线程同步之生产者消费者

#include <stdio.h> 
#include <stdlib.h>
#include <time.h> 
#include <pthread.h>   
#define BUFFER_SIZE 16 

struct prodcons   
{   
   
  int buffer[BUFFER_SIZE]; 
  pthread_mutex_t lock; 
  int readpos, writepos; 
  pthread_cond_t notempty; 
  pthread_cond_t notfull;
};   
 
void init(struct prodcons *b)   
{   
  pthread_mutex_init(&b->lock, NULL);   
  pthread_cond_init(&b->notempty, NULL);   
  pthread_cond_init(&b->notfull, NULL);   

//  this not work
//  b->lock = PTHREAD_MUTEX_INITIALIZER;
//  b->notempty = PTHREAD_COND_INITIALIZER;
//  b->notfull = PTHREAD_COND_INITIALIZER;

  b->readpos = 0;   
  b->writepos = 0;   
}   

void put(struct prodcons *b, int data)   
{   
  pthread_mutex_lock(&b->lock);   

  if ((b->writepos + 1) % BUFFER_SIZE == b->readpos)   
  {   
    pthread_cond_wait(&b->notfull, &b->lock);   
  }   
 
  b->buffer[b->writepos] = data;   
  b->writepos++;   
  if (b->writepos >= BUFFER_SIZE)   
  b->writepos = 0;   
 
  pthread_cond_signal(&b->notempty);   
  pthread_mutex_unlock(&b->lock);   
}    
 
int get(struct prodcons *b)   
{   
  int data;   
  pthread_mutex_lock(&b->lock);   
  
  if (b->writepos == b->readpos)   
  {   
    pthread_cond_wait(&b->notempty, &b->lock);   
  }   
   
  data = b->buffer[b->readpos];   
  b->readpos++;   
  if (b->readpos >= BUFFER_SIZE)   
  b->readpos = 0;   
  
  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 < 100; 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);   
  
  pthread_create(&th_a, NULL, producer, 0);   
  pthread_create(&th_b, NULL, consumer, 0);   
   
  pthread_join(th_a, &retval);   
  pthread_join(th_b, &retval);   
  return 0;   
}