+++ /dev/null
-package org.apache.lucene.facet.search;
-
-import java.util.concurrent.ConcurrentLinkedQueue;
-
-/**
- * Licensed to the Apache Software Foundation (ASF) under one or more
- * contributor license agreements. See the NOTICE file distributed with
- * this work for additional information regarding copyright ownership.
- * The ASF licenses this file to You 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.
- */
-
-/**
- * An TemporaryObjectAllocator is an object which manages large, reusable,
- * temporary objects needed during multiple concurrent computations. The idea
- * is to remember some of the previously allocated temporary objects, and
- * reuse them if possible to avoid constant allocation and garbage-collection
- * of these objects.
- * <P>
- * This technique is useful for temporary counter arrays in faceted search
- * (see {@link FacetsAccumulator}), which can be reused across searches instead
- * of being allocated afresh on every search.
- * <P>
- * A TemporaryObjectAllocator is thread-safe.
- *
- * @lucene.experimental
- */
-public abstract class TemporaryObjectAllocator<T> {
-
- // In the "pool" we hold up to "maxObjects" old objects, and if the pool
- // is not empty, we return one of its objects rather than allocating a new
- // one.
- ConcurrentLinkedQueue<T> pool = new ConcurrentLinkedQueue<T>();
- int maxObjects;
-
- /**
- * Construct an allocator for objects of a certain type, keeping around a
- * pool of up to <CODE>maxObjects</CODE> old objects.
- * <P>
- * Note that the pool size only restricts the number of objects that hang
- * around when not needed, but <I>not</I> the maximum number of objects
- * that are allocated when actually is use: If a number of concurrent
- * threads ask for an allocation, all of them will get an object, even if
- * their number is greater than maxObjects. If an application wants to
- * limit the number of concurrent threads making allocations, it needs to
- * do so on its own - for example by blocking new threads until the
- * existing ones have finished. If more than maxObjects are freed, only
- * maxObjects of them will be kept in the pool - the rest will not and
- * will eventually be garbage-collected by Java.
- * <P>
- * In particular, when maxObjects=0, this object behaves as a trivial
- * allocator, always allocating a new array and never reusing an old one.
- */
- public TemporaryObjectAllocator(int maxObjects) {
- this.maxObjects = maxObjects;
- }
-
- /**
- * Subclasses must override this method to actually create a new object
- * of the desired type.
- *
- */
- protected abstract T create();
-
- /**
- * Subclasses must override this method to clear an existing object of
- * the desired type, to prepare it for reuse. Note that objects will be
- * cleared just before reuse (on allocation), not when freed.
- */
- protected abstract void clear(T object);
-
- /**
- * Allocate a new object. If there's a previously allocated object in our
- * pool, we return it immediately. Otherwise, a new object is allocated.
- * <P>
- * Don't forget to call {@link #free(Object)} when you're done with the object,
- * to return it to the pool. If you don't, memory is <I>not</I> leaked,
- * but the pool will remain empty and a new object will be allocated each
- * time (just like the maxArrays=0 case).
- */
- public final T allocate() {
- T object = pool.poll();
- if (object==null) {
- return create();
- }
- clear(object);
- return object;
- }
-
- /**
- * Return a no-longer-needed object back to the pool. If we already have
- * enough objects in the pool (maxObjects as specified in the constructor),
- * the array will not be saved, and Java will eventually garbage collect
- * it.
- * <P>
- * In particular, when maxArrays=0, the given array is never saved and
- * free does nothing.
- */
- public final void free(T object) {
- if (pool.size() < maxObjects && object != null) {
- pool.add(object);
- }
- }
-
-}
fnp / pylucene.git / blobdiff