text: #ifndef foopulseoncehfoo
  #define foopulseoncehfoo
  
  /***
    This file is part of PulseAudio.
  
    Copyright 2006 Lennart Poettering
  
    PulseAudio is free software; you can redistribute it and/or modify
    it under the terms of the GNU Lesser General Public License as
    published by the Free Software Foundation; either version 2.1 of the
    License, or (at your option) any later version.
  
    PulseAudio is distributed in the hope that it will be useful, but
    WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
    General Public License for more details.
  
    You should have received a copy of the GNU Lesser General Public
    License along with PulseAudio; if not, see <http://www.gnu.org/licenses/>.
  ***/
  
  #include <pulsecore/atomic.h>
  #include <pulsecore/mutex.h>
  
  typedef struct pa_once {
      pa_static_mutex mutex;
      pa_atomic_t done;
  } pa_once;
  
  #define PA_ONCE_INIT                                                    \
      {                                                                   \
          .mutex = PA_STATIC_MUTEX_INIT,                                  \
          .done = PA_ATOMIC_INIT(0)                                       \
      }
  
  /* Not to be called directly, use the macros defined below instead */
  bool pa_once_begin(pa_once *o);
  void pa_once_end(pa_once *o);
  
  #define PA_ONCE_BEGIN                                                   \
      do {                                                                \
          static pa_once _once = PA_ONCE_INIT;                            \
          if (pa_once_begin(&_once)) {{
  
  #define PA_ONCE_END                                                     \
              }                                                           \
              pa_once_end(&_once);                                        \
          }                                                               \
      } while(0)
  
  /*
  
    Usage of these macros is like this:
  
    void foo() {
  
        PA_ONCE_BEGIN {
  
            ... stuff to be called just once ...
  
        } PA_ONCE_END;
    }
  
  */
  
  /* Same API but calls a function */
  typedef void (*pa_once_func_t) (void);
  void pa_run_once(pa_once *o, pa_once_func_t f);
  
  #endif
  