请教如何用pthread库实现一个生产者和两个消费者模型？

1.	#include <stdio.h> 

2.	#include <pthread.h> 

3.	#define BUFFER_SIZE 16 // 缓冲区数量 

4.	struct prodcons 

5.	{ 

6.	  // 缓冲区相关数据结构 

7.	  int buffer[BUFFER_SIZE]; /* 实际数据存放的数组*/ 

8.	  pthread_mutex_t lock; /* 互斥体lock 用于对缓冲区的互斥操作 */ 

9.	  int readpos, writepos; /* 读写指针*/ 

10.	  pthread_cond_t notempty; /* 缓冲区非空的条件变量 */ 

11.	  pthread_cond_t notfull; /* 缓冲区未满的条件变量 */ 

12.	}; 

13.	/* 初始化缓冲区结构 */ 

14.	void init(struct prodcons *b) 

15.	{ 

16.	  pthread_mutex_init(&b->lock, NULL); 

17.	  pthread_cond_init(&b->notempty, NULL); 

18.	  pthread_cond_init(&b->notfull, NULL); 

19.	  b->readpos = 0; 

20.	  b->writepos = 0; 

21.	} 

22.	/* 将产品放入缓冲区,这里是存入一个整数*/ 

23.	void put(struct prodcons *b, int data) 

24.	{ 

25.	  pthread_mutex_lock(&b->lock); 

26.	  /* 等待缓冲区未满*/ 

27.	  if ((b->writepos + 1) % BUFFER_SIZE == b->readpos) 

28.	  { 

29.	    pthread_cond_wait(&b->notfull, &b->lock); 

30.	  } 

31.	  /* 写数据,并移动指针 */ 

32.	  b->buffer[b->writepos] = data; 

33.	  b->writepos++; 

34.	  if (b->writepos >  = BUFFER_SIZE) 

35.	    b->writepos = 0; 

36.	  /* 设置缓冲区非空的条件变量*/ 

37.	  pthread_cond_signal(&b->notempty); 

38.	  pthread_mutex_unlock(&b->lock); 

39.	} 

40.	 

41.	/* 从缓冲区中取出整数*/ 

42.	int get(struct prodcons *b) 

43.	{ 

44.	  int data; 

45.	  pthread_mutex_lock(&b->lock); 

46.	  /* 等待缓冲区非空*/ 

47.	  if (b->writepos == b->readpos) 

48.	  { 

49.	    pthread_cond_wait(&b->notempty, &b->lock); 

50.	  } 

51.	  /* 读数据,移动读指针*/ 

52.	  data = b->buffer[b->readpos]; 

53.	  b->readpos++; 

54.	  if (b->readpos >  = BUFFER_SIZE) 

55.	    b->readpos = 0; 

56.	  /* 设置缓冲区未满的条件变量*/ 

57.	  pthread_cond_signal(&b->notfull); 

58.	  pthread_mutex_unlock(&b->lock); 

59.	  return data; 

60.	} 

61.	 

62.	/* 测试:生产者线程将1 到10000 的整数送入缓冲区,消费者线 

63.	程从缓冲区中获取整数,两者都打印信息*/ 

64.	#define OVER ( - 1) 

65.	struct prodcons buffer; 

66.	void *producer(void *data) 

67.	{ 

68.	  int n; 

69.	  for (n = 0; n < 10000; n++) 

70.	  { 

71.	    printf("%d --->\n", n); 

72.	    put(&buffer, n); 

73.	  } put(&buffer, OVER); 

74.	  return NULL; 

75.	} 

76.	 

77.	void *consumer(void *data) 

78.	{ 

79.	  int d; 

80.	  while (1) 

81.	  { 

82.	    d = get(&buffer); 

83.	    if (d == OVER) 

84.	      break; 

85.	    printf("--->%d \n", d); 

86.	  } 

87.	  return NULL; 

88.	} 

89.	 

90.	int main(void) 

91.	{ 

92.	  pthread_t th_a, th_b; 

93.	  void *retval; 

94.	  init(&buffer); 

95.	  /* 创建生产者和消费者线程*/ 

96.	  pthread_create(&th_a, NULL, producer, 0); 

97.	  pthread_create(&th_b, NULL, consumer, 0); 

98.	  /* 等待两个线程结束*/ 

99.	  pthread_join(th_a, &retval); 

100.	  pthread_join(th_b, &retval); 

101.	  return 0; 

102.	}