1 #ifndef CCAN_CAST_IF_TYPE_H
2 #define CCAN_CAST_IF_TYPE_H
5 #if HAVE_TYPEOF && HAVE_BUILTIN_CHOOSE_EXPR && HAVE_BUILTIN_TYPES_COMPATIBLE_P
7 * cast_if_type - only cast an expression if test matches a given type
8 * @desttype: the type to cast to
9 * @expr: the expression to cast
10 * @test: the expression to test
11 * @oktype: the type we allow
13 * This macro is used to create functions which allow multiple types.
14 * The result of this macro is used somewhere that a @desttype type is
15 * expected: if @test is exactly of type @oktype, then @expr will be
16 * cast to @desttype type, otherwise left alone.
18 * This macro can be used in static initializers.
20 * This is merely useful for warnings: if the compiler does not
21 * support the primitives required for cast_if_type(), it becomes an
22 * unconditional cast, and the @test and @oktype argument is not used. In
23 * particular, this means that @oktype can be a type which uses
24 * the "typeof": it will not be evaluated if typeof is not supported.
27 * // We can take either an unsigned long or a void *.
28 * void _set_some_value(void *val);
29 * #define set_some_value(e) \
30 * _set_some_value(cast_if_type(void *, (e), (e), unsigned long))
32 #define cast_if_type(desttype, expr, test, oktype) \
33 __builtin_choose_expr(__builtin_types_compatible_p(typeof(test), oktype), \
34 (desttype)(expr), (expr))
36 #define cast_if_type(desttype, expr, test, oktype) ((desttype)(expr))
40 * cast_if_any - only cast an expression if it is one of the three given types
41 * @desttype: the type to cast to
42 * @expr: the expression to cast
43 * @test: the expression to test
44 * @ok1: the first type we allow
45 * @ok2: the second type we allow
46 * @ok3: the third type we allow
48 * This is a convenient wrapper for multiple cast_if_type() calls. You can
49 * chain them inside each other (ie. use cast_if_any() for expr) if you need
50 * more than 3 arguments.
53 * // We can take either a long, unsigned long, void * or a const void *.
54 * void _set_some_value(void *val);
55 * #define set_some_value(expr) \
56 * _set_some_value(cast_if_any(void *, (expr), (expr), \
57 * long, unsigned long, const void *))
59 #define cast_if_any(desttype, expr, test, ok1, ok2, ok3) \
60 cast_if_type(desttype, \
61 cast_if_type(desttype, \
62 cast_if_type(desttype, (expr), (test), ok1), \
69 * typesafe_cb - cast a callback function if it matches the arg
70 * @rtype: the return type of the callback function
71 * @fn: the callback function to cast
72 * @arg: the (pointer) argument to hand to the callback function.
74 * If a callback function takes a single argument, this macro does
75 * appropriate casts to a function which takes a single void * argument if the
76 * callback provided matches the @arg (or a const or volatile version).
78 * It is assumed that @arg is of pointer type: usually @arg is passed
79 * or assigned to a void * elsewhere anyway.
81 * This will not work with a NULL @fn argument: see typesafe_cb_def or
85 * void _register_callback(void (*fn)(void *arg), void *arg);
86 * #define register_callback(fn, arg) \
87 * _register_callback(typesafe_cb(void, (fn), (arg)), (arg))
89 #define typesafe_cb(rtype, fn, arg) \
90 cast_if_type(rtype (*)(void *), (fn), (fn)(arg), rtype)
93 * typesafe_cb_def - cast a callback fn if it matches arg (of defined type)
94 * @rtype: the return type of the callback function
95 * @fn: the callback function to cast
96 * @arg: the (pointer) argument to hand to the callback function.
98 * This is typesafe_cb(), except the type must be defined (eg. if it's
99 * struct foo *, the definition of struct foo must be visible). For many
100 * applications, this is reasonable.
102 * This variant can accept @fn equal to NULL.
105 * void _register_callback(void (*fn)(void *arg), void *arg);
106 * #define register_callback(fn, arg) \
107 * _register_callback(typesafe_cb_def(void, (fn), (arg)), (arg))
109 #define typesafe_cb_def(rtype, fn, arg) \
110 cast_if_any(rtype (*)(void *), (fn), (fn)+0, \
111 rtype (*)(typeof(*arg)*), \
112 rtype (*)(const typeof(*arg)*), \
113 rtype (*)(volatile typeof(*arg)*))
116 * typesafe_cb_exact - cast a callback fn if it exactly matches arg
117 * @rtype: the return type of the callback function
118 * @fn: the callback function to cast
119 * @arg: the (pointer) argument to hand to the callback function.
121 * This is typesafe_cb(), except the @fn can be NULL, or must exactly match
122 * the @arg type (no const or volatile).
125 * void _register_callback(void (*fn)(void *arg), void *arg);
126 * #define register_callback(fn, arg) \
127 * _register_callback(typesafe_cb_exact(void, (fn), (arg)), (arg))
129 #define typesafe_cb_exact(rtype, fn, arg) \
130 cast_if_type(rtype (*)(void *), (fn), (fn)+0, rtype (*)(typeof(arg)))
133 * typesafe_cb_const - cast a const callback function if it matches the arg
134 * @rtype: the return type of the callback function
135 * @fn: the callback function to cast
136 * @arg: the (pointer) argument to hand to the callback function.
138 * If a callback function takes a single argument, this macro does appropriate
139 * casts to a function which takes a single const void * argument if the
140 * callback provided matches the @arg.
142 * It is assumed that @arg is of pointer type: usually @arg is passed
143 * or assigned to a void * elsewhere anyway.
146 * void _register_callback(void (*fn)(const void *arg), const void *arg);
147 * #define register_callback(fn, arg) \
148 * _register_callback(typesafe_cb_const(void, (fn), (arg)), (arg))
150 #define typesafe_cb_const(rtype, fn, arg) \
151 cast_if_type(rtype (*)(const void *), (fn), (fn)(arg), rtype)
154 * typesafe_cb_preargs - cast a callback function if it matches the arg
155 * @rtype: the return type of the callback function
156 * @fn: the callback function to cast
157 * @arg: the (pointer) argument to hand to the callback function.
159 * This is a version of typesafe_cb() for callbacks that take other arguments
163 * void _register_callback(void (*fn)(int, void *arg), void *arg);
164 * #define register_callback(fn, arg) \
165 * _register_callback(typesafe_cb_preargs(void, (fn), (arg), int),\
168 #define typesafe_cb_preargs(rtype, fn, arg, ...) \
169 cast_if_type(rtype (*)(__VA_ARGS__, void *), (fn), (fn)+0, \
170 rtype (*)(__VA_ARGS__, typeof(arg)))
173 * typesafe_cb_postargs - cast a callback function if it matches the arg
174 * @rtype: the return type of the callback function
175 * @fn: the callback function to cast
176 * @arg: the (pointer) argument to hand to the callback function.
178 * This is a version of typesafe_cb() for callbacks that take other arguments
182 * void _register_callback(void (*fn)(void *arg, int), void *arg);
183 * #define register_callback(fn, arg) \
184 * _register_callback(typesafe_cb_postargs(void, (fn), (arg), int),\
187 #define typesafe_cb_postargs(rtype, fn, arg, ...) \
188 cast_if_type(rtype (*)(void *, __VA_ARGS__), (fn), (fn)+0, \
189 rtype (*)(typeof(arg), __VA_ARGS__))
192 * typesafe_cb_cmp - cast a compare function if it matches the arg
193 * @rtype: the return type of the callback function
194 * @fn: the callback function to cast
195 * @arg: the (pointer) argument(s) to hand to the compare function.
197 * If a callback function takes two matching-type arguments, this macro does
198 * appropriate casts to a function which takes two const void * arguments if
199 * the callback provided takes two a const pointers to @arg.
201 * It is assumed that @arg is of pointer type: usually @arg is passed
202 * or assigned to a void * elsewhere anyway. Note also that the type
203 * arg points to must be defined.
206 * void _my_qsort(void *base, size_t nmemb, size_t size,
207 * int (*cmp)(const void *, const void *));
208 * #define my_qsort(base, nmemb, cmpfn) \
209 * _my_qsort((base), (nmemb), sizeof(*(base)), \
210 * typesafe_cb_cmp(int, (cmpfn), (base)), (arg))
212 #define typesafe_cb_cmp(rtype, cmpfn, arg) \
213 cast_if_type(rtype (*)(const void *, const void *), (cmpfn), (cmpfn)+0, \
214 rtype (*)(const typeof(*arg)*, const typeof(*arg)*))
216 #endif /* CCAN_CAST_IF_TYPE_H */