/*
 * Copyright 2010 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.filter;

import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import org.apache.hadoop.hbase.KeyValue;
import org.apache.hadoop.hbase.util.Bytes;

/**
 * A filter that will only return the key component of each KV (the value will
 * be rewritten as empty).
 * <p>
 * This filter can be used to grab all of the keys without having to also grab
 * the values.
 */
public class KeyOnlyFilter extends FilterBase {

  boolean lenAsVal;
  public KeyOnlyFilter() { this(false); }
  public KeyOnlyFilter(boolean lenAsVal) { this.lenAsVal = lenAsVal; }

  @Override
  public ReturnCode filterKeyValue(KeyValue kv) {
    kv.convertToKeyOnly(this.lenAsVal);
    return ReturnCode.INCLUDE;
  }

  public void write(DataOutput out) throws IOException {
    out.writeBoolean(this.lenAsVal);
  }

  public void readFields(DataInput in) throws IOException {
    this.lenAsVal = in.readBoolean();
  }
}