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);



int main(int argc, char *argv[]) {

pthread_t tid1, tid2; /* thread identifiers */

int i;



/* create the producer threads*/

if (pthread_create([1]) != 0) {

fprintf(stderr, "Unable to create producer threadn");

exit(1);

}



/* create the consumer threads*/

if (pthread_create([2]) != 0) {

fprintf(stderr, "Unable to create consumer threadn");

exit(1);

}



/* wait for created thread to exit */

pthread_join([3]);

pthread_join([4]);

printf("Parent quitingn");

return 0;

}



/* Produce value(s) */

void *producer(void *param) {

int i;

char mess[15];

for (i = 1; i <= 10; i++) {

/* Insert into buffer */

pthread_mutex_lock([5]);

if (num > BUF_SIZE) exit(1); /* overflow */

while (num == BUF_SIZE) /* block if buffer is full */

pthread_cond_wait([6]);

/* 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);

pthread_mutex_unlock([7]);

pthread_cond_signal([8]);

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) {

[9];

if (num < 0) exit(1); /* underflow */

while (num == 0) /* block if buffer empty */

[10];

/* if executing here, buffer not empty so remove element */

strcpy(mess, buffer[rem]);

rem = (rem + 1) % BUF_SIZE;

num--;

printf("Consume: reads %sn", mess);

[11];

[12];

fflush(stdout);

}

return 0;

}