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#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 */
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