105 lines
2.9 KiB
C
105 lines
2.9 KiB
C
#include <stdio.h>
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#include <stddef.h>
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#include <stdbool.h>
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#include <string.h>
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#include <stdlib.h>
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#include "process.h"
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#include "queue.h"
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/*
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* Queue implementation
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* 5 4 3 2 1
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* START END
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*
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* If you were to visualize the queue as a line, the end is the first person in line and the start is the last person in line
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* So when you enqueue, you are adding to the start of the line
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* And when you dequeue, you are exiting from the end of the line
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*/
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int contains(Queue *queue, char *username) {
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Process *current = queue->end;
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while (current != NULL) {
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if (strcmp(current->username, username) == 0) {
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return true;
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}
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current = current->prev_elem;
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}
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return false;
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}
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Process *search(Queue *queue, char *username) {
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Process *current = queue->end;
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while (current != NULL) {
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if (strcmp(current->username, username) == 0) {
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return current;
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}
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current = current->prev_elem;
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}
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return NULL;
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}
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void enqueue(Queue *queue, Process *process) {
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if (queue->end == NULL) { // If the queue is empty, set the start and end to the new process
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queue->end = process;
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queue->start = queue->end;
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} else {
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process->next_elem = queue->start; // Set the next element of the new process to the start of the queue
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queue->start->prev_elem = process; // Set the previous element of the start of the queue to the new process
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queue->start = process; // Set the start of the queue to the new process
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}
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queue->size++;
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}
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// WARNING: Returns a pointer to a process that is not in the queue, it is your responsibility to free it
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Process *dequeue(Queue *queue) {
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if (queue->end == NULL) { // If the queue is empty, return NULL
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return NULL;
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}
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Process *temp = queue->end; // Store the end of the queue for returning later
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if (queue->size == 1) { // If the queue has one element, set the start and end to NULL
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queue->start = NULL;
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queue->end = NULL;
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queue->size--;
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return temp;
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}
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queue->end = queue->end->prev_elem; // Set the end to the previous element
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queue->end->next_elem = NULL; // Set the next element of the new end to NULL
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temp->prev_elem = NULL; // The dequeued element should not point to anything
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queue->size--;
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return temp;
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}
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void printList(Queue *queue) {
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Process *current = queue->end;
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while (current != NULL) {
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printf("%s\t%d\n", current->username, current->finish_time);
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current = current->prev_elem;
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}
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}
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int stop(Queue *queue) {
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Process *current = queue->end;
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while (current != NULL) {
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Process *next = current->prev_elem;
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destroyProcess(current);
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current = next;
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}
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free(queue);
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return true;
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}
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Queue *createQueue() {
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Queue *queue = calloc(1, sizeof(Queue));
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if (queue == NULL) {
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printf("Error allocating memory for queue\n");
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exit(EXIT_FAILURE);
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}
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queue->start = NULL;
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queue->end = NULL;
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queue->size = 0;
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return queue;
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}
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