#include <stdio.h>
#include <pthread.h>
#include <semaphore.h>
#include <fcntl.h>

int counter = 0; // shared resource
sem_t *semaphore; // semaphore declaration

void* increment(void* arg) {
    for (int i = 0; i < 100000; i++) {
        sem_wait(semaphore); // lock
        counter++; // critical section
        sem_post(semaphore); // unlock
    }
    return NULL;
}

int main() {
    pthread_t t1, t2, t3, t4;

    // MacOS specific semaphore definition.
    semaphore = sem_open("/mysem", O_CREAT, 0644, 1);
    if (semaphore == SEM_FAILED) {
        perror("sem_open failed");
        return 1;
    }

    pthread_create(&t1, NULL, increment, NULL);
    pthread_create(&t2, NULL, increment, NULL);
    pthread_create(&t3, NULL, increment, NULL);
    pthread_create(&t4, NULL, increment, NULL);
    pthread_join(t1, NULL);
    pthread_join(t2, NULL);
    pthread_join(t3, NULL);
    pthread_join(t4, NULL);

    sem_close(semaphore);
    sem_unlink("/mysem");

    printf("Final Counter Value (with semaphores): %d\n", counter);

    return 0;
}