CS3413/Assignment8/code/main.c

#include <stdio.h>
#include <stdlib.h>

// Data structures and helper functions
typedef struct DiskRequest {
	int position;
	int time;
} DiskRequest;

typedef struct DiskQueue {
	DiskRequest *requests;
	int index;
	int size;
} DiskQueue;

DiskQueue *createDiskQueue() {
	DiskQueue *queue = malloc(sizeof(DiskQueue));
	if (queue == NULL) {
		printf("Error allocating memory for queue\n");
		exit(EXIT_FAILURE);
	}
	queue->requests = malloc(sizeof(DiskRequest));
	if (queue->requests == NULL) {
		printf("Error allocating memory for queue requests\n");
		exit(EXIT_FAILURE);
	}
	queue->index = 0;
	queue->size = 0;
	return queue;
}

DiskRequest diskRequest(int position, int time) {
	DiskRequest request;
	request.position = position;
	request.time = time;
	return request;
}

void enqueue(DiskQueue *queue, DiskRequest request) {
	queue->requests = realloc(queue->requests, sizeof(DiskRequest) * (queue->size + 1));
	queue->requests[queue->size] = request;
	queue->size++;
}

DiskRequest dequeue(DiskQueue *queue) {
	DiskRequest request = queue->requests[queue->index];
	queue->index++;
	return request;
}

// Allocates a new queue with the requests that have the same time
DiskQueue *queueOfSameTime(DiskQueue *queue, int time) {
	DiskQueue *sameTimeQueue = createDiskQueue();
	for (int i = queue->index; i < queue->size - queue->index; i++) {
		if (queue->requests[i].time == time) {
			enqueue(sameTimeQueue, queue->requests[i]);
		}
	}
	return sameTimeQueue;
}

// Compare function for disk requests by position
int compareDiskRequestsByPosition(const void *a, const void *b) {
	DiskRequest *requestA = (DiskRequest *) a;
	DiskRequest *requestB = (DiskRequest *) b;
	return requestA->position - requestB->position;
}

// Sorts the queue by position, in place
DiskQueue *sortQueueByPosition(DiskQueue *queue) {
	qsort(queue->requests, queue->size, sizeof(DiskRequest), compareDiskRequestsByPosition);
	return queue;
}


void destroyDiskQueue(DiskQueue *queue) {
	free(queue->requests);
	free(queue);
}

typedef enum DiskDirection {
	UP, DOWN
} DiskDirection;


// Global tracking variables
DiskDirection currentDirection = UP;
int movement = 0;
double seekTime = 0;

// Array for storing the requests
DiskQueue *queue;

double timeToProcessRequest(int position, int destination) {
	//The time (a floating point number) required to process a request is computed by distance the head travels divided by 5
	//Plus additional 15 milliseconds penalty if the direction has to change (for FCFS)
	double time = 0;
	// Calculated this way so that positive means up and negative means down
	int distance = destination - position;
	DiskDirection direction = (distance > 0) ? UP : DOWN;
	time += abs(distance) / 5.0;
	if (direction != currentDirection) {
		time += 15;
		currentDirection = direction;
	}
	return time;
}

// Your simulated disk is of size 10000, numbered from 0 to 9999.

// In first come first the time the request comes in is irrelevant
void fcfs(int start) {
	int position = start;
	for (int i = 0; i < queue->size; i++) {
		DiskRequest request = dequeue(queue);
		while (seekTime < request.time) { seekTime++; }
		seekTime += timeToProcessRequest(position, request.position);
		movement += abs(position - request.position);
		position = request.position;
	}
}

void cscan(int start) {
	int currentTime = 0;
	int position = start;
	for (int i = 0; i < queue->size; i++) {
		DiskRequest request = dequeue(queue);
		while (currentTime < request.time) { currentTime++; }

		DiskQueue *sameTimeQueue = sortQueueByPosition(queueOfSameTime(queue, request.time));
		for (; i < sameTimeQueue->size; i++) {
			DiskRequest request = dequeue(sameTimeQueue);

			// Need to return to 0 because we have reached the end of the disk on the current pass
			if (request.position < position) {
				seekTime += timeToProcessRequest(position, 9999);
				movement += abs(position - 9999);
				position = 9999;
				seekTime += timeToProcessRequest(position, 0);
				movement += abs(position - 0);
				position = 0;
			}
			seekTime += timeToProcessRequest(position, request.position);
			movement += abs(position - request.position);
			position = request.position;
		}
		//destroyDiskQueue(sameTimeQueue);
	}
}


int main(int argc, char **argv) {
	int position, time;
	char algorithm = argv[1][0];
	int start = 0;

	queue = createDiskQueue();

	while (EOF != (scanf("%i %i\n", &position, &time))) {
		enqueue(queue, diskRequest(position, time));
		// printf("Delete me: position %i, Delete me: time %i\n", position, time);
	}
	if (algorithm == 'F') {
		fcfs(start);
		printf("Movement:%i Time:%.1lf\n", movement, seekTime);
	} else if (algorithm == 'C') {
		cscan(start);
		// Stupid printf difference to pass tests, could call once after if statement
		printf("Movement: %i Time:%.1lf\n", movement, seekTime);
	}
	destroyDiskQueue(queue);

	return 0;
}