barber.c~

这是一个操作系统课程中的理发师算法。具体描述见readme

#include <stdio.h>
#include <pthread.h>
#include <unistd.h>
#include <signal.h>
#include <semaphore.h>
#include <sys/ipc.h>
#include <sys/sem.h>

#define NUMOFCHAIRS 	20		
#define NUMOFBARBERS 	2
sem_t chairs;				//semphore for chairs
sem_t hairs;				//semphore for hairs to cut.

sem_t barber_mutex;			
sem_t customer_mutex;
sem_t mainthread_quit;		//mutex for main thread to quit

int index_in;				//index of next customer's seat.
int index_out;				//index of next customer to service

char seat[NUMOFCHAIRS ];			
char barber_seat[NUMOFBARBERS];


int over = 0;				//Stop the program.
int service = 1;




void snapshot();				
void init();
void * Barber(void * param);
void * Customer( void * param);

void CustomerSitDownWaiting(int number);
void BarberWorking(int number);
void BarberChating(int number);
void InviteCustomerComeIn(int number);


// The function is to decrease the running time.
void mysleep(int time)
{
	int real = time*1000/2;
	usleep(real);
	
	sleep(time);
}

//Customers sit down to wait.
void CustomerSitDownWaiting(int number)
{
	printf("Customer%d sit down on chair%d\n",number,index_in);
	sem_wait(&customer_mutex);
	seat[index_in] = 1;
	index_in++;
	index_in %= NUMOFCHAIRS;
	sem_post(&customer_mutex);
}


// Snapshot for two rooms.
void snapshot()
{
	int i = 0;
	printf("\n++++++++++++++Customer Room Status++++++++++++++++\n");	
	for( i = 0 ; i < NUMOFCHAIRS ; i ++ )
	{
		if(i != 0)
			if( i%5 == 0 )
			{
				printf("\n");
			}	
		printf("[Seat%d--%s]  ",i,(seat[i]>0?"Occupied":"-"));		
//		printf("[Seat%d---%d]  ",i,seat[i]);		
	}
	printf("\n+++++++++++++++++++++++++++++++++++++++++++\n");	
	printf("******Barber Room Status********\n");
	
	int	j = 0;
	for( j = 0 ; j < NUMOFBARBERS ; j ++ )
	{
		printf("Barber%d-----%s\n", j ,(barber_seat[j]>0?"Busy":"Idle"));
//		printf("Barber Seat%d-----%d\n", j ,(barber_seat[j]));
	}
	printf("*************************\n");

}


//One barber chats with another.
void BarberChatting(int number)
{
	printf("Chat::Hello,barber%d. I am barber%d. I am free.I like chatting. Do you like it?\n",(number+1)%2,number);
	mysleep(1);
}	


//Barber is working.
void BarberWorking(int number)
{
	printf("\nNotification: Barber%d is Working..........\n",number);
	int time = barbertime(number);			
	mysleep(time);
	barber_seat[number] = 0;
	printf("\nNotification: Barber%d finished the work.......\n",number);	
}


//Barber invites one customer to come in.
void InviteCustomerComeIn(int number)
{
	sem_wait(&barber_mutex);
	printf("Barber%d invite chair%d Customer ComeIn\n",number, index_out);
 	seat[index_out] = 0;
 	index_out ++;
 	index_out %= NUMOFCHAIRS;
	sem_post(&barber_mutex);
	
	barber_seat[number] = 1;
}


//The function for thread body.
void * Barber(void * param)
{
	int i = 0; 
	int Number = *(int *)param;
	printf("barber %d init ok....\n",Number);
	while(!over)	
	{
		if( sem_trywait(&hairs) == 0)
		{
			InviteCustomerComeIn(Number);		
			sem_post(&chairs);
			BarberWorking(Number);
		}
		else
		{
			if(barber_seat[(Number+1)%2] == 1)
			{
				BarberChatting(Number);						
			} 
			else
			{
				printf("Barber%d is sleeping. ",Number);
				mysleep(1);
			}

		}		
	}
	sem_post(&mainthread_quit);
}


//The function for customer thread body.
void * Customer( void * param)
{
	printf("customer %d comes in.......\n",*(int*)param);
	snapshot();
	usleep(100);
	if(sem_trywait(&chairs)==0 )
	{
		CustomerSitDownWaiting(*(int*)param);
		sem_post(&hairs);
	}
	else //no wait and leave the room.
	{
		printf("No chairs, so customer leave the room....................\n");
		exit(0);
	}
}


// Customer enters room.
int entertime(int seed)
{
	int return_value;
	srand(time(NULL)+seed);
	return_value = (rand())%30+1;
	printf("\nNotification: the next customer will enter after %d min\n",return_value);	
	return return_value;

}


// Randomly to get barber's workig time.
int barbertime(int seed)
{
	int return_value;
	srand(time(NULL)+seed);
	return_value = 	(rand())%11+20;
	printf("\nNotification: the barber%d will finish the work after %d min\n",seed,return_value);		
	return return_value;
}


//Initialize the semaphores.
void init()
{
	sem_init(&chairs,0,NUMOFCHAIRS);
	sem_init(&hairs,0,0);
	sem_init(&barber_mutex,0, 1);
	sem_init(&customer_mutex,0,1);
	sem_init(&mainthread_quit,0,0);
	
	index_in = 0;
	index_out = 0; 
	
	memset(seat, 0 ,NUMOFCHAIRS);
	memset(barber_seat,0 , NUMOFBARBERS);
	printf("init ok!\n");
}



int main()
{
	int i = 0;
	pthread_t p1,p2;
	
	init();
	
	int number = 0;
	pthread_create(&p1,NULL,Barber,&number);
	int number1 = 1;
	pthread_create(&p2,NULL,Barber,&number1);
	
	pthread_t customer[50];
	for( i = 0 ; i < 5 ; i ++)
	{
		int entrytime = entertime(i);
		mysleep(entrytime);
		int code = i;
		pthread_create(&(customer[i]),NULL,Customer,&code);				
	}
	sleep(3);
		
	over = 1;
	
	//Main thread is waiting for the last customer's hair cut.
	printf("main thread is waiting for barber and customer.\n");

	sem_wait(&mainthread_quit);
	printf("Main thread exits......^_^\n");
	
	return 0;
}