From 754c677b0bbf3ea6c7d2a73c93848f1b0d68c91e Mon Sep 17 00:00:00 2001 From: Rusty Russell Date: Mon, 20 Jun 2011 16:54:15 +0930 Subject: lib: import ccan modules for tdb2 Imported from git://git.ozlabs.org/~ccan/ccan init-1161-g661d41f Signed-off-by: Rusty Russell --- lib/ccan/typesafe_cb/typesafe_cb.h | 133 +++++++++++++++++++++++++++++++++++++ 1 file changed, 133 insertions(+) create mode 100644 lib/ccan/typesafe_cb/typesafe_cb.h (limited to 'lib/ccan/typesafe_cb/typesafe_cb.h') diff --git a/lib/ccan/typesafe_cb/typesafe_cb.h b/lib/ccan/typesafe_cb/typesafe_cb.h new file mode 100644 index 0000000000..40cfa39798 --- /dev/null +++ b/lib/ccan/typesafe_cb/typesafe_cb.h @@ -0,0 +1,133 @@ +#ifndef CCAN_TYPESAFE_CB_H +#define CCAN_TYPESAFE_CB_H +#include "config.h" + +#if HAVE_TYPEOF && HAVE_BUILTIN_CHOOSE_EXPR && HAVE_BUILTIN_TYPES_COMPATIBLE_P +/** + * typesafe_cb_cast - only cast an expression if it matches a given type + * @desttype: the type to cast to + * @oktype: the type we allow + * @expr: the expression to cast + * + * 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 is exactly of type @oktype, then it 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 typesafe_cb_cast(), it becomes an + * unconditional cast, and the @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(typesafe_cb_cast(void *, (e), unsigned long)) + */ +#define typesafe_cb_cast(desttype, oktype, expr) \ + __builtin_choose_expr( \ + __builtin_types_compatible_p(__typeof__(0?(expr):(expr)), \ + oktype), \ + (desttype)(expr), (expr)) +#else +#define typesafe_cb_cast(desttype, oktype, expr) ((desttype)(expr)) +#endif + +/** + * typesafe_cb_cast3 - only cast an expression if it matches given types + * @desttype: the type to cast to + * @ok1: the first type we allow + * @ok2: the second type we allow + * @ok3: the third type we allow + * @expr: the expression to cast + * + * This is a convenient wrapper for multiple typesafe_cb_cast() calls. + * You can chain them inside each other (ie. use typesafe_cb_cast() + * 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(typesafe_cb_cast3(void *,, \ + * long, unsigned long, const void *,\ + * (expr))) + */ +#define typesafe_cb_cast3(desttype, ok1, ok2, ok3, expr) \ + typesafe_cb_cast(desttype, ok1, \ + typesafe_cb_cast(desttype, ok2, \ + typesafe_cb_cast(desttype, ok3, \ + (expr)))) + +/** + * typesafe_cb - cast a callback function if it matches the arg + * @rtype: the return type of the callback function + * @atype: the (pointer) type which the callback function expects. + * @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 atype 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)(void *arg), void *arg); + * #define register_callback(fn, arg) \ + * _register_callback(typesafe_cb(void, (fn), void*, (arg)), (arg)) + */ +#define typesafe_cb(rtype, atype, fn, arg) \ + typesafe_cb_cast(rtype (*)(atype), \ + rtype (*)(__typeof__(arg)), \ + (fn)) + +/** + * typesafe_cb_preargs - cast a callback function if it matches the arg + * @rtype: the return type of the callback function + * @atype: the (pointer) type which the callback function expects. + * @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), void *, \ + * (arg), int), \ + * (arg)) + */ +#define typesafe_cb_preargs(rtype, atype, fn, arg, ...) \ + typesafe_cb_cast(rtype (*)(__VA_ARGS__, atype), \ + rtype (*)(__VA_ARGS__, __typeof__(arg)), \ + (fn)) + +/** + * typesafe_cb_postargs - cast a callback function if it matches the arg + * @rtype: the return type of the callback function + * @atype: the (pointer) type which the callback function expects. + * @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), void *, \ + * (arg), int), \ + * (arg)) + */ +#define typesafe_cb_postargs(rtype, atype, fn, arg, ...) \ + typesafe_cb_cast(rtype (*)(atype, __VA_ARGS__), \ + rtype (*)(__typeof__(arg), __VA_ARGS__), \ + (fn)) +#endif /* CCAN_CAST_IF_TYPE_H */ -- cgit