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11 package org.eclipse.jdt.internal.compiler.util;
12 import java.lang.ref.ReferenceQueue  ;
13 import java.lang.ref.WeakReference ;
14
15
18 public class WeakHashSet {
19
20 public 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 index = (obj.hashCode() & 0x7FFFFFFF) % this.values.length;
69 HashableWeakReference currentValue;
70 while ((currentValue = this.values[index]) != null) {
71 Object referent;
72 if (obj.equals(referent = currentValue.get())) {
73 return referent;
74 }
75 index = (index + 1) % this.values.length;
76 }
77 this.values[index] = new HashableWeakReference(obj, this.referenceQueue);
78
79 if (++this.elementSize > this.threshold)
81 rehash();
82
83 return obj;
84 }
85
86 private void addValue(HashableWeakReference value) {
87 Object obj = value.get();
88 if (obj == null) return;
89 int valuesLength = this.values.length;
90 int index = (value.hashCode & 0x7FFFFFFF) % valuesLength;
91 HashableWeakReference currentValue;
92 while ((currentValue = this.values[index]) != null) {
93 if (obj.equals(currentValue.get())) {
94 return;
95 }
96 index = (index + 1) % valuesLength;
97 }
98 this.values[index] = value;
99
100 if (++this.elementSize > this.threshold)
102 rehash();
103 }
104
105 private void cleanupGarbageCollectedValues() {
106 HashableWeakReference toBeRemoved;
107 while ((toBeRemoved = (HashableWeakReference) this.referenceQueue.poll()) != null) {
108 int hashCode = toBeRemoved.hashCode;
109 int valuesLength = this.values.length;
110 int index = (hashCode & 0x7FFFFFFF) % valuesLength;
111 HashableWeakReference currentValue;
112 while ((currentValue = this.values[index]) != null) {
113 if (currentValue == toBeRemoved) {
114 int sameHash = index;
116 int current;
117 while ((currentValue = this.values[current = (sameHash + 1) % valuesLength]) != null && currentValue.hashCode == hashCode)
118 sameHash = current;
119 this.values[index] = this.values[sameHash];
120 this.values[sameHash] = null;
121 this.elementSize--;
122 break;
123 }
124 index = (index + 1) % valuesLength;
125 }
126 }
127 }
128
129 public boolean contains(Object obj) {
130 return get(obj) != null;
131 }
132
133
137 public Object get(Object obj) {
138 cleanupGarbageCollectedValues();
139 int valuesLength = this.values.length;
140 int index = (obj.hashCode() & 0x7FFFFFFF) % valuesLength;
141 HashableWeakReference currentValue;
142 while ((currentValue = this.values[index]) != null) {
143 Object referent;
144 if (obj.equals(referent = currentValue.get())) {
145 return referent;
146 }
147 index = (index + 1) % valuesLength;
148 }
149 return null;
150 }
151
152 private void rehash() {
153 WeakHashSet newHashSet = new WeakHashSet(this.elementSize * 2); newHashSet.referenceQueue = this.referenceQueue;
155 HashableWeakReference currentValue;
156 for (int i = 0, length = this.values.length; i < length; i++)
157 if ((currentValue = this.values[i]) != null)
158 newHashSet.addValue(currentValue);
159
160 this.values = newHashSet.values;
161 this.threshold = newHashSet.threshold;
162 this.elementSize = newHashSet.elementSize;
163 }
164
165
169 public Object remove(Object obj) {
170 cleanupGarbageCollectedValues();
171 int valuesLength = this.values.length;
172 int index = (obj.hashCode() & 0x7FFFFFFF) % valuesLength;
173 HashableWeakReference currentValue;
174 while ((currentValue = this.values[index]) != null) {
175 Object referent;
176 if (obj.equals(referent = currentValue.get())) {
177 this.elementSize--;
178 this.values[index] = null;
179 rehash();
180 return referent;
181 }
182 index = (index + 1) % valuesLength;
183 }
184 return null;
185 }
186
187 public int size() {
188 return this.elementSize;
189 }
190
191 public String toString() {
192 StringBuffer buffer = new StringBuffer ("{"); for (int i = 0, length = this.values.length; i < length; i++) {
194 HashableWeakReference value = this.values[i];
195 if (value != null) {
196 Object ref = value.get();
197 if (ref != null) {
198 buffer.append(ref.toString());
199 buffer.append(", "); }
201 }
202 }
203 buffer.append("}"); return buffer.toString();
205 }
206 }
207 |
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