mirror of
https://sourceware.org/git/glibc.git
synced 2024-11-26 15:00:06 +00:00
114 lines
2.7 KiB
C
114 lines
2.7 KiB
C
/* The classic producer-consumer example.
|
|
Illustrates mutexes and conditions.
|
|
All integers between 0 and 9999 should be printed exactly twice,
|
|
once to the right of the arrow and once to the left. */
|
|
|
|
#include <stdio.h>
|
|
#include "pthread.h"
|
|
|
|
#define BUFFER_SIZE 16
|
|
|
|
/* Circular buffer of integers. */
|
|
|
|
struct prodcons {
|
|
int buffer[BUFFER_SIZE]; /* the actual data */
|
|
pthread_mutex_t lock; /* mutex ensuring exclusive access to buffer */
|
|
int readpos, writepos; /* positions for reading and writing */
|
|
pthread_cond_t notempty; /* signaled when buffer is not empty */
|
|
pthread_cond_t notfull; /* signaled when buffer is not full */
|
|
};
|
|
|
|
/* Initialize a buffer */
|
|
|
|
void init(struct prodcons * b)
|
|
{
|
|
pthread_mutex_init(&b->lock, NULL);
|
|
pthread_cond_init(&b->notempty, NULL);
|
|
pthread_cond_init(&b->notfull, NULL);
|
|
b->readpos = 0;
|
|
b->writepos = 0;
|
|
}
|
|
|
|
/* Store an integer in the buffer */
|
|
|
|
void put(struct prodcons * b, int data)
|
|
{
|
|
pthread_mutex_lock(&b->lock);
|
|
/* Wait until buffer is not full */
|
|
while ((b->writepos + 1) % BUFFER_SIZE == b->readpos) {
|
|
pthread_cond_wait(&b->notfull, &b->lock);
|
|
/* pthread_cond_wait reacquired b->lock before returning */
|
|
}
|
|
/* Write the data and advance write pointer */
|
|
b->buffer[b->writepos] = data;
|
|
b->writepos++;
|
|
if (b->writepos >= BUFFER_SIZE) b->writepos = 0;
|
|
/* Signal that the buffer is now not empty */
|
|
pthread_cond_signal(&b->notempty);
|
|
pthread_mutex_unlock(&b->lock);
|
|
}
|
|
|
|
/* Read and remove an integer from the buffer */
|
|
|
|
int get(struct prodcons * b)
|
|
{
|
|
int data;
|
|
pthread_mutex_lock(&b->lock);
|
|
/* Wait until buffer is not empty */
|
|
while (b->writepos == b->readpos) {
|
|
pthread_cond_wait(&b->notempty, &b->lock);
|
|
}
|
|
/* Read the data and advance read pointer */
|
|
data = b->buffer[b->readpos];
|
|
b->readpos++;
|
|
if (b->readpos >= BUFFER_SIZE) b->readpos = 0;
|
|
/* Signal that the buffer is now not full */
|
|
pthread_cond_signal(&b->notfull);
|
|
pthread_mutex_unlock(&b->lock);
|
|
return data;
|
|
}
|
|
|
|
/* A test program: one thread inserts integers from 1 to 10000,
|
|
the other reads them and prints them. */
|
|
|
|
#define OVER (-1)
|
|
|
|
struct prodcons buffer;
|
|
|
|
void * producer(void * data)
|
|
{
|
|
int n;
|
|
for (n = 0; n < 10000; n++) {
|
|
printf("%d --->\n", n);
|
|
put(&buffer, n);
|
|
}
|
|
put(&buffer, OVER);
|
|
return NULL;
|
|
}
|
|
|
|
void * consumer(void * data)
|
|
{
|
|
int d;
|
|
while (1) {
|
|
d = get(&buffer);
|
|
if (d == OVER) break;
|
|
printf("---> %d\n", d);
|
|
}
|
|
return NULL;
|
|
}
|
|
|
|
int main(void)
|
|
{
|
|
pthread_t th_a, th_b;
|
|
void * retval;
|
|
|
|
init(&buffer);
|
|
/* Create the threads */
|
|
pthread_create(&th_a, NULL, producer, 0);
|
|
pthread_create(&th_b, NULL, consumer, 0);
|
|
/* Wait until producer and consumer finish. */
|
|
pthread_join(th_a, &retval);
|
|
pthread_join(th_b, &retval);
|
|
return 0;
|
|
}
|