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Diffstat (limited to 'ctdb/include/ctdb_typesafe_cb.h')
-rw-r--r-- | ctdb/include/ctdb_typesafe_cb.h | 177 |
1 files changed, 177 insertions, 0 deletions
diff --git a/ctdb/include/ctdb_typesafe_cb.h b/ctdb/include/ctdb_typesafe_cb.h new file mode 100644 index 0000000000..b1f2c5f5b5 --- /dev/null +++ b/ctdb/include/ctdb_typesafe_cb.h @@ -0,0 +1,177 @@ +#ifndef CCAN_CAST_IF_TYPE_H +#define CCAN_CAST_IF_TYPE_H + +#if (__GNUC__ >= 3) +#define HAVE_TYPEOF 1 +#define HAVE_BUILTIN_CHOOSE_EXPR 1 +#define HAVE_BUILTIN_TYPES_COMPATIBLE_P 1 +#endif + +#if HAVE_TYPEOF && HAVE_BUILTIN_CHOOSE_EXPR && HAVE_BUILTIN_TYPES_COMPATIBLE_P +/** + * 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 + * + * 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. + * + * 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 @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(e) \ + * _set_some_value(cast_if_type(void *, (e), (e), unsigned long)) + */ +#define cast_if_type(desttype, expr, test, oktype) \ +__builtin_choose_expr(__builtin_types_compatible_p(typeof(1?(test):0), oktype), \ + (desttype)(expr), (expr)) +#else +#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), \ + ok2), \ + ok3) + +/** + * typesafe_cb - cast a 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 void * argument if the + * callback provided matches the @arg (or a const or volatile version). + * + * 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)(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(rtype (*)(void *), (fn), (fn)(arg), rtype) + +/** + * 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) \ + sizeof((fn)((const void *)0)), \ + cast_if_type(rtype (*)(const void *), \ + (fn), (fn)(arg), rtype (*)(typeof(arg))) + +/** + * typesafe_cb_preargs - cast a 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. + * + * This is a version of typesafe_cb() for callbacks that take other arguments + * before the @arg. + * + * Example: + * void _register_callback(void (*fn)(int, void *arg), void *arg); + * #define register_callback(fn, arg) \ + * _register_callback(typesafe_cb_preargs(void, (fn), (arg), int),\ + * (arg)) + */ +#define typesafe_cb_preargs(rtype, fn, arg, ...) \ + cast_if_type(rtype (*)(__VA_ARGS__, void *), (fn), (fn), \ + rtype (*)(__VA_ARGS__, typeof(arg))) +/** + * typesafe_cb_postargs - cast a 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. + * + * This is a version of typesafe_cb() for callbacks that take other arguments + * after the @arg. + * + * Example: + * void _register_callback(void (*fn)(void *arg, int), void *arg); + * #define register_callback(fn, arg) \ + * _register_callback(typesafe_cb_postargs(void, (fn), (arg), int),\ + * (arg)) + */ +#define typesafe_cb_postargs(rtype, fn, arg, ...) \ + cast_if_type(rtype (*)(void *, __VA_ARGS__), (fn), (fn), \ + rtype (*)(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. Note also that the type + * arg points to must be defined. + * + * 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 */ |