X-Git-Url: http://git.ozlabs.org/?p=ccan;a=blobdiff_plain;f=ccan%2Ftypesafe_cb%2Ftypesafe_cb.h;h=7347b7b2912c20291bfbdd9adfdcbb430334c07c;hp=0eb57d9524b2771e7cf3b43ba089e91fbd8c5992;hb=37e247dbcb57f4b2effd44b37b96dc679ee525d0;hpb=517114490e7153643b4c0a12c59a060568d7ae00

diff --git a/ccan/typesafe_cb/typesafe_cb.h b/ccan/typesafe_cb/typesafe_cb.h
index 0eb57d95..7347b7b2 100644
--- a/ccan/typesafe_cb/typesafe_cb.h
+++ b/ccan/typesafe_cb/typesafe_cb.h
@@ -4,38 +4,67 @@
 
 #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
+ * cast_if_type - only cast an expression if test matches a given type
+ * @desttype: the type to cast to
  * @expr: the expression to cast
+ * @test: the expression to test
  * @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
- * expected: if @expr was of type @oktype, it will be cast to
- * @desttype type.  As a result, if @expr is any type other than
- * @oktype or @desttype, a compiler warning will be issued.
+ * expected: if @test is exactly of type @oktype, then @expr will be
+ * cast to @desttype type, otherwise left alone.
  *
  * This macro can be used in static initializers.
  *
  * This is merely useful for warnings: if the compiler does not
  * support the primitives required for cast_if_type(), it becomes an
- * unconditional cast, and the @oktype argument is not used.  In
+ * unconditional cast, and the @test and @oktype argument is not used.  In
  * particular, this means that @oktype can be a type which uses
  * the "typeof": it will not be evaluated if typeof is not supported.
  *
  * Example:
  *	// 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 *))
+ *	#define set_some_value(e)			\
+ *		_set_some_value(cast_if_type(void *, (e), (e), unsigned long))
  */
-#define cast_if_type(expr, oktype, desttype)				\
-__builtin_choose_expr(__builtin_types_compatible_p(typeof(1?(expr):0), oktype), \
+#define cast_if_type(desttype, expr, test, oktype)			\
+	__builtin_choose_expr(__builtin_types_compatible_p(typeof(test), oktype), \
 			(desttype)(expr), (expr))
 #else
-#define cast_if_type(expr, oktype, desttype) ((desttype)(expr))
+#define cast_if_type(desttype, expr, test, 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
+ * @test: the expression to test
+ * @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), (expr),	\
+ *					    long, unsigned long, const void *))
+ */
+#define cast_if_any(desttype, expr, test, ok1, ok2, ok3)		\
+	cast_if_type(desttype,						\
+		     cast_if_type(desttype,				\
+				  cast_if_type(desttype, (expr), (test), ok1), \
+				  (test),				\
+				  ok2),					\
+		     (test),						\
+		     ok3)
+
 /**
  * typesafe_cb - cast a callback function if it matches the arg
  * @rtype: the return type of the callback function
@@ -49,19 +78,56 @@ __builtin_choose_expr(__builtin_types_compatible_p(typeof(1?(expr):0), oktype),
  * It is assumed that @arg is of pointer type: usually @arg is passed
  * or assigned to a void * elsewhere anyway.
  *
+ * This will not work with a NULL @fn argument: see typesafe_cb_def or
+ * typesafe_cb_exact.
+ *
  * Example:
  *	void _register_callback(void (*fn)(void *arg), void *arg);
  *	#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_type(rtype (*)(void *), (fn), (fn)(arg), rtype)
+
+/**
+ * typesafe_cb_def - cast a callback fn if it matches arg (of defined type)
+ * @rtype: the return type of the callback function
+ * @fn: the callback function to cast
+ * @arg: the (pointer) argument to hand to the callback function.
+ *
+ * This is typesafe_cb(), except the type must be defined (eg. if it's
+ * struct foo *, the definition of struct foo must be visible).  For many
+ * applications, this is reasonable.
+ *
+ * This variant can accept @fn equal to NULL.
+ *
+ * Example:
+ *	void _register_callback(void (*fn)(void *arg), void *arg);
+ *	#define register_callback(fn, arg) \
+ *		_register_callback(typesafe_cb_def(void, (fn), (arg)), (arg))
+ */
+#define typesafe_cb_def(rtype, fn, arg)			\
+	cast_if_any(rtype (*)(void *), (fn), (fn)+0,	\
+		    rtype (*)(typeof(*arg)*),		\
+		    rtype (*)(const typeof(*arg)*),	\
+		    rtype (*)(volatile typeof(*arg)*))
+
+/**
+ * typesafe_cb_exact - cast a callback fn if it exactly matches 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.
+ *
+ * This is typesafe_cb(), except the @fn can be NULL, or must exactly match
+ * the @arg type (no const or volatile).
+ *
+ * Example:
+ *	void _register_callback(void (*fn)(void *arg), void *arg);
+ *	#define register_callback(fn, arg) \
+ *		_register_callback(typesafe_cb_exact(void, (fn), (arg)), (arg))
+ */
+#define typesafe_cb_exact(rtype, fn, arg)				\
+	cast_if_type(rtype (*)(void *), (fn), (fn)+0, rtype (*)(typeof(arg)))
 
 /**
  * typesafe_cb_const - cast a const callback function if it matches the arg
@@ -81,9 +147,8 @@ __builtin_choose_expr(__builtin_types_compatible_p(typeof(1?(expr):0), oktype),
  *	#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 *))
+#define typesafe_cb_const(rtype, fn, arg)			\
+	cast_if_type(rtype (*)(const void *), (fn), (fn)(arg), rtype)
 
 /**
  * typesafe_cb_preargs - cast a callback function if it matches the arg
@@ -101,16 +166,8 @@ __builtin_choose_expr(__builtin_types_compatible_p(typeof(1?(expr):0), oktype),
  *				   (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_type(rtype (*)(__VA_ARGS__, void *), (fn), (fn)+0,	\
+		     rtype (*)(__VA_ARGS__, typeof(arg)))
 
 /**
  * typesafe_cb_postargs - cast a callback function if it matches the arg
@@ -124,20 +181,12 @@ __builtin_choose_expr(__builtin_types_compatible_p(typeof(1?(expr):0), oktype),
  * 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_type(rtype (*)(void *, __VA_ARGS__), (fn), (fn)+0,	\
+		     rtype (*)(typeof(arg), __VA_ARGS__))
 
 /**
  * typesafe_cb_cmp - cast a compare function if it matches the arg
@@ -150,7 +199,8 @@ __builtin_choose_expr(__builtin_types_compatible_p(typeof(1?(expr):0), oktype),
  * 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.
+ * or assigned to a void * elsewhere anyway.  Note also that the type
+ * arg points to must be defined.
  *
  * Example:
  *	void _my_qsort(void *base, size_t nmemb, size_t size,
@@ -160,7 +210,7 @@ __builtin_choose_expr(__builtin_types_compatible_p(typeof(1?(expr):0), oktype),
  *			  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 *))
+	cast_if_type(rtype (*)(const void *, const void *), (cmpfn), (cmpfn)+0, \
+		     rtype (*)(const typeof(*arg)*, const typeof(*arg)*))
+		     
 #endif /* CCAN_CAST_IF_TYPE_H */