Quadcap Embeddable Database

com/quadcap/sql/MultiCursor.java

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package com.quadcap.sql;

/* Copyright 1999 - 2003 Quadcap Software.  All rights reserved.
 *
 * This software is distributed under the Quadcap Free Software License.
 * This software may be used or modified for any purpose, personal or
 * commercial.  Open Source redistributions are permitted.  Commercial
 * redistribution of larger works derived from, or works which bundle
 * this software requires a "Commercial Redistribution License"; see
 * http://www.quadcap.com/purchase.
 *
 * Redistributions qualify as "Open Source" under  one of the following terms:
 *   
 *    Redistributions are made at no charge beyond the reasonable cost of
 *    materials and delivery.
 *
 *    Redistributions are accompanied by a copy of the Source Code or by an
 *    irrevocable offer to provide a copy of the Source Code for up to three
 *    years at the cost of materials and delivery.  Such redistributions
 *    must allow further use, modification, and redistribution of the Source
 *    Code under substantially the same terms as this license.
 *
 * Redistributions of source code must retain the copyright notices as they
 * appear in each source code file, these license terms, and the
 * disclaimer/limitation of liability set forth as paragraph 6 below.
 *
 * Redistributions in binary form must reproduce this Copyright Notice,
 * these license terms, and the disclaimer/limitation of liability set
 * forth as paragraph 6 below, in the documentation and/or other materials
 * provided with the distribution.
 *
 * The Software is provided on an "AS IS" basis.  No warranty is
 * provided that the Software is free of defects, or fit for a
 * particular purpose.  
 *
 * Limitation of Liability. Quadcap Software shall not be liable
 * for any damages suffered by the Licensee or any third party resulting
 * from use of the Software.
 */

import java.sql.SQLException;

import java.util.ArrayList;

import com.quadcap.util.Debug;

/**
 * Cursor implementation that concatenates multiple cursors together and
 * makes them appear as a single cursor.
 *
 * @author Stan Bailes
 */
public class MultiCursor extends FilterCursor {
    ArrayList                           cursors         = new ArrayList();
    int                                 cursorNum       = 0;

    public MultiCursor(Session session) throws SQLException {
        super(session);
    }
    
    public MultiCursor(Session session, Cursor cursor) throws SQLException {
        super(session, cursor);
        appendCursor(session, cursor);
    }

    public void appendCursor(Session session, Cursor cursor) throws SQLException {
        cursors.add(cursor);
        if (this.cursor == null) {
            this.cursor = cursor;
            addColumns(session, cursor);
        }
    }

    public void beforeFirst() throws SQLException {
        for (int i = 0; i < cursors.size(); i++) {
            Cursor c = ((Cursor)cursors.get(i));
            c.beforeFirst();
            if (i == 0) cursor = c;
        }
        cursorNum = 0;
    }

    public boolean next() throws SQLException {
        boolean ret = cursor.next();
        while (!ret && ++cursorNum < cursors.size()) {
            cursor = (Cursor)cursors.get(cursorNum);
            cursor.beforeFirst();
            ret = cursor.next();
        }
        return ret;
    }

    public boolean prev() throws SQLException {
        throw new SQLException("MultiCursor.prev() not implemented");
    }

    public void close() throws SQLException {
        for (int i = 0; i < cursors.size(); i++) {
            try {
                ((Cursor)cursors.get(i)).close();
            } catch (Throwable t) {}
        }
    }
}