/**
    * Copyright The Apache Software Foundation
    *
    * 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.hadoop.hbase.client;
  
  import static org.apache.hadoop.hbase.client.ConnectionUtils.noMoreResultsForReverseScan;
  
  import java.io.IOException;
  import java.util.concurrent.ExecutorService;
  
  import org.apache.hadoop.conf.Configuration;
  import org.apache.hadoop.hbase.TableName;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.hbase.ipc.RpcControllerFactory;
  
  /**
   * A reversed client scanner which support backward scanning
   */
  @InterfaceAudience.Private
  public class ReversedClientScanner extends ClientScanner {
  
    /**
     * Create a new ReversibleClientScanner for the specified table Note that the passed
     * {@link Scan}'s start row maybe changed.
     * @param conf
     * @param scan
     * @param tableName
     * @param connection
     * @param pool
     * @param primaryOperationTimeout
     * @throws IOException
     */
    public ReversedClientScanner(Configuration conf, Scan scan, TableName tableName,
        ClusterConnection connection, RpcRetryingCallerFactory rpcFactory,
        RpcControllerFactory controllerFactory, ExecutorService pool, int primaryOperationTimeout)
        throws IOException {
      super(conf, scan, tableName, connection, rpcFactory, controllerFactory, pool,
          primaryOperationTimeout);
    }
  
    @Override
    protected boolean setNewStartKey() {
      if (noMoreResultsForReverseScan(scan, currentRegion)) {
        return false;
      }
      scan.withStartRow(currentRegion.getStartKey(), false);
      return true;
    }
  
    @Override
    protected ReversedScannerCallable createScannerCallable() {
      return new ReversedScannerCallable(getConnection(), getTable(), scan, this.scanMetrics,
          this.rpcControllerFactory);
    }
  }