content: /*
   * 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.carbondata.core.datastore.impl;
  
  import java.io.IOException;
  import java.nio.ByteBuffer;
  import java.util.HashMap;
  import java.util.Map;
  import java.util.Map.Entry;
  
  import org.apache.carbondata.core.constants.CarbonCommonConstants;
  import org.apache.carbondata.core.datastore.FileReader;
  
  import org.apache.hadoop.conf.Configuration;
  import org.apache.hadoop.fs.FSDataInputStream;
  import org.apache.hadoop.fs.FileSystem;
  import org.apache.hadoop.fs.Path;
  
  public class DFSFileReaderImpl implements FileReader {
    /**
     * cache to hold filename and its stream
     */
    protected Map<String, FSDataInputStream> fileNameAndStreamCache;
  
    private boolean readPageByPage;
  
    private Configuration configuration;
  
    public DFSFileReaderImpl(Configuration configuration) {
      this.configuration = configuration;
      this.fileNameAndStreamCache =
          new HashMap<String, FSDataInputStream>(CarbonCommonConstants.DEFAULT_COLLECTION_SIZE);
    }
  
    @Override
    public byte[] readByteArray(String filePath, long offset, int length)
        throws IOException {
      FSDataInputStream fileChannel = updateCache(filePath);
      return read(fileChannel, length, offset);
    }
  
    /**
     * This method will be used to check whether stream is already present in
     * cache or not for filepath if not present then create it and then add to
     * cache, other wise get from cache
     *
     * @param filePath fully qualified file path
     * @return channel
     */
    public FSDataInputStream updateCache(String filePath) throws IOException {
      FSDataInputStream fileChannel = fileNameAndStreamCache.get(filePath);
      if (null == fileChannel) {
        Path pt = new Path(filePath);
        FileSystem fs = pt.getFileSystem(configuration);
        fileChannel = fs.open(pt);
        fileNameAndStreamCache.put(filePath, fileChannel);
      }
      return fileChannel;
    }
  
    /**
     * This method will be used to read from file based on number of bytes to be read and position
     *
     * @param channel file channel
     * @param size    number of bytes
     * @param offset  position
     * @return byte buffer
     */
    private byte[] read(FSDataInputStream channel, int size, long offset) throws IOException {
      byte[] byteBuffer = new byte[size];
      channel.seek(offset);
      channel.readFully(byteBuffer);
      return byteBuffer;
    }
  
    /**
     * This method will be used to read from file based on number of bytes to be read and position
     *
     * @param channel file channel
     * @param size    number of bytes
     * @return byte buffer
     */
    private byte[] read(FSDataInputStream channel, int size) throws IOException {
      byte[] byteBuffer = new byte[size];
      channel.readFully(byteBuffer);
      return byteBuffer;
    }
  
    @Override
    public int readInt(String filePath, long offset) throws IOException {
      FSDataInputStream fileChannel = updateCache(filePath);
      fileChannel.seek(offset);
      return fileChannel.readInt();
    }
  
    @Override
    public long readDouble(String filePath, long offset) throws IOException {
      FSDataInputStream fileChannel = updateCache(filePath);
      fileChannel.seek(offset);
      return fileChannel.readLong();
    }
  
    @Override
    public void finish() throws IOException {
      for (Entry<String, FSDataInputStream> entry : fileNameAndStreamCache.entrySet()) {
        FSDataInputStream channel = entry.getValue();
        if (null != channel) {
          channel.close();
        }
      }
    }
  
    @Override
    public byte[] readByteArray(String filePath, int length) throws IOException {
      FSDataInputStream fileChannel = updateCache(filePath);
      return read(fileChannel, length);
    }
  
    @Override
    public long readLong(String filePath, long offset) throws IOException {
      FSDataInputStream fileChannel = updateCache(filePath);
      fileChannel.seek(offset);
      return fileChannel.readLong();
    }
  
    @Override
    public int readInt(String filePath) throws IOException {
      FSDataInputStream fileChannel = updateCache(filePath);
      return fileChannel.readInt();
    }
  
    @Override
    public ByteBuffer readByteBuffer(String filePath, long offset, int length)
        throws IOException {
      byte[] readByteArray = readByteArray(filePath, offset, length);
      ByteBuffer byteBuffer = ByteBuffer.wrap(readByteArray);
      byteBuffer.rewind();
      return byteBuffer;
    }
  
    @Override
    public void setReadPageByPage(boolean isReadPageByPage) {
      this.readPageByPage = isReadPageByPage;
    }
  
    @Override
    public boolean isReadPageByPage() {
      return readPageByPage;
    }
  
    public Map<String, FSDataInputStream> getFileNameAndStreamCache() {
      return fileNameAndStreamCache;
    }
  
  }
  