程序要求:
在程序当中,创建两个线程,其中一个为生产者,一个为消费者。同时创建一把互斥锁保证两者不能够同时访问结构体当中buffer,可以把它比作是一个“仓库”。必须要等生产完成之后才可以去采用读取。添加条件变量是与锁综合起来的条件判定。
具体程序如下:
- #include <stdio.h>
- #include <stdlib.h>
- #include <time.h>
- #include "pthread.h"
- #define BUFFER_SIZE 2
- /* 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 *prod)
- {
- pthread_mutex_init(&prod->lock,NULL);
- pthread_cond_init(&prod->notempty,NULL);
- pthread_cond_init(&prod->notfull,NULL);
- prod->readpos = 0;
- prod->writepos = 0;
- }
- /* Store an integer in the buffer */
- void put(struct prodcons * prod, int data)
- {
- pthread_mutex_lock(&prod->lock);
- /* Wait until buffer is not full */
- while ((prod->writepos + 1) % BUFFER_SIZE == prod->readpos)
- {
- printf("producer wait for not full\n");
- pthread_cond_wait(&prod->notfull, &prod->lock);
- }
- /* Write the data and advance write pointer */
- prod->buffer[prod->writepos] = data;
- prod->writepos++;
- if (prod->writepos >= BUFFER_SIZE)
- prod->writepos = 0;
- /*Signal that the buffer is now not empty */
- pthread_cond_signal(&prod->notempty);
- pthread_mutex_unlock(&prod->lock);
- }
- /* Read and remove an integer from the buffer */
- int get(struct prodcons *prod)
- {
- int data;
- pthread_mutex_lock(&prod->lock);
- /* Wait until buffer is not empty */
- while (prod->writepos == prod->readpos)
- {
- printf("consumer wait for not empty\n");
- pthread_cond_wait(&prod->notempty, &prod->lock);
- }
- /* Read the data and advance read pointer */
- data = prod->buffer[prod->readpos];
- prod->readpos++;
- if (prod->readpos >= BUFFER_SIZE)
- prod->readpos = 0;
- /* Signal that the buffer is now not full */
- pthread_cond_signal(&prod->notfull);
- pthread_mutex_unlock(&prod->lock);
- return data;
- }
- #define OVER (-1)
- struct prodcons buffer;
- /*--------------------------------------------------------*/
- void * producer(void * data)
- {
- int n;
- for (n = 0; n < 5; n++)
- {
- printf("producer sleep 1 second......\n");
- sleep(1);
- printf("put the %d product\n", n);
- put(&buffer, n);
- }
- for(n=5; n<10; n++)
- {
- printf("producer sleep 3 second......\n");
- sleep(3);
- printf("put the %d product\n",n);
- put(&buffer,n);
- }
- put(&buffer, OVER);
- printf("producer stopped!\n");
- return NULL;
- }
- /*--------------------------------------------------------*/
- void * consumer(void * data)
- {
- int d=0;
- while (1)
- {
- printf("consumer sleep 2 second......\n");
- sleep(2);
- d=get(&buffer);
- printf("get the %d product\n", d);
- // d = get(&buffer);
- if (d == OVER ) break;
- }
- printf("consumer stopped!\n");
- return NULL;
- }
- /*--------------------------------------------------------*/
- int main(int argc,char *argv[])
- {
- 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;
- }
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