1 /*******************************************************************************
2 * Copyright (c) 2000, 2004 IBM Corporation and others.
3 * All rights reserved. This program and the accompanying materials
4 * are made available under the terms of the Common Public License v1.0
5 * which accompanies this distribution, and is available at
6 * http://www.eclipse.org/legal/cpl-v10.html
9 * IBM Corporation - initial API and implementation
10 *******************************************************************************/
11 package org.eclipse.jdt.internal.compiler.util;
14 * A simple lookup table is a non-synchronized Hashtable, whose keys
15 * and values are Objects. It also uses linear probing to resolve collisions
16 * rather than a linked list of hash table entries.
18 public final class SimpleLookupTable implements Cloneable {
20 // to avoid using Enumerations, walk the individual tables skipping nulls
21 public Object[] keyTable;
22 public Object[] valueTable;
23 public int elementSize; // number of elements in the table
26 public SimpleLookupTable() {
30 public SimpleLookupTable(int size) {
32 this.threshold = size; // size represents the expected number of elements
33 int extraRoom = (int) (size * 1.5f);
34 if (this.threshold == extraRoom)
36 this.keyTable = new Object[extraRoom];
37 this.valueTable = new Object[extraRoom];
40 public Object clone() throws CloneNotSupportedException {
41 SimpleLookupTable result = (SimpleLookupTable) super.clone();
42 result.elementSize = this.elementSize;
43 result.threshold = this.threshold;
45 int length = this.keyTable.length;
46 result.keyTable = new Object[length];
47 System.arraycopy(this.keyTable, 0, result.keyTable, 0, length);
49 length = this.valueTable.length;
50 result.valueTable = new Object[length];
51 System.arraycopy(this.valueTable, 0, result.valueTable, 0, length);
55 public boolean containsKey(Object key) {
56 int length = keyTable.length;
57 int index = (key.hashCode() & 0x7FFFFFFF) % length;
59 while ((currentKey = keyTable[index]) != null) {
60 if (currentKey.equals(key)) return true;
61 if (++index == length) index = 0;
66 public Object get(Object key) {
67 int length = keyTable.length;
68 int index = (key.hashCode() & 0x7FFFFFFF) % length;
70 while ((currentKey = keyTable[index]) != null) {
71 if (currentKey.equals(key)) return valueTable[index];
72 if (++index == length) index = 0;
77 public Object keyForValue(Object valueToMatch) {
78 if (valueToMatch != null)
79 for (int i = 0, l = valueTable.length; i < l; i++)
80 if (valueToMatch.equals(valueTable[i]))
85 public Object put(Object key, Object value) {
86 int length = keyTable.length;
87 int index = (key.hashCode() & 0x7FFFFFFF) % length;
89 while ((currentKey = keyTable[index]) != null) {
90 if (currentKey.equals(key)) return valueTable[index] = value;
91 if (++index == length) index = 0;
93 keyTable[index] = key;
94 valueTable[index] = value;
96 // assumes the threshold is never equal to the size of the table
97 if (++elementSize > threshold) rehash();
101 public Object removeKey(Object key) {
102 int length = keyTable.length;
103 int index = (key.hashCode() & 0x7FFFFFFF) % length;
105 while ((currentKey = keyTable[index]) != null) {
106 if (currentKey.equals(key)) {
108 Object oldValue = valueTable[index];
109 keyTable[index] = null;
110 valueTable[index] = null;
111 if (keyTable[index + 1 == length ? 0 : index + 1] != null)
112 rehash(); // only needed if a possible collision existed
115 if (++index == length) index = 0;
120 public void removeValue(Object valueToRemove) {
121 boolean rehash = false;
122 for (int i = 0, l = valueTable.length; i < l; i++) {
123 Object value = valueTable[i];
124 if (value != null && value.equals(valueToRemove)) {
127 valueTable[i] = null;
128 if (!rehash && keyTable[i + 1 == l ? 0 : i + 1] != null)
129 rehash = true; // only needed if a possible collision existed
132 if (rehash) rehash();
135 private void rehash() {
136 SimpleLookupTable newLookupTable = new SimpleLookupTable(elementSize * 2); // double the number of expected elements
138 for (int i = keyTable.length; --i >= 0;)
139 if ((currentKey = keyTable[i]) != null)
140 newLookupTable.put(currentKey, valueTable[i]);
142 this.keyTable = newLookupTable.keyTable;
143 this.valueTable = newLookupTable.valueTable;
144 this.elementSize = newLookupTable.elementSize;
145 this.threshold = newLookupTable.threshold;
148 public String toString() {
149 String s = ""; //$NON-NLS-1$
151 for (int i = 0, l = valueTable.length; i < l; i++)
152 if ((object = valueTable[i]) != null)
153 s += keyTable[i].toString() + " -> " + object.toString() + "\n"; //$NON-NLS-2$ //$NON-NLS-1$