/*
 * An implementation of the not-recently-used algorithm.  This version scans
 * the pages for a selection starting from the previous selection, which makes
 * it resemble second change a little.
 *
 * This NRU gives quite poor performance.  That may just be because NRU isn't
 * very good, but I'm worried there might be something wrong with the 
 * simulation.  Haven't found any error.
 */

#ifndef _nru_h_
#define _nru_h_

#include "replacement.h"

class NRUReplacementAlg: public ReplacementAlg {
public:
	NRUReplacementAlg(unsigned long num_frame, int page_bits, 
			  int clear_freq = 1000):
		ReplacementAlg(num_frame, page_bits, clear_freq), 
		m_scan_start(0) { }

	virtual string name() { return "nru"; }

	virtual unsigned long fault(const Ref &r);

	virtual void maint();
protected:
	// Return the class of a page.  Pointer might be NULL.
	int cl(PTE *pte) { 
		return pte ? pte->get_mod() << 1 | pte->get_ref() : 0;
	}

	unsigned long m_scan_start;		// Where to start scanning.
};

#endif