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11 package org.eclipse.jdt.internal.core.util;
12 import java.lang.ref.ReferenceQueue  ;
13 import java.lang.ref.WeakReference ;
14
15
18 public class WeakHashSet {
19
20 public static class HashableWeakReference extends WeakReference {
21 public int hashCode;
22 public HashableWeakReference(Object referent, ReferenceQueue queue) {
23 super(referent, queue);
24 this.hashCode = referent.hashCode();
25 }
26 public boolean equals(Object obj) {
27 if (!(obj instanceof HashableWeakReference)) return false;
28 Object referent = get();
29 Object other = ((HashableWeakReference) obj).get();
30 if (referent == null) return other == null;
31 return referent.equals(other);
32 }
33 public int hashCode() {
34 return this.hashCode;
35 }
36 public String toString() {
37 Object referent = get();
38 if (referent == null) return "[hashCode=" + this.hashCode + "] <referent was garbage collected>"; return "[hashCode=" + this.hashCode + "] " + referent.toString(); }
41 }
42
43 HashableWeakReference[] values;
44 public int elementSize; int threshold;
46 ReferenceQueue referenceQueue = new ReferenceQueue ();
47
48 public WeakHashSet() {
49 this(5);
50 }
51
52 public WeakHashSet(int size) {
53 this.elementSize = 0;
54 this.threshold = size; int extraRoom = (int) (size * 1.75f);
56 if (this.threshold == extraRoom)
57 extraRoom++;
58 this.values = new HashableWeakReference[extraRoom];
59 }
60
61
66 public Object add(Object obj) {
67 cleanupGarbageCollectedValues();
68 int valuesLength = this.values.length,
69 index = (obj.hashCode() & 0x7FFFFFFF) % valuesLength;
70 HashableWeakReference currentValue;
71 while ((currentValue = this.values[index]) != null) {
72 Object referent;
73 if (obj.equals(referent = currentValue.get())) {
74 return referent;
75 }
76 if (++index == valuesLength) {
77 index = 0;
78 }
79 }
80 this.values[index] = new HashableWeakReference(obj, this.referenceQueue);
81
82 if (++this.elementSize > this.threshold)
84 rehash();
85
86 return obj;
87 }
88
89 private void addValue(HashableWeakReference value) {
90 Object obj = value.get();
91 if (obj == null) return;
92 int valuesLength = this.values.length;
93 int index = (value.hashCode & 0x7FFFFFFF) % valuesLength;
94 HashableWeakReference currentValue;
95 while ((currentValue = this.values[index]) != null) {
96 if (obj.equals(currentValue.get())) {
97 return;
98 }
99 if (++index == valuesLength) {
100 index = 0;
101 }
102 }
103 this.values[index] = value;
104
105 if (++this.elementSize > this.threshold)
107 rehash();
108 }
109
110 private void cleanupGarbageCollectedValues() {
111 HashableWeakReference toBeRemoved;
112 while ((toBeRemoved = (HashableWeakReference) this.referenceQueue.poll()) != null) {
113 int hashCode = toBeRemoved.hashCode;
114 int valuesLength = this.values.length;
115 int index = (hashCode & 0x7FFFFFFF) % valuesLength;
116 HashableWeakReference currentValue;
117 while ((currentValue = this.values[index]) != null) {
118 if (currentValue == toBeRemoved) {
119 int sameHash = index;
121 int current;
122 while ((currentValue = this.values[current = (sameHash + 1) % valuesLength]) != null && currentValue.hashCode == hashCode)
123 sameHash = current;
124 this.values[index] = this.values[sameHash];
125 this.values[sameHash] = null;
126 this.elementSize--;
127 break;
128 }
129 if (++index == valuesLength) {
130 index = 0;
131 }
132 }
133 }
134 }
135
136 public boolean contains(Object obj) {
137 return get(obj) != null;
138 }
139
140
144 public Object get(Object obj) {
145 cleanupGarbageCollectedValues();
146 int valuesLength = this.values.length;
147 int index = (obj.hashCode() & 0x7FFFFFFF) % valuesLength;
148 HashableWeakReference currentValue;
149 while ((currentValue = this.values[index]) != null) {
150 Object referent;
151 if (obj.equals(referent = currentValue.get())) {
152 return referent;
153 }
154 if (++index == valuesLength) {
155 index = 0;
156 }
157 }
158 return null;
159 }
160
161 private void rehash() {
162 WeakHashSet newHashSet = new WeakHashSet(this.elementSize * 2); newHashSet.referenceQueue = this.referenceQueue;
164 HashableWeakReference currentValue;
165 for (int i = 0, length = this.values.length; i < length; i++)
166 if ((currentValue = this.values[i]) != null)
167 newHashSet.addValue(currentValue);
168
169 this.values = newHashSet.values;
170 this.threshold = newHashSet.threshold;
171 this.elementSize = newHashSet.elementSize;
172 }
173
174
178 public Object remove(Object obj) {
179 cleanupGarbageCollectedValues();
180 int valuesLength = this.values.length;
181 int index = (obj.hashCode() & 0x7FFFFFFF) % valuesLength;
182 HashableWeakReference currentValue;
183 while ((currentValue = this.values[index]) != null) {
184 Object referent;
185 if (obj.equals(referent = currentValue.get())) {
186 this.elementSize--;
187 this.values[index] = null;
188 rehash();
189 return referent;
190 }
191 if (++index == valuesLength) {
192 index = 0;
193 }
194 }
195 return null;
196 }
197
198 public int size() {
199 return this.elementSize;
200 }
201
202 public String toString() {
203 StringBuffer buffer = new StringBuffer ("{"); for (int i = 0, length = this.values.length; i < length; i++) {
205 HashableWeakReference value = this.values[i];
206 if (value != null) {
207 Object ref = value.get();
208 if (ref != null) {
209 buffer.append(ref.toString());
210 buffer.append(", "); }
212 }
213 }
214 buffer.append("}"); return buffer.toString();
216 }
217 }
218 |
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