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34 package smallsql.database;
35
36
40 class Scrollable extends RowSource {
41
42
43 private final RowSource rowSource;
44
45
46 private int rowIdx;
47
48
49 private final LongList rowList = new LongList();
50
51
52
54
55 Scrollable(RowSource rowSource){
56 this.rowSource = rowSource;
57 }
58
59
60 final boolean isScrollable(){
61 return true;
62 }
63
64
65 void beforeFirst() throws Exception  {
66 rowIdx = -1;
67 rowSource.beforeFirst();
68 }
69
70
71 boolean isBeforeFirst(){
72 return rowIdx == -1;
73 }
74
75
76 boolean isFirst(){
77 return rowIdx == 0;
78 }
79
80
81 boolean first() throws Exception {
82 rowIdx = -1;
83 return next();
84 }
85
86
87 boolean previous() throws Exception {
88 if(rowIdx > -1){
89 rowIdx--;
90 if(rowIdx > -1 && rowIdx < rowList.size()){
91 rowSource.setRowPosition( rowList.get(rowIdx) );
92 return true;
93 }
94 }
95 rowSource.beforeFirst();
96 return false;
97 }
98
99
100 boolean next() throws Exception {
101 if(++rowIdx < rowList.size()){
102 rowSource.setRowPosition( rowList.get(rowIdx) );
103 return true;
104 }
105 final boolean result = rowSource.next();
106 if(result){
107 rowList.add( rowSource.getRowPosition());
108 return true;
109 }
110 return false;
111 }
112
113
114 boolean last() throws Exception {
115 afterLast();
116 return previous();
117 }
118
119
120 boolean isLast() throws Exception {
121 if(rowIdx+1 != rowList.size()) return false;
122 if(next()){
123 previous();
124 return false;
125 }
126 return true;
127 }
128
129 boolean isAfterLast() throws Exception {
130 if(rowIdx >= rowList.size()) return true;
131 if(isBeforeFirst() && rowList.size() == 0){
132 next();
133 previous();
134 if(rowList.size() == 0) return true;
135 }
136 return false;
137 }
138
139
140 void afterLast() throws Exception {
141 if(rowIdx+1 < rowList.size()){
142 rowIdx = rowList.size()-1;
143 rowSource.setRowPosition( rowList.get(rowIdx) );
144 }
145 while(next()){}
146 }
147
148
149 boolean absolute(int row) throws Exception {
150 if(row == 0)
151 throw Utils.createSQLException("The call absolute(0) is invalid.");
152 if(row < 0){
153 afterLast();
154 rowIdx = rowList.size() + row;
155 if(rowIdx < 0){
156 beforeFirst();
157 return false;
158 }else{
159 rowSource.setRowPosition( rowList.get(rowIdx) );
160 return true;
161 }
162 }
163 if(row <= rowList.size()){
164 rowIdx = row-1;
165 rowSource.setRowPosition( rowList.get(rowIdx) );
166 return true;
167 }
168
169 rowIdx = rowList.size()-1;
170 if(rowIdx >= 0)
171 rowSource.setRowPosition( rowList.get(rowIdx) );
172 boolean result;
173 while((result = next()) && row-1 > rowIdx){}
174 return result;
175 }
176
177
178 boolean relative(int rows) throws Exception {
179 int newRow = rows + rowIdx + 1;
180 if(newRow <= 0){
181 beforeFirst();
182 return false;
183 }else{
184 return absolute(newRow);
185 }
186 }
187
188
189 int getRow() throws Exception {
190 if(rowIdx >= rowList.size()) return 0;
191 return rowIdx + 1;
192 }
193
194
195 long getRowPosition() {
196 return rowIdx;
197 }
198
199
200 void setRowPosition(long rowPosition) throws Exception {
201 rowIdx = (int)rowPosition;
202 }
203
204
205 final boolean rowInserted(){
206 return rowSource.rowInserted();
207 }
208
209
210 final boolean rowDeleted(){
211 return rowSource.rowDeleted();
212 }
213
214
215 void nullRow() {
216 rowSource.nullRow();
217 rowIdx = -1;
218 }
219
220
221 void noRow() {
222 rowSource.noRow();
223 rowIdx = -1;
224 }
225
226
227 void execute() throws Exception {
228 rowSource.execute();
229 rowList.clear();
230 rowIdx = -1;
231 }
232 }
233 |
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