/*
 * 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.lucene.codecs;

import java.io.Closeable;
import java.io.IOException;

import org.apache.lucene.index.FieldInfo;
import org.apache.lucene.index.NumericDocValues;
import org.apache.lucene.util.Accountable;


Abstract API that produces field normalization values
@lucene.experimental
/** Abstract API that produces field normalization values
 *
 * @lucene.experimental
 */
public abstract class NormsProducer implements Closeable, Accountable {
  
  
Sole constructor. (For invocation by subclass 
 constructors, typically implicit.) /** Sole constructor. (For invocation by subclass 
   *  constructors, typically implicit.) */
  protected NormsProducer() {}

  
Returns NumericDocValues for this field. The returned instance need not be thread-safe: it will only be used by a single thread. /** Returns {@link NumericDocValues} for this field.
   *  The returned instance need not be thread-safe: it will only be
   *  used by a single thread. */
  public abstract NumericDocValues getNorms(FieldInfo field) throws IOException;
  
  
Checks consistency of this producer

Note that this may be costly in terms of I/O, e.g. 
may involve computing a checksum value against large data files.
@lucene.internal
/** 
   * Checks consistency of this producer
   * <p>
   * Note that this may be costly in terms of I/O, e.g. 
   * may involve computing a checksum value against large data files.
   * @lucene.internal
   */
  public abstract void checkIntegrity() throws IOException;
  
  
Returns an instance optimized for merging. This instance may only be used
from the thread that acquires it.
 The default implementation returns this /** 
   * Returns an instance optimized for merging. This instance may only be used
   * from the thread that acquires it.
   * <p>
   * The default implementation returns {@code this} */
  public NormsProducer getMergeInstance() {
    return this;
  }
}