typesafe_cb: more support for typesafe compare functions.

[ccan] / ccan / typesafe_cb / typesafe_cb.h

diff --git a/ccan/typesafe_cb/typesafe_cb.h b/ccan/typesafe_cb/typesafe_cb.h
index 594e894ad33e1b649f9fa3b184c81b9146b89d02..0eb57d9524b2771e7cf3b43ba089e91fbd8c5992 100644 (file)
--- a/ccan/typesafe_cb/typesafe_cb.h
+++ b/ccan/typesafe_cb/typesafe_cb.h
@@ -63,6 +63,28 @@ __builtin_choose_expr(__builtin_types_compatible_p(typeof(1?(expr):0), oktype),
                     rtype (*)(typeof(arg)),                            \
                     rtype (*)(void *))
 
+/**
+ * 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((fn),                                              \
+                    rtype (*)(const typeof(*arg)*), rtype (*)(const void *))
+
 /**
  * typesafe_cb_preargs - cast a callback function if it matches the arg
  * @rtype: the return type of the callback function
@@ -117,4 +139,28 @@ __builtin_choose_expr(__builtin_types_compatible_p(typeof(1?(expr):0), oktype),
                     rtype (*)(typeof(arg), __VA_ARGS__),               \
                     rtype (*)(void *, __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((cmpfn),                                           \
+                    rtype (*)(const typeof(*arg)*, const typeof(*arg)*), \
+                    rtype (*)(const void *, const void *))
 #endif /* CCAN_CAST_IF_TYPE_H */