/*
 * Copyright (c) "Neo4j"
 * Neo4j Sweden AB [http://neo4j.com]
 *
 * This file is part of Neo4j.
 *
 * Neo4j is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
package org.neo4j.index.internal.gbptree;

/**
 * Defines special page ids for {@link GBPTree}.
 */
public final class IdSpace {
    /**
     * Page id of the meta page holding information about root id and custom user meta information.
     * This page id is statically allocated throughout the life of a tree.
     */
    static final long META_PAGE_ID = 0L;

    /**
     * State page with IDs such as free-list, highId, rootId and more. There are two such pages alternating
     * between checkpoints, this is the first.
     */
    static final long STATE_PAGE_A = 1L;

    /**
     * State page with IDs such as free-list, highId, rootId and more. There are two such pages alternating
     * between checkpoints, this is the second.
     */
    static final long STATE_PAGE_B = 2L;

    /**
     * Min value allowed as tree node id.
     */
    static final long MIN_TREE_NODE_ID = 3L;

    /**
     * Page id for the first freelist node.
     */
    static final long MIN_FREELIST_NODE_ID = 4L;

    private IdSpace() {}
}
