001    /**
002     * Licensed to the Apache Software Foundation (ASF) under one or more
003     * contributor license agreements.  See the NOTICE file distributed with
004     * this work for additional information regarding copyright ownership.
005     * The ASF licenses this file to You under the Apache License, Version 2.0
006     * (the "License"); you may not use this file except in compliance with
007     * the License.  You may obtain a copy of the License at
008     *
009     *      http://www.apache.org/licenses/LICENSE-2.0
010     *
011     * Unless required by applicable law or agreed to in writing, software
012     * distributed under the License is distributed on an "AS IS" BASIS,
013     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014     * See the License for the specific language governing permissions and
015     * limitations under the License.
016     */
017    package org.fusesource.hawtdb.api;
018    
019    /**
020     * Interface used to determine the simple prefix of two keys.  Used by BTree indexes
021     * to implement the variable magnitude optimization.
022     * 
023     * @author <a href="http://hiramchirino.com">Hiram Chirino</a>
024     */
025    public interface Prefixer<Key> {
026    
027        /**
028         * This methods should return shortest prefix of value2 where the
029         * following still holds:<br/>
030         * value1 <= prefix <= value2.<br/>
031         * <br/>
032         * 
033         * When this method is called, the following is guaranteed:<br/>
034         * value1 < value2<br/>
035         * <br/>
036         * 
037         * 
038         * @param value1
039         * @param value2
040         * @return
041         */
042        public Key getSimplePrefix(Key value1, Key value2);
043    }