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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
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 }
181 |
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