org.apache.hadoop.hbase.io.hfile.slab.Slab.java Source code

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Here is the source code for org.apache.hadoop.hbase.io.hfile.slab.Slab.java

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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.hadoop.hbase.io.hfile.slab;

import java.nio.ByteBuffer;
import java.util.concurrent.ConcurrentLinkedQueue;
import java.util.concurrent.LinkedBlockingQueue;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.hbase.util.ClassSize;
import org.apache.hadoop.hbase.util.DirectMemoryUtils;
import com.google.common.base.Preconditions;

/**
 * Slab is a class which is designed to allocate blocks of a certain size.
 * Constructor creates a number of DirectByteBuffers and slices them into the
 * requisite size, then puts them all in a buffer.
 **/

@InterfaceAudience.Private
class Slab implements org.apache.hadoop.hbase.io.HeapSize {
    static final Log LOG = LogFactory.getLog(Slab.class);

    /** This is where our items, or blocks of the slab, are stored. */
    private LinkedBlockingQueue<ByteBuffer> buffers;

    /** This is where our Slabs are stored */
    private ConcurrentLinkedQueue<ByteBuffer> slabs;

    private final int blockSize;
    private final int numBlocks;
    private long heapSize;

    Slab(int blockSize, int numBlocks) {
        buffers = new LinkedBlockingQueue<ByteBuffer>();
        slabs = new ConcurrentLinkedQueue<ByteBuffer>();

        this.blockSize = blockSize;
        this.numBlocks = numBlocks;

        this.heapSize = ClassSize.estimateBase(this.getClass(), false);

        int maxBlocksPerSlab = Integer.MAX_VALUE / blockSize;
        int maxSlabSize = maxBlocksPerSlab * blockSize;

        int numFullSlabs = numBlocks / maxBlocksPerSlab;
        int partialSlabSize = (numBlocks % maxBlocksPerSlab) * blockSize;
        for (int i = 0; i < numFullSlabs; i++) {
            allocateAndSlice(maxSlabSize, blockSize);
        }

        if (partialSlabSize > 0) {
            allocateAndSlice(partialSlabSize, blockSize);
        }
    }

    private void allocateAndSlice(int size, int sliceSize) {
        ByteBuffer newSlab = ByteBuffer.allocateDirect(size);
        slabs.add(newSlab);
        for (int j = 0; j < newSlab.capacity(); j += sliceSize) {
            newSlab.limit(j + sliceSize).position(j);
            ByteBuffer aSlice = newSlab.slice();
            buffers.add(aSlice);
            heapSize += ClassSize.estimateBase(aSlice.getClass(), false);
        }
    }

    /*
     * Shutdown deallocates the memory for all the DirectByteBuffers. Each
     * DirectByteBuffer has a "cleaner" method, which is similar to a
     * deconstructor in C++.
     */
    void shutdown() {
        for (ByteBuffer aSlab : slabs) {
            try {
                DirectMemoryUtils.destroyDirectByteBuffer(aSlab);
            } catch (Exception e) {
                LOG.warn("Unable to deallocate direct memory during shutdown", e);
            }
        }
    }

    int getBlockSize() {
        return this.blockSize;
    }

    int getBlockCapacity() {
        return this.numBlocks;
    }

    int getBlocksRemaining() {
        return this.buffers.size();
    }

    /*
     * Throws an exception if you try to allocate a
     * bigger size than the allocator can handle. Alloc will block until a buffer is available.
     */
    ByteBuffer alloc(int bufferSize) throws InterruptedException {
        int newCapacity = Preconditions.checkPositionIndex(bufferSize, blockSize);

        ByteBuffer returnedBuffer = buffers.take();

        returnedBuffer.clear().limit(newCapacity);
        return returnedBuffer;
    }

    void free(ByteBuffer toBeFreed) {
        Preconditions.checkArgument(toBeFreed.capacity() == blockSize);
        buffers.add(toBeFreed);
    }

    @Override
    public long heapSize() {
        return heapSize;
    }
}