alluxio.worker.block.io.LocalFileBlockReader.java Source code

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Here is the source code for alluxio.worker.block.io.LocalFileBlockReader.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.worker.block.io;

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

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

import javax.annotation.concurrent.NotThreadSafe;

/**
 * This class provides read access to a block data file locally stored in managed storage.
 */
@NotThreadSafe
public final class LocalFileBlockReader implements BlockReader {
    private final String mFilePath;
    private final RandomAccessFile mLocalFile;
    private final FileChannel mLocalFileChannel;
    private final Closer mCloser = Closer.create();
    private final long mFileSize;
    private boolean mClosed;

    /**
     * Constructs a Block reader given the file path of the block.
     *
     * @param path file path of the block
     * @throws IOException if its file can not be open with "r" mode
     */
    public LocalFileBlockReader(String path) throws IOException {
        mFilePath = Preconditions.checkNotNull(path);
        mLocalFile = mCloser.register(new RandomAccessFile(mFilePath, "r"));
        mLocalFileChannel = mCloser.register(mLocalFile.getChannel());
        mFileSize = mLocalFile.length();
    }

    @Override
    public ReadableByteChannel getChannel() {
        return mLocalFileChannel;
    }

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

    @Override
    public ByteBuffer read(long offset, long length) throws IOException {
        Preconditions.checkArgument(offset + length <= mFileSize, "offset=%s, length=%s, exceeding fileSize=%s",
                offset, length, mFileSize);
        // TODO(calvin): May need to make sure length is an int.
        if (length == -1L) {
            length = mFileSize - offset;
        }
        return mLocalFileChannel.map(FileChannel.MapMode.READ_ONLY, offset, length);
    }

    @Override
    public int transferTo(ByteBuf buf) throws IOException {
        return buf.writeBytes(mLocalFileChannel, buf.writableBytes());
    }

    @Override
    public void close() throws IOException {
        if (mClosed) {
            return;
        }
        try {
            mCloser.close();
        } finally {
            mClosed = true;
        }
    }

    @Override
    public boolean isClosed() {
        return mClosed;
    }
}