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RIOT/sys/posix/pthread/include/pthread_once.h 1.5 KB
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  /*
   * Copyright (C) 2014 René Kijewski <rene.kijewski@fu-berlin.de>
   *
   * This file is subject to the terms and conditions of the GNU Lesser
   * General Public License v2.1. See the file LICENSE in the top level
   * directory for more details.
   */
  
  /**
   * @ingroup pthread
   * @{
   * @file
   * @brief   Singletons features / single-shot execution.
   * @note    Do not include this header file directly, but pthread.h.
   */
  
  #ifndef PTHREAD_ONCE_H
  #define PTHREAD_ONCE_H
  
  #ifdef __cplusplus
  extern "C" {
  #endif
  
  /**
   * @brief           Datatype to supply to pthread_once().
   */
  typedef volatile int pthread_once_t;
  
  /**
   * @def             PTHREAD_ONCE_INIT
   * @brief           Initialization for pthread_once_t.
   * @details         A zeroed out pthread_once_t is initialized.
   */
  #define PTHREAD_ONCE_INIT 0
  
  /**
   * @brief           Helper function that ensures that `init_routine` is called at once.
   * @details         Calling pthread_once() changes `once_control`.
   *                  For the same `once_control` the supplied `init_routine` won't get called again,
   *                  unless `once_control` is reset to #PTHREAD_ONCE_INIT or zeroed out.
   * @param[in,out]   once_control   Flag to ensure that the `init_routine` is called only once.
   * @param[in]       init_routine   Function to call if `once_control` was not used, yet.
   * @returns         0, this invocation cannot fail.
   */
  int pthread_once(pthread_once_t *once_control, void (*init_routine)(void));
  
  #ifdef __cplusplus
  }
  #endif
  
  #endif /* PTHREAD_ONCE_H */
  
  /**
   * @}
   */