alluxio.network.protocol.databuffer.DataNettyBuffer.java Source code

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Here is the source code for alluxio.network.protocol.databuffer.DataNettyBuffer.java

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/*
 * The Alluxio Open Foundation licenses this work under the Apache License, version 2.0
 * (the "License"). You may not use this work except in compliance with the License, which is
 * available at www.apache.org/licenses/LICENSE-2.0
 *
 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
 * either express or implied, as more fully set forth in the License.
 *
 * See the NOTICE file distributed with this work for information regarding copyright ownership.
 */

package alluxio.network.protocol.databuffer;

import com.google.common.base.Preconditions;
import io.netty.buffer.ByteBuf;

import java.nio.ByteBuffer;

/**
 * A DataBuffer with the underlying data being a {@link ByteBuf}.
 */
public final class DataNettyBuffer implements DataBuffer {
    private final ByteBuffer mBuffer;
    private final long mLength;
    private final ByteBuf mNettyBuf;

    /**
    * Constructor for creating a DataNettyBuffer, by passing a Netty ByteBuf.
    * This way we avoid one copy from ByteBuf to another ByteBuffer,
    * and making sure the buffer would not be recycled.
    * IMPORTANT: {@link #release()} must be called after
    * reading is finished. Otherwise the memory space for the ByteBuf might never be reclaimed.
    *
    * @param bytebuf The ByteBuf having the data
    * @param length The length of the underlying ByteBuffer data
    */
    public DataNettyBuffer(ByteBuf bytebuf, long length) {
        // throws exception if there are multiple nioBuffers, or reference count is not 1
        Preconditions.checkArgument(bytebuf.nioBufferCount() == 1,
                "Number of nioBuffers of this bytebuf is %s (1 expected).", bytebuf.nioBufferCount());
        Preconditions.checkArgument(bytebuf.refCnt() == 1, "Reference count of this bytebuf is %s (1 expected).",
                bytebuf.refCnt());

        // increase the bytebuf reference count so it would not be recycled by Netty
        bytebuf.retain();
        mNettyBuf = bytebuf;
        mBuffer = bytebuf.nioBuffer();
        mLength = length;
    }

    /**
     * We would not support this method in DataNettyBuffer because this class is only for
     * reading netty buffers. Throws an {@link UnsupportedOperationException} whenever called.
     * TODO(qifan): Investigate if using NettyDataBuffer for outgoing message is fine.
     *
     * @return {@link UnsupportedOperationException} whenever called
     */
    @Override
    public Object getNettyOutput() {
        throw new UnsupportedOperationException("DataNettyBuffer doesn't support getNettyOutput()");
    }

    @Override
    public long getLength() {
        return mLength;
    }

    @Override
    public ByteBuffer getReadOnlyByteBuffer() {
        ByteBuffer buffer = mBuffer.asReadOnlyBuffer();
        buffer.position(0);
        return buffer;
    }

    /**
     * Release the Netty ByteBuf.
     */
    @Override
    public void release() {
        Preconditions.checkState(mNettyBuf != null);
        Preconditions.checkState(mNettyBuf.refCnt() == 1, "Reference count of the netty buffer is %s (1 expected).",
                mNettyBuf.refCnt());
        Preconditions.checkState(mNettyBuf.release(), "Release Netty ByteBuf failed.");
    }
}