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.reader;
  
  import java.io.BufferedReader;
  import java.io.DataInputStream;
  import java.io.IOException;
  import java.io.InputStreamReader;
  import java.io.StringWriter;
  
  import org.apache.carbondata.core.constants.CarbonCommonConstants;
  import org.apache.carbondata.core.datastore.impl.FileFactory;
  import org.apache.carbondata.core.fileoperations.AtomicFileOperationFactory;
  import org.apache.carbondata.core.fileoperations.AtomicFileOperations;
  import org.apache.carbondata.core.mutate.DeleteDeltaBlockDetails;
  import org.apache.carbondata.core.util.CarbonUtil;
  
  import com.google.gson.Gson;
  
  /**
   * This class perform the functionality of reading the delete delta file
   */
  public class CarbonDeleteDeltaFileReaderImpl implements CarbonDeleteDeltaFileReader {
  
    private String filePath;
  
    private static final int DEFAULT_BUFFER_SIZE = 258;
  
    /**
     * @param filePath
     */
    public CarbonDeleteDeltaFileReaderImpl(String filePath) {
      this.filePath = filePath;
    }
  
    /**
     * This method will be used to read complete delete delta file.
     * scenario:
     * Whenever a query is executed then read the delete delta file
     * to exclude the deleted data.
     *
     * @return All deleted records for the specified block
     * @throws IOException if an I/O error occurs
     */
    @Override
    public String read() throws IOException {
      // Configure Buffer based on our requirement
      char[] buffer = new char[DEFAULT_BUFFER_SIZE];
      StringWriter sw = new StringWriter();
      try (DataInputStream dataInputStream = FileFactory.getDataInputStream(filePath);
          InputStreamReader inputStream = new InputStreamReader(dataInputStream,
              CarbonCommonConstants.DEFAULT_CHARSET)) {
        int n = 0;
        while (-1 != (n = inputStream.read(buffer))) {
          sw.write(buffer, 0, n);
        }
        return sw.toString();
      }
    }
  
    /**
     * Reads delete delta file (json file) and returns DeleteDeltaBlockDetails
     * @return DeleteDeltaBlockDetails
     */
    @Override
    public DeleteDeltaBlockDetails readJson() {
      Gson gsonObjectToRead = new Gson();
      DataInputStream dataInputStream = null;
      BufferedReader buffReader = null;
      InputStreamReader inStream = null;
      DeleteDeltaBlockDetails deleteDeltaBlockDetails;
      AtomicFileOperations fileOperation =
          AtomicFileOperationFactory.getAtomicFileOperations(filePath);
      try {
        if (!FileFactory.isFileExist(filePath)) {
          return new DeleteDeltaBlockDetails("");
        }
        dataInputStream = fileOperation.openForRead();
        inStream = new InputStreamReader(dataInputStream,
            CarbonCommonConstants.DEFAULT_CHARSET);
        buffReader = new BufferedReader(inStream);
        deleteDeltaBlockDetails =
            gsonObjectToRead.fromJson(buffReader, DeleteDeltaBlockDetails.class);
      } catch (IOException e) {
        return new DeleteDeltaBlockDetails("");
      } finally {
        CarbonUtil.closeStreams(buffReader, inStream, dataInputStream);
      }
  
      return deleteDeltaBlockDetails;
    }
  }
  