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A module that is everything required to understands Druid Segments
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/*
 * 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.druid.data.input;

import com.google.common.base.Predicate;
import com.google.common.io.CountingInputStream;
import org.apache.druid.java.util.common.FileUtils;

import javax.annotation.Nullable;
import java.io.File;
import java.io.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.URI;

/**
 * Wrapper around an {@link InputEntity} that counts the number of bytes read.
 */
public class BytesCountingInputEntity implements InputEntity
{
  private final InputStats inputStats;
  private final InputEntity baseInputEntity;

  public BytesCountingInputEntity(InputEntity baseInputEntity, InputStats inputStats)
  {
    this.baseInputEntity = baseInputEntity;
    this.inputStats = inputStats;
  }

  @Nullable
  @Override
  public URI getUri()
  {
    return baseInputEntity.getUri();
  }

  @Override
  public InputStream open() throws IOException
  {
    return new BytesCountingInputStream(baseInputEntity.open(), inputStats);
  }

  public InputEntity getBaseInputEntity()
  {
    return baseInputEntity;
  }

  @Override
  public CleanableFile fetch(File temporaryDirectory, byte[] fetchBuffer) throws IOException
  {
    final CleanableFile cleanableFile = baseInputEntity.fetch(temporaryDirectory, fetchBuffer);
    inputStats.incrementProcessedBytes(FileUtils.getFileSize(cleanableFile.file()));
    return cleanableFile;
  }

  @Override
  public Predicate getRetryCondition()
  {
    return baseInputEntity.getRetryCondition();
  }

  /**
   * Wraps an input stream, and counts the number of bytes read.
   * 
   * Similar to {@link CountingInputStream} but does not reset count on call to
   * {@link CountingInputStream#reset()}.
   */
  private static class BytesCountingInputStream extends FilterInputStream
  {
    private final InputStats inputStats;

    BytesCountingInputStream(@Nullable InputStream in, InputStats inputStats)
    {
      super(in);
      this.inputStats = inputStats;
    }

    @Override
    public int read() throws IOException
    {
      int result = in.read();
      if (result != -1) {
        inputStats.incrementProcessedBytes(1);
      }
      return result;
    }

    @Override
    public int read(byte[] b, int off, int len) throws IOException
    {
      int result = in.read(b, off, len);
      if (result != -1) {
        inputStats.incrementProcessedBytes(result);
      }
      return result;
    }

    @Override
    public long skip(long n) throws IOException
    {
      long result = in.skip(n);
      inputStats.incrementProcessedBytes(result);
      return result;
    }
  }
}