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 import java.util.List; 020 021 022 /** 023 * Encodes objects to a page file and decodes them from a page file. 024 * 025 * @author <a href="http://hiramchirino.com">Hiram Chirino</a> 026 * @param <T> 027 */ 028 public interface PagedAccessor<T> { 029 030 /** 031 * Store a value at the specified page. 032 * 033 * Object encoding will be deferred as long as possible. This allows multiple updates 034 * the the same page to avoid paying the cost of multiple encoding passes. Only when 035 * the value is evicted from the cache or the page file is flushed, will the encoding 036 * take place. 037 * 038 * Since the deferred encoding is no longer taking place in the context of a transaction, 039 * there are several restrictions of what pages the Marshaler can update so that transaction 040 * isolation is not violated: 041 * <ul> 042 * <li>It can update the specified page<li> 043 * <li>It can allocate new pages and update or free those pages</li> 044 * </ul> 045 * 046 * @param paged 047 * @param page 048 * @param value 049 * @return a list of any pages allocated by the method. 050 */ 051 List<Integer> store(Paged paged, int page, T value); 052 053 /** 054 * Load a value from a specified page. It should not attempt do any 055 * update operations against the {@link Paged} object. 056 * 057 * @param paged 058 * @param page 059 * @return 060 */ 061 T load(Paged paged, int page); 062 063 /** 064 * Returns a list of the pages linked to the specified page. 065 * 066 * @param paged 067 * @param page 068 */ 069 List<Integer> pagesLinked(Paged paged, int page); 070 }