DocumentReader


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.ui.editors.text;
12  
13  import java.io.IOException  ;
14  import java.io.Reader  ;
15  
16  import org.eclipse.core.runtime.Assert;
17  
18  import org.eclipse.jface.text.BadLocationException;
19  import org.eclipse.jface.text.DocumentEvent;
20  import org.eclipse.jface.text.IDocument;
21  import org.eclipse.jface.text.IDocumentListener;
22  
23  
24  /**
25   * A <code>Reader</code> that reads from an <code>IDocument</code>.
26   * The reader ensures that its content is the same as the document
27   * content when the stream was created.
28   * <p>
29   * Note that {@link #close()} must be called to release any acquired
30   * resources.
31   * </p>
32   *
33   * @since 3.1
34   */
35  class DocumentReader extends Reader   {
36  
37      /**
38       * Document based character sequence.
39       */
40      private static class DocumentCharSequence implements CharSequence   {
41  
42          /** Document */
43          private IDocument fDocument;
44  
45          /**
46           * Initialize with the sequence of characters in the given
47           * document.
48           *
49           * @param document the document
50           */
51          public DocumentCharSequence(IDocument document) {
52              fDocument= document;
53          }
54  
55          /*
56           * @see java.lang.CharSequence#length()
57           */
58          public int length() {
59              return fDocument.getLength();
60          }
61  
62          /*
63           * @see java.lang.CharSequence#charAt(int)
64           */
65          public char charAt(int index) {
66              try {
67                  return fDocument.getChar(index);
68              } catch (BadLocationException x) {
69                  throw new IndexOutOfBoundsException  (x.getLocalizedMessage());
70              }
71          }
72  
73          /*
74           * @see java.lang.CharSequence#subSequence(int, int)
75           */
76          public CharSequence   subSequence(int start, int end) {
77              try {
78                  return fDocument.get(start, end - start);
79              } catch (BadLocationException x) {
80                  throw new IndexOutOfBoundsException  (x.getLocalizedMessage());
81              }
82          }
83      }
84  
85      /**
86       * Internal document listener.
87       */
88      private class InternalDocumentListener implements IDocumentListener {
89  
90          /*
91           * @see org.eclipse.jface.text.IDocumentListener#documentAboutToBeChanged(org.eclipse.jface.text.DocumentEvent)
92           */
93          public void documentAboutToBeChanged(DocumentEvent event) {
94              handleDocumentAboutToBeChanged();
95          }
96  
97          /*
98           * @see org.eclipse.jface.text.IDocumentListener#documentChanged(org.eclipse.jface.text.DocumentEvent)
99           */
100         public void documentChanged(DocumentEvent event) {
101         }
102     }
103 
104     /** The character sequence. */
105     private volatile CharSequence   fCharSequence;
106 
107     /** Document length. */
108     private int fLength;
109 
110     /** The current offset. */
111     private int fOffset= 0;
112 
113     /** The document. */
114     private IDocument fDocument;
115 
116     /** The document listener. */
117     private IDocumentListener fDocumentListener= new InternalDocumentListener();
118 
119     /**
120      * Creates a new document input stream and initializes
121      * the stream to read from the given document.
122      *
123      * @param document the document
124      */
125     public DocumentReader(IDocument document) {
126         Assert.isNotNull(document);
127         fDocument= document;
128         fCharSequence= new DocumentCharSequence(fDocument);
129         fDocument.addDocumentListener(fDocumentListener);
130         fLength= fCharSequence.length();
131     }
132 
133     /*
134      * @see java.io.InputStream#close()
135      */
136     public void close() throws IOException   {
137         synchronized (this) {
138             fCharSequence= null;
139         }
140         releaseDocument();
141     }
142 
143     /**
144      * Copies the document prior to modification and removes the document listener.
145      */
146     private void handleDocumentAboutToBeChanged() {
147         IDocument document= fDocument;
148         if (fCharSequence == null || document == null)
149             return;
150         String   content= document.get();
151         synchronized (this) {
152             if (fCharSequence == null)
153                 return;
154             fCharSequence= content;
155         }
156         releaseDocument();
157     }
158 
159     /**
160      * Removes the document listener.
161      */
162     private synchronized void releaseDocument() {
163         if (fDocument != null)
164             fDocument.removeDocumentListener(fDocumentListener);
165         fDocument= null;
166         fDocumentListener= null;
167     }
168 
169     /*
170      * @see java.io.Reader#read(char[], int, int)
171      * @since 3.1
172      */
173     public int read(char[] cbuf, int off, int len) throws IOException   {
174         int i= 0;
175         try {
176             for (; i < len && fOffset < fLength; i++)
177                 cbuf[off + i]=  fCharSequence.charAt(fOffset++);
178             if (i > 0)
179                 return i;
180 
181             return -1;
182         } catch (NullPointerException   x) {
183             throw new IOException  (TextEditorMessages.DocumentInputStream_error_streamClosed);
184         } catch (IndexOutOfBoundsException   x) {
185             return i-1;
186         }
187     }
188 }
189
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