Linux多线程（九）条件变量2

      接着上一个博文，如果实际场所有两条线程需要读数据，一条线程需要些数据，两条读线程都要等写线程设置完数据才能读取数据，其实只要把条件变量当成一个计数器就行，而不是像上一个例子，当成一个bool型，这里需要等待两条线程准备好

实验源码如下：

#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
typedef struct
{
   int res;
   int counter;
   pthread_cond_t cond;
   pthread_mutex_t mutex;
}Result;
void * func_set(void *arg)
{
   Result *r=(Result *)arg;
   int i=1,sum=0;
   for(;i<=100;i++)
   {
     sum=sum+i;
   }
   r->res=sum;
   printf("the pthread %lx has write done\n",pthread_self());
   pthread_mutex_lock(&r->mutex);
   while(r->counter<2)
   {
     pthread_mutex_unlock(&r->mutex);
     usleep(1000);
     pthread_mutex_lock(&r->mutex);
   }
   pthread_mutex_unlock(&r->mutex);
   printf("I am ready to broadcast\n");
   pthread_cond_broadcast(&r->cond);
}
void *func_get(void *arg)
{
   Result *r=(Result *)arg;
   pthread_mutex_lock(&r->mutex);
   r->counter++;
   pthread_cond_wait(&r->cond,&r->mutex);
   printf("I have receive the infomation\n");
   pthread_mutex_unlock(&r->mutex);
   int res=r->res;
   printf("the pthread %lx read the result is %d\n",pthread_self(),res);
}
int main(void)
{
   int err;
   pthread_t rabbit,turtle,cal;
   Result r;
   r.counter=0;
   pthread_mutex_init(&r.mutex,NULL);
   pthread_cond_init(&r.cond,NULL);
   if((err=pthread_create(&rabbit,NULL,func_set,(void *)&r))!=0)
   {
      perror("pthread_create error");
   }
   if((err=pthread_create(&turtle,NULL,func_get,(void *)&r))!=0)
   {
      perror("pthread_create error");
   }
   if((err=pthread_create(&cal,NULL,func_get,(void *)&r))!=0)
   {
      perror("pthread_create error");
   }
   pthread_join(rabbit,NULL);
   pthread_join(turtle,NULL);
   pthread_mutex_destroy(&r.mutex);
   pthread_cond_destroy(&r.cond);
   printf("control thread id: %lx\n",pthread_self());
   printf("finished!\n");
   return 0;
}