| /** |
| * JDBM LICENSE v1.00 |
| * |
| * Redistribution and use of this software and associated documentation |
| * ("Software"), with or without modification, are permitted provided |
| * that the following conditions are met: |
| * |
| * 1. Redistributions of source code must retain copyright |
| * statements and notices. Redistributions must also contain a |
| * copy of this document. |
| * |
| * 2. 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. |
| * |
| * 3. The name "JDBM" must not be used to endorse or promote |
| * products derived from this Software without prior written |
| * permission of Cees de Groot. For written permission, |
| * please contact cg@cdegroot.com. |
| * |
| * 4. Products derived from this Software may not be called "JDBM" |
| * nor may "JDBM" appear in their names without prior written |
| * permission of Cees de Groot. |
| * |
| * 5. Due credit should be given to the JDBM Project |
| * (http://jdbm.sourceforge.net/). |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE JDBM PROJECT AND CONTRIBUTORS |
| * ``AS IS'' AND ANY EXPRESSED 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 |
| * CEES DE GROOT OR ANY 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. |
| * |
| * Copyright 2000 (C) Cees de Groot. All Rights Reserved. |
| * Contributions are Copyright (C) 2000 by their associated contributors. |
| * |
| * $Id: PageCursor.java,v 1.1 2000/05/06 00:00:31 boisvert Exp $ |
| */ |
| package jdbm.recman; |
| |
| |
| import java.io.IOException; |
| |
| |
| /** |
| * This class provides a cursor that can follow lists of pages bi-directionally. |
| */ |
| final class PageCursor |
| { |
| PageManager pageman; |
| long current; |
| short type; |
| |
| |
| /** |
| * Constructs a page cursor that starts at the indicated block. |
| */ |
| PageCursor( PageManager pageman, long current ) |
| { |
| this.pageman = pageman; |
| this.current = current; |
| } |
| |
| |
| /** |
| * Constructs a page cursor that starts at the first block of the |
| * indicated list. |
| */ |
| PageCursor( PageManager pageman, short type ) throws IOException |
| { |
| this.pageman = pageman; |
| this.type = type; |
| } |
| |
| |
| /** |
| * Returns the current value of the cursor. |
| */ |
| long getCurrent() throws IOException |
| { |
| return current; |
| } |
| |
| |
| /** |
| * Returns the next value of the cursor. |
| */ |
| long next() throws IOException |
| { |
| if ( current == 0 ) |
| { |
| current = pageman.getFirst( type ); |
| } |
| else |
| { |
| current = pageman.getNext( current ); |
| } |
| |
| return current; |
| } |
| |
| |
| /** |
| * Returns the previous value of the cursor |
| */ |
| long prev() throws IOException |
| { |
| current = pageman.getPrev( current ); |
| return current; |
| } |
| } |