btreehead.java

来自「非常棒的java数据库」· Java 代码 · 共 64 行

/*
 * Copyright 2004-2008 H2 Group. Licensed under the H2 License, Version 1.0
 * (http://h2database.com/html/license.html).
 * Initial Developer: H2 Group
 */
package org.h2.index;

import java.sql.SQLException;

import org.h2.store.DataPage;
import org.h2.store.Record;

/**
 * The head page of a b-tree index. There is exactly one head page for each such
 * index, and it contains meta data such as the location of the root page.
 * Unlike the root page of a b-tree index, the head page always stays at the
 * same place.
 */
public class BtreeHead extends Record {

    private int rootPosition;
    private boolean consistent;

    public BtreeHead() {
        // nothing to do
    }

    public BtreeHead(DataPage s) throws SQLException {
        rootPosition = s.readInt();
        consistent = s.readInt() == 1;
    }

    public boolean getConsistent() {
        return consistent;
    }

    public void setConsistent(boolean b) {
        this.consistent = b;
    }

    public int getByteCount(DataPage dummy) throws SQLException {
        return 1 + dummy.getIntLen();
    }

    public void write(DataPage buff) throws SQLException {
        buff.writeByte((byte) 'H');
        buff.writeInt(rootPosition);
        buff.writeInt(consistent ? 1 : 0);
    }

    void setRootPosition(int rootPosition) {
        this.rootPosition = rootPosition;
    }

    int getRootPosition() {
        return rootPosition;
    }

    public boolean isPinned() {
        return true;
    }

}