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The Apache Cassandra Project develops a highly scalable second-generation distributed database, bringing together Dynamo's fully distributed design and Bigtable's ColumnFamily-based data model.

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/*
 * 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.cassandra.utils.memory;

import java.nio.ByteBuffer;
import java.util.ArrayList;
import java.util.List;

import org.apache.cassandra.db.Cell;
import org.apache.cassandra.db.DecoratedKey;
import org.apache.cassandra.utils.concurrent.OpOrder;

public class HeapPool extends MemtablePool
{
    public HeapPool(long maxOnHeapMemory, float cleanupThreshold, Runnable cleaner)
    {
        super(maxOnHeapMemory, 0, cleanupThreshold, cleaner);
    }

    public boolean needToCopyOnHeap()
    {
        return false;
    }

    public MemtableAllocator newAllocator()
    {
        return new Allocator(this);
    }

    public static class Allocator extends MemtableBufferAllocator
    {
        Allocator(HeapPool pool)
        {
            super(pool.onHeap.newAllocator(), pool.offHeap.newAllocator());
        }

        public ByteBuffer allocate(int size, OpOrder.Group opGroup)
        {
            super.onHeap().allocate(size, opGroup);
            return ByteBuffer.allocate(size);
        }

        public DataReclaimer reclaimer()
        {
            return new Reclaimer();
        }

        private class Reclaimer implements DataReclaimer
        {
            List delayed;

            public Reclaimer reclaim(Cell cell)
            {
                if (delayed == null)
                    delayed = new ArrayList<>();
                delayed.add(cell);
                return this;
            }

            public Reclaimer reclaimImmediately(Cell cell)
            {
                onHeap().released(cell.name().dataSize() + cell.value().remaining());
                return this;
            }

            public Reclaimer reclaimImmediately(DecoratedKey key)
            {
                onHeap().released(key.getKey().remaining());
                return this;
            }

            public void cancel()
            {
                if (delayed != null)
                    delayed.clear();
            }

            public void commit()
            {
                if (delayed != null)
                    for (Cell cell : delayed)
                        reclaimImmediately(cell);
            }
        }
    }
}