org.hibernate.hql.internal.ast.util.NodeTraverser 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.ArrayDeque;
import java.util.Deque;
import antlr.collections.AST;
/**
* A visitor for traversing an AST tree.
*
* @author Steve Ebersole
* @author Philip R. "Pib" Burns.
* @author Strong Liu
*
*/
public class NodeTraverser {
public static interface VisitationStrategy {
public void visit( AST node );
}
private final VisitationStrategy strategy;
public NodeTraverser( VisitationStrategy strategy ) {
this.strategy = strategy;
}
/**
* Traverse the AST tree depth first.
*
* @param ast
* Root node of subtree to traverse.
*
*
* Note that the AST passed in is not visited itself. Visitation
* starts with its children.
*
*/
public void traverseDepthFirst( AST ast ) {
if ( ast == null ) {
throw new IllegalArgumentException(
"node to traverse cannot be null!" );
}
visitDepthFirst( ast.getFirstChild() );
}
private void visitDepthFirst(AST ast) {
if ( ast == null ) {
return;
}
Deque stack = new ArrayDeque();
stack.addLast( ast );
while ( !stack.isEmpty() ) {
ast = stack.removeLast();
strategy.visit( ast );
if ( ast.getNextSibling() != null ) {
stack.addLast( ast.getNextSibling() );
}
if ( ast.getFirstChild() != null ) {
stack.addLast( ast.getFirstChild() );
}
}
}
}