row.java

Java写的含有一个jdbc驱动的小型数据库数据库引擎

/*
 * Row.java
 *
 * Copyright (c) 2001, The HSQL Development Group
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * 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.
 *
 * 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.
 *
 *
 * Neither the name of the HSQL Development Group nor the names of its
 * 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"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE FOR
 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * This package is based on HypersonicSQL, originally developed by Thomas Mueller.
 *
 */
package org.hsqldb;

import java.sql.*;
import java.io.*;

/**
 * Class declaration
 *
 *
 * @version 1.0.0.1
 */
class Row {
    private Object oData[];
    private Table  tTable;    // null: memory row; otherwise: cached table

    // only required for cached table
    static int     iCurrentAccess = 0;

    // todo: use int iLastChecked;
    int		   iLastAccess;
    Row		   rLast, rNext;
    int		   iPos;
    int		   iSize;
    boolean	   bChanged;
    private Node   nFirstIndex;

    /**
     * Constructor declaration
     *
     *
     * @param t
     * @param o
     */
    Row(Table t, Object o[]) throws SQLException {
	tTable = t;

	int index = tTable.getIndexCount();

	nFirstIndex = new Node(this, 0);

	Node n = nFirstIndex;

	for (int i = 1; i < index; i++) {
	    n.nNext = new Node(this, i);
	    n = n.nNext;
	}

	oData = o;

	if (tTable != null && tTable.cCache != null) {
	    iLastAccess = iCurrentAccess++;

	    // todo: 32 bytes overhead for each index + iSize, iPos
	    iSize = 8 + Column.getSize(o, tTable)
		    + 32 * tTable.getIndexCount();
	    iSize = ((iSize + 7) / 8) * 8;    // align to 8 byte blocks

	    tTable.cCache.add(this);
	}

	bChanged = true;
    }

    /**
     * Method declaration
     *
     *
     * @throws SQLException
     */
    void cleanUpCache() throws SQLException {
	if (tTable != null && tTable.cCache != null) {

	    // so that this row is not cleaned
	    iLastAccess = iCurrentAccess++;

	    tTable.cCache.cleanUp();
	}
    }

    /**
     * Method declaration
     *
     */
    void changed() {
	bChanged = true;
	iLastAccess = iCurrentAccess++;
    }

    /**
     * Method declaration
     *
     *
     * @param pos
     * @param index
     *
     * @return
     *
     * @throws SQLException
     */
    Node getNode(int pos, int index) throws SQLException {

	// return getRow(pos).getNode(index);
	Row r = tTable.cCache.getRow(pos, tTable);

	r.iLastAccess = iCurrentAccess++;

	return r.getNode(index);
    }

    /**
     * Method declaration
     *
     *
     * @param pos
     *
     * @return
     *
     * @throws SQLException
     */
    private Row getRow(int pos) throws SQLException {
	return tTable.cCache.getRow(pos, tTable);
    }

    /**
     * Method declaration
     *
     *
     * @param index
     *
     * @return
     */
    Node getNode(int index) {
	Node n = nFirstIndex;

	while (index-- > 0) {
	    n = n.nNext;
	}

	return n;
    }

    /**
     * Method declaration
     *
     *
     * @return
     */
    Object[] getData() {
	iLastAccess = iCurrentAccess++;

	return oData;
    }

    // if read from cache

    /**
     * Constructor declaration
     *
     *
     * @param t
     * @param in
     * @param pos
     * @param before
     */
    Row(Table t, DataInput in, int pos,
	    Row before) throws IOException, SQLException {
	tTable = t;

	int index = tTable.getIndexCount();

	iPos = pos;
	nFirstIndex = new Node(this, in, 0);

	Node n = nFirstIndex;

	for (int i = 1; i < index; i++) {
	    n.nNext = new Node(this, in, i);
	    n = n.nNext;
	}

	int l = tTable.getInternalColumnCount();

	oData = Column.readData(in, l);

	Trace.check(in.readInt() == iPos, Trace.INPUTSTREAM_ERROR);
	insert(before);

	iLastAccess = iCurrentAccess++;
    }

    /**
     * Method declaration
     *
     *
     * @param before
     */
    void insert(Row before) {
	if (before == null) {
	    rNext = this;
	    rLast = this;
	} else {
	    rNext = before;
	    rLast = before.rLast;
	    before.rLast = this;
	    rLast.rNext = this;
	}
    }

    /**
     * Method declaration
     *
     *
     * @return
     *
     * @throws SQLException
     */
    boolean canRemove() throws SQLException {
	Node n = nFirstIndex;

	while (n != null) {
	    if (Trace.ASSERT) {
		Trace.assert(n.iBalance != -2);
	    }

	    if (Trace.STOP) {
		Trace.stop();
	    }

	    if (n.iParent == 0 && n.nParent == null) {
		return true;
	    }

	    n = n.nNext;
	}

	return false;
    }

    /**
     * Method declaration
     *
     *
     * @return
     *
     * @throws IOException
     * @throws SQLException
     */
    byte[] write() throws IOException, SQLException {
	ByteArrayOutputStream bout = new ByteArrayOutputStream(iSize);
	DataOutputStream      out = new DataOutputStream(bout);

	out.writeInt(iSize);
	nFirstIndex.write(out);
	Column.writeData(out, oData, tTable);
	out.writeInt(iPos);

	bChanged = false;

	return bout.toByteArray();
    }

    /**
     * Method declaration
     *
     *
     * @throws SQLException
     */
    void delete() throws SQLException {
	if (tTable != null && tTable.cCache != null) {
	    bChanged = false;

	    tTable.cCache.free(this, iPos, iSize);
	}
    }

    /**
     * Method declaration
     *
     *
     * @throws SQLException
     */
    void free() throws SQLException {
	rLast.rNext = rNext;
	rNext.rLast = rLast;

	if (rNext == this) {
	    rNext = rLast = null;
	}
    }

}