text: /*
    Copyright 2016 David Robillard <http://drobilla.net>
  
    Permission to use, copy, modify, and/or distribute this software for any
    purpose with or without fee is hereby granted, provided that the above
    copyright notice and this permission notice appear in all copies.
  
    THIS SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
    WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
    MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
    ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
    WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
    ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  */
  
  /**
     @defgroup util Utilities
     @ingroup lv2core
     @{
  */
  
  #include "lv2/core/lv2.h"
  
  #include <stdarg.h>
  #include <stdbool.h>
  #include <string.h>
  
  #ifdef __cplusplus
  extern "C" {
  #endif
  
  /**
     Return the data for a feature in a features array.
  
     If the feature is not found, NULL is returned.  Note that this function is
     only useful for features with data, and can not detect features that are
     present but have NULL data.
  */
  static inline void*
  lv2_features_data(const LV2_Feature*const* features,
                    const char* const        uri)
  {
  	if (features) {
  		for (const LV2_Feature*const* f = features; *f; ++f) {
  			if (!strcmp(uri, (*f)->URI)) {
  				return (*f)->data;
  			}
  		}
  	}
  	return NULL;
  }
  
  /**
     Query a features array.
  
     This function allows getting several features in one call, and detect
     missing required features, with the same caveat of lv2_features_data().
  
     The arguments should be a series of const char* uri, void** data, bool
     required, terminated by a NULL URI.  The data pointers MUST be initialized
     to NULL.  For example:
  
     @code
     LV2_URID_Log* log = NULL;
     LV2_URID_Map* map = NULL;
     const char* missing = lv2_features_query(
          features,
          LV2_LOG__log,  &log, false,
          LV2_URID__map, &map, true,
          NULL);
     @endcode
  
     @return NULL on success, otherwise the URI of this missing feature.
  */
  static inline const char*
  lv2_features_query(const LV2_Feature* const* features, ...)
  {
  	va_list args;
  	va_start(args, features);
  
  	const char* uri = NULL;
  	while ((uri = va_arg(args, const char*))) {
  		void** data     = va_arg(args, void**);
  		bool   required = va_arg(args, int);
  
  		*data = lv2_features_data(features, uri);
  		if (required && !*data) {
  			return uri;
  		}
  	}
  
  	return NULL;
  }
  
  #ifdef __cplusplus
  }  /* extern "C" */
  #endif
  
  /**
     @}
     @}
  */
  