void barber()
{
printf("barber started\n");
while(1)
{
sem_change(sem_ID, 0, -1);
if(customers_count==0)
{
printf("barber sleeping\n");
eflag=1;
sem_change(sem_ID, 0, 1);
sem_change(sem_ID, 1, -1);
sem_change(sem_ID, 0, -1);
}
customers_count--;
sem_change(sem_ID, 0, 1);
sem_change(sem_ID, 3, 1);
// printf("tail:%d\n", tail);
// pthread_mutex_lock(&B);
sem_change(sem_ID, 4, -1);
// pthread_mutex_unlock(&B);
}
}
void consumer()
{
printf("consumer started\n");
while(1)
{
int v=0;
sem_change(sem_ID, 0, -1);
if(count==0)
{
printf("Consumer Waiting\n");
eflag=1;
sem_change(sem_ID, 0, 1);
sem_change(sem_ID, 1, -1);
sem_change(sem_ID, 0, -1);
//Waits until an item is produced
}
count--;
printf("consumed item:%d \n", buffer[tail]);
tail=(tail+1)%MAX_BUF;
if(count==MAX_BUF-1 && fflag==1)
{
fflag=0;
sem_change(sem_ID, 2, 1); //To signal the producer thread that
}
buffer is not full
sem_change(sem_ID, 0, 1);
sleep(rand()%4);
}
}
void producer()
{
printf("Producer started\n");
while(1)
{
int v=0;
sem_change(sem_ID, 0, -1);
if(count==MAX_BUF)
{
printf("Producer waiting\n");
fflag=1;
sem_change(sem_ID, 0, 1);
sem_change(sem_ID, 2, -1);
sem_change(sem_ID, 0, -1); //Waits until a free slot is available
}
count++;
buffer[head]=item_id++;
if(count==1 && eflag==1)
{
eflag=0;
sem_change(sem_ID, 1, 1); //To signal consumer thread that buffer is not empty
}
printf("produced item:%d \n", buffer[head]);
head=(head+1)%MAX_BUF;
sem_change(sem_ID, 0, 1);
sleep(rand()%3);
}
}
void write_thread()
{
char arg1[10], arg2[10000], ch;
while(1)
{
scanf("%s", arg1);
scanf("%c", &ch); // consumes the space in between
fgets(arg2, sizeof(arg2), stdin);
//printf("%s\n%s", arg1, arg2);
printf("\n1..2 -> %s %s\n", arg1, arg2);
sem_change(write_sem_id, 0, -1);
if(isdigit(arg1[0]))
{
if(atoi(arg1) > *(pids)) // invalid reference ID
{
printf("Invalid reference ID\n");
}
else if(ref_id == atoi(arg1))//sender and receiver are the same,
{
printf("Self-addressing is not viable\n");
}
else
{
m->send_index = ref_id;
m->recv_index = atoi(arg1);
strcpy(m->msg, arg2);
}
}
else if(arg1[0] == ':' && arg1[1] == 'a' && arg1[2] == 'l' && arg1[3] == 'l') // ":all"
{
m->recv_index = -1;
strcpy(m->msg, arg2);
}
else
{
printf("Please enter in the correct format\n");
}
sem_change(write_sem_id, 1, 1);
}
}
void customer(void *arg)
{
//printf("C\n");
sem_change(sem_ID, 0, -1);
if(customers_count==MAX_C) // If all seats are occupied exit the thread
{
int *ptr=(int*)arg;
*ptr=0;
printf("No place for customer %d so leaving\n", pthread_self());
sem_change(sem_ID, 0, 1);
return;
}
customers_count++;
if(customers_count==1 && eflag==1)
{
sem_change(sem_ID, 1, 1);
eflag=0;
}
sem_change(sem_ID, 0, 1);
printf("Customer %d got a place\n", pthread_self());
sem_change(sem_ID, 3, -1);
printf("Cutting for %d customer\n", pthread_self());
sleep(rand()%5+4);
sem_change(sem_ID, 4, 1);
// printf("head:%d\n", head);
// pthread_mutex_lock(&B);
// pthread_mutex_unlock(&B);
int *ptr=(int*)arg;
*ptr=0;
}
int main()
{
printf("hell\n");
signal(SIGUSR1, sigusr1);
char pathname[1000];
getwd(pathname);
//creating the write-semaphore(two)
key_t keyw = ftok(pathname, 'A');
write_sem_id = semget(keyw, 2, IPC_CREAT|0666);
if(write_sem_id < 0)
{
printf("Semaphore init error\n");
exit(1);
}
printf("%d %d", sem_val(write_sem_id, 0), sem_val(write_sem_id, 1));
//acquire semaphore to register the process..
sem_change(write_sem_id, 0, -1);
printf("%d %d", sem_val(write_sem_id, 0), sem_val(write_sem_id, 1));
//accessing shared memory for storing process IDs of max 50 processes
//the first memory location stores the current number of active processes
key_t pid_shm_key = ftok(pathname, 'C');
int pid_shm_id = shmget(pid_shm_key, 60*sizeof(int), IPC_CREAT|0666);
if(pid_shm_id < 0)
{
printf("shmget error\n");
exit(1);
}
pids = (int*)shmat(pid_shm_id, NULL, 0);
*(pids) = *(pids) + 1; //increase the number of active processes..
ref_id = *(pids);
*(pids + ref_id) = getpid();
printf("Registered PID of this process: %d\nThe reference ID for this process is: %d\n", getpid(), ref_id);
sem_change(write_sem_id, 0, 1);
//creating shared memory for storing message contents
//can store maximum of 10000 characters.
//Each process/client(max 50) has its own memory-block
//0th block is server's. Rest are allocated according to reference IDs..
key_t msg_shm_key = ftok(pathname, 'D');
int msg_shm_id = shmget(msg_shm_key, 60*sizeof(struct message), IPC_CREAT|0666);
if(msg_shm_id < 0)
{
printf("shmget error\n");
exit(1);
}
m = (struct message *)shmat(msg_shm_id, NULL, 0);
if(m == (struct message*)-1)
{
printf("shmat error\n");
exit(1);
}
//creating tot_read_count
key_t count_shm_key = ftok(pathname, 'H');
int count_shm_id = shmget(count_shm_key, sizeof(int), IPC_CREAT|0666);
if(count_shm_id < 0)
{
printf("shmget error\n");
exit(1);
}
count = (int*)shmat(count_shm_id, NULL, 0);
if(count == (int*)-1)
{
printf("shmat error\n");
exit(1);
}
printf("%d %d %d %d %d %d\n", write_sem_id, pid_shm_id, msg_shm_id, count_shm_id);
printf("%d %d", sem_val(write_sem_id, 0), sem_val(write_sem_id, 1));
sleep(5);
pthread_create(&reader, NULL, (void *)&read_thread, NULL);
pthread_create(&writer, NULL, (void *)&write_thread, NULL);
pthread_join(reader, NULL);
pthread_join(writer, NULL);
return 0;
}
int main(){
int prod_count=0;
int con_count = 0;
int shmid;
key_t key=1234;
int pid;
int *shm;
int retstatus;
int sem_id;
int *arr=(int *)malloc(3);
sem_id=sem_init(3,arr);
printf("Sem id: %d\n",sem_id);
shm=(int *)malloc(50);
if((shmid = shmget(key,27,IPC_CREAT|0666))<0)
{
printf("SHM error...........\n");
exit(0);
}
if((shm=(int *)shmat(shmid,NULL,0)) == (char *)-1){
printf("Attachment error\n");
exit(0);
}
pid=fork();
if(pid == 0)
{
printf("Producer is going on:\n");
while(count < max_count)
{
sem_change(sem_id,0,1);
count++;
sem_change(sem_id,1,1);
*(shm+prod_count)=value;
printf("Producer produced : %d\n",value);
value++;
prod_count++;
if(count == 1)
sem_change(sem_id,2,1);
sem_change(sem_id,1,-1);
sem_change(sem_id,0,-1);
sleep(1);
}
}
else{
int pid2=fork();
if(pid2 == 0){
printf("Consumer is starting");
while(con_count < max_count){
sem_change(sem_id,0,1);
count--;
sem_change(sem_id,2,1);
printf("Value consumed: %d\n",*(shm+con_count));
con_count++;
if(count < max_count)
sem_change(sem_id,1,1);
sem_change(sem_id,2,-1);
sem_change(sem_id,0,-1);
sleep(3);
}
}
else{
pid=wait(retstatus);
}
}
exit(0);
}
