org.hibernate.hql.internal.ast.util.ASTParentsFirstIterator Maven / Gradle / Ivy
/*
* Hibernate, Relational Persistence for Idiomatic Java
*
* Copyright (c) 2008, Red Hat Middleware LLC or third-party contributors as
* indicated by the @author tags or express copyright attribution
* statements applied by the authors. All third-party contributions are
* distributed under license by Red Hat Middleware LLC.
*
* This copyrighted material is made available to anyone wishing to use, modify,
* copy, or redistribute it subject to the terms and conditions of the GNU
* Lesser General Public License, as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
* for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this distribution; if not, write to:
* Free Software Foundation, Inc.
* 51 Franklin Street, Fifth Floor
* Boston, MA 02110-1301 USA
*
*/
package org.hibernate.hql.internal.ast.util;
import java.util.Iterator;
import java.util.LinkedList;
import antlr.collections.AST;
/**
* Depth first iteration of an ANTLR AST.
*
* @author josh
*/
public class ASTParentsFirstIterator implements Iterator {
private AST next, current, tree;
private LinkedList parents = new LinkedList();
public void remove() {
throw new UnsupportedOperationException( "remove() is not supported" );
}
public boolean hasNext() {
return next != null;
}
public Object next() {
return nextNode();
}
public ASTParentsFirstIterator(AST tree) {
this.tree = next = tree;
}
public AST nextNode() {
current = next;
if ( next != null ) {
AST child = next.getFirstChild();
if ( child == null ) {
AST sibling = next.getNextSibling();
if ( sibling == null ) {
AST parent = pop();
while ( parent != null && parent.getNextSibling() == null )
parent = pop();
next = ( parent != null ) ? parent.getNextSibling() : null;
}
else {
next = sibling;
}
}
else {
if ( next != tree ) {
push( next );
}
next = child;
}
}
return current;
}
private void push(AST parent) {
parents.addFirst( parent );
}
private AST pop() {
if ( parents.size() == 0 ) {
return null;
}
else {
return ( AST ) parents.removeFirst();
}
}
}