);
return diffs;
}
/**
* Split two texts into a list of strings. Reduce the texts to a string of
* hashes where each Unicode character represents one line.
* @param text1 First string.
* @param text2 Second string.
* @return An object containing the encoded text1, the encoded text2 and
* the List of unique strings. The zeroth element of the List of
* unique strings is intentionally blank.
*/
protected LinesToCharsResult diff_linesToChars(String text1, String text2) {
List lineArray = new ArrayList();
Map lineHash = new HashMap();
// 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.add("");
String chars1 = diff_linesToCharsMunge(text1, lineArray, lineHash);
String chars2 = diff_linesToCharsMunge(text2, lineArray, lineHash);
return new LinesToCharsResult(chars1, chars2, lineArray);
}
/**
* Split a text into a list of strings. Reduce the texts to a string of
* hashes where each Unicode character represents one line.
* @param text String to encode.
* @param lineArray List of unique strings.
* @param lineHash Map of strings to indices.
* @return Encoded string.
*/
private String diff_linesToCharsMunge(String text, List lineArray,
Map lineHash) {
int lineStart = 0;
int lineEnd = -1;
String line;
StringBuilder chars = new StringBuilder();
// 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 = text.substring(lineStart, lineEnd + 1);
lineStart = lineEnd + 1;
if (lineHash.containsKey(line)) {
chars.append(String.valueOf((char) (int) lineHash.get(line)));
} else {
lineArray.add(line);
lineHash.put(line, lineArray.size() - 1);
chars.append(String.valueOf((char) (lineArray.size() - 1)));
}
}
return chars.toString();
}
/**
* Rehydrate the text in a diff from a string of line hashes to real lines of
* text.
* @param diffs LinkedList of Diff objects.
* @param lineArray List of unique strings.
*/
protected void diff_charsToLines(LinkedList diffs,
List lineArray) {
StringBuilder text;
for (Diff diff : diffs) {
text = new StringBuilder();
for (int y = 0; y < diff.text.length(); y++) {
text.append(lineArray.get(diff.text.charAt(y)));
}
diff.text = text.toString();
}
}
/**
* Determine the common prefix of two strings
* @param text1 First string.
* @param text2 Second string.
* @return The number of characters common to the start of each string.
*/
public int diff_commonPrefix(String text1, String text2) {
// Performance analysis: http://neil.fraser.name/news/2007/10/09/
int n = Math.min(text1.length(), text2.length());
for (int i = 0; i < n; i++) {
if (text1.charAt(i) != text2.charAt(i)) {
return i;
}
}
return n;
}
/**
* Determine the common suffix of two strings
* @param text1 First string.
* @param text2 Second string.
* @return The number of characters common to the end of each string.
*/
public int diff_commonSuffix(String text1, String text2) {
// Performance analysis: http://neil.fraser.name/news/2007/10/09/
int text1_length = text1.length();
int text2_length = text2.length();
int n = Math.min(text1_length, text2_length);
for (int i = 1; i <= n; i++) {
if (text1.charAt(text1_length - i) != text2.charAt(text2_length - 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.
*/
protected int diff_commonOverlap(String text1, String text2) {
// Cache the text lengths to prevent multiple calls.
int text1_length = text1.length();
int 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.substring(text1_length - text2_length);
} else if (text1_length < text2_length) {
text2 = text2.substring(0, text1_length);
}
int text_length = Math.min(text1_length, text2_length);
// Quick check for the worst case.
if (text1.equals(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.substring(text_length - length);
int found = text2.indexOf(pattern);
if (found == -1) {
return best;
}
length += found;
if (found == 0 || text1.substring(text_length - length).equals(
text2.substring(0, length))) {
best = length;
length++;
}
}
}
/**
* 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.
*/
protected String[] diff_halfMatch(String text1, String text2) {
if (Diff_Timeout <= 0) {
// Don't risk returning a non-optimal diff if we have unlimited time.
return null;
}
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 null; // Pointless.
}
// First check if the second quarter is the seed for a half-match.
String[] hm1 = diff_halfMatchI(longtext, shorttext,
(longtext.length() + 3) / 4);
// Check again based on the third quarter.
String[] hm2 = diff_halfMatchI(longtext, shorttext,
(longtext.length() + 1) / 2);
String[] hm;
if (hm1 == null && hm2 == null) {
return null;
} else if (hm2 == null) {
hm = hm1;
} else if (hm1 == null) {
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;
//return new String[]{hm[0], hm[1], hm[2], hm[3], hm[4]};
} else {
return new String[]{hm[2], hm[3], hm[0], hm[1], hm[4]};
}
}
/**
* Does a substring of shorttext exist within longtext such that the
* substring is at least half the length of longtext?
* @param longtext Longer string.
* @param shorttext Shorter string.
* @param i Start index of quarter length substring within longtext.
* @return Five element String array, containing the prefix of longtext, the
* suffix of longtext, the prefix of shorttext, the suffix of shorttext
* and the common middle. Or null if there was no match.
*/
private String[] diff_halfMatchI(String longtext, String shorttext, int i) {
// Start with a 1/4 length substring at position i as a seed.
String seed = longtext.substring(i, i + longtext.length() / 4);
int j = -1;
String best_common = "";
String best_longtext_a = "", best_longtext_b = "";
String best_shorttext_a = "", best_shorttext_b = "";
while ((j = shorttext.indexOf(seed, j + 1)) != -1) {
int prefixLength = diff_commonPrefix(longtext.substring(i),
shorttext.substring(j));
int suffixLength = diff_commonSuffix(longtext.substring(0, i),
shorttext.substring(0, j));
if (best_common.length() < suffixLength + prefixLength) {
best_common = shorttext.substring(j - suffixLength, j)
+ shorttext.substring(j, j + prefixLength);
best_longtext_a = longtext.substring(0, i - suffixLength);
best_longtext_b = longtext.substring(i + prefixLength);
best_shorttext_a = shorttext.substring(0, j - suffixLength);
best_shorttext_b = shorttext.substring(j + prefixLength);
}
}
if (best_common.length() * 2 >= longtext.length()) {
return new String[]{best_longtext_a, best_longtext_b,
best_shorttext_a, best_shorttext_b, best_common};
} else {
return null;
}
}
/**
* Reduce the number of edits by eliminating semantically trivial equalities.
* @param diffs LinkedList of Diff objects.
*/
public void diff_cleanupSemantic(LinkedList diffs) {
if (diffs.isEmpty()) {
return;
}
boolean changes = false;
Stack equalities = new Stack(); // Stack of qualities.
String lastequality = null; // Always equal to equalities.lastElement().text
ListIterator pointer = diffs.listIterator();
// 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.next();
while (thisDiff != null) {
if (thisDiff.operation == 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 == 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 != null && (lastequality.length()
<= Math.max(length_insertions1, length_deletions1))
&& (lastequality.length()
<= Math.max(length_insertions2, length_deletions2))) {
//System.out.println("Splitting: '" + lastequality + "'");
// Walk back to offending equality.
while (thisDiff != equalities.lastElement()) {
thisDiff = pointer.previous();
}
pointer.next();
// Replace equality with a delete.
pointer.set(new Diff(Operation.DELETE, lastequality));
// Insert a corresponding an insert.
pointer.add(new Diff(Operation.INSERT, lastequality));
equalities.pop(); // Throw away the equality we just deleted.
if (!equalities.empty()) {
// Throw away the previous equality (it needs to be reevaluated).
equalities.pop();
}
if (equalities.empty()) {
// 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.lastElement();
while (thisDiff != pointer.previous()) {
// Intentionally empty loop.
}
}
length_insertions1 = 0; // Reset the counters.
length_insertions2 = 0;
length_deletions1 = 0;
length_deletions2 = 0;
lastequality = null;
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: abcxxxxxxdef
// -> abcxxxdef
// e.g: xxxabcdefxxx
// -> defxxxabc
// Only extract an overlap if it is as big as the edit ahead or behind it.
pointer = diffs.listIterator();
Diff prevDiff = null;
thisDiff = null;
if (pointer.hasNext()) {
prevDiff = pointer.next();
if (pointer.hasNext()) {
thisDiff = pointer.next();
}
}
while (thisDiff != null) {
if (prevDiff.operation == Operation.DELETE &&
thisDiff.operation == Operation.INSERT) {
String deletion = prevDiff.text;
String insertion = thisDiff.text;
int overlap_length1 = this.diff_commonOverlap(deletion, insertion);
int overlap_length2 = this.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.add(new Diff(Operation.EQUAL,
insertion.substring(0, overlap_length1)));
prevDiff.text =
deletion.substring(0, deletion.length() - overlap_length1);
thisDiff.text = insertion.substring(overlap_length1);
// pointer.add 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.add(new Diff(Operation.EQUAL,
deletion.substring(0, overlap_length2)));
prevDiff.operation = Operation.INSERT;
prevDiff.text =
insertion.substring(0, insertion.length() - overlap_length2);
thisDiff.operation = Operation.DELETE;
thisDiff.text = deletion.substring(overlap_length2);
// pointer.add 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;
}
}
/**
* 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 cat came. -> The cat came.
* @param diffs LinkedList of Diff objects.
*/
public void diff_cleanupSemanticLossless(LinkedList diffs) {
String equality1, edit, equality2;
String commonString;
int commonOffset;
int score, bestScore;
String bestEquality1, bestEdit, bestEquality2;
// Create a new iterator at the start.
ListIterator pointer = diffs.listIterator();
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 == Operation.EQUAL &&
nextDiff.operation == 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 = edit.substring(edit.length() - commonOffset);
equality1 = equality1.substring(0, equality1.length() - commonOffset);
edit = commonString + edit.substring(0, 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.length() != 0 && equality2.length() != 0
&& edit.charAt(0) == equality2.charAt(0)) {
equality1 += edit.charAt(0);
edit = edit.substring(1) + equality2.charAt(0);
equality2 = equality2.substring(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.equals(bestEquality1)) {
// We have an improvement, save it back to the diff.
if (bestEquality1.length() != 0) {
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.length() != 0) {
nextDiff.text = bestEquality2;
} else {
pointer.remove(); // Delete nextDiff.
nextDiff = thisDiff;
thisDiff = prevDiff;
}
}
}
prevDiff = thisDiff;
thisDiff = nextDiff;
nextDiff = pointer.hasNext() ? pointer.next() : null;
}
}
/**
* Given two strings, compute 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.
*/
private int diff_cleanupSemanticScore(String one, String two) {
if (one.length() == 0 || two.length() == 0) {
// 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.
char char1 = one.charAt(one.length() - 1);
char char2 = two.charAt(0);
boolean nonAlphaNumeric1 = !Character.isLetterOrDigit(char1);
boolean nonAlphaNumeric2 = !Character.isLetterOrDigit(char2);
boolean whitespace1 = nonAlphaNumeric1 && Character.isWhitespace(char1);
boolean whitespace2 = nonAlphaNumeric2 && Character.isWhitespace(char2);
boolean lineBreak1 = whitespace1
&& Character.getType(char1) == Character.CONTROL;
boolean lineBreak2 = whitespace2
&& Character.getType(char2) == Character.CONTROL;
boolean blankLine1 = lineBreak1 && BLANKLINEEND.matcher(one).find();
boolean blankLine2 = lineBreak2 && BLANKLINESTART.matcher(two).find();
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.
private Pattern BLANKLINEEND
= Pattern.compile("\\n\\r?\\n\\Z", Pattern.DOTALL);
private Pattern BLANKLINESTART
= Pattern.compile("\\A\\r?\\n\\r?\\n", Pattern.DOTALL);
/**
* Reduce the number of edits by eliminating operationally trivial equalities.
* @param diffs LinkedList of Diff objects.
*/
public void diff_cleanupEfficiency(LinkedList diffs) {
if (diffs.isEmpty()) {
return;
}
boolean changes = false;
Stack equalities = new Stack(); // Stack of equalities.
String lastequality = null; // Always equal to equalities.lastElement().text
ListIterator pointer = diffs.listIterator();
// Is there an insertion operation before the last equality.
boolean pre_ins = false;
// Is there a deletion operation before the last equality.
boolean pre_del = false;
// Is there an insertion operation after the last equality.
boolean post_ins = false;
// Is there a deletion operation after the last equality.
boolean post_del = false;
Diff thisDiff = pointer.next();
Diff safeDiff = thisDiff; // The last Diff that is known to be unsplitable.
while (thisDiff != null) {
if (thisDiff.operation == Operation.EQUAL) {
// Equality found.
if (thisDiff.text.length() < Diff_EditCost && (post_ins || post_del)) {
// Candidate found.
equalities.push(thisDiff);
pre_ins = post_ins;
pre_del = post_del;
lastequality = thisDiff.text;
} else {
// Not a candidate, and can never become one.
equalities.clear();
lastequality = null;
safeDiff = thisDiff;
}
post_ins = post_del = false;
} else {
// An insertion or deletion.
if (thisDiff.operation == Operation.DELETE) {
post_del = true;
} else {
post_ins = true;
}
/*
* Five types to be split:
* ABXYCD
* AXCD
* ABXC
* AXCD
* ABXC
*/
if (lastequality != null
&& ((pre_ins && pre_del && post_ins && post_del)
|| ((lastequality.length() < Diff_EditCost / 2)
&& ((pre_ins ? 1 : 0) + (pre_del ? 1 : 0)
+ (post_ins ? 1 : 0) + (post_del ? 1 : 0)) == 3))) {
//System.out.println("Splitting: '" + lastequality + "'");
// Walk back to offending equality.
while (thisDiff != equalities.lastElement()) {
thisDiff = pointer.previous();
}
pointer.next();
// Replace equality with a delete.
pointer.set(new Diff(Operation.DELETE, lastequality));
// Insert a corresponding an insert.
pointer.add(thisDiff = new Diff(Operation.INSERT, lastequality));
equalities.pop(); // Throw away the equality we just deleted.
lastequality = null;
if (pre_ins && pre_del) {
// No changes made which could affect previous entry, keep going.
post_ins = post_del = true;
equalities.clear();
safeDiff = thisDiff;
} else {
if (!equalities.empty()) {
// Throw away the previous equality (it needs to be reevaluated).
equalities.pop();
}
if (equalities.empty()) {
// There are no previous questionable equalities,
// walk back to the last known safe diff.
thisDiff = safeDiff;
} else {
// There is an equality we can fall back to.
thisDiff = equalities.lastElement();
}
while (thisDiff != pointer.previous()) {
// Intentionally empty loop.
}
post_ins = post_del = false;
}
changes = true;
}
}
thisDiff = pointer.hasNext() ? pointer.next() : null;
}
if (changes) {
diff_cleanupMerge(diffs);
}
}
/**
* Reorder and merge like edit sections. Merge equalities.
* Any edit section can move as long as it doesn't cross an equality.
* @param diffs LinkedList of Diff objects.
*/
public void diff_cleanupMerge(LinkedList diffs) {
diffs.add(new Diff(Operation.EQUAL, "")); // Add a dummy entry at the end.
ListIterator pointer = diffs.listIterator();
int count_delete = 0;
int count_insert = 0;
String text_delete = "";
String text_insert = "";
Diff thisDiff = pointer.next();
Diff prevEqual = null;
int commonlength;
while (thisDiff != null) {
switch (thisDiff.operation) {
case INSERT:
count_insert++;
text_insert += thisDiff.text;
prevEqual = null;
break;
case DELETE:
count_delete++;
text_delete += thisDiff.text;
prevEqual = null;
break;
case EQUAL:
if (count_delete + count_insert > 1) {
boolean both_types = count_delete != 0 && count_insert != 0;
// Delete the offending records.
pointer.previous(); // Reverse direction.
while (count_delete-- > 0) {
pointer.previous();
pointer.remove();
}
while (count_insert-- > 0) {
pointer.previous();
pointer.remove();
}
if (both_types) {
// Factor out any common prefixies.
commonlength = diff_commonPrefix(text_insert, text_delete);
if (commonlength != 0) {
if (pointer.hasPrevious()) {
thisDiff = pointer.previous();
assert thisDiff.operation == Operation.EQUAL
: "Previous diff should have been an equality.";
thisDiff.text += text_insert.substring(0, commonlength);
pointer.next();
} else {
pointer.add(new Diff(Operation.EQUAL,
text_insert.substring(0, commonlength)));
}
text_insert = text_insert.substring(commonlength);
text_delete = text_delete.substring(commonlength);
}
// Factor out any common suffixies.
commonlength = diff_commonSuffix(text_insert, text_delete);
if (commonlength != 0) {
thisDiff = pointer.next();
thisDiff.text = text_insert.substring(text_insert.length()
- commonlength) + thisDiff.text;
text_insert = text_insert.substring(0, text_insert.length()
- commonlength);
text_delete = text_delete.substring(0, text_delete.length()
- commonlength);
pointer.previous();
}
}
// Insert the merged records.
if (text_delete.length() != 0) {
pointer.add(new Diff(Operation.DELETE, text_delete));
}
if (text_insert.length() != 0) {
pointer.add(new Diff(Operation.INSERT, text_insert));
}
// Step forward to the equality.
thisDiff = pointer.hasNext() ? pointer.next() : null;
} else if (prevEqual != null) {
// Merge this equality with the previous one.
prevEqual.text += thisDiff.text;
pointer.remove();
thisDiff = pointer.previous();
pointer.next(); // Forward direction
}
count_insert = 0;
count_delete = 0;
text_delete = "";
text_insert = "";
prevEqual = thisDiff;
break;
}
thisDiff = pointer.hasNext() ? pointer.next() : null;
}
if (diffs.getLast().text.length() == 0) {
diffs.removeLast(); // Remove the dummy entry at the end.
}
/*
* Second pass: look for single edits surrounded on both sides by equalities
* which can be shifted sideways to eliminate an equality.
* e.g: ABAC -> ABAC
*/
boolean changes = false;
// Create a new iterator at the start.
// (As opposed to walking the current one back.)
pointer = diffs.listIterator();
Diff prevDiff = pointer.hasNext() ? pointer.next() : null;
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 == Operation.EQUAL &&
nextDiff.operation == Operation.EQUAL) {
// This is a single edit surrounded by equalities.
if (thisDiff.text.endsWith(prevDiff.text)) {
// Shift the edit over the previous equality.
thisDiff.text = prevDiff.text
+ thisDiff.text.substring(0, thisDiff.text.length()
- prevDiff.text.length());
nextDiff.text = prevDiff.text + nextDiff.text;
pointer.previous(); // Walk past nextDiff.
pointer.previous(); // Walk past thisDiff.
pointer.previous(); // Walk past prevDiff.
pointer.remove(); // Delete prevDiff.
pointer.next(); // Walk past thisDiff.
thisDiff = pointer.next(); // Walk past nextDiff.
nextDiff = pointer.hasNext() ? pointer.next() : null;
changes = true;
} else if (thisDiff.text.startsWith(nextDiff.text)) {
// Shift the edit over the next equality.
prevDiff.text += nextDiff.text;
thisDiff.text = thisDiff.text.substring(nextDiff.text.length())
+ nextDiff.text;
pointer.remove(); // Delete nextDiff.
nextDiff = pointer.hasNext() ? pointer.next() : null;
changes = true;
}
}
prevDiff = thisDiff;
thisDiff = nextDiff;
nextDiff = pointer.hasNext() ? pointer.next() : null;
}
// If shifts were made, the diff needs reordering and another shift sweep.
if (changes) {
diff_cleanupMerge(diffs);
}
}
/**
* loc is a location in text1, compute and return the equivalent location in
* text2.
* e.g. "The cat" vs "The big cat", 1->1, 5->8
* @param diffs LinkedList of Diff objects.
* @param loc Location within text1.
* @return Location within text2.
*/
public int diff_xIndex(LinkedList diffs, int loc) {
int chars1 = 0;
int chars2 = 0;
int last_chars1 = 0;
int last_chars2 = 0;
Diff lastDiff = null;
for (Diff aDiff : diffs) {
if (aDiff.operation != Operation.INSERT) {
// Equality or deletion.
chars1 += aDiff.text.length();
}
if (aDiff.operation != Operation.DELETE) {
// Equality or insertion.
chars2 += aDiff.text.length();
}
if (chars1 > loc) {
// Overshot the location.
lastDiff = aDiff;
break;
}
last_chars1 = chars1;
last_chars2 = chars2;
}
if (lastDiff != null && lastDiff.operation == Operation.DELETE) {
// The location was deleted.
return last_chars2;
}
// Add the remaining character length.
return last_chars2 + (loc - last_chars1);
}
/**
* Convert a Diff list into a pretty HTML report.
* @param diffs LinkedList of Diff objects.
* @return HTML representation.
*/
public String diff_prettyHtml(LinkedList diffs) {
StringBuilder html = new StringBuilder();
for (Diff aDiff : diffs) {
String text = aDiff.text.replace("&", "&").replace("<", "<")
.replace(">", ">").replace("\n", "¶
");
switch (aDiff.operation) {
case INSERT:
html.append("").append(text)
.append("");
break;
case DELETE:
html.append("").append(text)
.append("");
break;
case EQUAL:
html.append("").append(text).append("");
break;
}
}
return html.toString();
}
/**
* Compute and return the source text (all equalities and deletions).
* @param diffs LinkedList of Diff objects.
* @return Source text.
*/
public String diff_text1(LinkedList diffs) {
StringBuilder text = new StringBuilder();
for (Diff aDiff : diffs) {
if (aDiff.operation != Operation.INSERT) {
text.append(aDiff.text);
}
}
return text.toString();
}
/**
* Compute and return the destination text (all equalities and insertions).
* @param diffs LinkedList of Diff objects.
* @return Destination text.
*/
public String diff_text2(LinkedList diffs) {
StringBuilder text = new StringBuilder();
for (Diff aDiff : diffs) {
if (aDiff.operation != Operation.DELETE) {
text.append(aDiff.text);
}
}
return text.toString();
}
/**
* Compute the Levenshtein distance; the number of inserted, deleted or
* substituted characters.
* @param diffs LinkedList of Diff objects.
* @return Number of changes.
*/
public int diff_levenshtein(LinkedList diffs) {
int levenshtein = 0;
int insertions = 0;
int deletions = 0;
for (Diff aDiff : diffs) {
switch (aDiff.operation) {
case INSERT:
insertions += aDiff.text.length();
break;
case DELETE:
deletions += aDiff.text.length();
break;
case EQUAL:
// A deletion and an insertion is one substitution.
levenshtein += Math.max(insertions, deletions);
insertions = 0;
deletions = 0;
break;
}
}
levenshtein += Math.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.
*/
public String diff_toDelta(LinkedList diffs) {
StringBuilder text = new StringBuilder();
for (Diff aDiff : diffs) {
switch (aDiff.operation) {
case INSERT:
try {
text.append("+").append(URLEncoder.encode(aDiff.text, "UTF-8")
.replace('+', ' ')).append("\t");
} catch (UnsupportedEncodingException e) {
// Not likely on modern system.
throw new Error("This system does not support UTF-8.", e);
}
break;
case DELETE:
text.append("-").append(aDiff.text.length()).append("\t");
break;
case EQUAL:
text.append("=").append(aDiff.text.length()).append("\t");
break;
}
}
String delta = text.toString();
if (delta.length() != 0) {
// Strip off trailing tab character.
delta = delta.substring(0, delta.length() - 1);
delta = unescapeForEncodeUriCompatability(delta);
}
return delta;
}
/**
* Given the original text1, and an encoded string which describes the
* operations required to transform text1 into text2, compute the full diff.
* @param text1 Source string for the diff.
* @param delta Delta text.
* @return Array of Diff objects or null if invalid.
* @throws IllegalArgumentException If invalid input.
*/
public LinkedList diff_fromDelta(String text1, String delta)
throws IllegalArgumentException {
LinkedList diffs = new LinkedList();
int pointer = 0; // Cursor in text1
String[] tokens = delta.split("\t");
for (String token : tokens) {
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.substring(1);
switch (token.charAt(0)) {
case '+':
// decode would change all "+" to " "
param = param.replace("+", "%2B");
try {
param = URLDecoder.decode(param, "UTF-8");
} 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.add(new Diff(Operation.INSERT, param));
break;
case '-':
// Fall through.
case '=':
int n;
try {
n = Integer.parseInt(param);
} catch (NumberFormatException e) {
throw new IllegalArgumentException(
"Invalid number in diff_fromDelta: " + param, e);
}
if (n < 0) {
throw new IllegalArgumentException(
"Negative number in diff_fromDelta: " + param);
}
String text;
try {
text = text1.substring(pointer, pointer += n);
} catch (StringIndexOutOfBoundsException e) {
throw new IllegalArgumentException("Delta length (" + pointer
+ ") larger than source text length (" + text1.length()
+ ").", e);
}
if (token.charAt(0) == '=') {
diffs.add(new Diff(Operation.EQUAL, text));
} else {
diffs.add(new Diff(Operation.DELETE, text));
}
break;
default:
// Anything else is an error.
throw new IllegalArgumentException(
"Invalid diff operation in diff_fromDelta: " + token.charAt(0));
}
}
if (pointer != text1.length()) {
throw new IllegalArgumentException("Delta length (" + pointer
+ ") smaller than source text length (" + text1.length() + ").");
}
return diffs;
}
// MATCH FUNCTIONS
/**
* Locate the best instance of 'pattern' in 'text' near 'loc'.
* Returns -1 if no match found.
* @param text The text to search.
* @param pattern The pattern to search for.
* @param loc The location to search around.
* @return Best match index or -1.
*/
public int match_main(String text, String pattern, int loc) {
// Check for null inputs.
if (text == null || pattern == null) {
throw new IllegalArgumentException("Null inputs. (match_main)");
}
loc = Math.max(0, Math.min(loc, text.length()));
if (text.equals(pattern)) {
// Shortcut (potentially not guaranteed by the algorithm)
return 0;
} else if (text.length() == 0) {
// Nothing to match.
return -1;
} else if (loc + pattern.length() <= text.length()
&& text.substring(loc, loc + pattern.length()).equals(pattern)) {
// Perfect match at the perfect spot! (Includes case of null pattern)
return loc;
} else {
// Do a fuzzy compare.
return match_bitap(text, pattern, loc);
}
}
/**
* Locate the best instance of 'pattern' in 'text' near 'loc' using the
* Bitap algorithm. Returns -1 if no match found.
* @param text The text to search.
* @param pattern The pattern to search for.
* @param loc The location to search around.
* @return Best match index or -1.
*/
protected int match_bitap(String text, String pattern, int loc) {
assert (Match_MaxBits == 0 || pattern.length() <= Match_MaxBits)
: "Pattern too long for this application.";
// Initialise the alphabet.
Map s = match_alphabet(pattern);
// Highest score beyond which we give up.
double score_threshold = Match_Threshold;
// Is there a nearby exact match? (speedup)
int best_loc = text.indexOf(pattern, loc);
if (best_loc != -1) {
score_threshold = Math.min(match_bitapScore(0, best_loc, loc, pattern),
score_threshold);
// What about in the other direction? (speedup)
best_loc = text.lastIndexOf(pattern, loc + pattern.length());
if (best_loc != -1) {
score_threshold = Math.min(match_bitapScore(0, best_loc, loc, pattern),
score_threshold);
}
}
// Initialise the bit arrays.
int matchmask = 1 << (pattern.length() - 1);
best_loc = -1;
int bin_min, bin_mid;
int bin_max = pattern.length() + text.length();
// Empty initialization added to appease Java compiler.
int[] last_rd = new int[0];
for (int d = 0; d < pattern.length(); d++) {
// Scan for the best match; each iteration allows for one more error.
// Run a binary search to determine how far from 'loc' we can stray at
// this error level.
bin_min = 0;
bin_mid = bin_max;
while (bin_min < bin_mid) {
if (match_bitapScore(d, loc + bin_mid, loc, pattern)
<= score_threshold) {
bin_min = bin_mid;
} else {
bin_max = bin_mid;
}
bin_mid = (bin_max - bin_min) / 2 + bin_min;
}
// Use the result from this iteration as the maximum for the next.
bin_max = bin_mid;
int start = Math.max(1, loc - bin_mid + 1);
int finish = Math.min(loc + bin_mid, text.length()) + pattern.length();
int[] rd = new int[finish + 2];
rd[finish + 1] = (1 << d) - 1;
for (int j = finish; j >= start; j--) {
int charMatch;
if (text.length() <= j - 1 || !s.containsKey(text.charAt(j - 1))) {
// Out of range.
charMatch = 0;
} else {
charMatch = s.get(text.charAt(j - 1));
}
if (d == 0) {
// First pass: exact match.
rd[j] = ((rd[j + 1] << 1) | 1) & charMatch;
} else {
// Subsequent passes: fuzzy match.
rd[j] = (((rd[j + 1] << 1) | 1) & charMatch)
| (((last_rd[j + 1] | last_rd[j]) << 1) | 1) | last_rd[j + 1];
}
if ((rd[j] & matchmask) != 0) {
double score = match_bitapScore(d, j - 1, loc, pattern);
// This match will almost certainly be better than any existing
// match. But check anyway.
if (score <= score_threshold) {
// Told you so.
score_threshold = score;
best_loc = j - 1;
if (best_loc > loc) {
// When passing loc, don't exceed our current distance from loc.
start = Math.max(1, 2 * loc - best_loc);
} else {
// Already passed loc, downhill from here on in.
break;
}
}
}
}
if (match_bitapScore(d + 1, loc, loc, pattern) > score_threshold) {
// No hope for a (better) match at greater error levels.
break;
}
last_rd = rd;
}
return best_loc;
}
/**
* Compute and return the score for a match with e errors and x location.
* @param e Number of errors in match.
* @param x Location of match.
* @param loc Expected location of match.
* @param pattern Pattern being sought.
* @return Overall score for match (0.0 = good, 1.0 = bad).
*/
private double match_bitapScore(int e, int x, int loc, String pattern) {
float accuracy = (float) e / pattern.length();
int proximity = Math.abs(loc - x);
if (Match_Distance == 0) {
// Dodge divide by zero error.
return proximity == 0 ? accuracy : 1.0;
}
return accuracy + (proximity / (float) Match_Distance);
}
/**
* Initialise the alphabet for the Bitap algorithm.
* @param pattern The text to encode.
* @return Hash of character locations.
*/
protected Map match_alphabet(String pattern) {
Map s = new HashMap();
char[] char_pattern = pattern.toCharArray();
for (char c : char_pattern) {
s.put(c, 0);
}
int i = 0;
for (char c : char_pattern) {
s.put(c, s.get(c) | (1 << (pattern.length() - i - 1)));
i++;
}
return s;
}
// PATCH FUNCTIONS
/**
* Increase the context until it is unique,
* but don't let the pattern expand beyond Match_MaxBits.
* @param patch The patch to grow.
* @param text Source text.
*/
protected void patch_addContext(Patch patch, String text) {
if (text.length() == 0) {
return;
}
String pattern = text.substring(patch.start2, patch.start2 + patch.length1);
int padding = 0;
// Look for the first and last matches of pattern in text. If two different
// matches are found, increase the pattern length.
while (text.indexOf(pattern) != text.lastIndexOf(pattern)
&& pattern.length() < Match_MaxBits - Patch_Margin - Patch_Margin) {
padding += Patch_Margin;
pattern = text.substring(Math.max(0, patch.start2 - padding),
Math.min(text.length(), patch.start2 + patch.length1 + padding));
}
// Add one chunk for good luck.
padding += Patch_Margin;
// Add the prefix.
String prefix = text.substring(Math.max(0, patch.start2 - padding),
patch.start2);
if (prefix.length() != 0) {
patch.diffs.addFirst(new Diff(Operation.EQUAL, prefix));
}
// Add the suffix.
String suffix = text.substring(patch.start2 + patch.length1,
Math.min(text.length(), patch.start2 + patch.length1 + padding));
if (suffix.length() != 0) {
patch.diffs.addLast(new Diff(Operation.EQUAL, suffix));
}
// Roll back the start points.
patch.start1 -= prefix.length();
patch.start2 -= prefix.length();
// Extend the lengths.
patch.length1 += prefix.length() + suffix.length();
patch.length2 += prefix.length() + suffix.length();
}
/**
* Compute a list of patches to turn text1 into text2.
* A set of diffs will be computed.
* @param text1 Old text.
* @param text2 New text.
* @return LinkedList of Patch objects.
*/
public LinkedList patch_make(String text1, String text2) {
if (text1 == null || text2 == null) {
throw new IllegalArgumentException("Null inputs. (patch_make)");
}
// No diffs provided, compute our own.
LinkedList diffs = diff_main(text1, text2, true);
if (diffs.size() > 2) {
diff_cleanupSemantic(diffs);
diff_cleanupEfficiency(diffs);
}
return patch_make(text1, diffs);
}
/**
* Compute a list of patches to turn text1 into text2.
* text1 will be derived from the provided diffs.
* @param diffs Array of Diff objects for text1 to text2.
* @return LinkedList of Patch objects.
*/
public LinkedList patch_make(LinkedList diffs) {
if (diffs == null) {
throw new IllegalArgumentException("Null inputs. (patch_make)");
}
// No origin string provided, compute our own.
String text1 = diff_text1(diffs);
return patch_make(text1, diffs);
}
/**
* Compute a list of patches to turn text1 into text2.
* text2 is ignored, diffs are the delta between text1 and text2.
* @param text1 Old text
* @param text2 Ignored.
* @param diffs Array of Diff objects for text1 to text2.
* @return LinkedList of Patch objects.
* @deprecated Prefer patch_make(String text1, LinkedList diffs).
*/
public LinkedList patch_make(String text1, String text2,
LinkedList diffs) {
return patch_make(text1, diffs);
}
/**
* Compute a list of patches to turn text1 into text2.
* text2 is not provided, diffs are the delta between text1 and text2.
* @param text1 Old text.
* @param diffs Array of Diff objects for text1 to text2.
* @return LinkedList of Patch objects.
*/
public LinkedList patch_make(String text1, LinkedList diffs) {
if (text1 == null || diffs == null) {
throw new IllegalArgumentException("Null inputs. (patch_make)");
}
LinkedList patches = new LinkedList();
if (diffs.isEmpty()) {
return patches; // Get rid of the null case.
}
Patch patch = new Patch();
int char_count1 = 0; // Number of characters into the text1 string.
int char_count2 = 0; // Number of characters into the text2 string.
// Start with text1 (prepatch_text) and apply the diffs until we arrive at
// text2 (postpatch_text). We recreate the patches one by one to determine
// context info.
String prepatch_text = text1;
String postpatch_text = text1;
for (Diff aDiff : diffs) {
if (patch.diffs.isEmpty() && aDiff.operation != Operation.EQUAL) {
// A new patch starts here.
patch.start1 = char_count1;
patch.start2 = char_count2;
}
switch (aDiff.operation) {
case INSERT:
patch.diffs.add(aDiff);
patch.length2 += aDiff.text.length();
postpatch_text = postpatch_text.substring(0, char_count2)
+ aDiff.text + postpatch_text.substring(char_count2);
break;
case DELETE:
patch.length1 += aDiff.text.length();
patch.diffs.add(aDiff);
postpatch_text = postpatch_text.substring(0, char_count2)
+ postpatch_text.substring(char_count2 + aDiff.text.length());
break;
case EQUAL:
if (aDiff.text.length() <= 2 * Patch_Margin
&& !patch.diffs.isEmpty() && aDiff != diffs.getLast()) {
// Small equality inside a patch.
patch.diffs.add(aDiff);
patch.length1 += aDiff.text.length();
patch.length2 += aDiff.text.length();
}
if (aDiff.text.length() >= 2 * Patch_Margin) {
// Time for a new patch.
if (!patch.diffs.isEmpty()) {
patch_addContext(patch, prepatch_text);
patches.add(patch);
patch = new Patch();
// Unlike Unidiff, our patch lists have a rolling context.
// http://code.google.com/p/google-diff-match-patch/wiki/Unidiff
// Update prepatch text & pos to reflect the application of the
// just completed patch.
prepatch_text = postpatch_text;
char_count1 = char_count2;
}
}
break;
}
// Update the current character count.
if (aDiff.operation != Operation.INSERT) {
char_count1 += aDiff.text.length();
}
if (aDiff.operation != Operation.DELETE) {
char_count2 += aDiff.text.length();
}
}
// Pick up the leftover patch if not empty.
if (!patch.diffs.isEmpty()) {
patch_addContext(patch, prepatch_text);
patches.add(patch);
}
return patches;
}
/**
* Given an array of patches, return another array that is identical.
* @param patches Array of Patch objects.
* @return Array of Patch objects.
*/
public LinkedList patch_deepCopy(LinkedList patches) {
LinkedList patchesCopy = new LinkedList();
for (Patch aPatch : patches) {
Patch patchCopy = new Patch();
for (Diff aDiff : aPatch.diffs) {
Diff diffCopy = new Diff(aDiff.operation, aDiff.text);
patchCopy.diffs.add(diffCopy);
}
patchCopy.start1 = aPatch.start1;
patchCopy.start2 = aPatch.start2;
patchCopy.length1 = aPatch.length1;
patchCopy.length2 = aPatch.length2;
patchesCopy.add(patchCopy);
}
return patchesCopy;
}
/**
* Merge a set of patches onto the text. Return a patched text, as well
* as an array of true/false values indicating which patches were applied.
* @param patches Array of Patch objects
* @param text Old text.
* @return Two element Object array, containing the new text and an array of
* boolean values.
*/
public Object[] patch_apply(LinkedList patches, String text) {
if (patches.isEmpty()) {
return new Object[]{text, new boolean[0]};
}
// Deep copy the patches so that no changes are made to originals.
patches = patch_deepCopy(patches);
String nullPadding = patch_addPadding(patches);
text = nullPadding + text + nullPadding;
patch_splitMax(patches);
int x = 0;
// delta keeps track of the offset between the expected and actual location
// of the previous patch. If there are patches expected at positions 10 and
// 20, but the first patch was found at 12, delta is 2 and the second patch
// has an effective expected position of 22.
int delta = 0;
boolean[] results = new boolean[patches.size()];
for (Patch aPatch : patches) {
int expected_loc = aPatch.start2 + delta;
String text1 = diff_text1(aPatch.diffs);
int start_loc;
int end_loc = -1;
if (text1.length() > this.Match_MaxBits) {
// patch_splitMax will only provide an oversized pattern in the case of
// a monster delete.
start_loc = match_main(text,
text1.substring(0, this.Match_MaxBits), expected_loc);
if (start_loc != -1) {
end_loc = match_main(text,
text1.substring(text1.length() - this.Match_MaxBits),
expected_loc + text1.length() - this.Match_MaxBits);
if (end_loc == -1 || start_loc >= end_loc) {
// Can't find valid trailing context. Drop this patch.
start_loc = -1;
}
}
} else {
start_loc = match_main(text, text1, expected_loc);
}
if (start_loc == -1) {
// No match found. :(
results[x] = false;
// Subtract the delta for this failed patch from subsequent patches.
delta -= aPatch.length2 - aPatch.length1;
} else {
// Found a match. :)
results[x] = true;
delta = start_loc - expected_loc;
String text2;
if (end_loc == -1) {
text2 = text.substring(start_loc,
Math.min(start_loc + text1.length(), text.length()));
} else {
text2 = text.substring(start_loc,
Math.min(end_loc + this.Match_MaxBits, text.length()));
}
if (text1.equals(text2)) {
// Perfect match, just shove the replacement text in.
text = text.substring(0, start_loc) + diff_text2(aPatch.diffs)
+ text.substring(start_loc + text1.length());
} else {
// Imperfect match. Run a diff to get a framework of equivalent
// indices.
LinkedList diffs = diff_main(text1, text2, false);
if (text1.length() > this.Match_MaxBits
&& diff_levenshtein(diffs) / (float) text1.length()
> this.Patch_DeleteThreshold) {
// The end points match, but the content is unacceptably bad.
results[x] = false;
} else {
diff_cleanupSemanticLossless(diffs);
int index1 = 0;
for (Diff aDiff : aPatch.diffs) {
if (aDiff.operation != Operation.EQUAL) {
int index2 = diff_xIndex(diffs, index1);
if (aDiff.operation == Operation.INSERT) {
// Insertion
text = text.substring(0, start_loc + index2) + aDiff.text
+ text.substring(start_loc + index2);
} else if (aDiff.operation == Operation.DELETE) {
// Deletion
text = text.substring(0, start_loc + index2)
+ text.substring(start_loc + diff_xIndex(diffs,
index1 + aDiff.text.length()));
}
}
if (aDiff.operation != Operation.DELETE) {
index1 += aDiff.text.length();
}
}
}
}
}
x++;
}
// Strip the padding off.
text = text.substring(nullPadding.length(), text.length()
- nullPadding.length());
return new Object[]{text, results};
}
/**
* Add some padding on text start and end so that edges can match something.
* Intended to be called only from within patch_apply.
* @param patches Array of Patch objects.
* @return The padding string added to each side.
*/
public String patch_addPadding(LinkedList patches) {
short paddingLength = this.Patch_Margin;
String nullPadding = "";
for (short x = 1; x <= paddingLength; x++) {
nullPadding += String.valueOf((char) x);
}
// Bump all the patches forward.
for (Patch aPatch : patches) {
aPatch.start1 += paddingLength;
aPatch.start2 += paddingLength;
}
// Add some padding on start of first diff.
Patch patch = patches.getFirst();
LinkedList diffs = patch.diffs;
if (diffs.isEmpty() || diffs.getFirst().operation != Operation.EQUAL) {
// Add nullPadding equality.
diffs.addFirst(new Diff(Operation.EQUAL, nullPadding));
patch.start1 -= paddingLength; // Should be 0.
patch.start2 -= paddingLength; // Should be 0.
patch.length1 += paddingLength;
patch.length2 += paddingLength;
} else if (paddingLength > diffs.getFirst().text.length()) {
// Grow first equality.
Diff firstDiff = diffs.getFirst();
int extraLength = paddingLength - firstDiff.text.length();
firstDiff.text = nullPadding.substring(firstDiff.text.length())
+ firstDiff.text;
patch.start1 -= extraLength;
patch.start2 -= extraLength;
patch.length1 += extraLength;
patch.length2 += extraLength;
}
// Add some padding on end of last diff.
patch = patches.getLast();
diffs = patch.diffs;
if (diffs.isEmpty() || diffs.getLast().operation != Operation.EQUAL) {
// Add nullPadding equality.
diffs.addLast(new Diff(Operation.EQUAL, nullPadding));
patch.length1 += paddingLength;
patch.length2 += paddingLength;
} else if (paddingLength > diffs.getLast().text.length()) {
// Grow last equality.
Diff lastDiff = diffs.getLast();
int extraLength = paddingLength - lastDiff.text.length();
lastDiff.text += nullPadding.substring(0, extraLength);
patch.length1 += extraLength;
patch.length2 += extraLength;
}
return nullPadding;
}
/**
* Look through the patches and break up any which are longer than the
* maximum limit of the match algorithm.
* Intended to be called only from within patch_apply.
* @param patches LinkedList of Patch objects.
*/
public void patch_splitMax(LinkedList patches) {
short patch_size = Match_MaxBits;
String precontext, postcontext;
Patch patch;
int start1, start2;
boolean empty;
Operation diff_type;
String diff_text;
ListIterator pointer = patches.listIterator();
Patch bigpatch = pointer.hasNext() ? pointer.next() : null;
while (bigpatch != null) {
if (bigpatch.length1 <= Match_MaxBits) {
bigpatch = pointer.hasNext() ? pointer.next() : null;
continue;
}
// Remove the big old patch.
pointer.remove();
start1 = bigpatch.start1;
start2 = bigpatch.start2;
precontext = "";
while (!bigpatch.diffs.isEmpty()) {
// Create one of several smaller patches.
patch = new Patch();
empty = true;
patch.start1 = start1 - precontext.length();
patch.start2 = start2 - precontext.length();
if (precontext.length() != 0) {
patch.length1 = patch.length2 = precontext.length();
patch.diffs.add(new Diff(Operation.EQUAL, precontext));
}
while (!bigpatch.diffs.isEmpty()
&& patch.length1 < patch_size - Patch_Margin) {
diff_type = bigpatch.diffs.getFirst().operation;
diff_text = bigpatch.diffs.getFirst().text;
if (diff_type == Operation.INSERT) {
// Insertions are harmless.
patch.length2 += diff_text.length();
start2 += diff_text.length();
patch.diffs.addLast(bigpatch.diffs.removeFirst());
empty = false;
} else if (diff_type == Operation.DELETE && patch.diffs.size() == 1
&& patch.diffs.getFirst().operation == Operation.EQUAL
&& diff_text.length() > 2 * patch_size) {
// This is a large deletion. Let it pass in one chunk.
patch.length1 += diff_text.length();
start1 += diff_text.length();
empty = false;
patch.diffs.add(new Diff(diff_type, diff_text));
bigpatch.diffs.removeFirst();
} else {
// Deletion or equality. Only take as much as we can stomach.
diff_text = diff_text.substring(0, Math.min(diff_text.length(),
patch_size - patch.length1 - Patch_Margin));
patch.length1 += diff_text.length();
start1 += diff_text.length();
if (diff_type == Operation.EQUAL) {
patch.length2 += diff_text.length();
start2 += diff_text.length();
} else {
empty = false;
}
patch.diffs.add(new Diff(diff_type, diff_text));
if (diff_text.equals(bigpatch.diffs.getFirst().text)) {
bigpatch.diffs.removeFirst();
} else {
bigpatch.diffs.getFirst().text = bigpatch.diffs.getFirst().text
.substring(diff_text.length());
}
}
}
// Compute the head context for the next patch.
precontext = diff_text2(patch.diffs);
precontext = precontext.substring(Math.max(0, precontext.length()
- Patch_Margin));
// Append the end context for this patch.
if (diff_text1(bigpatch.diffs).length() > Patch_Margin) {
postcontext = diff_text1(bigpatch.diffs).substring(0, Patch_Margin);
} else {
postcontext = diff_text1(bigpatch.diffs);
}
if (postcontext.length() != 0) {
patch.length1 += postcontext.length();
patch.length2 += postcontext.length();
if (!patch.diffs.isEmpty()
&& patch.diffs.getLast().operation == Operation.EQUAL) {
patch.diffs.getLast().text += postcontext;
} else {
patch.diffs.add(new Diff(Operation.EQUAL, postcontext));
}
}
if (!empty) {
pointer.add(patch);
}
}
bigpatch = pointer.hasNext() ? pointer.next() : null;
}
}
/**
* Take a list of patches and return a textual representation.
* @param patches List of Patch objects.
* @return Text representation of patches.
*/
public String patch_toText(List patches) {
StringBuilder text = new StringBuilder();
for (Patch aPatch : patches) {
text.append(aPatch);
}
return text.toString();
}
/**
* Parse a textual representation of patches and return a List of Patch
* objects.
* @param textline Text representation of patches.
* @return List of Patch objects.
* @throws IllegalArgumentException If invalid input.
*/
public List patch_fromText(String textline)
throws IllegalArgumentException {
List patches = new LinkedList();
if (textline.length() == 0) {
return patches;
}
List textList = Arrays.asList(textline.split("\n"));
LinkedList text = new LinkedList(textList);
Patch patch;
Pattern patchHeader
= Pattern.compile("^@@ -(\\d+),?(\\d*) \\+(\\d+),?(\\d*) @@$");
Matcher m;
char sign;
String line;
while (!text.isEmpty()) {
m = patchHeader.matcher(text.getFirst());
if (!m.matches()) {
throw new IllegalArgumentException(
"Invalid patch string: " + text.getFirst());
}
patch = new Patch();
patches.add(patch);
patch.start1 = Integer.parseInt(m.group(1));
if (m.group(2).length() == 0) {
patch.start1--;
patch.length1 = 1;
} else if (m.group(2).equals("0")) {
patch.length1 = 0;
} else {
patch.start1--;
patch.length1 = Integer.parseInt(m.group(2));
}
patch.start2 = Integer.parseInt(m.group(3));
if (m.group(4).length() == 0) {
patch.start2--;
patch.length2 = 1;
} else if (m.group(4).equals("0")) {
patch.length2 = 0;
} else {
patch.start2--;
patch.length2 = Integer.parseInt(m.group(4));
}
text.removeFirst();
while (!text.isEmpty()) {
try {
sign = text.getFirst().charAt(0);
} catch (IndexOutOfBoundsException e) {
// Blank line? Whatever.
text.removeFirst();
continue;
}
line = text.getFirst().substring(1);
line = line.replace("+", "%2B"); // decode would change all "+" to " "
try {
line = URLDecoder.decode(line, "UTF-8");
} 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 patch_fromText: " + line, e);
}
if (sign == '-') {
// Deletion.
patch.diffs.add(new Diff(Operation.DELETE, line));
} else if (sign == '+') {
// Insertion.
patch.diffs.add(new Diff(Operation.INSERT, line));
} else if (sign == ' ') {
// Minor equality.
patch.diffs.add(new Diff(Operation.EQUAL, line));
} else if (sign == '@') {
// Start of next patch.
break;
} else {
// WTF?
throw new IllegalArgumentException(
"Invalid patch mode '" + sign + "' in: " + line);
}
text.removeFirst();
}
}
return patches;
}
/**
* Class representing one diff operation.
*/
public static class Diff {
/**
* One of: INSERT, DELETE or EQUAL.
*/
public Operation operation;
/**
* The text associated with this diff operation.
*/
public String text;
/**
* Constructor. Initializes the diff with the provided values.
* @param operation One of INSERT, DELETE or EQUAL.
* @param text The text being applied.
*/
public Diff(Operation operation, String text) {
// Construct a diff with the specified operation and text.
this.operation = operation;
this.text = text;
}
/**
* Display a human-readable version of this Diff.
* @return text version.
*/
public String toString() {
String prettyText = this.text.replace('\n', '\u00b6');
return "Diff(" + this.operation + ",\"" + prettyText + "\")";
}
/**
* Create a numeric hash value for a Diff.
* This function is not used by DMP.
* @return Hash value.
*/
@Override
public int hashCode() {
final int prime = 31;
int result = (operation == null) ? 0 : operation.hashCode();
result += prime * ((text == null) ? 0 : text.hashCode());
return result;
}
/**
* Is this Diff equivalent to another Diff?
* @param obj Another Diff to compare against.
* @return true or false.
*/
@Override
public boolean equals(Object obj) {
if (this == obj) {
return true;
}
if (obj == null) {
return false;
}
if (getClass() != obj.getClass()) {
return false;
}
Diff other = (Diff) obj;
if (operation != other.operation) {
return false;
}
if (text == null) {
if (other.text != null) {
return false;
}
} else if (!text.equals(other.text)) {
return false;
}
return true;
}
}
/**
* Class representing one patch operation.
*/
public static class Patch {
public LinkedList diffs;
public int start1;
public int start2;
public int length1;
public int length2;
/**
* Constructor. Initializes with an empty list of diffs.
*/
public Patch() {
this.diffs = new LinkedList();
}
/**
* Emmulate GNU diff's format.
* Header: @@ -382,8 +481,9 @@
* Indicies are printed as 1-based, not 0-based.
* @return The GNU diff string.
*/
public String toString() {
String coords1, coords2;
if (this.length1 == 0) {
coords1 = this.start1 + ",0";
} else if (this.length1 == 1) {
coords1 = Integer.toString(this.start1 + 1);
} else {
coords1 = (this.start1 + 1) + "," + this.length1;
}
if (this.length2 == 0) {
coords2 = this.start2 + ",0";
} else if (this.length2 == 1) {
coords2 = Integer.toString(this.start2 + 1);
} else {
coords2 = (this.start2 + 1) + "," + this.length2;
}
StringBuilder text = new StringBuilder();
text.append("@@ -").append(coords1).append(" +").append(coords2)
.append(" @@\n");
// Escape the body of the patch with %xx notation.
for (Diff aDiff : this.diffs) {
switch (aDiff.operation) {
case INSERT:
text.append('+');
break;
case DELETE:
text.append('-');
break;
case EQUAL:
text.append(' ');
break;
}
try {
text.append(URLEncoder.encode(aDiff.text, "UTF-8").replace('+', ' '))
.append("\n");
} catch (UnsupportedEncodingException e) {
// Not likely on modern system.
throw new Error("This system does not support UTF-8.", e);
}
}
return unescapeForEncodeUriCompatability(text.toString());
}
}
/**
* 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
* URLEncoder.encode which returns uppercase hex.
*
* Example: "%3F" -> "?", "%24" -> "$", etc.
*
* @param str The string to escape.
* @return The escaped string.
*/
private static String unescapeForEncodeUriCompatability(String str) {
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", "#");
}
}