8 * particular file as subject to the "Classpath" exception as provided 9 * by Oracle in the LICENSE file that accompanied this code. 10 * 11 * This code is distributed in the hope that it will be useful, but WITHOUT 12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 14 * version 2 for more details (a copy is included in the LICENSE file that 15 * accompanied this code). 16 * 17 * You should have received a copy of the GNU General Public License version 18 * 2 along with this work; if not, write to the Free Software Foundation, 19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 20 * 21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22 * or visit www.oracle.com if you need additional information or have any 23 * questions. 24 */ 25 26 package sun.misc; 27 28 import java.util.Dictionary; 29 import java.util.Enumeration; 30 import java.util.NoSuchElementException; 31 32 /** 33 * Caches the collision list. 34 */ 35 class CacheEntry extends Ref { 36 int hash; 37 Object key; 38 CacheEntry next; 39 public Object reconstitute() { 40 return null; 41 } 42 } 43 44 /** 45 * The Cache class. Maps keys to values. Any object can be used as 46 * a key and/or value. This is very similar to the Hashtable 47 * class, except that after putting an object into the Cache, 48 * it is not guaranteed that a subsequent get will return it. 49 * The Cache will automatically remove entries if memory is 50 * getting tight and if the entry is not referenced from outside 51 * the Cache.<p> 52 * 53 * To sucessfully store and retrieve objects from a hash table the 54 * object used as the key must implement the hashCode() and equals() 55 * methods.<p> 56 * 57 * This example creates a Cache of numbers. It uses the names of 58 * the numbers as keys: 59 * <pre> 60 * Cache numbers = new Cache(); 175 * @see Cache#keys 176 * @see Enumeration 177 */ 178 public synchronized Enumeration<Object> elements() { 179 return new CacheEnumerator(table, false); 180 } 181 182 /** 183 * Gets the object associated with the specified key in the Cache. 184 * @param key the key in the hash table 185 * @returns the element for the key or null if the key 186 * is not defined in the hash table. 187 * @see Cache#put 188 */ 189 public synchronized Object get(Object key) { 190 CacheEntry tab[] = table; 191 int hash = key.hashCode(); 192 int index = (hash & 0x7FFFFFFF) % tab.length; 193 for (CacheEntry e = tab[index]; e != null; e = e.next) { 194 if ((e.hash == hash) && e.key.equals(key)) { 195 return e.check(); 196 } 197 } 198 return null; 199 } 200 201 /** 202 * Rehashes the contents of the table into a bigger table. 203 * This is method is called automatically when the Cache's 204 * size exceeds the threshold. 205 */ 206 protected void rehash() { 207 int oldCapacity = table.length; 208 CacheEntry oldTable[] = table; 209 210 int newCapacity = oldCapacity * 2 + 1; 211 CacheEntry newTable[] = new CacheEntry[newCapacity]; 212 213 threshold = (int) (newCapacity * loadFactor); 214 table = newTable; 215 216 // System.out.println("rehash old=" + oldCapacity + ", new=" + 217 // newCapacity + ", thresh=" + threshold + ", count=" + count); 218 219 for (int i = oldCapacity; i-- > 0;) { 220 for (CacheEntry old = oldTable[i]; old != null;) { 221 CacheEntry e = old; 222 old = old.next; 223 if (e.check() != null) { 224 int index = (e.hash & 0x7FFFFFFF) % newCapacity; 225 e.next = newTable[index]; 226 newTable[index] = e; 227 } else 228 count--; /* remove entries that have disappeared */ 229 } 230 } 231 } 232 233 /** 234 * Puts the specified element into the Cache, using the specified 235 * key. The element may be retrieved by doing a get() with the same 236 * key. The key and the element cannot be null. 237 * @param key the specified hashtable key 238 * @param value the specified element 239 * @return the old value of the key, or null if it did not have one. 240 * @exception NullPointerException If the value of the specified 241 * element is null. 242 * @see Cache#get 243 */ 244 public synchronized Object put(Object key, Object value) { 245 // Make sure the value is not null 246 if (value == null) { 247 throw new NullPointerException(); 248 } 249 // Makes sure the key is not already in the cache. 250 CacheEntry tab[] = table; 251 int hash = key.hashCode(); 252 int index = (hash & 0x7FFFFFFF) % tab.length; 253 CacheEntry ne = null; 254 for (CacheEntry e = tab[index]; e != null; e = e.next) { 255 if ((e.hash == hash) && e.key.equals(key)) { 256 Object old = e.check(); 257 e.setThing(value); 258 return old; 259 } else if (e.check() == null) 260 ne = e; /* reuse old flushed value */ 261 } 262 263 if (count >= threshold) { 264 // Rehash the table if the threshold is exceeded 265 rehash(); 266 return put(key, value); 267 } 268 // Creates the new entry. 269 if (ne == null) { 270 ne = new CacheEntry (); 271 ne.next = tab[index]; 272 tab[index] = ne; 273 count++; 274 } 275 ne.hash = hash; 276 ne.key = key; 277 ne.setThing(value); 278 return null; 279 } 280 281 /** 282 * Removes the element corresponding to the key. Does nothing if the 283 * key is not present. 284 * @param key the key that needs to be removed 285 * @return the value of key, or null if the key was not found. 286 */ 287 public synchronized Object remove(Object key) { 288 CacheEntry tab[] = table; 289 int hash = key.hashCode(); 290 int index = (hash & 0x7FFFFFFF) % tab.length; 291 for (CacheEntry e = tab[index], prev = null; e != null; prev = e, e = e.next) { 292 if ((e.hash == hash) && e.key.equals(key)) { 293 if (prev != null) { 294 prev.next = e.next; 295 } else { 296 tab[index] = e.next; 297 } 298 count--; 299 return e.check(); 300 } 301 } 302 return null; 303 } 304 } 305 306 /** 307 * A Cache enumerator class. This class should remain opaque 308 * to the client. It will use the Enumeration interface. 309 */ 310 class CacheEnumerator implements Enumeration<Object> { 311 boolean keys; 312 int index; 313 CacheEntry table[]; 314 CacheEntry entry; 315 316 CacheEnumerator (CacheEntry table[], boolean keys) { 317 this.table = table; 318 this.keys = keys; 319 this.index = table.length; 320 } 321 322 public boolean hasMoreElements() { 323 while (index >= 0) { 324 while (entry != null) 325 if (entry.check() != null) 326 return true; 327 else 328 entry = entry.next; 329 while (--index >= 0 && (entry = table[index]) == null) ; 330 } 331 return false; 332 } 333 334 public Object nextElement() { 335 while (index >= 0) { 336 if (entry == null) 337 while (--index >= 0 && (entry = table[index]) == null) ; 338 if (entry != null) { 339 CacheEntry e = entry; 340 entry = e.next; 341 if (e.check() != null) 342 return keys ? e.key : e.check(); 343 } 344 } 345 throw new NoSuchElementException("CacheEnumerator"); 346 } 347 348 } | 8 * particular file as subject to the "Classpath" exception as provided 9 * by Oracle in the LICENSE file that accompanied this code. 10 * 11 * This code is distributed in the hope that it will be useful, but WITHOUT 12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 14 * version 2 for more details (a copy is included in the LICENSE file that 15 * accompanied this code). 16 * 17 * You should have received a copy of the GNU General Public License version 18 * 2 along with this work; if not, write to the Free Software Foundation, 19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 20 * 21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22 * or visit www.oracle.com if you need additional information or have any 23 * questions. 24 */ 25 26 package sun.misc; 27 28 import java.lang.ref.SoftReference; 29 import java.util.Dictionary; 30 import java.util.Enumeration; 31 import java.util.NoSuchElementException; 32 33 /** 34 * Caches the collision list. 35 */ 36 class CacheEntry { 37 int hash; 38 Object key; 39 CacheEntry next; 40 SoftReference<Object> value; 41 42 public CacheEntry() { 43 value = null; 44 } 45 46 public CacheEntry(Object o) { 47 value = new SoftReference<>(o); 48 } 49 50 public Object get() { 51 return value.get(); 52 } 53 54 public void setThing(Object thing) { 55 value = new SoftReference<>(thing); 56 } 57 } 58 59 /** 60 * The Cache class. Maps keys to values. Any object can be used as 61 * a key and/or value. This is very similar to the Hashtable 62 * class, except that after putting an object into the Cache, 63 * it is not guaranteed that a subsequent get will return it. 64 * The Cache will automatically remove entries if memory is 65 * getting tight and if the entry is not referenced from outside 66 * the Cache.<p> 67 * 68 * To sucessfully store and retrieve objects from a hash table the 69 * object used as the key must implement the hashCode() and equals() 70 * methods.<p> 71 * 72 * This example creates a Cache of numbers. It uses the names of 73 * the numbers as keys: 74 * <pre> 75 * Cache numbers = new Cache(); 190 * @see Cache#keys 191 * @see Enumeration 192 */ 193 public synchronized Enumeration<Object> elements() { 194 return new CacheEnumerator(table, false); 195 } 196 197 /** 198 * Gets the object associated with the specified key in the Cache. 199 * @param key the key in the hash table 200 * @returns the element for the key or null if the key 201 * is not defined in the hash table. 202 * @see Cache#put 203 */ 204 public synchronized Object get(Object key) { 205 CacheEntry tab[] = table; 206 int hash = key.hashCode(); 207 int index = (hash & 0x7FFFFFFF) % tab.length; 208 for (CacheEntry e = tab[index]; e != null; e = e.next) { 209 if ((e.hash == hash) && e.key.equals(key)) { 210 return e.get(); 211 } 212 } 213 return null; 214 } 215 216 /** 217 * Rehashes the contents of the table into a bigger table. 218 * This is method is called automatically when the Cache's 219 * size exceeds the threshold. 220 */ 221 protected void rehash() { 222 int oldCapacity = table.length; 223 CacheEntry oldTable[] = table; 224 225 int newCapacity = oldCapacity * 2 + 1; 226 CacheEntry newTable[] = new CacheEntry[newCapacity]; 227 228 threshold = (int) (newCapacity * loadFactor); 229 table = newTable; 230 231 // System.out.println("rehash old=" + oldCapacity + ", new=" + 232 // newCapacity + ", thresh=" + threshold + ", count=" + count); 233 234 for (int i = oldCapacity; i-- > 0;) { 235 for (CacheEntry old = oldTable[i]; old != null;) { 236 CacheEntry e = old; 237 old = old.next; 238 if (e.get() != null) { 239 int index = (e.hash & 0x7FFFFFFF) % newCapacity; 240 e.next = newTable[index]; 241 newTable[index] = e; 242 } else 243 count--; /* remove entries that have disappeared */ 244 } 245 } 246 } 247 248 /** 249 * Puts the specified element into the Cache, using the specified 250 * key. The element may be retrieved by doing a get() with the same 251 * key. The key and the element cannot be null. 252 * @param key the specified hashtable key 253 * @param value the specified element 254 * @return the old value of the key, or null if it did not have one. 255 * @exception NullPointerException If the value of the specified 256 * element is null. 257 * @see Cache#get 258 */ 259 public synchronized Object put(Object key, Object value) { 260 // Make sure the value is not null 261 if (value == null) { 262 throw new NullPointerException(); 263 } 264 // Makes sure the key is not already in the cache. 265 CacheEntry tab[] = table; 266 int hash = key.hashCode(); 267 int index = (hash & 0x7FFFFFFF) % tab.length; 268 CacheEntry ne = null; 269 for (CacheEntry e = tab[index]; e != null; e = e.next) { 270 if ((e.hash == hash) && e.key.equals(key)) { 271 Object old = e.get(); 272 e.setThing(value); 273 return old; 274 } else if (e.get() == null) 275 ne = e; /* reuse old flushed value */ 276 } 277 278 if (count >= threshold) { 279 // Rehash the table if the threshold is exceeded 280 rehash(); 281 return put(key, value); 282 } 283 // Creates the new entry. 284 if (ne == null) { 285 ne = new CacheEntry (); 286 ne.next = tab[index]; 287 tab[index] = ne; 288 count++; 289 } 290 ne.hash = hash; 291 ne.key = key; 292 ne.setThing(value); 293 return null; 294 } 295 296 /** 297 * Removes the element corresponding to the key. Does nothing if the 298 * key is not present. 299 * @param key the key that needs to be removed 300 * @return the value of key, or null if the key was not found. 301 */ 302 public synchronized Object remove(Object key) { 303 CacheEntry tab[] = table; 304 int hash = key.hashCode(); 305 int index = (hash & 0x7FFFFFFF) % tab.length; 306 for (CacheEntry e = tab[index], prev = null; e != null; prev = e, e = e.next) { 307 if ((e.hash == hash) && e.key.equals(key)) { 308 if (prev != null) { 309 prev.next = e.next; 310 } else { 311 tab[index] = e.next; 312 } 313 count--; 314 return e.get(); 315 } 316 } 317 return null; 318 } 319 } 320 321 /** 322 * A Cache enumerator class. This class should remain opaque 323 * to the client. It will use the Enumeration interface. 324 */ 325 class CacheEnumerator implements Enumeration<Object> { 326 boolean keys; 327 int index; 328 CacheEntry table[]; 329 CacheEntry entry; 330 331 CacheEnumerator (CacheEntry table[], boolean keys) { 332 this.table = table; 333 this.keys = keys; 334 this.index = table.length; 335 } 336 337 public boolean hasMoreElements() { 338 while (index >= 0) { 339 while (entry != null) 340 if (entry.get() != null) 341 return true; 342 else 343 entry = entry.next; 344 while (--index >= 0 && (entry = table[index]) == null) ; 345 } 346 return false; 347 } 348 349 public Object nextElement() { 350 while (index >= 0) { 351 if (entry == null) 352 while (--index >= 0 && (entry = table[index]) == null) ; 353 if (entry != null) { 354 CacheEntry e = entry; 355 entry = e.next; 356 if (e.get() != null) 357 return keys ? e.key : e.get(); 358 } 359 } 360 throw new NoSuchElementException("CacheEnumerator"); 361 } 362 363 } |