| 1 | /* ============================================================= |
| 2 | * SmallSQL : a free Java DBMS library for the Java(tm) platform |
| 3 | * ============================================================= |
| 4 | * |
| 5 | * (C) Copyright 2004-2006, by Volker Berlin. |
| 6 | * |
| 7 | * Project Info: http://www.smallsql.de/ |
| 8 | * |
| 9 | * This library is free software; you can redistribute it and/or modify it |
| 10 | * under the terms of the GNU Lesser General Public License as published by |
| 11 | * the Free Software Foundation; either version 2.1 of the License, or |
| 12 | * (at your option) any later version. |
| 13 | * |
| 14 | * This library is distributed in the hope that it will be useful, but |
| 15 | * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY |
| 16 | * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public |
| 17 | * License for more details. |
| 18 | * |
| 19 | * You should have received a copy of the GNU Lesser General Public |
| 20 | * License along with this library; if not, write to the Free Software |
| 21 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, |
| 22 | * USA. |
| 23 | * |
| 24 | * [Java is a trademark or registered trademark of Sun Microsystems, Inc. |
| 25 | * in the United States and other countries.] |
| 26 | * |
| 27 | * --------------- |
| 28 | * Where.java |
| 29 | * --------------- |
| 30 | * Author: Volker Berlin |
| 31 | * |
| 32 | * Created on 14.08.2004 |
| 33 | */ |
| 34 | package smallsql.database; |
| 35 | |
| 36 | |
| 37 | class Where extends RowSource { |
| 38 | |
| 39 | final private RowSource rowSource; |
| 40 | final private Expression where; |
| 41 | private int row = 0; |
| 42 | private boolean isCurrentRow; |
| 43 | |
| 44 | Where(RowSource rowSource, Expression where){ |
| 45 | this.rowSource = rowSource; |
| 46 | this.where = where; |
| 47 | } |
| 48 | |
| 49 | RowSource getFrom(){ |
| 50 | return rowSource; |
| 51 | } |
| 52 | |
| 53 | /** |
| 54 | * Verify if the valid row of the underlying RowSource (Variable join) |
| 55 | * is valid for the current ResultSet. |
| 56 | * @return |
| 57 | */ |
| 58 | final private boolean isValidRow() throws Exception{ |
| 59 | return where == null || rowSource.rowInserted() || where.getBoolean(); |
| 60 | } |
| 61 | |
| 62 | |
| 63 | final boolean isScrollable() { |
| 64 | return rowSource.isScrollable(); |
| 65 | } |
| 66 | |
| 67 | |
| 68 | final boolean isBeforeFirst(){ |
| 69 | return row == 0; |
| 70 | } |
| 71 | |
| 72 | |
| 73 | final boolean isFirst(){ |
| 74 | return row == 1 && isCurrentRow; |
| 75 | } |
| 76 | |
| 77 | |
| 78 | final boolean isLast() throws Exception{ |
| 79 | if(!isCurrentRow) return false; |
| 80 | long rowPos = rowSource.getRowPosition(); |
| 81 | boolean isNext = next(); |
| 82 | rowSource.setRowPosition(rowPos); |
| 83 | return !isNext; |
| 84 | } |
| 85 | |
| 86 | |
| 87 | final boolean isAfterLast(){ |
| 88 | return row > 0 && !isCurrentRow; |
| 89 | } |
| 90 | |
| 91 | |
| 92 | final void beforeFirst() throws Exception { |
| 93 | rowSource.beforeFirst(); |
| 94 | row = 0; |
| 95 | } |
| 96 | |
| 97 | |
| 98 | final boolean first() throws Exception { |
| 99 | isCurrentRow = rowSource.first(); |
| 100 | while(isCurrentRow && !isValidRow()){ |
| 101 | isCurrentRow = rowSource.next(); |
| 102 | } |
| 103 | row = 1; |
| 104 | return isCurrentRow; |
| 105 | } |
| 106 | |
| 107 | |
| 108 | final boolean previous() throws Exception { |
| 109 | boolean oldIsCurrentRow = isCurrentRow; |
| 110 | do{ |
| 111 | isCurrentRow = rowSource.previous(); |
| 112 | }while(isCurrentRow && !isValidRow()); |
| 113 | if(oldIsCurrentRow || isCurrentRow) row--; |
| 114 | return isCurrentRow; |
| 115 | } |
| 116 | |
| 117 | |
| 118 | final boolean next() throws Exception { |
| 119 | boolean oldIsCurrentRow = isCurrentRow; |
| 120 | do{ |
| 121 | isCurrentRow = rowSource.next(); |
| 122 | }while(isCurrentRow && !isValidRow()); |
| 123 | if(oldIsCurrentRow || isCurrentRow) row++; |
| 124 | return isCurrentRow; |
| 125 | } |
| 126 | |
| 127 | |
| 128 | final boolean last() throws Exception{ |
| 129 | while(next()); |
| 130 | return previous(); |
| 131 | } |
| 132 | |
| 133 | |
| 134 | final void afterLast() throws Exception { |
| 135 | while(next()); |
| 136 | } |
| 137 | |
| 138 | |
| 139 | final int getRow() throws Exception { |
| 140 | return isCurrentRow ? row : 0; |
| 141 | } |
| 142 | |
| 143 | |
| 144 | final long getRowPosition() { |
| 145 | return rowSource.getRowPosition(); |
| 146 | } |
| 147 | |
| 148 | |
| 149 | final void setRowPosition(long rowPosition) throws Exception { |
| 150 | rowSource.setRowPosition(rowPosition); |
| 151 | } |
| 152 | |
| 153 | |
| 154 | final void nullRow() { |
| 155 | rowSource.nullRow(); |
| 156 | row = 0; |
| 157 | } |
| 158 | |
| 159 | |
| 160 | final void noRow() { |
| 161 | rowSource.noRow(); |
| 162 | row = 0; |
| 163 | } |
| 164 | |
| 165 | |
| 166 | final boolean rowInserted() { |
| 167 | return rowSource.rowInserted(); |
| 168 | } |
| 169 | |
| 170 | |
| 171 | final boolean rowDeleted() { |
| 172 | return rowSource.rowDeleted(); |
| 173 | } |
| 174 | |
| 175 | |
| 176 | final void execute() throws Exception{ |
| 177 | rowSource.execute(); |
| 178 | } |
| 179 | |
| 180 | } |