//?sleeping?barber?implementation
//?UML-CS?91.308?Fall?2005?fredm
//?based?on?solution?in?Tanenbaum

//?this?version?requires?that?you?compile?with?“-lm“?flag
//?so?that?trig?functions?included?in?normal?and?bursty?work.
//gcc?-o?barbershop?-lpthread?-lm?barbershop.c

#include?
#include?
#include?
#include?
#include?
#include?
#include?

#define?CHAIRS?5?/*?#?chairs?for?waiting?customers?*/?

sem_t?customers;?/*?#?of?customers?waiting?for?service?*/?
sem_t?barbers;?/*?#?of?barbers?waiting?for?customers?*/?

pthread_mutex_t?mutex;?/*?for?mutual?exclusion?*/?

int?waiting?=?0;?/*?customers?are?waiting?（not?being?cut）?*/?

int?cust_num?=?1;??/*?count?of?potential?customers??*/

void?barber?（void）;
void?customer?（void?*num）;
void?cut_hair（void）;

double?timediff（struct?timeval?i?struct?timeval?j）;
void?seed_random（void）;
double?flat（void）;
double?normal（void）;
double?bursty（void）;

int?main（）
{
??int?i;

??pthread_t?barber_t;
??pthread_t?customer_t;

??struct?timeval?earlier?now;
??float?delay;

??seed_random（）;

??//?create?1?barber?thread
??pthread_create（&barber_t?NULL?（void?*）&barber?NULL）;

??//?create?customers?with?a?delay?between?each
??gettimeofday?（&earlier?（struct?timezone?*）0）;??//?capture?start?time

??for?（i=0;?i<1000;?i++）?{
????pthread_create（&customer_t?NULL?（void?*）&customer?（void?*）cust_num）;
????cust_num++;

????delay?=?0.010;??//?delay?between?arriving?customers?in?seconds
????while?（1）?{
??????//?loop?until?proper?amount?of?real?time?expires
??????gettimeofday?（&now?（struct?timezone?*）0）;
??????if?（timediff（now?earlier）?>=?delay）?{
	earlier.tv_sec?=?now.tv_sec;
	earlier.tv_usec?=?now.tv_usec;
	break;
??????}
????}
??}

??//?stay?alive?after?this?happens?for?the?last?few?customers?to?be?served
??sleep（3）;

??//?this?is?a?place?where?you?can?print?out?the?success?ratio
??
}

double?timediff（struct?timeval?now?struct?timeval?earlier）?{
??if?（now.tv_sec?==?earlier.tv_sec）?
????return?（now.tv_usec?-?earlier.tv_usec）?/?1000000.;
??else
????return?（1000000?*?（now.tv_sec?-?earlier.tv_sec）?+
??????now.tv_usec?-?earlier.tv_usec）?/?1000000.;
}

void?barber（void）?
{?
??while?（1）?{?
????sem_wait（&customers）;?/*?go?to?sleep?if?#?of?customers?is?0?*/?
????pthread_mutex_lock（&mutex）;?/*?acquire?access?to?