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/*******************************************************************************
* Copyright (c) 2000, 2009 IBM Corporation and others.
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
* Contributors:
* IBM Corporation - initial API and implementation
*******************************************************************************/
package org.eclipse.ui.internal.texteditor.quickdiff.compare.equivalence;
import java.util.ConcurrentModificationException;
import org.eclipse.core.runtime.Assert;
import org.eclipse.jface.text.source.ILineRange;
import org.eclipse.compare.rangedifferencer.IRangeComparator;
/**
* Implements the <code>IRangeComparator</code> interface for lines in
* a document. A <code>DocEquivalenceComparator</code> is used as the
* input for the <code>RangeDifferencer</code> engine to perform a
* line oriented compare on documents.
* <p>
* A <code>DocEquivalenceComparator</code> uses a
* <code>DocumentEquivalenceClass</code> to compare ranges.
* </p>
*/
public final class DocEquivalenceComparator implements IRangeComparator {
private final DocumentEquivalenceClass fEquivalenceClass;
private final int fLineOffset;
private final int fLines;
private boolean fSkip= false;
public DocEquivalenceComparator(DocumentEquivalenceClass equivalenceClass, ILineRange range) {
fEquivalenceClass= equivalenceClass;
if (range == null) {
fLineOffset= 0;
fLines= fEquivalenceClass.getCount();
} else {
fLineOffset= range.getStartLine();
fLines= range.getNumberOfLines();
Assert.isTrue(fLineOffset >= 0);
Assert.isTrue(fLineOffset + fLines <= fEquivalenceClass.getCount());
}
}
/**
* Returns the number of lines in the document.
*
* @return number of lines
*/
@Override
public int getRangeCount() {
return fLines;
}
/**
* Returns <code>true</code> if a line given by the first index
* matches a line specified by the other <code>IRangeComparator</code> and index.
*
* @param thisIndex the number of the line within this range comparator
* @param other the range comparator to compare this with
* @param otherIndex the number of the line within the other comparator
* @return <code>true</code> if the lines are equal
*/
@Override
public boolean rangesEqual(int thisIndex, IRangeComparator other, int otherIndex) {
if (other instanceof DocEquivalenceComparator) {
DocEquivalenceComparator dec= (DocEquivalenceComparator) other;
try {
Hash ourHash= getHash(thisIndex);
Hash otherHash= dec.getHash(otherIndex);
return ourHash.equals(otherHash);
} catch (ConcurrentModificationException e) {
fSkip= true;
} catch (IndexOutOfBoundsException e) {
fSkip= true;
}
}
return false;
}
Hash getHash(int index) {
return fEquivalenceClass.getHash(fLineOffset + index);
}
/**
* Aborts the comparison if the number of tokens is too large.
*
* @param length the current edit distance
* @param max the maximal edit distance
* @param other the comparator with which to compare
* @return <code>true</code> to abort a token comparison
*/
@Override
public boolean skipRangeComparison(int length, int max, IRangeComparator other) {
return fSkip;
}
}
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