void read_lock()
{
    //Locks the mutex
    pthread_mutex_lock(&lock);

    while (writerWaiting)
    {
        pthread_cond_wait(&cond, &lock);
    }

    ++readersWaiting;
}

void read_unlock()
{
    --readersWaiting;

    //IMPL1
    while (readersWaiting > 0)
    {
        pthread_cond_wait(&cond, &lock);
    }

    pthread_cond_signal(&cond);
    pthread_mutex_unlock(&lock);
}

void write_lock()
{
    pthread_mutex_lock(&lock);

    while (writerWaiting)
    {
        pthread_cond_wait(&cond, &lock);
    }
}

void write_unlock()
{
    writerWaiting = true;

    while (readersWaiting > 0)
    {
        pthread_cond_wait(&cond, &lock);
    }

    writerWaiting = false;

    pthread_cond_broadcast(&cond);
    pthread_mutex_unlock(&lock);
}