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package org.kohsuke.github;
import java.util.Arrays;
import java.util.Iterator;
import java.util.List;
import java.util.NoSuchElementException;
/**
* Iterator over a pagenated data source.
*
* Aside from the normal iterator operation, this method exposes {@link #nextPage()}
* that allows the caller to retrieve items per page.
*
* @author Kohsuke Kawaguchi
*/
public abstract class PagedIterator implements Iterator {
private final Iterator base;
/**
* Current batch that we retrieved but haven't returned to the caller.
*/
private T[] current;
private int pos;
/*package*/ PagedIterator(Iterator base) {
this.base = base;
}
protected abstract void wrapUp(T[] page);
public boolean hasNext() {
fetch();
return current!=null;
}
public T next() {
fetch();
if (current==null) throw new NoSuchElementException();
return current[pos++];
}
private void fetch() {
while (current==null || current.length<=pos) {
if (!base.hasNext()) {// no more to retrieve
current = null;
pos = 0;
return;
}
current = base.next();
wrapUp(current);
pos = 0;
}
// invariant at the end: there's some data to retrieve
}
public void remove() {
throw new UnsupportedOperationException();
}
/**
* Gets the next page worth of data.
*/
public List nextPage() {
fetch();
List r = Arrays.asList(current);
r = r.subList(pos,r.size());
current = null;
pos = 0;
return r;
}
}