HashtableOfLong


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.jdt.internal.compiler.util;
12   
13   /**
14    * Hashtable for non-zero long keys.
15    */
16    
17  public final class HashtableOfLong {
18      // to avoid using Enumerations, walk the individual tables skipping nulls
19      public long[] keyTable;
20      public Object  [] valueTable;
21  
22      public int elementSize; // number of elements in the table
23      int threshold;
24  public HashtableOfLong() {
25      this(13);
26  }
27  public HashtableOfLong(int size) {
28      this.elementSize = 0;
29      this.threshold = size; // size represents the expected number of elements
30      int extraRoom = (int) (size * 1.75f);
31      if (this.threshold == extraRoom)
32          extraRoom++;
33      this.keyTable = new long[extraRoom];
34      this.valueTable = new Object  [extraRoom];
35  }
36  public boolean containsKey(long key) {
37      int length = keyTable.length,
38          index = ((int)(key >>> 32)) % length;
39      long currentKey;
40      while ((currentKey = keyTable[index]) != 0) {
41          if (currentKey == key)
42              return true;
43          if (++index == length) {
44              index = 0;
45          }
46      }
47      return false;
48  }
49  public Object   get(long key) {
50      int length = keyTable.length,
51          index = ((int)(key >>> 32)) % length;
52      long currentKey;
53      while ((currentKey = keyTable[index]) != 0) {
54          if (currentKey == key)  return valueTable[index];
55          if (++index == length) {
56              index = 0;
57          }
58      }
59      return null;
60  }
61  public Object   put(long key, Object   value) {
62      int length = keyTable.length,
63          index = ((int)(key >>> 32)) % length;
64      long currentKey;
65      while ((currentKey = keyTable[index]) != 0) {
66          if (currentKey == key)  return valueTable[index] = value;
67          if (++index == length) {
68              index = 0;
69          }
70      }
71      keyTable[index] = key;
72      valueTable[index] = value;
73  
74      // assumes the threshold is never equal to the size of the table
75      if (++elementSize > threshold)
76          rehash();
77      return value;
78  }
79  private void rehash() {
80      HashtableOfLong newHashtable = new HashtableOfLong(elementSize * 2); // double the number of expected elements
81      long currentKey;
82      for (int i = keyTable.length; --i >= 0;)
83          if ((currentKey = keyTable[i]) != 0)
84              newHashtable.put(currentKey, valueTable[i]);
85  
86      this.keyTable = newHashtable.keyTable;
87      this.valueTable = newHashtable.valueTable;
88      this.threshold = newHashtable.threshold;
89  }
90  public int size() {
91      return elementSize;
92  }
93  public String   toString() {
94      String   s = ""; //$NON-NLS-1$
95      Object   object;
96      for (int i = 0, length = valueTable.length; i < length; i++)
97          if ((object = valueTable[i]) != null)
98              s += keyTable[i] + " -> " + object.toString() + "\n"; //$NON-NLS-2$ //$NON-NLS-1$
99      return s;
100 }
101 }
102
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