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1
4 package com.tc.object.cache;
5
6 import com.tc.logging.TCLogger;
7 import com.tc.logging.TCLogging;
8 import com.tc.text.PrettyPrinter;
9
10 import gnu.trove.TLinkedList;
11
12 import java.util.Collection  ;
13 import java.util.Collections ;
14 import java.util.HashSet ;
15
16
19 public class LRUEvictionPolicy implements EvictionPolicy {
20 private static final TCLogger logger = TCLogging.getLogger(LRUEvictionPolicy.class);
21 private final TLinkedList cache = new TLinkedList();
22 private final int capacity;
23 private final int evictionSize;
24
25 public LRUEvictionPolicy(int capacity) {
26 this(capacity, capacity / 10);
27 }
28
29 public LRUEvictionPolicy(int capacity, int evictionSize) {
30 if (logger.isDebugEnabled()) {
31 logger.debug("new " + getClass().getName() + "(" + capacity + ")");
32 }
33 this.capacity = capacity;
34 this.evictionSize = (evictionSize <= 0 ? 1 : evictionSize);
35 }
36
37 public synchronized boolean add(Cacheable obj) {
38 if (logger.isDebugEnabled()) {
40 logger.debug("Adding: " + obj);
41 }
42 cache.addLast(obj);
43
44 return isCacheFull();
45 }
46
47 private boolean isCacheFull() {
48 return (capacity > 0 && cache.size() > capacity);
49 }
50
51 public synchronized Collection getRemovalCandidates(int maxCount) {
52 if (capacity > 0) {
53 if (!isCacheFull()) { return Collections.EMPTY_LIST; }
54 if (maxCount <= 0 || maxCount > evictionSize) {
55 maxCount = evictionSize;
56 }
57 } else if (maxCount <= 0) {
58 throw new AssertionError ("Please specify maxcount > 0 as capacity is set to : " + capacity + " Max Count = "
60 + maxCount);
61 }
62
63 Collection rv = new HashSet ();
64 int count = Math.min(cache.size(), maxCount);
65 Cacheable c = (Cacheable) cache.getFirst();
66 Object save = c;
67 while (cache.size() - rv.size() > capacity && count > 0) {
68 moveToTail(c);
69 if (c.canEvict()) {
70 rv.add(c);
71 count--;
72 }
73 c = (Cacheable) cache.getFirst();
74 if (save == c) break;
75 }
76 return rv;
77 }
78
79 public synchronized void remove(Cacheable obj) {
80 if (logger.isDebugEnabled()) {
81 logger.debug("Removing: " + obj);
82 }
83 if (contains(obj)) cache.remove(obj);
84 }
85
86 private boolean contains(Cacheable obj) {
87 return obj != null && (obj.getNext() != null || obj.getPrevious() != null);
89 }
90
91 public synchronized void markReferenced(Cacheable obj) {
92 moveToTail(obj);
93 }
94
95 private synchronized void moveToTail(Cacheable obj) {
96 if (contains(obj)) {
97 cache.remove(obj);
98 cache.addLast(obj);
99 }
100 }
101
102 public synchronized PrettyPrinter prettyPrint(PrettyPrinter out) {
103 PrettyPrinter rv = out;
104 out.println(getClass().getName());
105 out = out.duplicateAndIndent();
106 out.indent().println("max size: " + capacity).indent().print("cache: ").visit(cache).println();
107 return rv;
108 }
109
110 public int getCacheCapacity() {
111 return capacity;
112 }
113
114 }
115 |
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