node.java

一个用java写的开源的数据库系统

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 * All rights reserved.
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 * modification, are permitted provided that the following conditions are met:
 *
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 * list of conditions and the following disclaimer, including earlier
 * license statements (above) and comply with all above license conditions.
 *
 * Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation
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 * license statements (above) and comply with all above license conditions.
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package org.hsqldb;

import java.sql.SQLException;
import java.io.IOException;

// fredt@users 20020221 - patch 513005 by sqlbob@users (RMP)
// fredt@users 20020920 - path 1.7.1 by fredt - refactoring to cut mamory footprint

/**
 *  The parent for all AVL node implementations, features factory methods for
 *  its subclasses. Subclasses of Node vary in the way they hold
 *  references to other nodes in the AVL tree.<br>
 *
 *  nNext links the Node objects belonging to different indexes for each
 *  table row. It is used solely by Row to locate the node belonging to a
 *  particular index. (fredt@users)
 *
 *
 * @version 1.7.1
 */
abstract class Node {

    static final int TYPE_MEMORY  = 0;
    static final int TYPE_DISK    = 1;
    static final int TYPE_POINTER = 2;
    static final int NO_POS       = CachedRow.NO_POS;
    protected int    iBalance;    // currently, -2 means 'deleted'
    protected Row    rData;
    Node             nNext;       // node of next index (nNext==null || nNext.iId=iId+1)

    static final Node newNode(Row r, int id, Table t) {

        switch (t.getIndexType()) {

            case Index.MEMORY_INDEX :
                return new MemoryNode(r);

            case Index.POINTER_INDEX :
                return new PointerNode((CachedRow) r);

            case Index.DISK_INDEX :
            default :
                return new DiskNode((CachedRow) r, id);
        }
    }

    static final Node newNode(Row r, DatabaseRowInputInterface in, int id,
                              Table t) throws IOException, SQLException {

        switch (t.getIndexType()) {

            case Index.MEMORY_INDEX :
                return new MemoryNode(r);

            case Index.POINTER_INDEX :
                return new PointerNode((CachedRow) r);

            case Index.DISK_INDEX :
            default :
                return new DiskNode((CachedRow) r, in, id);
        }
    }

    /**
     *  Method declaration
     */
    abstract void delete();

    /**
     *  File offset of Node. Used with CachedRow objects only
     *
     * @return file offset
     */
    abstract int getKey();

    /**
     *  Used with CachedRow objects only
     *
     * @param  pos file offset of node
     */
    abstract void setKey(int pos);

    abstract Row getRow() throws SQLException;

    abstract Node getLeft() throws SQLException;

    abstract void setLeft(Node n) throws SQLException;

    abstract Node getRight() throws SQLException;

    /**
     *  Used with PointerNode objects only
     *
     * @param  pos file offset of node
     */
    abstract Node getRightPointer() throws SQLException;

    abstract void setRight(Node n) throws SQLException;

    abstract Node getParent() throws SQLException;

    abstract boolean isRoot();

    abstract void setParent(Node n) throws SQLException;

    final int getBalance() throws SQLException {

        if (Trace.DOASSERT) {
            Trace.doAssert(iBalance != -2);
        }

        return iBalance;
    }

    abstract void setBalance(int b) throws SQLException;

    /**
     * Method declaration
     *
     *
     * @param x
     *
     * @return
     *
     * @throws SQLException
     */
    abstract boolean from() throws SQLException;

    /**
     *  Returns the data held in the table Row for this Node
     *
     */
    abstract Object[] getData() throws SQLException;

    abstract boolean equals(Node n) throws SQLException;

    /**
     *  Writes out the node in an implementation dependent way.
     *
     * @param  out interface providing the different write methods
     */
    abstract void write(DatabaseRowOutputInterface out)
    throws IOException, SQLException;
}