#include <pthread.h>
#include <semaphore.h>
#include <stdatomic.h>

typedef struct rw_lock{
  atomic_int reader_count;
  sem_t writer_semaphore;
  pthread_mutex_t count_sem_guard;
} rw_lock_t;

void write_lock(rw_lock_t *l){
  sem_wait(&l->writer_semaphore);
}

void write_unlock(rw_lock_t *l){
  sem_post(&l->writer_semaphore);
}

void read_lock(rw_lock_t *l){
  pthread_mutex_lock(&l->count_sem_guard);
  if (atomic_fetch_add(&l->reader_count,1) == 0)
    write_lock(l);
  pthread_mutex_unlock(&l->count_sem_guard);
}

void read_unlock(rw_lock_t *l){
  if (atomic_fetch_add(&l->reader_count,-1) == 0)
    //is this racy? Let's think!
    write_unlock(l);
}

typedef struct rw_lock_writer{
  
} rw_lock_writer_t ;

int main(){
  
}