org.hibernate.hql.internal.ast.util.ASTParentsFirstIterator Maven / Gradle / Ivy
/*
* Hibernate, Relational Persistence for Idiomatic Java
*
* License: GNU Lesser General Public License (LGPL), version 2.1 or later.
* See the lgpl.txt file in the root directory or .
*/
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;
private AST 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() {
AST 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 parents.removeFirst();
}
}
}