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.activemq.store.kahadb.disk.index;
  
  import java.io.IOException;
  import java.util.Iterator;
  import java.util.Map;
  
  import org.apache.activemq.store.kahadb.disk.page.Transaction;
  import org.apache.activemq.store.kahadb.disk.util.Marshaller;
  
  /**
   * Simpler than a Map
   * 
   * 
   */
  public interface Index<Key,Value> {
      
      /**
       * Set the marshaller for key objects
       * 
       * @param marshaller
       */
      void setKeyMarshaller(Marshaller<Key> marshaller);
      
      /**
       * Set the marshaller for key objects
       * 
       * @param marshaller
       */
      void setValueMarshaller(Marshaller<Value> marshaller);
  
      /**
       * load indexes
       */
      void load(Transaction tx) throws IOException;
  
      /**
       * unload indexes
       * 
       * @throws IOException
       */
      void unload(Transaction tx) throws IOException;
  
      /**
       * clear the index
       * 
       * @throws IOException
       * 
       */
      void clear(Transaction tx) throws IOException;
  
      /**
       * @param key
       * @return true if it contains the key
       * @throws IOException
       */
      boolean containsKey(Transaction tx, Key key) throws IOException;
  
      /**
       * remove the index key
       * 
       * @param key
       * @return StoreEntry removed
       * @throws IOException
       */
      Value remove(Transaction tx, Key key) throws IOException;
  
      /**
       * store the key, item
       * 
       * @param key
       * @param entry
       * @throws IOException
       */
      Value put(Transaction tx, Key key, Value entry) throws IOException;
  
      /**
       * @param key
       * @return the entry
       * @throws IOException
       */
      Value get(Transaction tx, Key key) throws IOException;
  
      /**
       * @return true if the index is transient
       */
      boolean isTransient();
      
      /**
       * @param tx
       * @return
       * @throws IOException
       * @trhows UnsupportedOperationException 
       *         if the index does not support fast iteration of the elements.
       */
      Iterator<Map.Entry<Key,Value>> iterator(final Transaction tx) throws IOException, UnsupportedOperationException;
      
  }
  