Application: gvSIG desktop

package com.iver.cit.gvsig.fmap.selection;

import java.util.BitSet;

import java.util.NoSuchElementException;

import com.hardcode.gdbms.driver.exceptions.ReadDriverException;

import com.hardcode.gdbms.engine.data.DataSource;

import com.hardcode.gdbms.engine.values.Value;

import com.iver.cit.gvsig.fmap.layers.SelectableDataSource;

/**

 * <p>Allows to access a field from a selection of rows in a DataSource,

 * using an Iterator interface (instead of the painful BitSet interface).</p>

 * 

 * <p>This class is intended to smooth transition to 2.0 version, in which

 * random access has been replaced by iterators.</p>

 * 

 * <p>Warning: This object is not thread-safe!!! Use external synchronization

 * if you plan to use it from different threads, otherwise it is warranted

 * to fail!!</p>

 * 

 * @author Cesar Martinez Izquierdo <cesar.martinez@iver.es> 18/02/2009

 * @author IVER T.I. <http://www.iver.es> 18/02/2009

 */

public class SelectionFieldIterator

                implements ResettableIterator<Value>, Cloneable {

        DataSource ds = null;

        BitSet selectedRows = null;

        int fieldIndex;

        int currBit;

        int nextSet;

        boolean hasNext;

        boolean usedNext = true;

        /**

         * <p>Creates a new Iterator, which is able to access the provided

         * <code>selection</code> from <code>ds</code>.</p>

         * 

         * @param ds 

         * @param selection The selection of rows to iterate through

         * @param fieldIndex The index of the field to iterate on

         */

        public SelectionFieldIterator(DataSource ds, BitSet selection, int fieldIndex) {

                this.selectedRows = selection;

                this.ds = ds;

                this.fieldIndex = fieldIndex;

                reset();

        }

        /**

         * <p>Creates a new Iterator, which is able to access the provided

         * <code>selection</code> from <code>ds</code>.</p>

         * 

         * @param ds 

         * @param selection The selection of rows to iterate through

         * @param fieldIndex The name of the field to iterate on

         */

        public SelectionFieldIterator(DataSource ds, BitSet selection, String fieldName) throws ReadDriverException {

                this(ds, selection, ds.getFieldIndexByName(fieldName));

        }

        public boolean hasNext() {

                if (usedNext==true) {

                        currBit = selectedRows.nextSetBit(currBit+1);

                        if (currBit<0) {

                                hasNext = false;

                        }

                        else {

                                hasNext = true; 

                        }

                        usedNext = false;

                }

                return hasNext;

        }

        public Value next() {

                if (!hasNext()) {

                        throw new NoSuchElementException();

                }

                usedNext = true;

                try {

                        return ds.getFieldValue(currBit, fieldIndex);        

                } catch (ReadDriverException e) {

                        NoSuchElementException e1 = new NoSuchElementException();

                        e1.initCause(e);

                        throw e1;

                }

        }

        public void remove() {

                throw new UnsupportedOperationException();

        }

        public void reset() {

                currBit = -1;

                usedNext = true;

        }

        public Object clone() throws CloneNotSupportedException {

                SelectionFieldIterator obj = (SelectionFieldIterator) super.clone();

                obj.reset();

                return obj;

        }

}