sem.c

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#include "sem.h"

int create_sem(void) {
    int sem_id = semget(SEM_KEY, NUM_SEMS, IPC_CREAT | S_IRWXU);
    if(sem_id < 0) {
        rl_log(ERROR, "failed to create semaphores. Errno = %d", errno);
    }
    return sem_id;
}

int remove_sem(int sem_id) {
    // remove semaphores
    if(semctl(sem_id, DATA_SEM, IPC_RMID) < 0) {
        rl_log(ERROR, "failed to remove semaphores. Errno = %d", errno);
        return FAILURE;
    }
    return SUCCESS;
}

int open_sem(void) {
    int sem_id = semget(SEM_KEY, NUM_SEMS, S_IRWXU);
    if(sem_id < 0) {
        rl_log(ERROR, "failed to open semaphores. Errno = %d", errno);
    }
    return sem_id;
}

int wait_sem(int sem_id, int sem_num, int time_out) {
    // operation on semaphore
    int num_ops = 1;
    int sem_op = -1;
    struct sembuf sem_ops = {sem_num, sem_op, NO_FLAG};
    struct timespec t_out = {time_out, 0};
    
    if(semtimedop(sem_id, &sem_ops, num_ops, &t_out) < 0) {
        if(errno == EAGAIN) {
            rl_log(WARNING, "time-out waiting on semaphore");
            return TIME_OUT;
        } else if(errno == EIDRM) {
            rl_log(INFO, "waiting on semaphore failed: semaphore removed");
            return TIME_OUT;
        } else if(errno == EINVAL) {
            rl_log(WARNING, "waiting on semaphore failed: semaphore not existing");
            return FAILURE;
        } else {
            rl_log(ERROR, "failed doing operation on semaphore. Errno = %d", errno);
            return FAILURE;
        }
    }
    
    return SUCCESS;
}

int set_sem(int sem_id, int sem_num, int val) {
    // operation on semaphore
    int num_ops = 1;
    int sem_op = val;
    struct sembuf sem_ops = {sem_num, sem_op, NO_FLAG};
    struct timespec time_out = {SEM_SET_TIME_OUT, 0};
    
    if(semtimedop(sem_id, &sem_ops, num_ops, &time_out) < 0) {
        if(errno == EAGAIN) {
            rl_log(ERROR, "time-out waiting on semaphore");
            return TIME_OUT;
        } else {
            rl_log(ERROR, "failed doing operation on semaphore. Errno = %d", errno);
            return FAILURE;
        }
    }
    
    return SUCCESS;
}