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Java > Open Source Codes > org > eclipse > compare > rangedifferencer > IRangeComparator


1 /*******************************************************************************
2  * Copyright (c) 2000, 2006 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.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 public interface IRangeComparator {
30
31     /**
32      * Returns the number of comparable entities.
33      *
34      * @return the number of comparable entities
35      */
36     int getRangeCount();
37
38     /**
39      * Returns whether the comparable entity given by the first index
40      * matches an entity specified by the other <code>IRangeComparator</code> and index.
41      *
42      * @param thisIndex the index of the comparable entity within this <code>IRangeComparator</code>
43      * @param other the IRangeComparator to compare this with
44      * @param otherIndex the index of the comparable entity within the other <code>IRangeComparator</code>
45      * @return <code>true</code> if the comparable entities are equal
46      */
47     boolean rangesEqual(int thisIndex, IRangeComparator other, int otherIndex);
48
49     /**
50      * Returns whether a comparison should be skipped because it would be too costly (or lengthy).
51      *
52      * @param length a number on which to base the decision whether to return
53      * <code>true</code> or <code>false</code>
54      * @param maxLength another number on which to base the decision whether to return
55      * <code>true</code> or <code>false</code>
56      * @param other the other <code>IRangeComparator</code> to compare with
57      * @return <code>true</code> to avoid a too lengthy range comparison
58      */
59     boolean skipRangeComparison(int length, int maxLength, IRangeComparator other);
60 }
61
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