/*
 * once.c
 *
 * Demonstrate the use of pthread_once() one-time
 * initialization.
 */
#include <pthread.h>
#include "errors.h"

pthread_once_t once_block = PTHREAD_ONCE_INIT;
pthread_mutex_t mutex;

/*
 * This is the one-time initialization routine. It will be
 * called exactly once, no matter how many calls to pthread_once
 * with the same control structure are made during the course of
 * the program.
 */
void
once_init_routine(void)
{
  int status;

  status = pthread_mutex_init(&mutex, NULL);
  if (status != 0)
    err_abort(status, "Init Mutex");
}

/*
 * Thread start routine that calls pthread_once.
 */
void*
thread_routine(void* arg)
{
  int status;

  status = pthread_once(&once_block, once_init_routine);
  if (status != 0)
    err_abort(status, "Once init");
  status = pthread_mutex_lock(&mutex);
  if (status != 0)
    err_abort(status, "Lock mutex");
  printf("thread_routine has locked the mutex.\n");
  status = pthread_mutex_unlock(&mutex);
  if (status != 0)
    err_abort(status, "Unlock mutex");
  return NULL;
}

int
main(int argc, char* argv[])
{
  pthread_t thread_id;
  char *input, buffer[64];
  int status;

  status = pthread_create(&thread_id, NULL, thread_routine, NULL);
  if (status != 0)
    err_abort(status, "Create thread");
  status = pthread_once(&once_block, once_init_routine);
  if (status != 0)
    err_abort(status, "Once init");
  status = pthread_mutex_lock(&mutex);
  if (status != 0)
    err_abort(status, "Lock mutex");
  printf("Main has locked the mutex.\n");
  status = pthread_mutex_unlock(&mutex);
  if (status != 0)
    err_abort(status, "Unlock mutex");
  status = pthread_join(thread_id, NULL);
  if (status != 0)
    err_abort(status, "Join thread");
  return 0;
}