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An OSGi bundle for Saxon-HE
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// Copyright (c) 2013 Saxonica Limited.
// This Source Code Form is subject to the terms of the Mozilla Public License, v. 2.0.
// If a copy of the MPL was not distributed with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
// This Source Code Form is "Incompatible With Secondary Licenses", as defined by the Mozilla Public License, v. 2.0.
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
package net.sf.saxon.expr;
import net.sf.saxon.expr.sort.ItemOrderComparer;
import net.sf.saxon.om.Item;
import net.sf.saxon.om.NodeInfo;
import net.sf.saxon.om.SequenceIterator;
import net.sf.saxon.trans.XPathException;
import net.sf.saxon.tree.iter.LookaheadIterator;
/**
* An enumeration representing a nodeset that is a union of two other NodeSets.
*/
public class UnionEnumeration implements SequenceIterator, LookaheadIterator {
private SequenceIterator e1;
private SequenceIterator e2;
/*@Nullable*/ private NodeInfo nextNode1 = null;
private NodeInfo nextNode2 = null;
private ItemOrderComparer comparer;
private NodeInfo current = null;
private int position = 0;
/**
* Create the iterator. The two input iterators must return nodes in document
* order for this to work.
* @param p1 iterator over the first operand sequence (in document order)
* @param p2 iterator over the second operand sequence
* @param comparer used to test whether nodes are in document order. Different versions
* are used for intra-document and cross-document operations
*/
public UnionEnumeration(SequenceIterator p1, SequenceIterator p2,
ItemOrderComparer comparer) throws XPathException {
this.e1 = p1;
this.e2 = p2;
this.comparer = comparer;
nextNode1 = next(e1);
nextNode2 = next(e2);
}
/**
* Get the next item from one of the input sequences,
* checking that it is a node.
* @param iter the sequence from which a node is to be read
* @return the node that was read
*/
private NodeInfo next(SequenceIterator iter) throws XPathException {
return (NodeInfo)iter.next();
// we rely on the type-checking mechanism to prevent a ClassCastException here
}
public boolean hasNext() {
return nextNode1!=null || nextNode2!=null;
}
public Item next() throws XPathException {
// main merge loop: take a value from whichever set has the lower value
position++;
if (nextNode1 != null && nextNode2 != null) {
int c = comparer.compare(nextNode1, nextNode2);
if (c<0) {
current = nextNode1;
nextNode1 = next(e1);
return current;
} else if (c>0) {
current = nextNode2;
nextNode2 = next(e2);
return current;
} else {
current = nextNode2;
nextNode2 = next(e2);
nextNode1 = next(e1);
return current;
}
}
// collect the remaining nodes from whichever set has a residue
if (nextNode1!=null) {
current = nextNode1;
nextNode1 = next(e1);
return current;
}
if (nextNode2!=null) {
current = nextNode2;
nextNode2 = next(e2);
return current;
}
current = null;
position = -1;
return null;
}
public Item current() {
return current;
}
public int position() {
return position;
}
public void close() {
e1.close();
e2.close();
}
/*@NotNull*/
public SequenceIterator getAnother() throws XPathException {
return new UnionEnumeration(e1.getAnother(), e2.getAnother(), comparer);
}
/**
* Get properties of this iterator, as a bit-significant integer.
*
* @return the properties of this iterator. This will be some combination of
* properties such as {@link #GROUNDED}, {@link #LAST_POSITION_FINDER},
* and {@link #LOOKAHEAD}. It is always
* acceptable to return the value zero, indicating that there are no known special properties.
* It is acceptable for the properties of the iterator to change depending on its state.
*/
public int getProperties() {
return LOOKAHEAD;
}
}