/************************************************ * *	The classic producer-consumer example. * 	Illustrates mutexes and conditions. *  by Zou jian guo <ah_zou@tom.com>    *  2003-12-22 **************************************************/#include <stdio.h>#include <stdlib.h>#include <time.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) {		printf("wait for not full\n");    	pthread_cond_wait(&b->notfull, &b->lock);  	}  /* 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) {    	printf("wait for not empty\n");		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;}/*--------------------------------------------------------*/#define OVER (-1)struct prodcons buffer;/*--------------------------------------------------------*/void * producer(void * data){  	int n;  	for (n = 0; n < 1000; n++) {    	printf(" put-->%d\n", n);    	put(&buffer, n);	}  put(&buffer, OVER);  printf("producer stopped!\n");  return NULL;}/*--------------------------------------------------------*/void * consumer(void * data){  int d;  while (1) {    d = get(&buffer);    if (d == OVER ) break;    printf("              %d-->get\n", d);  }  printf("consumer stopped!\n");  return NULL;}/*--------------------------------------------------------*/int main(void){  	pthread_t th_a, th_b;  	void * retval;  	init(&buffer); 	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;}