#include<stdio.h>
#include<pthread.h>
#include<semaphore.h>
sem_t mutex, wrt;
int rc = 0, data = 0;
void *reader(void *arg);
void *writer(void *arg);
int main()
{
        int i;
        pthread_t rtid[5], wtid[5];
        sem_init(&mutex, 0, 1);
        sem_init(&wrt, 0, 1);
        for(i = 0; i <= 2; i++) {
                pthread_create(&wtid[i], NULL, writer, (void *)i);
                pthread_create(&rtid[i], NULL, reader, (void *)i);
        }
        for(i = 0; i <= 2; i++) {
                pthread_join(wtid[i], NULL);
                pthread_join(rtid[i], NULL);
        }
        return 0;
}
void *reader(void *arg)
{
        int f = ((int) arg);
        sem_wait(&mutex);
        rc++;
        if (rc == 1) {
                sem_wait(&wrt);
        }
        sem_post(&mutex); //signal
        printf("Data read by reader: %d is: %d \n", f, data);
        sem_wait(&mutex);
        rc--;
        if(rc == 0) {
                sem_post(&wrt);
        }
        sem_post(&mutex);
}
void *writer(void *arg)
{
        sem_wait(&wrt);
        data++;
        int f = ((int) arg);
        printf("Data written by writer: %d is: %d \n", f, data);
        sem_post(&wrt);
}