使用互斥锁和条件变量实现读写锁
代码
class rw_lock {
private:
int stat; //0 : 无锁，-1 : 写锁， >0 : 读锁的数量
pthread_mutex_t mutex;
pthread_cond_t cond;
public:
rw_lock() : stat(0) {
pthread_mutex_init(&mutex, NULL);
pthread_cond_init(&cond, NULL);
}
~rw_lock() {}
void rdlock() {
pthread_mutex_lock(&mutex);
while (stat < 0) {
pthread_cond_wait(&cond, &mutex);
}
++stat;
pthread_mutex_unlock(&mutex);
}
void rwunlock() {
pthread_mutex_lock(&mutex);
--stat;
if (stat == 0)
pthread_cond_signal(&cond);
pthread_mutex_unlock(&mutex);
}
void wrlock() {
pthread_mutex_lock(&mutex);
while (stat > 0) {
pthread_cond_wait(&cond, &mutex);
}
--stat;
pthread_mutex_unlock(&mutex);
}
void wrunlock() {
pthread_mutex_lock(&mutex);
++stat;
pthread_cond_signal(&cond);
pthread_mutex_unlock(&mutex);
}
};
