Notes

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

#define BUF_SIZE 3 /* Size of shared buffer */

char buffer[BUF_SIZE][15]; /* shared buffer */

int add = 0; /* place to add next element */
int rem = 0; /* place to remove next element */

int num = 0; /* number elements in buffer */

/* mutex lock for buffer */
pthread_mutex_t m = PTHREAD_MUTEX_INITIALIZER;

/* consumer waits on this cond var */
pthread_cond_t c_cons = PTHREAD_COND_INITIALIZER;

/* producer waits on this cond var */
pthread_cond_t c_prod = PTHREAD_COND_INITIALIZER;

void *producer(void *param);
void *consumer(void *param);

/* Produce value(s) */

void *producer(void *param) {
int i;
char mess[15];
for (i = 1; i <= 10; i++) {
/* TODO: Insert into buffer */
pthread_mutex_lock(&m);
if (num > BUF_SIZE) exit(1); /* overflow */
while (num == BUF_SIZE)
/* TODO: block if buffer is full */
pthread_cond_wait(&c_prod, &m);
/* if executing here, buffer not full so add element*/
sprintf(mess, "Message %d", i);
strcpy(buffer[add], mess);
add = (add + 1) % BUF_SIZE;
num++;
printf("Producer: writes %sn", mess);

// TODO
pthread_mutex_unlock(&m);
pthread_cond_signal(&c_cons);
fflush(stdout);
}
printf("producer quitingn");
fflush(stdout);
return 0;
}


/* Consume value(s); Note the consumer never terminates */
void *consumer(void *param) {
int i;
char mess[15];
while (1) {
// TODO: lock mutex
pthread_mutex_lock(&m);
if (num < 0) exit(1); /* underflow */
while (num == 0) /* TODO: block if buffer empty */
pthread_cond_wait(&c_cons, &m);
/* if executing here, buffer not empty so remove element */
strcpy(mess, buffer[rem]);
rem = (rem + 1) % BUF_SIZE;
num--;
printf("Consume: reads %sn", mess);

// TODO: unlock mutex
pthread_mutex_unlock(&m);

// TODO: send message to producer condition is running.
pthread_cond_signal(&c_prod);
fflush(stdout);
}
return 0;
}

int main(int argc, char *argv[]) {
pthread_t tid1, tid2; /* thread identifiers */
int i;
/* TODO: create the producer thread */
if (pthread_create(&tid1, NULL, producer, NULL) !=0) {
fprintf(stderr, "Unable to create producer threadn");
exit(1);
}
/* TODO: create the consumer thread */
if (pthread_create(&tid2, NULL, consumer, NULL) !=0) {
fprintf(stderr, "Unable to create consumer threadn");
exit(1);
}
/* TODO: wait for created threads to exit */
pthread_join(tid1, NULL);
pthread_join(tid2, NULL);
printf("Parent exitingn");
return 0;
}