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comparison src/fschmidt/db/util/CacheMap.java @ 68:00520880ad02

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add fschmidt source
author Franklin Schmidt <fschmidt@gmail.com>
date Sun, 05 Oct 2025 17:24:15 -0600
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67:9d0fefce6985 68:00520880ad02
1 /*
2 Copyright (c) 2008 Franklin Schmidt <fschmidt@gmail.com>
3
4 Permission is hereby granted, free of charge, to any person obtaining a copy
5 of this software and associated documentation files (the "Software"), to deal
6 in the Software without restriction, including without limitation the rights
7 to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
8 copies of the Software, and to permit persons to whom the Software is
9 furnished to do so, subject to the following conditions:
10
11 The above copyright notice and this permission notice shall be included in
12 all copies or substantial portions of the Software.
13
14 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
15 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
16 FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
17 AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
18 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
19 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
20 THE SOFTWARE.
21 */
22
23 package fschmidt.db.util;
24
25 import java.lang.ref.ReferenceQueue;
26 import java.util.Map;
27 import java.util.AbstractMap;
28 import java.util.HashMap;
29 import java.util.Set;
30 import java.util.AbstractSet;
31 import java.util.Iterator;
32
33
34 public abstract class CacheMap<K,V> extends AbstractMap<K,V> {
35
36 protected static interface MyReference<K,V> {
37 public K key();
38 public V get();
39 public void clear();
40 }
41
42 protected abstract MyReference<K,V> newReference(K key,V value,ReferenceQueue<V> q);
43
44 private final Map<K,MyReference<K,V>> cache = new HashMap<K,MyReference<K,V>>();
45 private final ReferenceQueue<V> queue = new ReferenceQueue<V>();
46
47 private void sweep() {
48 while(true) {
49 @SuppressWarnings("unchecked")
50 MyReference<K,V> ref = (MyReference<K,V>)queue.poll();
51 if( ref == null )
52 return;
53 MyReference<K,V> mappedRef = cache.remove(ref.key());
54 if( mappedRef != ref && mappedRef != null )
55 cache.put( mappedRef.key(), mappedRef ); // put it back
56 }
57 }
58
59 public int size() {
60 return cache.size();
61 }
62
63 public boolean isEmpty() {
64 return cache.isEmpty();
65 }
66
67 public boolean containsKey(Object key) {
68 return cache.containsKey(key);
69 }
70
71 public V get(Object key) {
72 MyReference<K,V> ref = cache.get(key);
73 return ref==null ? null : ref.get();
74 }
75
76 public V put(K key,V value) {
77 sweep();
78 MyReference<K,V> ref = cache.put( key, newReference(key,value,queue) );
79 return ref==null ? null : ref.get();
80 }
81
82 public V remove(Object key) {
83 sweep();
84 MyReference<K,V> ref = cache.remove(key);
85 return ref==null ? null : ref.get();
86 }
87
88 public void clear() {
89 sweep();
90 cache.clear();
91 }
92
93 /*
94 public Object clone() {
95 GCCacheMap map = new GCCacheMap();
96 map.cache = (HashMap)cache.clone();
97 return map;
98 }
99 */
100 public Set<K> keySet() {
101 return cache.keySet();
102 }
103
104 public Set<Map.Entry<K,V>> entrySet() {
105 return new MySet();
106 }
107
108
109 private class MySet extends AbstractSet<Map.Entry<K,V>> {
110
111 public int size() {
112 return CacheMap.this.size();
113 }
114
115 public Iterator<Map.Entry<K,V>> iterator() {
116 return new MyIterator(cache.entrySet().iterator());
117 }
118
119 }
120
121 private class MyIterator implements Iterator<Map.Entry<K,V>> {
122 Iterator<Map.Entry<K,MyReference<K,V>>> iter;
123
124 MyIterator(Iterator<Map.Entry<K,MyReference<K,V>>> iter) {
125 this.iter = iter;
126 }
127
128 public boolean hasNext() {
129 return iter.hasNext();
130 }
131
132 public void remove() {
133 iter.remove();
134 }
135
136 public Map.Entry<K,V> next() {
137 return new MyEntry( iter.next() );
138 }
139 }
140
141 private class MyEntry implements Map.Entry<K,V> {
142 Map.Entry<K,MyReference<K,V>> entry;
143
144 MyEntry(Map.Entry<K,MyReference<K,V>> entry) {
145 this.entry = entry;
146 }
147
148 public K getKey() {
149 return entry.getKey();
150 }
151
152 public V getValue() {
153 MyReference<K,V> ref = entry.getValue();
154 return ref.get();
155 }
156
157 public V setValue(V value) {
158 MyReference<K,V> ref = entry.setValue( newReference(getKey(),value,queue) );
159 return ref.get();
160 }
161
162 public boolean equals(Object o) {
163 if( o==null || !(o instanceof CacheMap.MyEntry) )
164 return false;
165 MyEntry m = (MyEntry)o;
166 return entry.equals(m.entry);
167 }
168
169 public int hashCode() {
170 K key = getKey();
171 V value = getValue();
172 return (key==null ? 0 : key.hashCode()) ^
173 (value==null ? 0 : value.hashCode());
174 }
175 }
176
177 }