/*cook.c*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <sys/shm.h>
#include <sys/stat.h>
#include <sys/mman.h>
#include <semaphore.h>

int main()
{
	const char *name = "shared_memory"; 
	const char *sema1= "fill";
	const char *sema2= "avail";
	const char *sema3= "mutex";

	int shm_fd;   //shared memory file discriptor
	int *shelf;
	int loop=6;
	sem_t *fill, *avail, *mutex;

	/* make *shelf shared between processes */
	//create the shared memory segment
	shm_fd = shm_open(name, O_CREAT | O_RDWR, 0666);
	//configure the size of the shared memory segment
	ftruncate(shm_fd,sizeof(int));
	//map the shared memory segment in process address space
	shelf = mmap(0,sizeof(int), PROT_READ | PROT_WRITE, MAP_SHARED, shm_fd, 0);
	/*creat/open semaphores*/
	//cook post semaphore fill after cooking a pizza
	fill = sem_open(sema1, O_CREAT,0666,0);
	//waiter post semaphore avail after picking up a pizza, at the beginning avail=3
	avail = sem_open(sema2, O_CREAT, 0666, 3);
	//mutex for mutual exclusion of shelf
	mutex = sem_open(sema3,O_CREAT,0666,1);
	printf("\nCook: I have started cooking pizza.\n");

	while(loop--){
		sem_wait(avail);
		sleep(rand()%2+1);
		sem_wait(mutex);
		(*shelf)++;
		sem_post(mutex);
		printf("Cook: cook a pizza, there are %d pizza now\n", *shelf);
		sem_post(fill);
	}
	printf("Cook: Time is up. I cooked 6 pizza. %d are left.\n", *shelf);
  	/*close and unlink semaphores*/
	sem_close(fill);
	sem_close(avail);
	sem_close(mutex);
	sem_unlink(sema1);
	sem_unlink(sema2);
	sem_unlink(sema3);
 	 /*close and unlink shared memory*/
  	munmap(shelf, sizeof(int));
	close(shm_fd);
	shm_unlink(name);
	return 0;
}