#if HAVE_TYPEOF && HAVE_BUILTIN_CHOOSE_EXPR && HAVE_BUILTIN_TYPES_COMPATIBLE_P
/**
* cast_if_type - only cast an expression if it is of a given type
+ * @desttype: the type to cast to
* @expr: the expression to cast
* @oktype: the type we allow
- * @desttype: the type to cast to
*
* This macro is used to create functions which allow multiple types.
* The result of this macro is used somewhere that a @desttype type is
* // We can take either an unsigned long or a void *.
* void _set_some_value(void *val);
* #define set_some_value(expr) \
- * _set_some_value(cast_if_type((expr), unsigned long, void *))
+ * _set_some_value(cast_if_type(void *, (expr), unsigned long))
*/
-#define cast_if_type(expr, oktype, desttype) \
+#define cast_if_type(desttype, expr, oktype) \
__builtin_choose_expr(__builtin_types_compatible_p(typeof(1?(expr):0), oktype), \
(desttype)(expr), (expr))
#else
-#define cast_if_type(expr, oktype, desttype) ((desttype)(expr))
+#define cast_if_type(desttype, expr, oktype) ((desttype)(expr))
#endif
+/**
+ * cast_if_any - only cast an expression if it is one of the three given types
+ * @desttype: the type to cast to
+ * @expr: the expression to cast
+ * @ok1: the first type we allow
+ * @ok2: the second type we allow
+ * @ok3: the third type we allow
+ *
+ * This is a convenient wrapper for multiple cast_if_type() calls. You can
+ * chain them inside each other (ie. use cast_if_any() for expr) if you need
+ * more than 3 arguments.
+ *
+ * Example:
+ * // We can take either a long, unsigned long, void * or a const void *.
+ * void _set_some_value(void *val);
+ * #define set_some_value(expr) \
+ * _set_some_value(cast_if_any(void *, (expr), \
+ * long, unsigned long, const void *))
+ */
+#define cast_if_any(desttype, expr, ok1, ok2, ok3) \
+ cast_if_type(desttype, \
+ cast_if_type(desttype, \
+ cast_if_type(desttype, (expr), ok1), \
+ ok2), \
+ ok3)
+
/**
* typesafe_cb - cast a callback function if it matches the arg
* @rtype: the return type of the callback function
* #define register_callback(fn, arg) \
* _register_callback(typesafe_cb(void, (fn), (arg)), (arg))
*/
-#define typesafe_cb(rtype, fn, arg) \
- cast_if_type(cast_if_type(cast_if_type((fn), \
- rtype (*)(const typeof(*arg)*), \
- rtype (*)(void *)), \
- rtype (*)(volatile typeof(*arg) *), \
- rtype (*)(void *)), \
- rtype (*)(typeof(arg)), \
- rtype (*)(void *))
+#define typesafe_cb(rtype, fn, arg) \
+ cast_if_any(rtype (*)(void *), (fn), \
+ rtype (*)(typeof(*arg)*), \
+ rtype (*)(const typeof(*arg)*), \
+ rtype (*)(volatile typeof(*arg)*))
+
+/**
+ * typesafe_cb_const - cast a const callback function if it matches the arg
+ * @rtype: the return type of the callback function
+ * @fn: the callback function to cast
+ * @arg: the (pointer) argument to hand to the callback function.
+ *
+ * If a callback function takes a single argument, this macro does appropriate
+ * casts to a function which takes a single const void * argument if the
+ * callback provided matches the @arg.
+ *
+ * It is assumed that @arg is of pointer type: usually @arg is passed
+ * or assigned to a void * elsewhere anyway.
+ *
+ * Example:
+ * void _register_callback(void (*fn)(const void *arg), const void *arg);
+ * #define register_callback(fn, arg) \
+ * _register_callback(typesafe_cb_const(void, (fn), (arg)), (arg))
+ */
+#define typesafe_cb_const(rtype, fn, arg) \
+ cast_if_type(rtype (*)(const void *), (fn), \
+ rtype (*)(const typeof(*arg)*))
/**
* typesafe_cb_preargs - cast a callback function if it matches the arg
* (arg))
*/
#define typesafe_cb_preargs(rtype, fn, arg, ...) \
- cast_if_type(cast_if_type(cast_if_type((fn), \
- rtype (*)(__VA_ARGS__, \
- const typeof(*arg) *),\
- rtype (*)(__VA_ARGS__, \
- void *)), \
- rtype (*)(__VA_ARGS__, \
- volatile typeof(*arg) *), \
- rtype (*)(__VA_ARGS__, void *)), \
- rtype (*)(__VA_ARGS__, typeof(arg)), \
- rtype (*)(__VA_ARGS__, void *))
+ cast_if_any(rtype (*)(__VA_ARGS__, void *), (fn), \
+ rtype (*)(__VA_ARGS__, typeof(arg)), \
+ rtype (*)(__VA_ARGS__, const typeof(*arg) *), \
+ rtype (*)(__VA_ARGS__, volatile typeof(*arg) *))
/**
* typesafe_cb_postargs - cast a callback function if it matches the arg
* Example:
* void _register_callback(void (*fn)(void *arg, int), void *arg);
* #define register_callback(fn, arg) \
- * _register_callback(typesafe_cb_preargs(void, (fn), (arg), int),\
+ * _register_callback(typesafe_cb_postargs(void, (fn), (arg), int),\
* (arg))
*/
#define typesafe_cb_postargs(rtype, fn, arg, ...) \
- cast_if_type(cast_if_type(cast_if_type((fn), \
- rtype (*)(const typeof(*arg) *, \
- __VA_ARGS__), \
- rtype (*)(void *, \
- __VA_ARGS__)), \
- rtype (*)(volatile typeof(*arg) *, \
- __VA_ARGS__), \
- rtype (*)(void *, __VA_ARGS__)), \
- rtype (*)(typeof(arg), __VA_ARGS__), \
- rtype (*)(void *, __VA_ARGS__))
+ cast_if_any(rtype (*)(void *, __VA_ARGS__), (fn), \
+ rtype (*)(typeof(arg), __VA_ARGS__), \
+ rtype (*)(const typeof(*arg) *, __VA_ARGS__), \
+ rtype (*)(volatile typeof(*arg) *, __VA_ARGS__))
+/**
+ * typesafe_cb_cmp - cast a compare function if it matches the arg
+ * @rtype: the return type of the callback function
+ * @fn: the callback function to cast
+ * @arg: the (pointer) argument(s) to hand to the compare function.
+ *
+ * If a callback function takes two matching-type arguments, this macro does
+ * appropriate casts to a function which takes two const void * arguments if
+ * the callback provided takes two a const pointers to @arg.
+ *
+ * It is assumed that @arg is of pointer type: usually @arg is passed
+ * or assigned to a void * elsewhere anyway.
+ *
+ * Example:
+ * void _my_qsort(void *base, size_t nmemb, size_t size,
+ * int (*cmp)(const void *, const void *));
+ * #define my_qsort(base, nmemb, cmpfn) \
+ * _my_qsort((base), (nmemb), sizeof(*(base)), \
+ * typesafe_cb_cmp(int, (cmpfn), (base)), (arg))
+ */
+#define typesafe_cb_cmp(rtype, cmpfn, arg) \
+ cast_if_type(rtype (*)(const void *, const void *), (cmpfn), \
+ rtype (*)(const typeof(*arg)*, const typeof(*arg)*))
+
#endif /* CCAN_CAST_IF_TYPE_H */
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