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Java > Open Source Codes > org > eclipse > ui > internal > texteditor > quickdiff > compare > equivalence > DocumentEquivalenceClass


1 /*******************************************************************************
2  * Copyright (c) 2005, 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.ui.internal.texteditor.quickdiff.compare.equivalence;
12
13 import java.util.ArrayList JavaDoc;
14 import java.util.Arrays JavaDoc;
15 import java.util.Collections JavaDoc;
16 import java.util.ConcurrentModificationException JavaDoc;
17
18 import org.eclipse.core.runtime.Assert;
19
20 import org.eclipse.jface.text.BadLocationException;
21 import org.eclipse.jface.text.DocumentEvent;
22 import org.eclipse.jface.text.IDocument;
23 import org.eclipse.jface.text.IRegion;
24
25 /**
26  * @since 3.2
27  */
28 public final class DocumentEquivalenceClass {
29
30     private static final boolean DEBUG= false;
31     
32     private final ArrayList JavaDoc fHashes;
33     private IDocument fDocument;
34     private final IHashFunction fHashFunction;
35     
36     public DocumentEquivalenceClass(IDocument document) {
37         this(document, new DJBHashFunction());
38     }
39     
40     public DocumentEquivalenceClass(IDocument document, IHashFunction hashFunction) {
41         fDocument= document;
42         Object JavaDoc[] nulls= new Object JavaDoc[fDocument.getNumberOfLines()];
43         fHashes= new ArrayList JavaDoc(Arrays.asList(nulls));
44
45         if (hashFunction == null)
46             throw new NullPointerException JavaDoc("hashFunction"); //$NON-NLS-1$
47 fHashFunction= hashFunction;
48     }
49     
50     /**
51      * Returns the equivalence hash for line <code>line</code>.
52      *
53      * @param line the line for which to get the equivalent hash
54      * @return the hash in the equivalence class defined by the hash
55      * function
56      * @throws IndexOutOfBoundsException if <code>line</code> is not a
57      * legal document line
58      * @throws ConcurrentModificationException if the document is
59      * modified concurrently to this method call
60      */
61     public Hash getHash(int line) {
62         try {
63             return internalGetHash(line);
64         } catch (BadLocationException x) {
65             throw new ConcurrentModificationException JavaDoc();
66         }
67     }
68
69     private Hash internalGetHash(int line) throws BadLocationException {
70         Hash hash= (Hash) fHashes.get(line);
71         if (hash == null) {
72             if (fDocument == null)
73                 throw new AssertionError JavaDoc("hash cannot be null after loadAndForget"); //$NON-NLS-1$
74
75             IRegion lineRegion= fDocument.getLineInformation(line);
76             String JavaDoc lineContents= fDocument.get(lineRegion.getOffset(), lineRegion.getLength());
77             hash= fHashFunction.computeHash(lineContents);
78             fHashes.set(line, hash);
79         }
80         
81         return hash;
82     }
83
84     /**
85      * Cleanses the lines affected by the document event from the
86      * internal hash cache. Must be called before the document is
87      * modified (in documentAboutToBeChanged).
88      *
89      * @param event the document event
90      */
91     public void update(DocumentEvent event) {
92         if (fDocument == null)
93             throw new IllegalStateException JavaDoc("update must not be called after loadAndForget"); //$NON-NLS-1$
94 try {
95             internalUpdate(event);
96         } catch (BadLocationException x) {
97             throw new ConcurrentModificationException JavaDoc();
98         }
99     }
100     
101     private void internalUpdate(DocumentEvent event) throws BadLocationException {
102         int linesBefore= fDocument.getNumberOfLines(event.getOffset(), event.getLength());
103         String JavaDoc text= event.getText();
104         int linesAfter= (text == null ? 0 : fDocument.computeNumberOfLines(text)) + 1;
105         int firstLine= fDocument.getLineOfOffset(event.getOffset());
106         
107         int delta= linesAfter - linesBefore;
108         int changed= Math.min(linesAfter, linesBefore);
109         
110         if (delta > 0) {
111             Object JavaDoc[] nulls= new Object JavaDoc[delta];
112             fHashes.addAll(firstLine + changed, Arrays.asList(nulls));
113         } else if (delta < 0) {
114             fHashes.subList(firstLine, firstLine - delta).clear();
115         }
116         Collections.fill(fHashes.subList(firstLine, firstLine + changed), null);
117     }
118
119     /**
120      * @return the number of items
121      */
122     public int getCount() {
123         return fHashes.size();
124     }
125
126     public void setDocument(IDocument document) {
127         Assert.isNotNull(document);
128         if (DEBUG)
129             Assert.isTrue(document.get().equals(fDocument.get()));
130         fDocument= document;
131     }
132
133     /**
134      * Computes all hashes and forgets the document. Don't call update
135      * afterwards.
136      */
137     public void loadAndForget() {
138         int count= getCount();
139         for (int line= 0; line < count; line++)
140             getHash(line);
141         
142         fDocument= null;
143     }
144 }
145
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