/**
 * Pff class
 */
class Pff {
	java.util.Vector dMemory;
/**
 * Pff constructor
 */
public Pff() {
	super();
	dMemory = new java.util.Vector();
}
/**
 * for testing: print the contexts of the memory
 */
public void printMemoryContext() {
	Page page;
	for (int j=0; j<dMemory.size(); j++) {
		page = (Page) dMemory.elementAt(j);
		System.out.print("|" + page.getId() + ", " + page.getCount() + "|");
	}
	System.out.println("");
}
/**
 * Pff run: replace the page depends on IFT and threshold
 * return: page fault and frames used
 */
public double[] run(int[] pageReference, int iThreshold) {
	int i = 0;
	int j;
	int pageFault = 0;
	boolean bInMemory = false;
	Page page;
	Page tmp;
	int threshold = iThreshold;
	int interFaultTime = 0;
	int framesUsed = 0;
	
	while (pageReference[i] != -1) {
		for (j = 0; j < dMemory.size(); j++) {
			bInMemory = false;
			page = (Page) dMemory.elementAt(j);
			// page already in memory
			if (page.getId() == pageReference[i]) {
				// set the reference bit to 1
				page.setCount(1);
				dMemory.removeElementAt(j);
				dMemory.insertElementAt(page, j);
				// the page is in memory => increment the inter-fault time
				interFaultTime++;
				bInMemory = true;
				break;
			}
		}
		// page is not in memory
		if (bInMemory == false) {
			// IFT < threshold
			if (interFaultTime < threshold - 1) {
				// reset the reference bit to 0
				for (j = 0; j < dMemory.size(); j++) {
					page = (Page) dMemory.elementAt(j);
					if (page.getCount() == 1) {
						page.setCount(0);
						dMemory.removeElementAt(j);
						dMemory.insertElementAt(page, j);
					}
				}
				// allocate a new frame to the process 
				page = new Page(pageReference[i], 0);
				dMemory.addElement(page);
				interFaultTime = 0;
				pageFault++;
			} else { // IFT >= threshold
				j = 0;
				while (j < dMemory.size()) {
					page = (Page) dMemory.elementAt(j);
					// deallocate all frames whose reference bit is not set
					if (page.getCount() == 0) {
						dMemory.removeElementAt(j);
					}
					else {
						j++;
					}
				}
				for (j = 0; j< dMemory.size(); j++) {
					page = (Page) dMemory.elementAt(j);
					// reset all reference bits
					if (page.getCount() == 1) {
						page.setCount(0);
						dMemory.removeElementAt(j);
						dMemory.insertElementAt(page, j);
					}
				}
				page = new Page(pageReference[i], 0);
				dMemory.addElement(page);
				interFaultTime = 0;
				pageFault++;
			}
		}
		// calculate number of frames used
		framesUsed += dMemory.size();
		i++;
		//printMemoryContext();
	}
	dMemory.removeAllElements();
	
	//System.out.println("framesUsed: " + framesUsed + " , pageFault: " + pageFault);
	double[] result = new double[2];
	result[0] = pageFault;
	result[1] = framesUsed;
	return result;
}
}