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

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Here is the source code for alluxio.network.protocol.databuffer.DataFileChannel.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.channel.DefaultFileRegion;

import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;

/**
 * A DataBuffer with the underlying data being a {@link FileChannel}.
 */
public final class DataFileChannel implements DataBuffer {
    private final FileChannel mFileChannel;
    private final long mOffset;
    private final long mLength;

    /**
     *
     * @param fileChannel The FileChannel representing the data
     * @param offset The offset into the FileChannel
     * @param length The length of the data to read
     */
    public DataFileChannel(FileChannel fileChannel, long offset, long length) {
        mFileChannel = Preconditions.checkNotNull(fileChannel);
        mOffset = offset;
        mLength = length;
    }

    @Override
    public Object getNettyOutput() {
        return new DefaultFileRegion(mFileChannel, mOffset, mLength);
    }

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

    @Override
    public ByteBuffer getReadOnlyByteBuffer() {
        ByteBuffer buffer = ByteBuffer.allocate((int) mLength);
        try {
            mFileChannel.position(mOffset);
            int bytesRead;
            long bytesRemaining = mLength;
            while (bytesRemaining > 0 && (bytesRead = mFileChannel.read(buffer)) >= 0) {
                bytesRemaining -= bytesRead;
            }
        } catch (IOException e) {
            return null;
        }
        ByteBuffer readOnly = buffer.asReadOnlyBuffer();
        readOnly.position(0);
        return readOnly;
    }

    @Override
    public void release() {
        // Nothing we need to release explicitly, let GC take care of all objects.
    }
}