Source Code Cross Referenced for CaseInsensitiveMap.java in  » Web-Framework » Tapestry » org » apache » tapestry » ioc » util » Java Source Code / Java DocumentationJava Source Code and Java Documentation

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Java Source Code / Java Documentation » Web Framework » Tapestry » org.apache.tapestry.ioc.util 
Source Cross Referenced  Class Diagram Java Document (Java Doc) 


001:        // Copyright 2007 The Apache Software Foundation
002:        //
003:        // Licensed under the Apache License, Version 2.0 (the "License");
004:        // you may not use this file except in compliance with the License.
005:        // You may obtain a copy of the License at
006:        //
007:        //     http://www.apache.org/licenses/LICENSE-2.0
008:        //
009:        // Unless required by applicable law or agreed to in writing, software
010:        // distributed under the License is distributed on an "AS IS" BASIS,
011:        // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
012:        // See the License for the specific language governing permissions and
013:        // limitations under the License.
014:
015:        package org.apache.tapestry.ioc.util;
016:
017:        import java.io.Serializable;
018:        import java.util.AbstractMap;
019:        import java.util.AbstractSet;
020:        import java.util.ConcurrentModificationException;
021:        import java.util.Iterator;
022:        import java.util.Map;
023:        import java.util.NoSuchElementException;
024:        import java.util.Set;
025:
026:        /**
027:         * An mapped collection where the keys are always strings and access to values is case-insensitive.
028:         * The case of keys in the map is <em>maintained</em>, but on any access to a key (directly or
029:         * indirectly), all key comparisons are performed in a case-insensitive manner. The map
030:         * implementation is intended to support a reasonably finite number (dozens or hundreds, not
031:         * thousands or millions of key/value pairs. Unlike HashMap, it is based on a sorted list of entries
032:         * rather than hash bucket. It is also geared towards a largely static map, one that is created and
033:         * then used without modification.
034:         * 
035:         * @param <V>
036:         *            the type of value stored
037:         */
038:        public class CaseInsensitiveMap<V> extends AbstractMap<String, V>
039:                implements  Serializable {
040:            private static final long serialVersionUID = 3362718337611953298L;
041:
042:            private static final int NULL_HASH = Integer.MIN_VALUE;
043:
044:            private static final int DEFAULT_SIZE = 20;
045:
046:            private static class CIMEntry<V> implements  Map.Entry<String, V>,
047:                    Serializable {
048:                private static final long serialVersionUID = 6713986085221148350L;
049:
050:                private String _key;
051:
052:                private final int _hashCode;
053:
054:                V _value;
055:
056:                public CIMEntry(final String key, final int hashCode, V value) {
057:                    _key = key;
058:                    _hashCode = hashCode;
059:                    _value = value;
060:                }
061:
062:                public String getKey() {
063:                    return _key;
064:                }
065:
066:                public V getValue() {
067:                    return _value;
068:                }
069:
070:                public V setValue(V value) {
071:                    V result = _value;
072:
073:                    _value = value;
074:
075:                    return result;
076:                }
077:
078:                /**
079:                 * Returns true if both keys are null, or if the provided key is the same as, or
080:                 * case-insensitively equal to, the entrie's key.
081:                 * 
082:                 * @param key
083:                 *            to compare against
084:                 * @return true if equal
085:                 */
086:                boolean matches(String key) {
087:                    return key == _key
088:                            || (key != null && key.equalsIgnoreCase(_key));
089:                }
090:
091:                boolean valueMatches(Object value) {
092:                    return value == _value
093:                            || (value != null && value.equals(_value));
094:                }
095:            }
096:
097:            private class EntrySetIterator implements  Iterator {
098:                int _expectedModCount = _modCount;
099:
100:                int _index;
101:
102:                int _current = -1;
103:
104:                public boolean hasNext() {
105:                    return _index < _size;
106:                }
107:
108:                public Object next() {
109:                    check();
110:
111:                    if (_index >= _size)
112:                        throw new NoSuchElementException();
113:
114:                    _current = _index++;
115:
116:                    return _entries[_current];
117:                }
118:
119:                public void remove() {
120:                    check();
121:
122:                    if (_current < 0)
123:                        throw new NoSuchElementException();
124:
125:                    new Position(_current, true).remove();
126:
127:                    _expectedModCount = _modCount;
128:                }
129:
130:                private void check() {
131:                    if (_expectedModCount != _modCount)
132:                        throw new ConcurrentModificationException();
133:                }
134:            }
135:
136:            @SuppressWarnings("unchecked")
137:            private class EntrySet extends AbstractSet {
138:                @Override
139:                public Iterator iterator() {
140:                    return new EntrySetIterator();
141:                }
142:
143:                @Override
144:                public int size() {
145:                    return _size;
146:                }
147:
148:                @Override
149:                public void clear() {
150:                    CaseInsensitiveMap.this .clear();
151:                }
152:
153:                @Override
154:                public boolean contains(Object o) {
155:                    if (!(o instanceof  Map.Entry))
156:                        return false;
157:
158:                    Map.Entry e = (Map.Entry) o;
159:
160:                    Position position = select(e.getKey());
161:
162:                    return position.isFound() ? position.entry().valueMatches(
163:                            e.getValue()) : false;
164:                }
165:
166:                @Override
167:                public boolean remove(Object o) {
168:                    if (!(o instanceof  Map.Entry))
169:                        return false;
170:
171:                    Map.Entry e = (Map.Entry) o;
172:
173:                    Position position = select(e.getKey());
174:
175:                    if (position.isFound()
176:                            && position.entry().valueMatches(e.getValue())) {
177:                        position.remove();
178:                        return true;
179:                    }
180:
181:                    return false;
182:                }
183:
184:            }
185:
186:            private class Position {
187:                private final int _cursor;
188:
189:                private final boolean _found;
190:
191:                Position(int cursor, boolean found) {
192:                    _cursor = cursor;
193:                    _found = found;
194:                }
195:
196:                boolean isFound() {
197:                    return _found;
198:                }
199:
200:                CIMEntry<V> entry() {
201:                    return _entries[_cursor];
202:                }
203:
204:                V get() {
205:                    return _found ? _entries[_cursor]._value : null;
206:                }
207:
208:                V remove() {
209:                    if (!_found)
210:                        return null;
211:
212:                    V result = _entries[_cursor]._value;
213:
214:                    // Remove the entry by shifting everything else down.
215:
216:                    System.arraycopy(_entries, _cursor + 1, _entries, _cursor,
217:                            _size - _cursor - 1);
218:
219:                    // We shifted down, leaving one (now duplicate) entry behind.
220:
221:                    _entries[--_size] = null;
222:
223:                    // A structural change for sure
224:
225:                    _modCount++;
226:
227:                    return result;
228:                }
229:
230:                @SuppressWarnings("unchecked")
231:                V put(String key, int hashCode, V newValue) {
232:                    if (_found) {
233:                        CIMEntry<V> e = _entries[_cursor];
234:
235:                        V result = e._value;
236:
237:                        // Not a structural change, so no change to _modCount
238:
239:                        // Update the key (to maintain case). By definition, the hash code
240:                        // will not change.
241:
242:                        e._key = key;
243:                        e._value = newValue;
244:
245:                        return result;
246:                    }
247:
248:                    // Not found, we're going to add it.
249:
250:                    int newSize = _size + 1;
251:
252:                    if (newSize == _entries.length) {
253:                        // Time to expand!
254:
255:                        int newCapacity = (_size * 3) / 2 + 1;
256:
257:                        CIMEntry<V>[] newEntries = new CIMEntry[newCapacity];
258:
259:                        System.arraycopy(_entries, 0, newEntries, 0, _cursor);
260:
261:                        System.arraycopy(_entries, _cursor, newEntries,
262:                                _cursor + 1, _size - _cursor);
263:
264:                        _entries = newEntries;
265:                    } else {
266:                        // Open up a space for the new entry
267:
268:                        System.arraycopy(_entries, _cursor, _entries,
269:                                _cursor + 1, _size - _cursor);
270:                    }
271:
272:                    CIMEntry<V> newEntry = new CIMEntry<V>(key, hashCode,
273:                            newValue);
274:                    _entries[_cursor] = newEntry;
275:
276:                    _size++;
277:
278:                    // This is definately a structural change
279:
280:                    _modCount++;
281:
282:                    return null;
283:                }
284:
285:            }
286:
287:            // The list of entries. This is kept sorted by hash code. In some cases, there may be different
288:            // keys with the same hash code in adjacent indexes.
289:            private CIMEntry<V>[] _entries;
290:
291:            private int _size = 0;
292:
293:            // Used by iterators to check for concurrent modifications
294:
295:            private transient int _modCount = 0;
296:
297:            private transient Set<Map.Entry<String, V>> _entrySet;
298:
299:            public CaseInsensitiveMap() {
300:                this (DEFAULT_SIZE);
301:            }
302:
303:            @SuppressWarnings("unchecked")
304:            public CaseInsensitiveMap(int size) {
305:                _entries = new CIMEntry[Math.max(size, 3)];
306:            }
307:
308:            public CaseInsensitiveMap(Map<String, ? extends V> map) {
309:                this (map.size());
310:
311:                for (Map.Entry<String, ? extends V> entry : map.entrySet()) {
312:                    put(entry.getKey(), entry.getValue());
313:                }
314:            }
315:
316:            @Override
317:            public void clear() {
318:                for (int i = 0; i < _size; i++)
319:                    _entries[i] = null;
320:
321:                _size = 0;
322:                _modCount++;
323:            }
324:
325:            @Override
326:            public boolean isEmpty() {
327:                return _size == 0;
328:            }
329:
330:            @Override
331:            public int size() {
332:                return _size;
333:            }
334:
335:            @SuppressWarnings("unchecked")
336:            @Override
337:            public V put(String key, V value) {
338:                int hashCode = caseInsenitiveHashCode(key);
339:
340:                return select(key, hashCode).put(key, hashCode, value);
341:            }
342:
343:            @Override
344:            public boolean containsKey(Object key) {
345:                return select(key).isFound();
346:            }
347:
348:            @Override
349:            public V get(Object key) {
350:                return select(key).get();
351:            }
352:
353:            @Override
354:            public V remove(Object key) {
355:                return select(key).remove();
356:            }
357:
358:            @SuppressWarnings("unchecked")
359:            @Override
360:            public Set<Map.Entry<String, V>> entrySet() {
361:                if (_entrySet == null)
362:                    _entrySet = new EntrySet();
363:
364:                return _entrySet;
365:            }
366:
367:            private Position select(Object key) {
368:                if (key == null || key instanceof  String) {
369:                    String keyString = (String) key;
370:                    return select(keyString, caseInsenitiveHashCode(keyString));
371:                }
372:
373:                return new Position(0, false);
374:            }
375:
376:            /**
377:             * Searches the elements for the index of the indicated key and (case insensitive) hash code.
378:             * Sets the _cursor and _found attributes.
379:             */
380:            private Position select(String key, int hashCode) {
381:                if (_size == 0)
382:                    return new Position(0, false);
383:
384:                int low = 0;
385:                int high = _size - 1;
386:
387:                int cursor = 0;
388:
389:                while (low <= high) {
390:                    cursor = (low + high) >> 1;
391:
392:                    CIMEntry e = _entries[cursor];
393:
394:                    if (e._hashCode < hashCode) {
395:                        low = cursor + 1;
396:                        continue;
397:                    }
398:
399:                    if (e._hashCode > hashCode) {
400:                        high = cursor - 1;
401:                        continue;
402:                    }
403:
404:                    return tunePosition(key, hashCode, cursor);
405:                }
406:
407:                return new Position(low, false);
408:            }
409:
410:            /**
411:             * select() has located a matching hashCode, but there's an outlying possibility that multiple
412:             * keys share the same hashCode. Backup the cursor until we get to locate the initial hashCode
413:             * match, then march forward until the key is located, or the hashCode stops matching.
414:             * 
415:             * @param key
416:             * @param hashCode
417:             */
418:            private Position tunePosition(String key, int hashCode, int cursor) {
419:                boolean found = false;
420:
421:                while (cursor > 0) {
422:                    if (_entries[cursor - 1]._hashCode != hashCode)
423:                        break;
424:
425:                    cursor--;
426:                }
427:
428:                while (true) {
429:                    if (_entries[cursor].matches(key)) {
430:                        found = true;
431:                        break;
432:                    }
433:
434:                    // Advance to the next entry.
435:
436:                    cursor++;
437:
438:                    // If out of entries,
439:                    if (cursor >= _size
440:                            || _entries[cursor]._hashCode != hashCode)
441:                        break;
442:                }
443:
444:                return new Position(cursor, found);
445:            }
446:
447:            static int caseInsenitiveHashCode(String input) {
448:                if (input == null)
449:                    return NULL_HASH;
450:
451:                int length = input.length();
452:                int hash = 0;
453:
454:                // This should end up more or less equal to input.toLowerCase().hashCode(), unless String
455:                // changes its implementation. Let's hope this is reasonably fast.
456:
457:                for (int i = 0; i < length; i++) {
458:                    int ch = input.charAt(i);
459:
460:                    int caselessCh = Character.toLowerCase(ch);
461:
462:                    hash = 31 * hash + caselessCh;
463:                }
464:
465:                return hash;
466:            }
467:
468:        }
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