enumerator: Add venumerate() method to enumerator_t that takes a va_list

This will allow us to implement e.g. enumerator_cleaner without having to
use that unportable 5 pointer forwarding or having to define a callback for
each instance.

A generic implementation for enumerate() is provided so only venumerate()
has to be implemented, which may be simplified by using the VA_ARGS_VGET()
macro.

src/libstrongswan/collections/enumerator.c

@@ -1,7 +1,7 @@
 /*
- * Copyright (C) 2008-2013 Tobias Brunner
+ * Copyright (C) 2008-2017 Tobias Brunner
  * Copyright (C) 2007 Martin Willi
- * Hochschule fuer Technik Rapperswil
+ * HSR Hochschule fuer Technik Rapperswil
  *
  * This program is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License as published by the
@@ -31,6 +31,25 @@
 
 #include <utils/debug.h>
 
+/*
+ * Described in header.
+ */
+bool enumerator_enumerate_default(enumerator_t *enumerator, ...)
+{
+	va_list args;
+	bool result;
+
+	if (!enumerator->venumerate)
+	{
+		DBG1(DBG_LIB, "!!! ENUMERATE DEFAULT: venumerate() missing !!!");
+		return FALSE;
+	}
+	va_start(args, enumerator);
+	result = enumerator->venumerate(enumerator, args);
+	va_end(args);
+	return result;
+}
+
 /**
  * Implementation of enumerator_create_empty().enumerate
  */
@@ -646,4 +665,3 @@ enumerator_t *enumerator_create_single(void *item, void (*cleanup)(void *item))
 
 	return &this->public;
 }
-

src/libstrongswan/collections/enumerator.h

@@ -1,7 +1,7 @@
 /*
- * Copyright (C) 2013 Tobias Brunner
+ * Copyright (C) 2013-2017 Tobias Brunner
  * Copyright (C) 2007 Martin Willi
- * Hochschule fuer Technik Rapperswil
+ * HSR Hochschule fuer Technik Rapperswil
  *
  * This program is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License as published by the
@@ -34,8 +34,11 @@ struct enumerator_t {
 	/**
 	 * Enumerate collection.
 	 *
-	 * The enumerate function takes a variable argument list containing
+	 * The enumerate() method takes a variable number of pointer arguments
-	 * pointers where the enumerated values get written.
+	 * where the enumerated values get written to.
+	 *
+	 * @note Just assigning the generic enumerator_enumerate_default() function
+	 * that calls the enumerator's venumerate() method is usually enough.
 	 *
 	 * @param ...	variable list of enumerated items, implementation dependent
 	 * @return		TRUE if pointers returned
@@ -43,11 +46,33 @@ struct enumerator_t {
 	bool (*enumerate)(enumerator_t *this, ...);
 
 	/**
-	 * Destroy a enumerator instance.
+	 * Enumerate collection.
+	 *
+	 * The venumerate() method takes a variable argument list containing
+	 * pointers where the enumerated values get written to.
+	 *
+	 * To simplify the implementation the VA_ARGS_VGET() macro may be used.
+	 *
+	 * @param args	variable list of enumerated items, implementation dependent
+	 * @return		TRUE if pointers returned
+	 */
+	bool (*venumerate)(enumerator_t *this, va_list args);
+
+	/**
+	 * Destroy an enumerator_t instance.
 	 */
 	void (*destroy)(enumerator_t *this);
 };
 
+/**
+ * Generic implementation of enumerator_t::enumerate() that simply calls
+ * the enumerator's venumerate() method.
+ *
+ * @param enumerator	the enumerator
+ * @param ...			arguments passed to enumerate()
+ */
+bool enumerator_enumerate_default(enumerator_t *enumerator, ...);
+
 /**
  * Create an enumerator which enumerates over nothing
  *