/*
    *
    * 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.regionserver;
  
  import java.io.IOException;
  import java.util.SortedSet;
  
  import org.apache.commons.lang.NotImplementedException;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.hbase.Cell;
  import org.apache.hadoop.hbase.client.Scan;
  
  /**
   * A "non-lazy" scanner which always does a real seek operation. Most scanners
   * are inherited from this class.
   */
  @InterfaceAudience.Private
  public abstract class NonLazyKeyValueScanner implements KeyValueScanner {
  
    @Override
    public boolean requestSeek(Cell kv, boolean forward, boolean useBloom)
        throws IOException {
      return doRealSeek(this, kv, forward);
    }
  
    @Override
    public boolean realSeekDone() {
      return true;
    }
  
    @Override
    public void enforceSeek() throws IOException {
      throw new NotImplementedException("enforceSeek must not be called on a " +
          "non-lazy scanner");
    }
  
    public static boolean doRealSeek(KeyValueScanner scanner,
        Cell kv, boolean forward) throws IOException {
      return forward ? scanner.reseek(kv) : scanner.seek(kv);
    }
  
    @Override
    public boolean shouldUseScanner(Scan scan, SortedSet<byte[]> columns,
        long oldestUnexpiredTS) {
      // No optimizations implemented by default.
      return true;
    }
  
    @Override
    public boolean isFileScanner() {
      // Not a file by default.
      return false;
    }
    @Override
    public Cell getNextIndexedKey() {
      return null;
    }
  }