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Diffstat (limited to 'include/libHX/cast.h')
| -rw-r--r-- | include/libHX/cast.h | 135 |
1 files changed, 135 insertions, 0 deletions
diff --git a/include/libHX/cast.h b/include/libHX/cast.h new file mode 100644 index 0000000..c8fe0ba --- /dev/null +++ b/include/libHX/cast.h @@ -0,0 +1,135 @@ +#ifndef _LIBHX_CAST_H +#define _LIBHX_CAST_H 1 + +#ifndef BUILD_BUG_ON_EXPR +# define BUILD_BUG_ON_EXPR(condition) (sizeof(char[1 - 2 * !!(condition)]) - 1) +#endif +#ifndef BUILD_BUG_ON +# define BUILD_BUG_ON(condition) ((void)BUILD_BUG_ON_EXPR(condition)) +#endif +#ifdef __cplusplus +# ifndef const_cast +# define const_cast(T, x) const_cast<T>(x) +# endif +# ifndef static_cast +# define static_cast(T, x) static_cast<T>(x) +# endif +# define const_cast1(type, expr) const_cast<type>(expr) +# define const_cast2(type, expr) const_cast<type>(expr) +# define const_cast3(type, expr) const_cast<type>(expr) + +template<typename new_type> +static __inline__ new_type signed_cast(const char *expr) +{ + return reinterpret_cast<new_type>(expr); +} + +template<typename new_type> +static __inline__ new_type signed_cast(const signed char *expr) +{ + return reinterpret_cast<new_type>(expr); +} + +template<typename new_type> +static __inline__ new_type signed_cast(const unsigned char *expr) +{ + return reinterpret_cast<new_type>(expr); +} + +template<typename new_type> +static __inline__ new_type signed_cast(char *expr) +{ + return reinterpret_cast<new_type>(expr); +} + +template<typename new_type> +static __inline__ new_type signed_cast(signed char *expr) +{ + return reinterpret_cast<new_type>(expr); +} + +template<typename new_type> +static __inline__ new_type signed_cast(unsigned char *expr) +{ + return reinterpret_cast<new_type>(expr); +} + +#else + /* N.B. signed_cast<> does not exist in C++. */ +# define __signed_cast_compatible(a, b) \ + __builtin_choose_expr( \ + __builtin_types_compatible_p(b, const char *) || \ + __builtin_types_compatible_p(b, const signed char *) || \ + __builtin_types_compatible_p(b, const unsigned char *), \ + /* if src has a const qualifier */ \ + __builtin_types_compatible_p(a, const char *) || \ + __builtin_types_compatible_p(a, const signed char *) || \ + __builtin_types_compatible_p(a, const unsigned char *), \ + /* and if it has none... */ \ + __builtin_types_compatible_p(a, const char *) || \ + __builtin_types_compatible_p(a, const signed char *) || \ + __builtin_types_compatible_p(a, const unsigned char *) || \ + __builtin_types_compatible_p(a, char *) || \ + __builtin_types_compatible_p(a, signed char *) || \ + __builtin_types_compatible_p(a, unsigned char *) \ + ) + +# if defined(__GNUC__) && !defined(__clang__) && !defined(signed_cast) +# define signed_cast(type, expr) ({ \ + BUILD_BUG_ON(!__signed_cast_compatible(__typeof__(type), __typeof__(expr))); \ + (type)(expr); \ + }) +# endif +# if defined(__GNUC__) && !defined(__clang__) && !defined(static_cast) +# define static_cast(type, expr) \ + ((struct { type x; }){(expr)}.x) +# endif +# if defined(__GNUC__) && !defined(__clang__) && !defined(const_cast1) + /* + * The idea starts with (in abstract notation) + * typeof deref typeof expr + * To deref something, we need an object, which we can get by + * creating a temporary aggregate, such as a union, of which + * the member is accessed and dereferenced. + * *(union { __typeof__(expr) x; }){init}.x + * union has two nice properties: + * - with an additional dummy member, we do not have to + * initialize x according to its type, which, if expr is + * an array type, may want extra braces. + * - and with that dummy member, we also avoid the ugly + * "literal 0 is implicitly convertible to a pointer". + * Unfortunately, this all requires C99 compound initializers. + * That's ok - gcc and clang only treat it as a warning even + * under strict C89 - and if you still force strict C89 on + * yourself, you have a lot to answer for either way. + */ +# define __const_cast_strip(ptrs, expr) \ + __typeof__(ptrs(union { int z; __typeof__(expr) x; }){0}.x) +# define __const_cast_p(ptrs, new_type, expr) ((new_type)( \ + (expr) + \ + BUILD_BUG_ON_EXPR(!__builtin_types_compatible_p(__const_cast_strip(ptrs, expr), __const_cast_strip(ptrs, new_type))) \ + )) +# define const_cast1(new_type, expr) __const_cast_p(*, new_type, expr) +# define const_cast2(new_type, expr) __const_cast_p(**, new_type, expr) +# define const_cast3(new_type, expr) __const_cast_p(***, new_type, expr) +# endif +# ifndef signed_cast +# define signed_cast(type, expr) ((type)(expr)) +# endif +# ifndef static_cast +# define static_cast(type, expr) ((type)(expr)) +# endif +# ifndef const_cast +# define const_cast(type, expr) ((type)(expr)) +# endif +# ifndef const_cast1 +# define const_cast1(type, expr) ((type)(expr)) +# define const_cast2(type, expr) ((type)(expr)) +# define const_cast3(type, expr) ((type)(expr)) +# endif +# ifndef reinterpret_cast +# define reinterpret_cast(type, expr) ((type)(expr)) +# endif +#endif + +#endif /* _LIBHX_CAST_H */ |