| /** |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| package org.apache.aurora.scheduler.storage.mem; |
| |
| import java.util.Map; |
| import java.util.Set; |
| |
| import com.google.common.annotations.VisibleForTesting; |
| import com.google.common.collect.ImmutableSet; |
| import com.google.common.collect.Maps; |
| import com.google.common.collect.Sets; |
| |
| /** |
| * An interning pool that can be used to retrieve the canonical instances of objects, while |
| * maintaining a reference count to the canonical instances. |
| * |
| * @param <T> The interned object type. |
| * @param <A> The type used for maintaining associations. |
| */ |
| class Interner<T, A> { |
| |
| private final Map<T, InternEntry<A, T>> pool = Maps.newHashMap(); |
| |
| /** |
| * Retrieves the canonical instance of {@code t} and maintains {@code association} with the |
| * interned value. If {@code t} was not previously interned, the provided instance is stored. |
| * |
| * @param t The object to intern, or get the previously-interned value for. |
| * @param association A value to associate with {@code t}. |
| * @return The interned value, which may be reference-equivalent to {@code t}. |
| */ |
| synchronized T addAssociation(T t, A association) { |
| InternEntry<A, T> entry = pool.get(t); |
| if (entry == null) { |
| entry = new InternEntry<>(t, association); |
| pool.put(t, entry); |
| } else { |
| entry.associations.add(association); |
| } |
| return entry.interned; |
| } |
| |
| /** |
| * Removes an association with an interned value, effectively decrementing the reference count. |
| * |
| * @param t The interned value that {@code association} was associated with. |
| * @param association The association to remove. |
| */ |
| synchronized void removeAssociation(T t, A association) { |
| InternEntry<A, T> entry = pool.get(t); |
| if (entry != null) { |
| entry.associations.remove(association); |
| if (entry.associations.isEmpty()) { |
| pool.remove(t); |
| } |
| } |
| } |
| |
| /** |
| * Removes all interned values and associations. |
| */ |
| synchronized void clear() { |
| pool.clear(); |
| } |
| |
| @VisibleForTesting |
| synchronized boolean isInterned(T t) { |
| return pool.containsKey(t); |
| } |
| |
| @VisibleForTesting |
| synchronized Set<A> getAssociations(T t) { |
| return ImmutableSet.copyOf(pool.get(t).associations); |
| } |
| |
| private static class InternEntry<A, T> { |
| private final T interned; |
| private final Set<A> associations = Sets.newHashSet(); |
| |
| InternEntry(T interned, A initialAssociation) { |
| this.interned = interned; |
| associations.add(initialAssociation); |
| } |
| } |
| } |