content: /*
   * 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.hadoop;
  
  import alluxio.AlluxioURI;
  import alluxio.client.file.FileInStream;
  import alluxio.client.file.FileSystem;
  import alluxio.exception.AlluxioException;
  import alluxio.exception.ExceptionMessage;
  import alluxio.exception.FileDoesNotExistException;
  
  import org.apache.hadoop.fs.ByteBufferReadable;
  import org.apache.hadoop.fs.FileSystem.Statistics;
  import org.apache.hadoop.fs.PositionedReadable;
  import org.apache.hadoop.fs.Seekable;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import java.io.EOFException;
  import java.io.FileNotFoundException;
  import java.io.IOException;
  import java.io.InputStream;
  import java.nio.ByteBuffer;
  import javax.annotation.concurrent.NotThreadSafe;
  
  /**
   * An input stream for reading a file from HDFS. This is just a wrapper around
   * {@link FileInStream} with additional statistics gathering in a {@link Statistics} object.
   */
  @NotThreadSafe
  public class BaseHdfsFileInputStream extends InputStream implements Seekable, PositionedReadable,
      ByteBufferReadable {
    private static final Logger LOG = LoggerFactory.getLogger(BaseHdfsFileInputStream.class);
  
    private final Statistics mStatistics;
    protected final FileInStream mInputStream;
  
    private boolean mClosed = false;
  
    /**
     * Constructs a new stream for reading a file from HDFS.
     *
     * @param fs the file system
     * @param uri the Alluxio file URI
     * @param stats filesystem statistics
     */
    public BaseHdfsFileInputStream(FileSystem fs, AlluxioURI uri, Statistics stats)
        throws IOException {
      LOG.debug("HdfsFileInputStream({}, {})", uri, stats);
  
      mStatistics = stats;
      try {
        mInputStream = fs.openFile(uri);
      } catch (FileDoesNotExistException e) {
        // Transform the Alluxio exception to a Java exception to satisfy the HDFS API contract.
        throw new FileNotFoundException(ExceptionMessage.PATH_DOES_NOT_EXIST.getMessage(uri));
      } catch (AlluxioException e) {
        throw new IOException(e);
      }
    }
  
    /**
     * Constructs a new stream for reading a file from HDFS.
     *
     * @param inputStream the input stream
     * @param stats filesystem statistics
     */
    public BaseHdfsFileInputStream(FileInStream inputStream, Statistics stats) {
      mInputStream = inputStream;
      mStatistics = stats;
    }
  
    @Override
    public int available() throws IOException {
      if (mClosed) {
        throw new IOException("Cannot query available bytes from a closed stream.");
      }
      return (int) mInputStream.remaining();
    }
  
    @Override
    public void close() throws IOException {
      if (mClosed) {
        return;
      }
      mInputStream.close();
      mClosed = true;
    }
  
    @Override
    public long getPos() throws IOException {
      return mInputStream.getPos();
    }
  
    @Override
    public int read() throws IOException {
      if (mClosed) {
        throw new IOException(ExceptionMessage.READ_CLOSED_STREAM.getMessage());
      }
  
      int data = mInputStream.read();
      if (data != -1 && mStatistics != null) {
        mStatistics.incrementBytesRead(1);
      }
      return data;
    }
  
    @Override
    public int read(byte[] buffer) throws IOException {
      return read(buffer, 0, buffer.length);
    }
  
    @Override
    public int read(byte[] buffer, int offset, int length) throws IOException {
      if (mClosed) {
        throw new IOException(ExceptionMessage.READ_CLOSED_STREAM.getMessage());
      }
  
      int bytesRead = mInputStream.read(buffer, offset, length);
      if (bytesRead != -1 && mStatistics != null) {
        mStatistics.incrementBytesRead(bytesRead);
      }
      return bytesRead;
    }
  
    @Override
    public int read(ByteBuffer buf) throws IOException {
      if (mClosed) {
        throw new IOException(ExceptionMessage.READ_CLOSED_STREAM.getMessage());
      }
      int bytesRead = mInputStream.read(buf);
      if (bytesRead != -1 && mStatistics != null) {
        mStatistics.incrementBytesRead(bytesRead);
      }
      return bytesRead;
    }
  
    @Override
    public int read(long position, byte[] buffer, int offset, int length) throws IOException {
      if (mClosed) {
        throw new IOException(ExceptionMessage.READ_CLOSED_STREAM.getMessage());
      }
  
      int bytesRead = mInputStream.positionedRead(position, buffer, offset, length);
      if (bytesRead != -1 && mStatistics != null) {
        mStatistics.incrementBytesRead(bytesRead);
      }
      return bytesRead;
    }
  
    @Override
    public void readFully(long position, byte[] buffer) throws IOException {
      readFully(position, buffer, 0, buffer.length);
    }
  
    @Override
    public void readFully(long position, byte[] buffer, int offset, int length) throws IOException {
      int totalBytesRead = 0;
      while (totalBytesRead < length) {
        int bytesRead =
            read(position + totalBytesRead, buffer, offset + totalBytesRead, length - totalBytesRead);
        if (bytesRead == -1) {
          throw new EOFException();
        }
        totalBytesRead += bytesRead;
      }
    }
  
    @Override
    public void seek(long pos) throws IOException {
      try {
        mInputStream.seek(pos);
      } catch (IllegalArgumentException e) { // convert back to IOException
        throw new IOException(e);
      }
    }
  
    /**
     * This method is not supported in {@link BaseHdfsFileInputStream}.
     *
     * @param targetPos N/A
     * @return N/A
     * @throws IOException always
     */
    @Override
    public boolean seekToNewSource(long targetPos) throws IOException {
      throw new IOException("This method is not supported.");
    }
  
    @Override
    public long skip(long n) throws IOException {
      if (mClosed) {
        throw new IOException("Cannot skip bytes in a closed stream.");
      }
      return mInputStream.skip(n);
    }
  }
  