1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
|
/*
* Copyright 2004-2011 H2 Group.
* Copyright 2011 James Moger.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.iciql.util;
import com.iciql.IciqlException;
import java.lang.ref.WeakReference;
import java.util.Collection;
import java.util.Map;
import java.util.Set;
/**
* This hash map uses weak references, so that elements that are no longer
* referenced elsewhere can be garbage collected. It also uses object identity
* to compare keys. The garbage collection happens when trying to add new data,
* or when resizing.
*
* @param <K> the keys
* @param <V> the value
*/
public class WeakIdentityHashMap<K, V> implements Map<K, V> {
private static final int MAX_LOAD = 90;
private static final WeakReference<Object> DELETED_KEY = new WeakReference<Object>(null);
private int mask, len, size, deletedCount, level;
private int maxSize, minSize, maxDeleted;
private WeakReference<K>[] keys;
private V[] values;
public WeakIdentityHashMap() {
reset(2);
}
public int size() {
return size;
}
private void checkSizePut() {
if (deletedCount > size) {
rehash(level);
}
if (size + deletedCount >= maxSize) {
rehash(level + 1);
}
}
private void checkSizeRemove() {
if (size < minSize && level > 0) {
rehash(level - 1);
} else if (deletedCount > maxDeleted) {
rehash(level);
}
}
private int getIndex(Object key) {
return System.identityHashCode(key) & mask;
}
@SuppressWarnings("unchecked")
private void reset(int newLevel) {
minSize = size * 3 / 4;
size = 0;
level = newLevel;
len = 2 << level;
mask = len - 1;
maxSize = (int) (len * MAX_LOAD / 100L);
deletedCount = 0;
maxDeleted = 20 + len / 2;
keys = new WeakReference[len];
values = (V[]) new Object[len];
}
public V put(K key, V value) {
checkSizePut();
int index = getIndex(key);
int plus = 1;
int deleted = -1;
do {
WeakReference<K> k = keys[index];
if (k == null) {
// found an empty record
if (deleted >= 0) {
index = deleted;
deletedCount--;
}
size++;
keys[index] = new WeakReference<K>(key);
values[index] = value;
return null;
} else if (k == DELETED_KEY) {
if (deleted < 0) {
// found the first deleted record
deleted = index;
}
} else {
Object r = k.get();
if (r == null) {
delete(index);
} else if (r == key) {
// update existing
V old = values[index];
values[index] = value;
return old;
}
}
index = (index + plus++) & mask;
} while (plus <= len);
throw new IciqlException("Hashmap is full");
}
public V remove(Object key) {
checkSizeRemove();
int index = getIndex(key);
int plus = 1;
do {
WeakReference<K> k = keys[index];
if (k == null) {
// found an empty record
return null;
} else if (k == DELETED_KEY) {
// continue
} else {
Object r = k.get();
if (r == null) {
delete(index);
} else if (r == key) {
// found the record
V old = values[index];
delete(index);
return old;
}
}
index = (index + plus++) & mask;
k = keys[index];
} while (plus <= len);
// not found
return null;
}
@SuppressWarnings("unchecked")
private void delete(int index) {
keys[index] = (WeakReference<K>) DELETED_KEY;
values[index] = null;
deletedCount++;
size--;
}
private void rehash(int newLevel) {
WeakReference<K>[] oldKeys = keys;
V[] oldValues = values;
reset(newLevel);
for (int i = 0; i < oldKeys.length; i++) {
WeakReference<K> k = oldKeys[i];
if (k != null && k != DELETED_KEY) {
K key = k.get();
if (key != null) {
put(key, oldValues[i]);
}
}
}
}
public V get(Object key) {
int index = getIndex(key);
int plus = 1;
do {
WeakReference<K> k = keys[index];
if (k == null) {
return null;
} else if (k == DELETED_KEY) {
// continue
} else {
Object r = k.get();
if (r == null) {
delete(index);
} else if (r == key) {
return values[index];
}
}
index = (index + plus++) & mask;
} while (plus <= len);
return null;
}
public void clear() {
reset(2);
}
public boolean containsKey(Object key) {
return get(key) != null;
}
public boolean containsValue(Object value) {
if (value == null) {
return false;
}
for (V item : values) {
if (value.equals(item)) {
return true;
}
}
return false;
}
public Set<java.util.Map.Entry<K, V>> entrySet() {
throw new UnsupportedOperationException();
}
public boolean isEmpty() {
return size == 0;
}
public Set<K> keySet() {
throw new UnsupportedOperationException();
}
public void putAll(Map<? extends K, ? extends V> m) {
throw new UnsupportedOperationException();
}
public Collection<V> values() {
throw new UnsupportedOperationException();
}
}
|
