/**
 * Fifo class 
 */
class Fifo {
/**
 * Fifo constructor
 */
public Fifo() {
	super();
}
/**
 * find the oldest page in memory
 * return the frame number of the oldest page
 */
public int findFrame(Memory memory, int size) {
	int frame[];
	int oldest;
	int oldestFrame;
	
	// initialize oldest and oldestFrame
	frame = memory.getMemory(0);
	oldest = frame[1];
	oldestFrame = 0;
	
	// check which frame is the oldest page
	for (int j=1; j<size; j++) {
		frame = memory.getMemory(j);
		if (frame[1] > 0) {
			if (frame[1] < oldest) {
				oldest = frame[1];
				oldestFrame = j;
			}
		} 
	}
	return oldestFrame;
}
/**
 * for testing: print out the context in memory
 */
public void printMemoryContext(Memory memory, int size) {
	for (int j=0; j<size; j++) {
		int tmp[] = memory.getMemory(j);
		System.out.print("|" + tmp[0] + ", " + tmp[1] + "|");
	}
	System.out.println("");
}
/**
 * Fifo run: replaces pages based on their order of arrival
 * oldest page is replaced
 */
public int run(int[] pageReference, int size) {
	int i = 0;
	int pageFault = 0;
	boolean bInMemory;
	Memory memory = new Memory(size);

	while (pageReference[i] != -1) {
		bInMemory = false;
		for (int j=0; j<size; j++) {
			// frame[0] = page number
			// frame[1] = time of arrival
			int frame[] = memory.getMemory(j);
			// the memory location is empty
			if (frame[0] == -1) {
				memory.writeMemory(j, pageReference[i], i);
				pageFault++;
				bInMemory = true;
				break;
			}
			// page already in memory, do nothing, no page fault
			else if (frame[0] == pageReference[i]) {
				bInMemory = true;
				break;
			}
		}
		// page not in memory, find the oldest page and replace it
		if (bInMemory == false) {
			int frameNo = findFrame(memory, size);
			memory.writeMemory(frameNo, pageReference[i], i);
			pageFault++;
		}	
		i++;
		//printMemoryContext(memory, size);
	}
	return pageFault;
}
}