TupleIterator.java

package simpledb;

import java.util.*;

/**
 * Implements a DbIterator by wrapping an Iterable<Tuple>.
 */
public class TupleIterator implements DbIterator {
 Iterator<Tuple> i = null;
 TupleDesc td = null;
 Iterable<Tuple> tuples = null;

 /**
 * Constructs an iterator from the specified Iterable, and the specified descriptor.
 * @param tuples The set of tuples to iterate over
 */
 public TupleIterator(TupleDesc td, Iterable<Tuple> tuples) {
 this.td = td;
 this.tuples = tuples;

 // check that all tuples are the right TupleDesc
 for (Tuple t : tuples) {
 if(!t.getTupleDesc().equals(td))
 throw new IllegalArgumentException("incompatible tuple in tuple set");
 }
 }

 public void open() {
 i = tuples.iterator();
 }

 public boolean hasNext() {
 return i.hasNext();
 }

 public Tuple next() {
 return i.next();
 }

 public void rewind() {
 close();
 open();
 }

 public TupleDesc getTupleDesc() {
 return td;
 }

 public void close() {
 i = null;
 }
}