#include <stdio.h>

#include <uv.h>

uv_barrier_t blocker;

uv_rwlock_t numlock;

int shared_num;

void reader(void *n)

{

    int num = *(int *)n;

    int i;

    for (i = 0; i < 20; i++) {

        uv_rwlock_rdlock(&numlock);

        printf("Reader %d: acquired lock\n", num);

        printf("Reader %d: shared num = %d\n", num, shared_num);

        uv_rwlock_rdunlock(&numlock);

        printf("Reader %d: released lock\n", num);

    }

    uv_barrier_wait(&blocker);

}

void writer(void *n)

{

    int num = *(int *)n;

    int i;

    for (i = 0; i < 20; i++) {

        uv_rwlock_wrlock(&numlock);

        printf("Writer %d: acquired lock\n", num);

        shared_num++;

        printf("Writer %d: incremented shared num = %d\n", num, shared_num);

        uv_rwlock_wrunlock(&numlock);

        printf("Writer %d: released lock\n", num);

    }

    uv_barrier_wait(&blocker);

}

int main()

{

    uv_barrier_init(&blocker, 4);

    shared_num = 0;

    uv_rwlock_init(&numlock);

    uv_thread_t threads[3];

    int thread_nums[] = {1, 2, 1};

    uv_thread_create(&threads[0], reader, &thread_nums[0]);

    uv_thread_create(&threads[1], reader, &thread_nums[1]);

    uv_thread_create(&threads[2], writer, &thread_nums[2]);

    uv_barrier_wait(&blocker);

    uv_barrier_destroy(&blocker);

    uv_rwlock_destroy(&numlock);

    return 0;

}