exec/java-exec/src/main/java/org/apache/drill/exec/store/parquet/ColumnDataReader.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.drill.exec.store.parquet;

import io.netty.buffer.DrillBuf;

import java.io.IOException;
import java.io.OutputStream;

import org.apache.hadoop.fs.FSDataInputStream;

import org.apache.parquet.bytes.BytesInput;
import org.apache.parquet.format.PageHeader;
import org.apache.parquet.format.Util;
import org.apache.parquet.hadoop.util.HadoopStreams;

public class ColumnDataReader {
  static final org.slf4j.Logger logger = org.slf4j.LoggerFactory.getLogger(ColumnDataReader.class);

  private final long endPosition;
  public final FSDataInputStream input;

  public ColumnDataReader(FSDataInputStream input, long start, long length) throws IOException{
    this.input = input;
    this.input.seek(start);
    this.endPosition = start + length;
  }

  public PageHeader readPageHeader() throws IOException{
    return Util.readPageHeader(input);
  }

  public FSDataInputStream getInputStream() {
    return input;
  }

  public BytesInput getPageAsBytesInput(int pageLength) throws IOException{
    byte[] b = new byte[pageLength];
    input.read(b);
    return new HadoopBytesInput(b);
  }

  public void loadPage(DrillBuf target, int pageLength) throws IOException {
    target.clear();
    HadoopStreams.wrap(input).read(target.nioBuffer(0, pageLength));
    target.writerIndex(pageLength);
  }

  public void clear(){
    try{
      input.close();
    }catch(IOException ex){
      logger.warn("Error while closing input stream.", ex);
    }
  }

  public boolean hasRemainder() throws IOException{
    return input.getPos() < endPosition;
  }

  public class HadoopBytesInput extends BytesInput{

    private final byte[] pageBytes;

    public HadoopBytesInput(byte[] pageBytes) {
      super();
      this.pageBytes = pageBytes;
    }

    @Override
    public byte[] toByteArray() throws IOException {
      return pageBytes;
    }

    @Override
    public long size() {
      return pageBytes.length;
    }

    @Override
    public void writeAllTo(OutputStream out) throws IOException {
      out.write(pageBytes);
    }

  }

}