问C中使用信号量的线程安全函数

EN

#include "queue.h"
#include <semaphore.h>

sem_t sem;

Queue queueCreate(unsigned capacity){
    sem_init(&sem, 0, 1);
    Queue q = malloc(sizeof(queue_t)); 
    q->capacity = capacity;
    q->front = q->size = 0;
    q->rear = capacity - 1;
    q->array = malloc(q->capacity * sizeof(*q->array));
    return q;
}

void queueDestroy(Queue q){
    free(q->array);
    free(q);
    sem_destroy(&sem);
}

int queueIsFull(Queue q){
    sem_wait(&sem);
    return (q->size == q->capacity);
    sem_post(&sem);
}

int queueIsEmpty(Queue q){
    sem_wait(&sem);
    return (q->size == 0);
    sem_post(&sem);
}

int queueEnqueue(Queue q, int* value){ 
    sem_wait(&sem);
    if (queueIsFull(q)) return -1;
    q->rear = (q->rear + 1) % q->capacity;
    q->array[q->rear] = *value;
    q->size = q->size + 1;
    sem_post(&sem);
    return 0;
}

int queueDequeueFront(Queue queue, int* container){
    sem_wait(&sem);
    if (queueIsEmpty(queue)) return -1; 
    *container = queue->array[queue->front];
    queue->front = (queue->front + 1) % queue->capacity;
    queue->size = queue->size - 1;
    sem_post(&sem);
    return 0;
}

int queueDequeueRear(Queue queue, int* container){
    sem_wait(&sem);
    if (queueIsEmpty(queue)) return -1; 
    *container = queue->array[queue->rear];
    queue->rear = (queue->capacity + queue->rear - 1) % queue->capacity;
    queue->size = queue->size - 1; 
    sem_post(&sem);
    return 0;
}

int* queueFront(Queue queue){
    sem_wait(&sem);
    if (queueIsEmpty(queue)) return NULL;
    return &queue->array[queue->front]; 
    sem_post(&sem);
}

int* queueRear(Queue queue){ 
    sem_wait(&sem);
    if (queueIsEmpty(queue)) return NULL;
    return &queue->array[queue->rear];
    sem_post(&sem);
}

void queuePrint(Queue q){
    printf("Queue(^: front, *: rear): [");
    int i;
    for(i = 0; i < q->capacity; i++){
        printf("%d", q->array[i]);
        if(i == q->front) printf("^");
        if(i == q->rear) printf("*");
        i == q->capacity - 1 ? printf("] ") : printf(", ");
    }
    printf("size=%d, capacity=%d\n", q->size, q->capacity);
    fflush(stdout);
}