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   [The "BSD license"]
   Copyright (c) 2005-2009 Terence Parr
   All rights reserved.
   Redistribution and use in source and binary forms, with or without
   modification, are permitted provided that the following conditions
   are met:
   1. Redistributions of source code must retain the above copyright
      notice, this list of conditions and the following disclaimer.
  2. Redistributions in binary form must reproduce the above copyright
      notice, this list of conditions and the following disclaimer in the
      documentation and/or other materials provided with the distribution.
  3. The name of the author may not be used to endorse or promote products
      derived from this software without specific prior written permission.
 package org.antlr.runtime.tree;
 import java.util.*;
 public class CommonTreeNodeStream extends LookaheadStream<Objectimplements TreeNodeStream {
 	public static final int DEFAULT_INITIAL_BUFFER_SIZE = 100;
 	public static final int INITIAL_CALL_STACK_SIZE = 10;

Pull nodes from which tree?
 	protected Object root;

If this tree (root) was created from a token stream, track it.
 	protected TokenStream tokens;

What tree adaptor was used to build these trees
 	TreeAdaptor adaptor;

The tree iterator we using
     protected TreeIterator it;

Stack of indexes used for push/pop calls
     protected IntArray calls;    

Tree (nil A B C) trees like flat A B C streams
     protected boolean hasNilRoot = false;

Tracks tree depth. Level=0 means we're at root node level.
     protected int level = 0;
 	public CommonTreeNodeStream(Object tree) {
 		this(new CommonTreeAdaptor(), tree);
 	public CommonTreeNodeStream(TreeAdaptor adaptorObject tree) {
 		this. = tree;
 		this. = adaptor;
          = new TreeIterator(adaptor,);
     public void reset() {
          = false;
          = 0;
         if (  != null ) .clear();
Pull elements from tree iterator. Track tree level 0..max_level. If nil rooted tree, don't give initial nil and DOWN nor final UP.
     public Object nextElement() {
         Object t = .next();
         //System.out.println("pulled "+adaptor.getType(t));
         if ( t == . ) {
             if ( ==0 &&  ) return .next(); // don't give last UP; get EOF
         else if ( t == . ) ++;
         if ( ==0 && .isNil(t) ) { // if nil root, scarf nil, DOWN
              = true;
             t = .next(); // t is now DOWN, so get first real node next
             t = .next();
         return t;
    public boolean isEOF(Object o) { return .getType(o) == .; }
    public void setUniqueNavigationNodes(boolean uniqueNavigationNodes) { }
	public Object getTreeSource() {	return ; }
	public String getSourceName() { return getTokenStream().getSourceName(); }
	public TokenStream getTokenStream() { return ; }
	public void setTokenStream(TokenStream tokens) { this. = tokens; }
	public TreeAdaptor getTreeAdaptor() { return ; }
	public void setTreeAdaptor(TreeAdaptor adaptor) { this. = adaptor; }
    public Object get(int i) {
        throw new UnsupportedOperationException("Absolute node indexes are meaningless in an unbuffered stream");
    public int LA(int i) { return .getType(LT(i)); }

Make stream jump to a new location, saving old location. Switch back with pop().
    public void push(int index) {
        if ( ==null ) {
             = new IntArray();
        .push(); // save current index

Seek back to previous index saved during last push() call. Return top of stack (return index).
    public int pop() {
        int ret = .pop();
        return ret;
	public void replaceChildren(Object parentint startChildIndexint stopChildIndexObject t) {
		if ( parent!=null ) {
	public String toString(Object startObject stop) {
        // we'll have to walk from start to stop in tree; we're not keeping
        // a complete node stream buffer
        return "n/a";

For debugging; destructive: moves tree iterator to end.
    public String toTokenTypeString() {
		StringBuffer buf = new StringBuffer();
        Object o = LT(1);
        int type = .getType(o);
        while ( type!=. ) {
            buf.append(" ");
            o = LT(1);
            type = .getType(o);
		return buf.toString();
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