1 /*
2 * $Source$
3 * $Revision$
4 *
5 * Copyright (C) 2000 William Chesters
6 *
7 * Part of Melati (http://melati.org), a framework for the rapid
8 * development of clean, maintainable web applications.
9 *
10 * Melati is free software; Permission is granted to copy, distribute
11 * and/or modify this software under the terms either:
12 *
13 * a) the GNU General Public License as published by the Free Software
14 * Foundation; either version 2 of the License, or (at your option)
15 * any later version,
16 *
17 * or
18 *
19 * b) any version of the Melati Software License, as published
20 * at http://melati.org
21 *
22 * You should have received a copy of the GNU General Public License and
23 * the Melati Software License along with this program;
24 * if not, write to the Free Software Foundation, Inc.,
25 * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA to obtain the
26 * GNU General Public License and visit http://melati.org to obtain the
27 * Melati Software License.
28 *
29 * Feel free to contact the Developers of Melati (http://melati.org),
30 * if you would like to work out a different arrangement than the options
31 * outlined here. It is our intention to allow Melati to be used by as
32 * wide an audience as possible.
33 *
34 * This program is distributed in the hope that it will be useful,
35 * but WITHOUT ANY WARRANTY; without even the implied warranty of
36 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
37 * GNU General Public License for more details.
38 *
39 * Contact details for copyright holder:
40 *
41 * William Chesters <williamc At paneris.org>
42 * http://paneris.org/~williamc
43 * Obrechtstraat 114, 2517VX Den Haag, The Netherlands
44 */
45
46 package org.melati.util;
47
48 import java.util.Enumeration;
49 import java.util.Vector;
50
51 import org.melati.poem.util.EnumUtils;
52
53 /**
54 * A {@link PagedEnumeration} which doesn't know how big it is.
55 * Ideally SQL would allow you to start at an offset.
56 */
57 public class DumbPagedEnumeration<T> extends PagedEnumerationBase<T> {
58
59 private boolean totalCountIsMinimum;
60
61 /**
62 * Constructor.
63 * @param base underlying Enumeration
64 * @param pageStart index of start of page
65 * @param pageSize how many Elements to include upon a page
66 * @param countHorizon where to count to, may be less than total size of underlying Enumeration
67 */
68 public DumbPagedEnumeration(Enumeration<T> base,
69 int pageStart, int pageSize, int countHorizon) {
70 pageStart = Math.max(pageStart, 1);
71 this.pageStart = pageStart;
72 this.pageSize = pageSize;
73 int offset = EnumUtils.skip(base, pageStart - 1);
74 page = EnumUtils.initial(base, pageSize);
75 // NOTE This is the bit that makes it dumb!
76 totalCount = offset + page.size() +
77 EnumUtils.skip(base, countHorizon - (offset + page.size()));
78 totalCountIsMinimum = base.hasMoreElements();
79 us = page.elements();
80 currentPosition = pageStart - 1;
81 }
82
83 @Override
84 public Integer getNextPageStart() {
85 int it = pageStart + pageSize;
86 return (totalCountIsMinimum || it <= totalCount) ? new Integer(it) : null;
87 }
88
89 /**
90 * @return whether there are more elements to come beyond horizon
91 */
92 public boolean getTotalCountIsMinimum() {
93 return totalCountIsMinimum;
94 }
95
96 public Vector<Page> getPageStartList() {
97 Vector<Page> ret = new Vector<Page>(totalCount / pageSize);
98 int i=1;
99 while((i-1)*pageSize < totalCount) {
100 ret.addElement(new Page(i,(i-1)*pageSize+1));
101 i++;
102 }
103 return ret;
104 }
105 }