CS3413/Assignment8/code/disk.c

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#include <stdlib.h>
#include <stdio.h>
#include "disk.h"
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DiskQueue *createDiskQueue() {
DiskQueue *queue = malloc(sizeof(DiskQueue));
if (queue == NULL) {
printf("Error allocating memory for queue\n");
exit(EXIT_FAILURE);
}
queue->head = NULL;
queue->size = 0;
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return queue;
}
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void enqueue(DiskQueue *queue, int time, int position) {
DiskRequest *request = malloc(sizeof(DiskRequest));
if (request == NULL) {
printf("Error allocating memory for request\n");
exit(EXIT_FAILURE);
}
request->time = time;
request->position = position;
request->next = NULL;
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if (queue->head == NULL) {
queue->head = request;
} else {
DiskRequest *current = queue->head;
while (current->next != NULL) {
current = current->next;
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}
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current->next = request;
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}
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queue->size++;
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}
void delete(DiskQueue *queue, DiskRequest request) {
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DiskRequest *current = queue->head;
DiskRequest *previous = NULL;
while (current != NULL) {
if (current->position == request.position && current->time == request.time) {
if (previous == NULL) {
queue->head = current->next;
} else {
previous->next = current->next;
}
queue->size--;
return;
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}
previous = current;
current = current->next;
}
printf("Error: Request not found\n");
exit(EXIT_FAILURE);
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}
DiskRequest peek(DiskQueue *queue) {
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return *queue->head;
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}
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DiskRequest dequeue(DiskQueue *queue) {
DiskRequest *head = queue->head;
queue->head = head->next;
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queue->size--;
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return *head;
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}
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void destroyDiskQueue(DiskQueue *queue) {
DiskRequest *current = queue->head;
DiskRequest *next = NULL;
while (current != NULL) {
next = current->next;
free(current);
current = next;
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}
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free(queue);
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}
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DiskRequest* findClosest(DiskQueue *queue, int position, double time) {
DiskRequest *current = queue->head;
DiskRequest *closest = NULL;
while (current != NULL) {
if (current->time <= time) { // Filter out requests that haven't come in yet
if (closest == NULL) { // If there is no closest yet, set it to the current
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closest = current;
} else {
int closestDistance = closest->position - position; // Distance from the closest to the current position, negative means down (bad)
int currentDistance = current->position - position; // Distance from the current to the current position, negative means down (bad)
if (currentDistance > 0) { // If the current is up
if (currentDistance < closestDistance) { // If the current is closer than the closest
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closest = current;
}
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}
}
}
current = current->next;
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}
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// Bad
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if (closest == NULL) {
return NULL;
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}
return closest;
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}