<NME> diff_match_patch.java <BEF> /* * 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 name.fraser.neil.plaintext; 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 fraser@google.com (Neil Fraser) */ /** * Class containing the diff, match and patch methods. * Also contains the behaviour settings. */ public class diff_match_patch { // Defaults. // Set these on your diff_match_patch 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<String> lineArray; protected LinesToCharsResult(String chars1, String chars2, List<String> 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> 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> 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> 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<Diff> diffs; if (text1.equals(text2)) { diffs = new LinkedList<Diff>(); 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> diff_compute(String text1, String text2, boolean checklines, long deadline) { LinkedList<Diff> diffs = new LinkedList<Diff>(); 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<Diff> diffs_a = diff_main(text1_a, text2_a, checklines, deadline); LinkedList<Diff> 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> 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<String> linearray = b.lineArray; LinkedList<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.add(new Diff(Operation.EQUAL, "")); int count_delete = 0; int count_insert = 0; String text_delete = ""; String text_insert = ""; ListIterator<Diff> 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> 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<Diff> diffs = new LinkedList<Diff>(); 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> 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<Diff> diffs = diff_main(text1a, text2a, false, deadline); LinkedList<Diff> 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<String> lineArray = new ArrayList<String>(); Map<String, Integer> lineHash = new HashMap<String, Integer>(); // 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<String> lineArray, Map<String, Integer> 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<Diff> diffs, List<String> 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); * @return A string made up of both ints. */ protected String diff_footprint(int x, int y) { // Performance note: Inlining this function seems to slow down execution. return x + "," + y; } 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<Diff> diffs) { if (diffs.isEmpty()) { return; } boolean changes = false; Stack<Diff> equalities = new Stack<Diff>(); // Stack of qualities. String lastequality = null; // Always equal to equalities.lastElement().text ListIterator<Diff> 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: <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 = 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 c<ins>at c</ins>ame. -> The <ins>cat </ins>came. * @param diffs LinkedList of Diff objects. */ public void diff_cleanupSemanticLossless(LinkedList<Diff> diffs) { String equality1, edit, equality2; String commonString; int commonOffset; int score, bestScore; String bestEquality1, bestEdit, bestEquality2; // Create a new iterator at the start. ListIterator<Diff> 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<Diff> diffs) { if (diffs.isEmpty()) { return; } boolean changes = false; Stack<Diff> equalities = new Stack<Diff>(); // Stack of equalities. String lastequality = null; // Always equal to equalities.lastElement().text ListIterator<Diff> 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: * <ins>A</ins><del>B</del>XY<ins>C</ins><del>D</del> * <ins>A</ins>X<ins>C</ins><del>D</del> * <ins>A</ins><del>B</del>X<ins>C</ins> * <ins>A</del>X<ins>C</ins><del>D</del> * <ins>A</ins><del>B</del>X<del>C</del> */ if (lastequality != 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<Diff> diffs) { diffs.add(new Diff(Operation.EQUAL, "")); // Add a dummy entry at the end. ListIterator<Diff> 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: A<ins>BA</ins>C -> <ins>AB</ins>AC */ 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<Diff> 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<Diff> diffs) { StringBuilder html = new StringBuilder(); for (Diff aDiff : diffs) { String text = aDiff.text.replace("&", "&amp;").replace("<", "&lt;") .replace(">", "&gt;").replace("\n", "&para;<br>"); switch (aDiff.operation) { case INSERT: html.append("<ins style=\"background:#e6ffe6;\">").append(text) .append("</ins>"); break; case DELETE: html.append("<del style=\"background:#ffe6e6;\">").append(text) .append("</del>"); break; case EQUAL: html.append("<span>").append(text).append("</span>"); 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<Diff> 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<Diff> 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<Diff> 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<Diff> 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> diff_fromDelta(String text1, String delta) throws IllegalArgumentException { LinkedList<Diff> diffs = new LinkedList<Diff>(); 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<Character, Integer> 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<Character, Integer> match_alphabet(String pattern) { Map<Character, Integer> s = new HashMap<Character, Integer>(); 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> 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<Diff> 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> patch_make(LinkedList<Diff> 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<Diff> diffs). */ public LinkedList<Patch> patch_make(String text1, String text2, LinkedList<Diff> 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> patch_make(String text1, LinkedList<Diff> diffs) { if (text1 == null || diffs == null) { throw new IllegalArgumentException("Null inputs. (patch_make)"); } LinkedList<Patch> patches = new LinkedList<Patch>(); 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;
{'addition_count': 1, 'commit_subject': 'Increase C# diff speed by more than 100%, increase Java diff speed by 14%.', 'deletion_count': 2, 'file_extension': '.java', 'lang': 'java', 'license': 'apache-2.0', 'repo_name': 'GerHobbelt/google-diff-match-patch'}