Notes

#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/msg.h>
#include <stdlib.h>
#include <sys/sem.h>
#include <signal.h>
#include <sys/shm.h>
#include <semaphore.h>

#include <stdio.h>
#include <stdlib.h>
#include <pthread.h> //compile and link with -pthread
#define BUFFER_SIZE 10000
int buffer[BUFFER_SIZE];
int in, out;
int num;
int x=0;
sem_t empty_sem_mutex; //producer semaphore
sem_t full_sem_mutex; //consumer semaphore
sem_t full_sem_mutex2;
sem_t empty_sem_mutex2; //consumer2 semaphore
void *produce( void *ptr ) {
int item;
while(1){
sem_wait(&empty_sem_mutex);
sem_wait(&empty_sem_mutex2);
if(x>100)
x=0;
sleep(1); //sleep
printf("Producer wants to produce.n");
//critical section below
item = x;
num+=2;
buffer[in] = item;
out=in;
in = in + 1;
//critical section above
printf("Producer entered %d. Buffer Size = %dn", item, num);
x++;
sem_post(&full_sem_mutex);
sem_post(&full_sem_mutex2);
}
}
void *consume( void *ptr ) {
int item;
while(1){
sem_wait(&full_sem_mutex);
sleep(1); //sleep
printf("Consumer1 wants to consume.n");
//critical section below
num--;
int item = buffer[out];
//critical section above
printf("Consumer1 consumed %d. Buffer Size = %dn", item, num);
sem_post(&empty_sem_mutex);
}
}
void *consume2( void *ptr ) {
int item;
while(1){
sem_wait(&full_sem_mutex2);
sleep(1); //sleep
printf("Consumer2 wants to consume.n");
//critical section below
num--;
int item = buffer[out];
//critical section above
printf("Consumer2 consumed %d. Buffer Size = %dn", item, num);
sem_post(&empty_sem_mutex2);
}
}
int main() {
sem_init(&empty_sem_mutex,0,1);
sem_init(&full_sem_mutex,0,0);
sem_init(&full_sem_mutex2,0,0);
sem_init(&empty_sem_mutex2,0,1);
pthread_t consumer, producer, consumer2;
out = 0; //index of the item to be consumed next
in = 0; //index of the item to be produced next
num = 0; //number of items in the buffer
pthread_create( &consumer, NULL, consume, NULL);
pthread_create( &consumer2, NULL, consume2, NULL);
pthread_create( &producer, NULL, produce, NULL);
pthread_join( producer, NULL);
pthread_join( consumer, NULL);
pthread_join( consumer2, NULL);
pthread_exit(NULL);
}