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1
52
53 package freemarker.cache;
54
55 import java.lang.ref.ReferenceQueue  ;
56 import java.lang.ref.SoftReference ;
57 import java.util.HashMap ;
58 import java.util.Map ;
59
60
77 public class MruCacheStorage implements CacheStorage
78 {
79 private final MruEntry strongHead = new MruEntry();
80 private final MruEntry softHead = new MruEntry();
81 {
82 softHead.linkAfter(strongHead);
83 }
84 private final Map map = new HashMap ();
85 private final ReferenceQueue refQueue = new ReferenceQueue ();
86 private final int maxStrongSize;
87 private final int maxSoftSize;
88 private int strongSize = 0;
89 private int softSize = 0;
90
91
97 public MruCacheStorage(int maxStrongSize, int maxSoftSize) {
98 if(maxStrongSize < 0) throw new IllegalArgumentException ("maxStrongSize < 0");
99 if(maxSoftSize < 0) throw new IllegalArgumentException ("maxSoftSize < 0");
100 this.maxStrongSize = maxStrongSize;
101 this.maxSoftSize = maxSoftSize;
102 }
103
104 public Object get(Object key) {
105 removeClearedReferences();
106 MruEntry entry = (MruEntry)map.get(key);
107 if(entry == null) {
108 return null;
109 }
110 relinkEntryAfterStrongHead(entry, null);
111 Object value = entry.getValue();
112 if(value instanceof MruReference) {
113 return ((MruReference)value).get();
115 }
116 return value;
117 }
118
119 public void put(Object key, Object value) {
120 removeClearedReferences();
121 MruEntry entry = (MruEntry)map.get(key);
122 if(entry == null) {
123 entry = new MruEntry(key, value);
124 map.put(key, entry);
125 linkAfterStrongHead(entry);
126 }
127 else {
128 relinkEntryAfterStrongHead(entry, value);
129 }
130
131 }
132
133 public void remove(Object key) {
134 removeClearedReferences();
135 MruEntry entry = (MruEntry)map.remove(key);
136 if(entry != null) {
137 unlinkEntryAndInspectIfSoft(entry);
138 }
139 }
140
141 public void clear() {
142 strongHead.makeHead();
143 softHead.linkAfter(strongHead);
144 map.clear();
145 strongSize = softSize = 0;
146 while(refQueue.poll() != null);
148 }
149
150 private void relinkEntryAfterStrongHead(MruEntry entry, Object newValue) {
151 if(unlinkEntryAndInspectIfSoft(entry) && newValue == null) {
152 MruReference mref = (MruReference)entry.getValue();
154 Object strongValue = mref.get();
155 if (strongValue != null) {
156 entry.setValue(strongValue);
157 linkAfterStrongHead(entry);
158 } else {
159 map.remove(mref.getKey());
160 }
161 } else {
162 if (newValue != null) {
163 entry.setValue(newValue);
164 }
165 linkAfterStrongHead(entry);
166 }
167 }
168
169 private void linkAfterStrongHead(MruEntry entry) {
170 entry.linkAfter(strongHead);
171 if(strongSize == maxStrongSize) {
172 MruEntry lruStrong = softHead.getPrevious();
174 if(lruStrong != strongHead) {
178 lruStrong.unlink();
179 if(maxSoftSize > 0) {
180 lruStrong.linkAfter(softHead);
181 lruStrong.setValue(new MruReference(lruStrong, refQueue));
182 if(softSize == maxSoftSize) {
183 MruEntry lruSoft = strongHead.getPrevious();
185 lruSoft.unlink();
186 map.remove(lruSoft.getKey());
187 }
188 else {
189 ++softSize;
190 }
191 }
192 else {
193 map.remove(lruStrong.getKey());
194 }
195 }
196 }
197 else {
198 ++strongSize;
199 }
200 }
201
202 private boolean unlinkEntryAndInspectIfSoft(MruEntry entry) {
203 entry.unlink();
204 if(entry.getValue() instanceof MruReference) {
205 --softSize;
206 return true;
207 }
208 else {
209 --strongSize;
210 return false;
211 }
212 }
213
214 private void removeClearedReferences() {
215 for(;;) {
216 MruReference ref = (MruReference)refQueue.poll();
217 if(ref == null) {
218 break;
219 }
220 remove(ref.getKey());
221 }
222 }
223
224 private static final class MruEntry
225 {
226 private MruEntry prev;
227 private MruEntry next;
228 private final Object key;
229 private Object value;
230
231
234 MruEntry()
235 {
236 makeHead();
237 key = value = null;
238 }
239
240 MruEntry(Object key, Object value) {
241 this.key = key;
242 this.value = value;
243 }
244
245 Object getKey() {
246 return key;
247 }
248
249 Object getValue() {
250 return value;
251 }
252
253 void setValue(Object value) {
254 this.value = value;
255 }
256
257 MruEntry getPrevious() {
258 return prev;
259 }
260
261 void linkAfter(MruEntry entry) {
262 next = entry.next;
263 entry.next = this;
264 prev = entry;
265 next.prev = this;
266 }
267
268 void unlink() {
269 next.prev = prev;
270 prev.next = next;
271 prev = null;
272 next = null;
273 }
274
275 void makeHead() {
276 prev = next = this;
277 }
278 }
279
280 private static class MruReference extends SoftReference
281 {
282 private final Object key;
283
284 MruReference(MruEntry entry, ReferenceQueue queue) {
285 super(entry.getValue(), queue);
286 this.key = entry.getKey();
287 }
288
289 Object getKey() {
290 return key;
291 }
292 }
293 } |
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