| 1 | #include "queue.h" |
| 2 | #include <stdlib.h> |
| 3 | #include <pthread.h> |
| 4 | |
| 5 | /* Requirements 4 & 5 for Homework 09 indicate that you should modify the add |
| 6 | * and pop methods for the queue to provide for thread safety. If you modify |
| 7 | * the producer and consumer methods instead you will not receive full credit |
| 8 | * for the solution. Additionally, the due date for the homework is now |
| 9 | * Thursday to provide for the necessary modifications to fulfill requirements |
| 10 | * 4 & 5. Please note that you should NOT be using a global mutex. Any |
| 11 | * structures you use to protect the queue should be associated with the |
| 12 | * particular queue that is being used (the one given to the add/pop methods). |
| 13 | * */ |
| 14 | |
| 15 | /* private methods */ |
| 16 | |
| 17 | static void clear_node(queue_node_t* node) |
| 18 | { |
| 19 | if (node != NULL) |
| 20 | { |
| 21 | clear_node(node->next); |
| 22 | free(node); |
| 23 | } |
| 24 | } |
| 25 | |
| 26 | static queue_node_t* create_node(int value) |
| 27 | { |
| 28 | queue_node_t* node = malloc(sizeof(queue_node_t)); |
| 29 | node->value = value; |
| 30 | node->next = NULL; |
| 31 | return node; |
| 32 | } |
| 33 | |
| 34 | /* public methods */ |
| 35 | |
| 36 | void queue_init(queue_t* queue) |
| 37 | { |
| 38 | queue->root = NULL; |
| 39 | |
| 40 | queue->mx_pop = (pthread_mutex_t *) calloc(1, sizeof(pthread_mutex_t)); |
| 41 | queue->mx_push = (pthread_mutex_t *) calloc(1, sizeof(pthread_mutex_t)); |
| 42 | queue->mx_valid_root = (pthread_mutex_t *) calloc(1, sizeof(pthread_mutex_t)); |
| 43 | queue->valid_root = (pthread_cond_t *) calloc(1, sizeof(pthread_cond_t)); |
| 44 | |
| 45 | pthread_mutex_init(queue->mx_pop, NULL); |
| 46 | pthread_mutex_init(queue->mx_push, NULL); |
| 47 | pthread_mutex_init(queue->mx_valid_root, NULL); |
| 48 | |
| 49 | pthread_cond_init(queue->valid_root, NULL); |
| 50 | |
| 51 | return; |
| 52 | } |
| 53 | |
| 54 | void queue_clear(queue_t* queue) |
| 55 | { |
| 56 | clear_node(queue->root); |
| 57 | free(queue->mx_pop); |
| 58 | free(queue->mx_push); |
| 59 | free(queue->valid_root); |
| 60 | return; |
| 61 | } |
| 62 | |
| 63 | /* edit */ |
| 64 | void queue_add(queue_t* queue, int value) |
| 65 | { |
| 66 | pthread_mutex_lock(queue->mx_push); |
| 67 | pthread_mutex_lock(queue->mx_valid_root); |
| 68 | |
| 69 | if (queue->root == NULL) |
| 70 | { |
| 71 | queue->root = create_node(value); |
| 72 | pthread_cond_signal(queue->valid_root); |
| 73 | pthread_mutex_unlock(queue->mx_valid_root); |
| 74 | } |
| 75 | else |
| 76 | { |
| 77 | pthread_cond_signal(queue->valid_root); |
| 78 | pthread_mutex_unlock(queue->mx_valid_root); |
| 79 | |
| 80 | queue_node_t* last = queue->root; |
| 81 | while (last->next != NULL) |
| 82 | { |
| 83 | last = last->next; |
| 84 | } |
| 85 | last->next = create_node(value); |
| 86 | } |
| 87 | pthread_mutex_unlock(queue->mx_push); |
| 88 | return; |
| 89 | } |
| 90 | |
| 91 | /* edit */ |
| 92 | int queue_pop(queue_t* queue) |
| 93 | { |
| 94 | if(queue->root == NULL) { |
| 95 | |
| 96 | pthread_mutex_lock(queue->mx_valid_root); |
| 97 | pthread_cond_wait(queue->valid_root, queue->mx_valid_root); |
| 98 | pthread_mutex_unlock(queue->mx_valid_root); |
| 99 | } |
| 100 | pthread_mutex_lock(queue->mx_pop); |
| 101 | queue_node_t* temp = queue->root->next; |
| 102 | int value = queue->root->value; |
| 103 | free(queue->root); |
| 104 | queue->root = temp; |
| 105 | pthread_mutex_unlock(queue->mx_pop); |
| 106 | return value; |
| 107 | } |