/*

  * 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.

  */

 package org.apache.giraph.object;

 import org.apache.giraph.function.Consumer;

 import org.apache.giraph.function.primitive.Int2ObjFunction;

 import org.apache.giraph.types.ops.PrimitiveIdTypeOps;

 import org.apache.giraph.types.ops.collections.Basic2ObjectMap;

 import org.apache.giraph.types.ops.collections.BasicSet;

 import com.google.common.base.Preconditions;

 import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;

 /**

  * Holds reusable objects of multiple sizes.

  * Example usecase, is when we need a hashmap - that we will insert and iterate

  * on, both clear() and iterate method depend on size. And if we want to reuse

  * objects, we want to have multiple objects of different sizes, that we will

  * reuse.

  *

  * Instead of creating object for each distinct size, it creates objects with

  * first larger power of 2.

  *

  * @param <T> Type of reusable object

  */

 public class MultiSizedReusable<T> implements Int2ObjFunction<T> {

   private final Int2ObjFunction<T> createSized;

   private final Consumer<T> init;

   @SuppressWarnings("unchecked")

   @SuppressFBWarnings("SE_TRANSIENT_FIELD_NOT_RESTORED")

   private final transient T[] holder = (T[]) new Object[Integer.SIZE];

   // No-arg constructor Kryo can call to initialize holder

   MultiSizedReusable() {

     this(null, null);

   }

   public MultiSizedReusable(Int2ObjFunction<T> createSized, Consumer<T> init) {

     this.createSized = createSized;

     this.init = init;

   }

   @Override

   public T apply(int size) {

     Preconditions.checkArgument(size >= 0);

     int shiftBits = (Integer.SIZE -

         Integer.numberOfLeadingZeros(Math.max(0, size - 1))) / 2;

     T result = holder[shiftBits];

     if (result == null) {

       if (shiftBits >= 15) {

         result = createSized.apply(Integer.MAX_VALUE);

       } else {

         result = createSized.apply(1 << (shiftBits * 2 + 1));

       }

       holder[shiftBits] = result;

     }

     if (init != null) {

       init.apply(result);

     }

     return result;

   }

   public static <I> MultiSizedReusable<BasicSet<I>> createForBasicSet(

       final PrimitiveIdTypeOps<I> idTypeOps) {

     return new MultiSizedReusable<>(

         new Int2ObjFunction<BasicSet<I>>() {

           @Override

           public BasicSet<I> apply(int value) {

             return idTypeOps.createOpenHashSet(value);

           }

         },

         new Consumer<BasicSet<I>>() {

           @Override

           public void apply(BasicSet<I> t) {

             t.clear();

           }

         });

   }

   public static <K, V>

   MultiSizedReusable<Basic2ObjectMap<K, V>> createForBasic2ObjectMap(

       final PrimitiveIdTypeOps<K> idTypeOps) {

     return new MultiSizedReusable<>(

         new Int2ObjFunction<Basic2ObjectMap<K, V>>() {

           @Override

           public Basic2ObjectMap<K, V> apply(int value) {

             return idTypeOps.create2ObjectOpenHashMap(value, null);

           }

         },

         new Consumer<Basic2ObjectMap<K, V>>() {

           @Override

           public void apply(Basic2ObjectMap<K, V> t) {

             t.clear();

           }

         });

   }

 }