org.hibernate.hql.internal.ast.util.ASTIterator Maven / Gradle / Ivy
/*
* Hibernate, Relational Persistence for Idiomatic Java
*
* Copyright (c) 2008, 2013, Red Hat Inc. 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 Inc.
*
* 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 ASTIterator implements Iterator {
private AST next;
private LinkedList parents = new LinkedList();
/**
* Constructs an Iterator for depth-first iteration of an AST
*
* @param tree THe tree whose nodes are to be iterated
*/
public ASTIterator(AST tree) {
next = tree;
down();
}
@Override
public void remove() {
throw new UnsupportedOperationException( "remove() is not supported" );
}
@Override
public boolean hasNext() {
return next != null;
}
@Override
public Object next() {
return nextNode();
}
/**
* Get the next node to be returned from iteration.
*
* @return The next node.
*/
public AST nextNode() {
AST current = next;
if ( next != null ) {
AST nextSibling = next.getNextSibling();
if ( nextSibling == null ) {
next = pop();
}
else {
next = nextSibling;
down();
}
}
return current;
}
private void down() {
while ( next != null && next.getFirstChild() != null ) {
push( next );
next = next.getFirstChild();
}
}
private void push(AST parent) {
parents.addFirst( parent );
}
private AST pop() {
if ( parents.size() == 0 ) {
return null;
}
else {
return parents.removeFirst();
}
}
}