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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.client.block;

import alluxio.client.ClientContext;
import alluxio.exception.AlluxioException;
import alluxio.exception.ExceptionMessage;
import alluxio.util.io.BufferUtils;
import alluxio.util.network.NetworkAddressUtils;
import alluxio.wire.LockBlockResult;
import alluxio.worker.block.io.LocalFileBlockReader;

import com.google.common.io.Closer;

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

import javax.annotation.concurrent.NotThreadSafe;

/**
 * This class provides a streaming API to read a block in Alluxio. The data will be directly read
 * from the local machine's storage.
 */
@NotThreadSafe
public final class LocalBlockInStream extends BufferedBlockInStream {
  /** Helper to manage closables. */
  private final Closer mCloser;
  /** Client to communicate with the local worker. */
  private final BlockWorkerClient mBlockWorkerClient;
  /** The block store context which provides block worker clients. */
  private final BlockStoreContext mContext;
  /** The file reader to read a local block. */
  private final LocalFileBlockReader mReader;

  /**
   * Creates a new local block input stream.
   *
   * @param blockId the block id
   * @param blockSize the size of the block
   * @throws IOException if I/O error occurs
   */
  public LocalBlockInStream(long blockId, long blockSize) throws IOException {
    super(blockId, blockSize);
    mContext = BlockStoreContext.INSTANCE;

    mCloser = Closer.create();
    mBlockWorkerClient =
        mContext.acquireWorkerClient(NetworkAddressUtils.getLocalHostName(ClientContext.getConf()));
    try {
      LockBlockResult result = mBlockWorkerClient.lockBlock(blockId);
      if (result == null) {
        throw new IOException(ExceptionMessage.BLOCK_NOT_LOCALLY_AVAILABLE.getMessage(mBlockId));
      }
      mReader = new LocalFileBlockReader(result.getBlockPath());
      mCloser.register(mReader);
    } catch (IOException e) {
      mContext.releaseWorkerClient(mBlockWorkerClient);
      throw e;
    }
  }

  @Override
  public void close() throws IOException {
    if (mClosed) {
      return;
    }
    try {
      if (mBlockIsRead) {
        mBlockWorkerClient.accessBlock(mBlockId);
        ClientContext.getClientMetrics().incBlocksReadLocal(1);
      }
      mBlockWorkerClient.unlockBlock(mBlockId);
    } catch (AlluxioException e) {
      throw new IOException(e);
    } finally {
      mContext.releaseWorkerClient(mBlockWorkerClient);
      mCloser.close();
      if (mBuffer != null && mBuffer.isDirect()) {
        BufferUtils.cleanDirectBuffer(mBuffer);
      }
    }

    mClosed = true;
  }

  @Override
  protected void bufferedRead(int len) throws IOException {
    if (mBuffer.isDirect()) { // Buffer may not be direct on initialization
      BufferUtils.cleanDirectBuffer(mBuffer);
    }
    mBuffer = mReader.read(getPosition(), len);
  }

  @Override
  public int directRead(byte[] b, int off, int len) throws IOException {
    ByteBuffer buf = mReader.read(getPosition(), len);
    buf.get(b, off, len);
    BufferUtils.cleanDirectBuffer(buf);
    return len;
  }

  @Override
  protected void incrementBytesReadMetric(int bytes) {
    ClientContext.getClientMetrics().incBytesReadLocal(bytes);
  }
}