org.pageseeder.ox.diffx.util.DiffXBasic Maven / Gradle / Ivy
/*
* Copyright 2021 Allette Systems (Australia)
* http://www.allette.com.au
*
* 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.pageseeder.ox.diffx.util;
import org.pageseeder.diffx.algorithm.*;
import org.pageseeder.diffx.event.AttributeEvent;
import org.pageseeder.diffx.event.DiffXEvent;
import org.pageseeder.diffx.format.DiffXFormatter;
import org.pageseeder.diffx.sequence.EventSequence;
import java.io.IOException;
/**
* Performs the diff comparison using the LCS algorithm.
*
* @author Christophe Lauret
* @version 30 October 2013
*/
public final class DiffXBasic extends DiffXAlgorithmBase {
// state variables ----------------------------------------------------------------------------
/**
* Matrix storing the paths.
*/
private transient Matrix matrix;
/**
* The state of the elements.
*/
private transient ElementState estate = new ElementState();
// constructor --------------------------------------------------------------------------------
/**
* Creates a new DiffXAlgorithmBase.
*
* @param seq0 The first sequence to compare.
* @param seq1 The second sequence to compare.
*/
public DiffXBasic(EventSequence seq0, EventSequence seq1) {
super(seq0, seq1);
this.matrix = setupMatrix(seq0, seq1);
}
// methods ------------------------------------------------------------------------------------
/**
* Returns the length of the longest common sequence.
*
* @return the length of the longest common sequence.
*/
@Override
public int length() {
// case when one of the sequences is empty
if (this.length1 == 0 || this.length2 == 0) {
this.length = 0;
}
// normal case
if (this.length < 0) {
this.matrix.setup(this.length1 + 1, this.length2 + 1);
// allocate storage for array L;
for (int i = super.length1; i >= 0; i--) {
for (int j = super.length2; j >= 0; j--) {
// we reach the end of the sequence (fill with 0)
if (i >= super.length1 || j >= super.length2) {
this.matrix.set(i, j, 0);
} else {
// the events are the same
if (this.sequence1.getEvent(i).equals(this.sequence2.getEvent(j))) {
this.matrix.incrementPathBy(i, j, maxWeight(this.sequence1.getEvent(i), this.sequence2.getEvent(j)));
// different events
} else {
this.matrix.incrementByMaxPath(i, j);
}
}
}
}
this.length = this.matrix.get(0, 0);
}
return this.length;
}
/**
* Writes the diff sequence using the specified formatter.
*
* @param formatter The formatter that will handle the output.
*
* @throws IOException If thrown by the formatter.
*/
@Override
public void process(DiffXFormatter formatter) throws IOException {
// handle the case when one of the two sequences is empty
processEmpty(formatter);
if (this.length1 == 0 || this.length2 == 0) return;
// calculate the LCS length to fill the matrix
length();
int i = 0;
int j = 0;
DiffXEvent e1 = this.sequence1.getEvent(i);
DiffXEvent e2 = this.sequence2.getEvent(j);
// start walking the matrix
while (i < super.length1 && j < super.length2) {
e1 = this.sequence1.getEvent(i);
e2 = this.sequence2.getEvent(j);
// both elements are considered equal
if (e1.equals(e2)) {
// if we can format checking at the stack, let's do it
if (this.estate.okFormat(e1)) {
formatter.format(e1);
this.estate.format(e1);
i++;
j++;
// otherwise maybe we should insert.
} else if (this.estate.okInsert(e1)) {
formatter.insert(e1);
this.estate.insert(e1);
i++;
// or delete.
} else if (this.estate.okDelete(e2)) {
formatter.delete(e2);
this.estate.delete(e2);
j++;
} else {
break;
}
// we can only insert or delete, priority to insert
} else if (this.matrix.isGreaterX(i, j)) {
// follow the natural path and insert
if (this.estate.okInsert(e1)) {
formatter.insert(e1);
this.estate.insert(e1);
i++;
// go counter current and delete
} else if (this.estate.okDelete(e2)) {
formatter.delete(e2);
this.estate.delete(e2);
j++;
} else {
break;
}
// we can only insert or delete, priority to delete
} else if (this.matrix.isGreaterY(i, j)) {
// follow the natural and delete
if (this.estate.okDelete(e2)) {
formatter.delete(e2);
this.estate.delete(e2);
j++;
// insert (counter-current)
} else if (this.estate.okInsert(e1)) {
formatter.insert(e1);
this.estate.insert(e1);
i++;
} else {
break;
}
// elements from i inserted and j deleted
// we have to make a choice for where we are going
} else if (this.matrix.isSameXY(i, j)) {
// we can insert the closing tag
if (this.estate.okInsert(e1)
&& !(e2 instanceof AttributeEvent && !(e1 instanceof AttributeEvent))) {
this.estate.insert(e1);
formatter.insert(e1);
i++;
// we can delete the closing tag
} else if (this.estate.okDelete(e2)
&& !(e1 instanceof AttributeEvent && !(e2 instanceof AttributeEvent))) {
formatter.delete(e2);
this.estate.delete(e2);
j++;
} else {
break;
}
} else {
break;
}
}
// finish off the events from the first sequence
while (i < super.length1) {
this.estate.insert(this.sequence1.getEvent(i));
formatter.insert(this.sequence1.getEvent(i));
i++;
}
// finish off the events from the second sequence
while (j < super.length2) {
this.estate.delete(this.sequence2.getEvent(j));
formatter.delete(this.sequence2.getEvent(j));
j++;
}
// free some resources
// matrix.release();
}
// private helpers (probably inlined by the compiler) -----------------------------------
/**
* Writes the diff sequence using the specified formatter when one of
* the sequences is empty.
*
* The result becomes either only insertions (when the second sequence is
* empty) or deletions (when the first sequence is empty).
*
* @param formatter The formatter that will handle the output.
*
* @throws IOException If thrown by the formatter.
*/
private void processEmpty(DiffXFormatter formatter) throws IOException {
// the first sequence is empty, events from the second sequence have been deleted
if (this.length1 == 0) {
for (int i = 0; i < this.length2; i++) {
formatter.delete(this.sequence2.getEvent(i));
}
}
// the second sequence is empty, events from the first sequence have been inserted
if (this.length2 == 0) {
for (int i = 0; i < this.length1; i++) {
formatter.insert(this.sequence1.getEvent(i));
}
}
}
/**
* Determines the most appropriate matrix to use.
*
*
Calculates the maximum length of the shortest weighted path if both sequences
* are totally different, which corresponds to the sum of all the events.
*
* @param s1 The first sequence.
* @param s2 The second sequence.
*
* @return The most appropriate matrix.
*/
private static Matrix setupMatrix(EventSequence s1, EventSequence s2) {
int max = 0;
for (int i = 0; i < s1.size(); i++) {
max += s1.getEvent(i).getWeight();
}
for (int i = 0; i < s2.size(); i++) {
max += s2.getEvent(i).getWeight();
}
if (max > Short.MAX_VALUE) return new MatrixInt();
else return new MatrixShort();
}
/**
* Returns the max weight of the two events.
*
* @param e1 The first event.
* @param e2 The second event.
*
* @return The weight for the event.
*/
private int maxWeight(DiffXEvent e1, DiffXEvent e2) {
return e1.getWeight() > e2.getWeight() ? e1.getWeight() : e2.getWeight();
}
}