// Mode: -*- C++ -*-

//          GiSTcursor.cpp
//
// Copyright (c) 1996, Regents of the University of California
// $Header: /schmorpforge/Tree-M/GiST/GiSTcursor.cpp,v 1.1 2001/05/06 00:45:51 root Exp $

#include "GiST.h"

GiSTcursor::GiSTcursor(const GiST& gist, const GiSTpredicate& query): gist(gist)
{
	this->query=(GiSTpredicate*) query.Copy();
	first=1;
	lastlevel=-1;
}

GiSTentry* 
GiSTcursor::Next()
{
	GiSTpage page;

	while(first||!stack.IsEmpty()) {
		if(first) {
			page=GiSTRootPage;
			first=0;
		}
		else {
			assert(lastlevel>=0);
			GiSTentry *entry=stack.RemoveFront();

			if(entry->IsLeaf()) return entry;
			// Pop off the stack
			for(int i=0; i<entry->Level()-lastlevel; i++) path.MakeParent();
			page=entry->Ptr();
			delete entry;
		}
		// Entry was a pointer to another node
		path.MakeChild(page);

		GiSTnode *node=gist.ReadNode(path);

		lastlevel=node->Level();

		GiSTlist<GiSTentry*> list=node->Search(*query);

		while(!list.IsEmpty()) {
			GiSTentry *entry=list.RemoveRear();
			stack.Prepend(entry);
		}
		delete node;
	}
	// The search is over...
	return NULL;
}

GiSTcursor::~GiSTcursor()
{
	if(query!=NULL) delete query;
	while(!stack.IsEmpty()) delete stack.RemoveFront();
}

const GiSTpath& 
GiSTcursor::Path() const
{
	return path;
}