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

/* about Stock methods */
int max=30;
int stock=0;

int get(){
	return stock;
}

void set(int x){stock=x;}
int inc(){
	set(get()+1);
	return get();
}
int dec(){
	set(get()-1);
	return get();
}

int full(){ return get()>=max;}
int empty(){ return get()<=0;}

pthread_mutex_t stockm;
pthread_cond_t stockc;

void buy(){
	pthread_mutex_lock( &stockm );
	while(empty()){
		pthread_cond_wait(&stockc, &stockm);
	}
	dec();
	pthread_cond_broadcast(&stockc);
	pthread_mutex_unlock( &stockm );
}

void supply(){
	pthread_mutex_lock( &stockm );
	while(full()){
		pthread_cond_wait(&stockc, &stockm);
	}
	inc();
	pthread_cond_broadcast(&stockc);
	pthread_mutex_unlock( &stockm );
}

/* Customer */

int buycount=0;

void* customer(void* x){
	while(1){
		buy();
		buycount++;
		usleep(random()%1000);
	}
}

/* Customer2 */

int buycount2=0;

void* customer2(void* x){
	while(1){
		buy();
		buycount2++;
		usleep(random()%1020);
	}
}

/* Supplyer */

int supplycount=0;

void* producer(void* x){
	while(1){
		supply();
		supplycount++;
		usleep(random()%1010);
	}
}

void* ui(void* x){
	while(1){
		printf("buy=%d supply=%d stock=%d\n",
			buycount, supplycount, get());
	}
}

main(){
pthread_t thre1, thre2, thre3, thre4;

	pthread_setconcurrency( 4 );
	pthread_mutex_init( &stockm, NULL );
	pthread_cond_init(&stockc, NULL );

	pthread_create(&thre3, NULL, ui, NULL);
	pthread_create(&thre1, NULL, customer, NULL);
	// pthread_create(&thre4, NULL, customer2, NULL);
	pthread_create(&thre2, NULL, producer, NULL);

	pthread_join(thre1, NULL);
	pthread_join(thre2, NULL);
	pthread_join(thre3, NULL);
	// pthread_join(thre4, NULL);
}