#include <stdio.h>
#include <pthread.h>
#include <semaphore.h>

#define MAX 5 //队列长度

pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
sem_t full;  //填充的个数
sem_t empty;  //空槽的个数

int top = 0;   //队尾
int bottom = 0; //队头

void* produce(void* arg)
{
 int i;
 for ( i = 0; i < MAX*2; i++)
 {
  printf("producer is preparing data\n");
  sem_wait(&empty);//若空槽个数低于0阻塞
  
  pthread_mutex_lock(&mutex);
  
  top = (top+1) % MAX;
  printf("now top is %d\n", top);

  pthread_mutex_unlock(&mutex);
  
  sem_post(&full);
 }
 return (void*)1;
}

void* consume(void* arg)
{
 int i;
 for ( i = 0; i < MAX*2; i++)
 {
  printf("consumer is preparing data\n");
  sem_wait(&full);//若填充个数低于0阻塞
 
  pthread_mutex_lock(&mutex);
  
  bottom = (bottom+1) % MAX;
  printf("now bottom is %d\n", bottom);

  pthread_mutex_unlock(&mutex);
  
  sem_post(&empty);
 }

 return (void*)2;
}

int main(int argc, char *argv[])
{
 pthread_t thid1;
 pthread_t thid2;
 pthread_t thid3;
 pthread_t thid4;

 int ret1;
 int ret2;
 int ret3;
 int ret4;

 sem_init(&full, 0, 0);
 sem_init(&empty, 0, MAX);

 pthread_create(&thid1, NULL, produce, NULL);
 pthread_create(&thid2, NULL, consume, NULL);
 pthread_create(&thid3, NULL, produce, NULL);
 pthread_create(&thid4, NULL, consume, NULL);

 pthread_join(thid1, (void**)&ret1);
 pthread_join(thid2, (void**)&ret2);
 pthread_join(thid3, (void**)&ret3);
 pthread_join(thid4, (void**)&ret4);

 return 0;
}

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

#define MAX 5

pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
pthread_cond_t notfull = PTHREAD_COND_INITIALIZER;  //是否队满
pthread_cond_t notempty = PTHREAD_COND_INITIALIZER;  //是否队空

int top = 0;
int bottom = 0;

void* produce(void* arg)
{
 int i;
 for ( i = 0; i < MAX*2; i++)
 {
  pthread_mutex_lock(&mutex);
  while ((top+1)%MAX == bottom)
  {
   printf("full! producer is waiting\n");
   pthread_cond_wait(¬full, &mutex);//等待队不满
  }

  top = (top+1) % MAX;
  printf("now top is %d\n", top);
  pthread_cond_signal(¬empty);//发出队非空的消息

  pthread_mutex_unlock(&mutex);
 }
 return (void*)1;
}

void* consume(void* arg)
{
 int i;
 for ( i = 0; i < MAX*2; i++)
 {
  pthread_mutex_lock(&mutex);
  while ( top%MAX == bottom)
  {
   printf("empty! consumer is waiting\n");
   pthread_cond_wait(¬empty, &mutex);//等待队不空
  }
  bottom = (bottom+1) % MAX;
  printf("now bottom is %d\n", bottom);
  pthread_cond_signal(¬full);//发出队不满的消息

  pthread_mutex_unlock(&mutex);
 }

 return (void*)2;
}

int main(int argc, char *argv[])
{
 pthread_t thid1;
 pthread_t thid2;
 pthread_t thid3;
 pthread_t thid4;

 int ret1;
 int ret2;
 int ret3;
 int ret4;

 pthread_create(&thid1, NULL, produce, NULL);
 pthread_create(&thid2, NULL, consume, NULL);
 pthread_create(&thid3, NULL, produce, NULL);
 pthread_create(&thid4, NULL, consume, NULL);

 pthread_join(thid1, (void**)&ret1);
 pthread_join(thid2, (void**)&ret2);
 pthread_join(thid3, (void**)&ret3);
 pthread_join(thid4, (void**)&ret4);

 return 0;
}