Magic.java

/*******************************************************************************
 * Copyright 2010 Cees De Groot, Alex Boisvert, Jan Kotek
 *
 * Licensed 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.jdbm;

/**
 * This interface contains magic cookies.
 */
interface Magic {
    /**
     * Magic cookie at start of file
     */
    short FILE_HEADER = 0x1350;

    /**
     * Magic for pages. They're offset by the page type magic codes.
     */
    short PAGE_MAGIC = 0x1351;

    /**
     * Magics for pages in certain lists.
     */
    short FREE_PAGE = 0;
    short USED_PAGE = 1;
    short TRANSLATION_PAGE = 2;
    short FREELOGIDS_PAGE = 3;
    short FREEPHYSIDS_PAGE = 4;
    short FREEPHYSIDS_ROOT_PAGE = 5;

    /**
     * Number of lists in a file
     */
    short NLISTS = 6;

    /**
     * Magic for transaction file
     */
    short LOGFILE_HEADER = 0x1360;

    /**
     * Size of an externalized byte
     */
    short SZ_BYTE = 1;
    /**
     * Size of an externalized short
     */
    short SZ_SHORT = 2;

    /**
     * Size of an externalized int
     */
    short SZ_INT = 4;
    /**
     * Size of an externalized long
     */
    short SZ_LONG = 8;

    /**
     * size of three byte integer
     */
    short SZ_SIX_BYTE_LONG = 6;


    /**offsets in file header (zero page in file)*/
    short FILE_HEADER_O_MAGIC = 0; // short magic
    short FILE_HEADER_O_LISTS = Magic.SZ_SHORT; // long[2*NLISTS]
    int FILE_HEADER_O_ROOTS = FILE_HEADER_O_LISTS + (Magic.NLISTS * 2 * Magic.SZ_LONG);
    /**
     * The number of "root" rowids available in the file.
     */
    int FILE_HEADER_NROOTS = 16;


    short PAGE_HEADER_O_MAGIC = 0; // short magic
    short PAGE_HEADER_O_NEXT = Magic.SZ_SHORT;
    short PAGE_HEADER_O_PREV = PAGE_HEADER_O_NEXT + Magic.SZ_SIX_BYTE_LONG;
    short PAGE_HEADER_SIZE = PAGE_HEADER_O_PREV + Magic.SZ_SIX_BYTE_LONG;

    short PhysicalRowId_O_LOCATION = 0; // long page
//    short PhysicalRowId_O_OFFSET = Magic.SZ_SIX_BYTE_LONG; // short offset
    int PhysicalRowId_SIZE = Magic.SZ_SIX_BYTE_LONG;
    
    short DATA_PAGE_O_FIRST = PAGE_HEADER_SIZE; // short firstrowid
    short DATA_PAGE_O_DATA = (short) (DATA_PAGE_O_FIRST + Magic.SZ_SHORT);
    short DATA_PER_PAGE = (short) (Storage.PAGE_SIZE - DATA_PAGE_O_DATA);






}