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Java > Open Source Codes > org > eclipse > ui > internal > texteditor > quickdiff > compare > rangedifferencer > IRangeComparator


1 /*******************************************************************************
2  * Copyright (c) 2000, 2005 IBM Corporation and others.
3  * All rights reserved. This program and the accompanying materials
4  * are made available under the terms of the Eclipse Public License v1.0
5  * which accompanies this distribution, and is available at
6  * http://www.eclipse.org/legal/epl-v10.html
7  *
8  * Contributors:
9  * IBM Corporation - initial API and implementation
10  *******************************************************************************/
11 package org.eclipse.ui.internal.texteditor.quickdiff.compare.rangedifferencer;
12
13 /**
14  * For breaking an object to compare into a sequence of comparable entities.
15  * <p>
16  * It is used by <code>RangeDifferencer</code> to find longest sequences of
17  * matching and non-matching ranges.
18  * <p>
19  * For example, to compare two text documents and find longest common sequences
20  * of matching and non-matching lines, the implementation must break the document
21  * into lines. <code>getRangeCount</code> would return the number of lines in the
22  * document, and <code>rangesEqual</code> would compare a specified line given
23  * with one in another <code>IRangeComparator</code>.
24  * </p>
25  * <p>
26  * Clients should implement this interface; there is no standard implementation.
27  * </p>
28  *
29  * @since 3.0
30  */
31 public interface IRangeComparator {
32
33     /**
34      * Returns the number of comparable entities.
35      *
36      * @return the number of comparable entities
37      */
38     int getRangeCount();
39
40     /**
41      * Returns whether the comparable entity given by the first index
42      * matches an entity specified by the other <code>IRangeComparator</code> and index.
43      *
44      * @param thisIndex the index of the comparable entity within this <code>IRangeComparator</code>
45      * @param other the IRangeComparator to compare this with
46      * @param otherIndex the index of the comparable entity within the other <code>IRangeComparator</code>
47      * @return <code>true</code> if the comparable entities are equal
48      */
49     boolean rangesEqual(int thisIndex, IRangeComparator other, int otherIndex);
50
51     /**
52      * Returns whether a comparison should be skipped because it would be too costly (or lengthy).
53      *
54      * @param length a number on which to base the decision whether to return
55      * <code>true</code> or <code>false</code>
56      * @param maxLength another number on which to base the decision whether to return
57      * <code>true</code> or <code>false</code>
58      * @param other the other <code>IRangeComparator</code> to compare with
59      * @return <code>true</code> to avoid a too lengthy range comparison
60      */
61     boolean skipRangeComparison(int length, int maxLength, IRangeComparator other);
62 }
63
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