pointernode.java

一个用java写的开源的数据库系统

/* Copyrights and Licenses
 *
 * This product includes Hypersonic SQL.
 * Originally developed by Thomas Mueller and the Hypersonic SQL Group. 
 *
 * Copyright (c) 1995-2000 by the Hypersonic SQL Group. All rights reserved. 
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 * provided that the following conditions are met: 
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 *         and the following disclaimer. 
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 *          product includes Hypersonic SQL." 
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 * software, even if advised of the possibility of such damage. 
 * This software consists of voluntary contributions made by many individuals on behalf of the
 * Hypersonic SQL Group.
 *
 *
 * For work added by the HSQL Development Group:
 *
 * Copyright (c) 2001-2002, The HSQL Development Group
 * All rights reserved.
 *
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 * modification, are permitted provided that the following conditions are met:
 *
 * Redistributions of source code must retain the above copyright notice, this
 * 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
 * and/or other materials provided with the distribution, including earlier
 * license statements (above) and comply with all above license conditions.
 *
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 * contributors may be used to endorse or promote products derived from this
 * software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */


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

/**
 *  Text table node implementation.<br>
 *  Nodes for the AVL tree are all built and kept in memory while the actual
 *  row data is accessed through TextCache from disk.<br>
 *  This extends MemoryNode by maintaining a disk based offset for the
 *  Row data. (fredt@users)
 *
 * @version    1.7.1
 */
class PointerNode extends MemoryNode {

    private int   iId;    // id of Index for this Node
    private int   iData = NO_POS;
    private Table tTable;
    private int   iRight = NO_POS;

    PointerNode(CachedRow r) {

        tTable = r.getTable();

        if (r.iPos == CachedRow.NO_POS) {
            rData = r;
        } else {
            iData = r.iPos;
        }
    }

    void delete() {

        iBalance = -2;
        nLeft    = nRight = nParent = null;
        iRight   = 0;
        tTable   = null;
    }

    int getKey() {

        if (rData != null) {
            return ((CachedRow) rData).iPos;
        }

        return iData;
    }

    void setKey(int pos) {
        iData = pos;
        rData = null;
    }

    Row getRow() throws SQLException {

        if (rData != null) {
            return rData;
        }

        if (iData == NO_POS) {
            return null;
        }

        return tTable.getRow(iData);
    }

    private Node findNode(int pos, int id) throws SQLException {

        Node ret = null;
        Row  r   = tTable.getRow(pos);

        if (r != null) {
            ret = r.getNode(id);
        }

        return ret;
    }

    Node getRight() throws SQLException {

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

        if (nRight != null) {
            return nRight;
        }

        if (iRight == NO_POS) {
            return null;
        }

        return findNode(iRight, iId);
    }

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

    void setRight(Node n) throws SQLException {

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

        iRight = NO_POS;
        nRight = n;
    }

    /**
     *  Used at construction
     *
     * @param  i file offset
     */
    void setNextKey(int i) throws SQLException {

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

        iRight = i;
        nRight = null;
    }

    Object[] getData() throws SQLException {

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

        return getRow().getData();
    }

    boolean equals(Node n) throws SQLException {

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

            if (n != this) {
                Trace.doAssert((getKey() == NO_POS) || (n == null)
                               || (n.getKey() != getKey()));
            } else {
                Trace.doAssert(n.getKey() == getKey());
            }
        }

        return n == this;
    }
}