Unix使用互斥量保护数据结构

#include
#include
struct foo
{
    int f_count;
    pthread_mutex_t f_lock;
    /* .. more stuff here ... */
};
struct foo* foo_alloc()
{
    struct foo  *fp;
    if ((fp = (struct foo*)malloc(sizeof(struct foo))) != NULL)
    {
fp->f_count = 1;
if (pthread_mutex_init(&fp->f_lock, NULL) != 0)
{
   free(fp);
   return NULL;
}
/* ... continue initialization ... */
    }
    return fp;
}
void foo_hold(struct foo *fp) // add a reference to the object
{
    pthread_mutex_lock(&fp->f_lock);
    fp->f_count++;
    pthread_mutex_unlock(&fp->f_lock);
}
void foo_rele(struct foo *fp) // release a reference to the object
{
    pthread_mutex_lock(&fp->f_lock);
    if (0 == --fp->f_count)  // last reference
    {
pthread_mutex_unlock(&fp->f_lock);
pthread_mutex_destroy(&fp->f_lock);
free(fp);
    }
    else
    {
pthread_mutex_unlock(&fp->f_lock);
    }
}