hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/AvroFSInput.java

/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.hadoop.fs;

import java.io.Closeable;
import java.io.IOException;

import org.apache.avro.file.SeekableInput;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;

import static org.apache.hadoop.fs.Options.OpenFileOptions.FS_OPTION_OPENFILE_READ_POLICY;
import static org.apache.hadoop.fs.Options.OpenFileOptions.FS_OPTION_OPENFILE_READ_POLICY_SEQUENTIAL;
import static org.apache.hadoop.util.functional.FutureIO.awaitFuture;

/** Adapts an {@link FSDataInputStream} to Avro's SeekableInput interface. */
@InterfaceAudience.Public
@InterfaceStability.Stable
public class AvroFSInput implements Closeable, SeekableInput {
  private final FSDataInputStream stream;
  private final long len;

  /**
   * Construct given an {@link FSDataInputStream} and its length.
   *
   * @param in inputstream.
   * @param len len.
   */
  public AvroFSInput(final FSDataInputStream in, final long len) {
    this.stream = in;
    this.len = len;
  }

  /** Construct given a {@link FileContext} and a {@link Path}.
   * @param fc filecontext.
   * @param p the path.
   * @throws IOException If an I/O error occurred.
   * */
  public AvroFSInput(final FileContext fc, final Path p) throws IOException {
    FileStatus status = fc.getFileStatus(p);
    this.len = status.getLen();
    this.stream = awaitFuture(fc.openFile(p)
        .opt(FS_OPTION_OPENFILE_READ_POLICY,
            FS_OPTION_OPENFILE_READ_POLICY_SEQUENTIAL)
        .withFileStatus(status)
        .build());
  }

  @Override
  public long length() {
    return len;
  }

  @Override
  public int read(byte[] b, int off, int len) throws IOException {
    return stream.read(b, off, len);
  }

  @Override
  public void seek(long p) throws IOException {
    stream.seek(p);
  }

  @Override
  public long tell() throws IOException {
    return stream.getPos();
  }

  @Override
  public void close() throws IOException {
    stream.close();
  }
}