text: /* Copyright 2001-2005 The Apache Software Foundation or its licensors, as
   * applicable.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  #ifndef APR_OPTIONAL_H
  #define APR_OPTIONAL_H
  
  #include "apu.h"
  /** 
   * @file apr_optional.h
   * @brief APR-UTIL registration of functions exported by modules
   */
  #ifdef __cplusplus
  extern "C" {
  #endif
  
  /** 
   * @defgroup APR_Util_Opt Optional Functions
   * @ingroup APR_Util
   *
   * Typesafe registration and retrieval of functions that may not be present
   * (i.e. functions exported by optional modules)
   * @{
   */
  
  /**
   * The type of an optional function.
   * @param name The name of the function
   */
  #define APR_OPTIONAL_FN_TYPE(name) apr_OFN_##name##_t
  
  /**
   * Declare an optional function.
   * @param ret The return type of the function
   * @param name The name of the function
   * @param args The function arguments (including brackets)
   */
  #define APR_DECLARE_OPTIONAL_FN(ret,name,args) \
  typedef ret (APR_OPTIONAL_FN_TYPE(name)) args
  
  /**
   * XXX: This doesn't belong here, then!
   * Private function! DO NOT USE! 
   * @internal
   */
  
  typedef void (apr_opt_fn_t)(void);
  /** @internal */
  APU_DECLARE_NONSTD(void) apr_dynamic_fn_register(const char *szName, 
                                                    apr_opt_fn_t *pfn);
  
  /**
   * Register an optional function. This can be later retrieved, type-safely, by
   * name. Like all global functions, the name must be unique. Note that,
   * confusingly but correctly, the function itself can be static!
   * @param name The name of the function
   */
  #define APR_REGISTER_OPTIONAL_FN(name) do { \
    APR_OPTIONAL_FN_TYPE(name) *apu__opt = name; \
    apr_dynamic_fn_register(#name,(apr_opt_fn_t *)apu__opt); \
  } while (0)
  
  /** @internal
   * Private function! DO NOT USE! 
   */
  APU_DECLARE(apr_opt_fn_t *) apr_dynamic_fn_retrieve(const char *szName);
  
  /**
   * Retrieve an optional function. Returns NULL if the function is not present.
   * @param name The name of the function
   */
  #define APR_RETRIEVE_OPTIONAL_FN(name) \
  	(APR_OPTIONAL_FN_TYPE(name) *)apr_dynamic_fn_retrieve(#name)
  
  /** @} */
  #ifdef __cplusplus
  }
  #endif
  
  #endif /* APR_OPTIONAL_H */
  