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.FileInputStream;
  import java.io.FileNotFoundException;
  import java.io.IOException;
  import java.nio.ByteBuffer;
  import java.nio.channels.FileChannel;
  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;
  
  public class FileReaderImpl implements FileReader {
    /**
     * cache to hold filename and its stream
     */
    private Map<String, FileChannel> fileNameAndStreamCache;
  
    private boolean readPageByPage;
  
    /**
     * FileReaderImpl Constructor
     * It will create the cache
     */
    public FileReaderImpl() {
      this.fileNameAndStreamCache =
          new HashMap<String, FileChannel>(CarbonCommonConstants.DEFAULT_COLLECTION_SIZE);
    }
  
    public FileReaderImpl(int capacity) {
      this.fileNameAndStreamCache = new HashMap<String, FileChannel>(capacity);
    }
  
    /**
     * This method will be used to read the byte array from file based on offset
     * and length(number of bytes) need to read
     *
     * @param filePath fully qualified file path
     * @param offset   reading start position,
     * @param length   number of bytes to be read
     * @return read byte array
     */
    @Override
    public byte[] readByteArray(String filePath, long offset, int length)
        throws IOException {
      FileChannel fileChannel = updateCache(filePath);
      ByteBuffer byteBuffer = read(fileChannel, length, offset);
      return byteBuffer.array();
    }
  
    /**
     * This method will be used to close all the streams currently present in the cache
     */
    @Override
    public void finish() throws IOException {
      for (Entry<String, FileChannel> entry : fileNameAndStreamCache.entrySet()) {
        FileChannel channel = entry.getValue();
        if (null != channel) {
          channel.close();
        }
      }
      fileNameAndStreamCache.clear();
    }
  
    /**
     * This method will be used to read int from file from position(offset), here
     * length will be always 4 because int byte size if 4
     *
     * @param filePath fully qualified file path
     * @param offset   reading start position,
     * @return read int
     */
    @Override
    public int readInt(String filePath, long offset) throws IOException {
      FileChannel fileChannel = updateCache(filePath);
      ByteBuffer byteBuffer = read(fileChannel, CarbonCommonConstants.INT_SIZE_IN_BYTE, offset);
      return byteBuffer.getInt();
    }
  
    /**
     * This method will be used to read int from file from position(offset), here
     * length will be always 4 because int byte size if 4
     *
     * @param filePath fully qualified file path
     * @return read int
     */
    @Override
    public int readInt(String filePath) throws IOException {
      FileChannel fileChannel = updateCache(filePath);
      ByteBuffer byteBuffer = read(fileChannel, CarbonCommonConstants.INT_SIZE_IN_BYTE);
      return byteBuffer.getInt();
    }
  
    /**
     * This method will be used to read int from file from position(offset), here
     * length will be always 4 because int byte size if 4
     *
     * @param filePath fully qualified file path
     * @param offset   reading start position,
     * @return read int
     */
    @Override
    public long readDouble(String filePath, long offset) throws IOException {
      FileChannel fileChannel = updateCache(filePath);
      ByteBuffer byteBuffer = read(fileChannel, CarbonCommonConstants.LONG_SIZE_IN_BYTE, offset);
      return byteBuffer.getLong();
    }
  
    /**
     * 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
     */
    private FileChannel updateCache(String filePath) throws FileNotFoundException {
      FileChannel fileChannel = fileNameAndStreamCache.get(filePath);
      if (null == fileChannel) {
        FileInputStream stream = new FileInputStream(filePath);
        fileChannel = stream.getChannel();
        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 ByteBuffer read(FileChannel channel, int size, long offset) throws IOException {
      ByteBuffer byteBuffer = ByteBuffer.allocate(size);
      channel.position(offset);
      channel.read(byteBuffer);
      byteBuffer.rewind();
      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 ByteBuffer read(FileChannel channel, int size) throws IOException {
      ByteBuffer byteBuffer = ByteBuffer.allocate(size);
      channel.read(byteBuffer);
      byteBuffer.rewind();
      return byteBuffer;
    }
  
  
    /**
     * This method will be used to read the byte array from file based on length(number of bytes)
     *
     * @param filePath fully qualified file path
     * @param length   number of bytes to be read
     * @return read byte array
     */
    @Override
    public byte[] readByteArray(String filePath, int length) throws IOException {
      FileChannel fileChannel = updateCache(filePath);
      ByteBuffer byteBuffer = read(fileChannel, length);
      return byteBuffer.array();
    }
  
    /**
     * This method will be used to read long from file from position(offset), here
     * length will be always 8 because int byte size is 8
     *
     * @param filePath fully qualified file path
     * @param offset   reading start position,
     * @return read long
     */
    @Override
    public long readLong(String filePath, long offset) throws IOException {
      FileChannel fileChannel = updateCache(filePath);
      ByteBuffer byteBuffer = read(fileChannel, CarbonCommonConstants.LONG_SIZE_IN_BYTE, offset);
      return byteBuffer.getLong();
    }
  
    @Override
    public ByteBuffer readByteBuffer(String filePath, long offset, int length)
        throws IOException {
      ByteBuffer byteBuffer = ByteBuffer.allocate(length);
      FileChannel fileChannel = updateCache(filePath);
      fileChannel.position(offset);
      fileChannel.read(byteBuffer);
      byteBuffer.rewind();
      return byteBuffer;
    }
  
    @Override
    public void setReadPageByPage(boolean isReadPageByPage) {
      this.readPageByPage = isReadPageByPage;
    }
  
    @Override
    public boolean isReadPageByPage() {
      return readPageByPage;
    }
  }
  