ElementTreeReaderImpl_1


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.core.internal.watson;
12  
13  import java.io.DataInput  ;
14  import java.io.IOException  ;
15  import org.eclipse.core.internal.dtree.DeltaDataTree;
16  
17  /** <code>ElementTreeReader_1</code> is an implementation
18   * of the <code>ElementTreeReader</code> for format version 1.
19   *
20   * <p>Instances of this reader read only format 1
21   * of a saved element tree (they do not deal with
22   * compatibility issues).
23   *
24   * @see ElementTreeReader
25   */
26  /* package */class ElementTreeReaderImpl_1 extends ElementTreeReader {
27  
28      /** 
29       * Constructs a new element tree reader that works for
30       * the given element info factory.
31       */
32      ElementTreeReaderImpl_1(IElementInfoFlattener factory) {
33          super(factory);
34      }
35  
36      /**
37       * Reads an element tree delta from the input stream, and
38       * reconstructs it as a delta on the given tree.
39       */
40      public ElementTree readDelta(ElementTree parentTree, DataInput   input) throws IOException   {
41          DeltaDataTree complete = parentTree.getDataTree();
42          DeltaDataTree delta = dataTreeReader.readTree(complete, input);
43  
44          //if the delta is empty, just return the parent
45          if (delta.isEmptyDelta())
46              return parentTree;
47  
48          ElementTree tree = new ElementTree(delta);
49  
50          //copy the user data forward
51          IElementTreeData data = parentTree.getTreeData();
52          if (data != null) {
53              tree.setTreeData((IElementTreeData) data.clone());
54          }
55  
56          //make the underlying data tree immutable
57          //can't call immutable() on the ElementTree because
58          //this would attempt to reroot.
59          delta.immutable();
60          return tree;
61      }
62  
63      /**
64       * Reads a chain of ElementTrees from the given input stream.
65       * @return A chain of ElementTrees, where the first tree in the list is
66       * complete, and all other trees are deltas on the previous tree in the list.
67       */
68      public ElementTree[] readDeltaChain(DataInput   input) throws IOException   {
69          /* read the number of trees */
70          int treeCount = readNumber(input);
71          ElementTree[] results = new ElementTree[treeCount];
72  
73          if (treeCount <= 0) {
74              return results;
75          }
76  
77          /* read the sort order */
78          int[] order = new int[treeCount];
79          for (int i = 0; i < treeCount; i++) {
80              order[i] = readNumber(input);
81          }
82  
83          /* read the complete tree */
84          results[order[0]] = super.readTree(input);
85  
86          /* reconstitute each of the remaining trees from their written deltas */
87          for (int i = 1; i < treeCount; i++) {
88              results[order[i]] = super.readDelta(results[order[i - 1]], input);
89          }
90  
91          return results;
92      }
93  
94      /** Part of <code>ElementTreeReader</code> interface.
95       * @see ElementTreeReader
96       */
97      public ElementTree readTree(DataInput   input) throws IOException   {
98  
99          /* The format version number has already been consumed
100          * by ElementTreeReader#readFrom.
101          */
102         ElementTree result = new ElementTree(dataTreeReader.readTree(null, input));
103         return result;
104     }
105 }
106
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