#include<stdio.h>
#include<semaphore.h>
#include<pthread.h>
#include<ipc.h>
#define NBUFF 10

int nitems;

struct{
int buff[NBUFF];
sem_t mutex,nempty,nstored;
}shared;

void *produce(void*);
void *consume(void*);


int main(int argc,char**argv){

pthread_t tid_produce,tid_consume;
if(argc!=2){
printf("usage:filename<nitems>");
return 0;
}
printf("\n\nproducer_consumer problem using semaphore \n");
printf(".......................................................................................\n");
nitems=atoi(argv[1]);
sem_init(&shared.mutex,0,1);
sem_init(&shared.nempty,0,NBUFF);
sem_init(&shared.nstored,0,0);
pthread_setconcurrency(2);
pthread_create(&tid_produce,NULL,produce,NULL);
pthread_create(&tid_consume,NULL,consume,NULL);
pthread_join(tid_produce,NULL);
pthread_join(tid_consume,NULL);
sem_destroy(&shared.mutex);
sem_destroy(&shared.nempty);
sem_destroy(&shared.nstored);
}


void *produce(void *arg){
int i;
for(i=0;i<nitems;i++){
sem_wait(&shared.nempty);
sem_wait(&shared.mutex);
shared.buff[i%NBUFF]=i;
printf("\tproducer........");
printf("buff[%d]=%d\n\n",i,shared.buff[i%NBUFF]);
sem_post(&shared.mutex);
sem_post(&shared.nstored);
sleep(3);
}
return NULL;
}




void *consume(void *arg){
int i;
for(i=0;i<nitems;i++){
sem_wait(&shared.nstored);
sem_wait(&shared.mutex);
printf("\tconsumer.............");
printf("buff[%d]=%d\n\n\n",i,shared.buff[i%NBUFF]);
sem_post(&shared.mutex);
sem_post(&shared.nempty);
sleep(3);
}
return NULL;
}

/*
Output:
Enter the value of n=4
Enter the item=1
Enter the item=2
Enter the item=3
Enter the item=5
Consumer item=1
Consumer item=2
Consumer item=3
Consumer item=5

*/