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.IOException;
  import java.util.ArrayList;
  import java.util.List;
  
  import org.apache.carbondata.core.datastore.impl.FileFactory;
  import org.apache.carbondata.core.metadata.schema.table.column.ColumnSchema;
  import org.apache.carbondata.format.FileHeader;
  
  import static org.apache.carbondata.core.util.CarbonUtil.thriftColumnSchemaToWrapperColumnSchema;
  
  import org.apache.hadoop.conf.Configuration;
  
  /**
   * Below class to read file header of version3
   * carbon data file
   */
  public class CarbonHeaderReader {
  
    //Fact file path
    private String filePath;
  
    private Configuration configuration;
  
    public CarbonHeaderReader(String filePath) {
      this.filePath = filePath;
    }
  
    public CarbonHeaderReader(String filePath, Configuration configuration) {
      this.filePath = filePath;
      this.configuration = configuration;
    }
  
    /**
     * It reads the metadata in FileFooter thrift object format.
     *
     * @return
     * @throws IOException
     */
    public FileHeader readHeader() throws IOException {
      ThriftReader thriftReader = openThriftReader(filePath);
      thriftReader.open();
      FileHeader header = (FileHeader) thriftReader.read();
      thriftReader.close();
      return header;
    }
  
    /**
     * Open the thrift reader
     *
     * @param filePath
     * @return
     * @throws IOException
     */
    private ThriftReader openThriftReader(String filePath) {
      Configuration conf = configuration != null ? configuration : FileFactory.getConfiguration();
      return new ThriftReader(filePath, FileHeader::new, conf);
    }
  
    /**
     * Read and return the schema in the header
     */
    public List<ColumnSchema> readSchema() throws IOException {
      FileHeader fileHeader = readHeader();
      List<ColumnSchema> columnSchemaList = new ArrayList<>();
      List<org.apache.carbondata.format.ColumnSchema> table_columns = fileHeader.getColumn_schema();
      for (org.apache.carbondata.format.ColumnSchema table_column : table_columns) {
        ColumnSchema col = thriftColumnSchemaToWrapperColumnSchema(table_column);
        col.setColumnReferenceId(col.getColumnUniqueId());
        columnSchemaList.add(col);
      }
      return columnSchemaList;
    }
  }
  