#include<stdio.h>
#include<stdlib.h>
#include<unistd.h>
#include<sys/ipc.h>
#include<sys/wait.h>
#include<semaphore.h>
#include<sys/shm.h>
#include<fcntl.h>

#define BUFFER_SIZE 5

struct shared{
    int buffer[BUFFER_SIZE];
    int in;
    int out;
};

int main(){
    int n;
    printf("\nhow many items to produce? ");
    scanf("%d", &n);

    int shmid = shmget(IPC_PRIVATE, sizeof(struct shared), IPC_CREAT | 0666);
    struct shared* s = (struct shared* )shmat(shmid, NULL, 0);
    s->in = 0;
    s->out = 0;

    sem_unlink("/mutex");
    sem_unlink("/empty");
    sem_unlink("/full");
    sem_t *mutex = sem_open("/mutex", O_CREAT, 0644, 1);
    sem_t *empty = sem_open("/empty", O_CREAT, 0644, BUFFER_SIZE);
    sem_t *full = sem_open("/full", O_CREAT, 0644, 0);

    if(fork()==0){
        for(int i =1;i<=n;i++){
            sem_wait(empty);
            sem_wait(mutex);
            s->buffer[s->in] = i;
            printf("produced: %d slot: %d\n", i, s->in);
            s->in = (s->in+1)%BUFFER_SIZE;

            sem_post(mutex);
            sem_post(full);
            sleep(1);

        }
        exit(0);
    }
    
    if(fork()==0){
        for(int i =1;i<=n;i++){
            sem_wait(full);
            sem_wait(mutex);
            int item = s->buffer[s->out];
            printf("consumed: %d slot: %d\n", item, s->out);
            s->out = (s->out+1)%BUFFER_SIZE;

            sem_post(mutex);
            sem_post(empty);
            sleep(2);

        }
        exit(0);
    }
    wait(NULL);
    wait(NULL);

    shmdt(s);
    shmctl(shmid, IPC_RMID, NULL);
    sem_unlink("/mutex");
    sem_unlink("/empty");
    sem_unlink("/full");
    
    return 0;




    
}