#include <stdio.h>
#include <pthread.h>
#include <unistd.h>

// 定义读写锁（需要 GNU99）
pthread_rwlock_t rwlock = PTHREAD_RWLOCK_INITIALIZER; // 静态初始化读写锁

void *read_task(void *data)
{
    int *n = (int *)data;

    while (1)
    {
        pthread_rwlock_rdlock(&rwlock); // 申请读锁 rdlock
        printf("(%ld)线程读取 num: %d\n", pthread_self(), *n);
        pthread_rwlock_unlock(&rwlock); // 解锁
        usleep(500 * 1000);
    }
    return NULL;
}

void *write_task(void *data)
{
    int *n = (int *)data;
    while (1)
    {
        pthread_rwlock_wrlock(&rwlock); // 申请写锁 wrlock
        (*n)++;
        printf("(%ld) 线程写 num: %d\n", pthread_self(), *n);
        pthread_rwlock_unlock(&rwlock); // 解锁
        sleep(2);
    }

    return NULL;
}

int main(int argc, char const *argv[])
{
    int num; // 公共资源
    pthread_t t1, t2, t3;
    pthread_create(&t1, NULL, read_task, &num);
    pthread_create(&t2, NULL, read_task, &num);
    pthread_create(&t3, NULL, write_task, &num);

    pthread_join(t1, NULL);
    pthread_join(t2, NULL);
    pthread_join(t3, NULL);

    pthread_rwlock_destroy(&rwlock); // 销毁读写锁

    return 0;
}