#include <errno.h>
#include <pthread.h>

static pthread_rwlock_t listlock;
static int lockiniterror = 0;
static pthread_once_t lockisinitialized = PTHREAD_ONCE_INIT;
 
static void ilock(void) {
   lockiniterror = pthread_rwlock_init(&listlock, NULL);
}

int initialize_r(void) {    /* must be called at least once before using list */
   if (pthread_once(&lockisinitialized, ilock))
      lockiniterror = EINVAL;
   return lockiniterror;
}

int accessdata_r(void) {               /* get a nonnegative key if successful */ 
   int error;
   int errorkey = 0;
   int key;
   if (error = pthread_rwlock_wrlock(&listlock)) {  /* no write lock, give up */
      errno = error;
      return -1;
   }
   key = accessdata();
   if (key == -1) {
      errorkey = errno;
      pthread_rwlock_unlock(&listlock);
      errno = errorkey;
      return -1;
   }
   if (error = pthread_rwlock_unlock(&listlock)) {  
      errno = error;
      return -1;
   }
   return key;
}

int adddata_r(data_t data) {          /* allocate a node on list to hold data */
   int error;
   if (error = pthread_rwlock_wrlock(&listlock)) { /* no writer lock, give up */
      errno = error;
      return -1;
   }
   if (adddata(data) == -1) {
      error = errno;
      pthread_rwlock_unlock(&listlock); 
      errno = error;
      return -1;
   }
   if (error = pthread_rwlock_unlock(&listlock)) {  
      errno = error;
      return -1;
   }
   return 0;
}

int getdata_r(int key, data_t *datap) {               /* retrieve node by key */
   int error;
   if (error = pthread_rwlock_rdlock(&listlock)) { /* no reader lock, give up */
      errno = error;
      return -1;
   }
   if (getdata(key, datap) == -1) {
      error = errno;
      pthread_rwlock_unlock(&listlock); 
      errno = error;
      return -1;
   }
   if (error = pthread_rwlock_unlock(&listlock)) { 
      errno = error;
      return -1;
   }
   return 0;
}

int freekey_r(int key) {                                      /* free the key */
   int error;
   if (error = pthread_rwlock_wrlock(&listlock)) {
      errno = error;
      return -1;
   }
   if (freekey(key) == -1) {
      error = errno;
      pthread_rwlock_unlock(&listlock);
      errno = error; 
      return -1;
   } 
   if (error = pthread_rwlock_unlock(&listlock)) {
      errno = error;
      return -1;
   }  
   return 0;
}