106 lines
5.4 KiB
C
106 lines
5.4 KiB
C
#ifndef POLYMORPHISM_H
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#define POLYMORPHISM_H
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/* Macros to declare inheriting types, and to (down-)cast and up-cast. */
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#define DERIVE_FROM_TYPE(t) t t##_parent
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#define STATIC_CAST(to, obj) (&(obj)->to##_parent)
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#ifdef __GNUC__
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#define STATIC_UPCAST(to, from, obj) __extension__({ \
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static_assert(__builtin_types_compatible_p(from, __typeof(*(obj))), \
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"Invalid upcast object from type"); \
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(to*)((char*)(obj) - offsetof(to, from##_parent)); \
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})
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#else
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#define STATIC_UPCAST(to, from, obj) ((to*)((char*)(obj) - offsetof(to, from##_parent)))
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#endif
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/* Defines method forwards, which call the given parent's (T2's) implementation. */
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#define DECLARE_FORWARD(T1, T2, rettype, func) \
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rettype T1##_##func(T1 *obj) \
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{ return T2##_##func(STATIC_CAST(T2, obj)); }
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#define DECLARE_FORWARD1(T1, T2, rettype, func, argtype1) \
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rettype T1##_##func(T1 *obj, argtype1 a) \
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{ return T2##_##func(STATIC_CAST(T2, obj), a); }
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#define DECLARE_FORWARD2(T1, T2, rettype, func, argtype1, argtype2) \
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rettype T1##_##func(T1 *obj, argtype1 a, argtype2 b) \
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{ return T2##_##func(STATIC_CAST(T2, obj), a, b); }
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#define DECLARE_FORWARD3(T1, T2, rettype, func, argtype1, argtype2, argtype3) \
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rettype T1##_##func(T1 *obj, argtype1 a, argtype2 b, argtype3 c) \
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{ return T2##_##func(STATIC_CAST(T2, obj), a, b, c); }
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/* Defines method thunks, functions that call to the child's method. */
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#define DECLARE_THUNK(T1, T2, rettype, func) \
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static rettype T1##_##T2##_##func(T2 *obj) \
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{ return T1##_##func(STATIC_UPCAST(T1, T2, obj)); }
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#define DECLARE_THUNK1(T1, T2, rettype, func, argtype1) \
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static rettype T1##_##T2##_##func(T2 *obj, argtype1 a) \
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{ return T1##_##func(STATIC_UPCAST(T1, T2, obj), a); }
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#define DECLARE_THUNK2(T1, T2, rettype, func, argtype1, argtype2) \
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static rettype T1##_##T2##_##func(T2 *obj, argtype1 a, argtype2 b) \
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{ return T1##_##func(STATIC_UPCAST(T1, T2, obj), a, b); }
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#define DECLARE_THUNK3(T1, T2, rettype, func, argtype1, argtype2, argtype3) \
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static rettype T1##_##T2##_##func(T2 *obj, argtype1 a, argtype2 b, argtype3 c) \
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{ return T1##_##func(STATIC_UPCAST(T1, T2, obj), a, b, c); }
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#define DECLARE_THUNK4(T1, T2, rettype, func, argtype1, argtype2, argtype3, argtype4) \
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static rettype T1##_##T2##_##func(T2 *obj, argtype1 a, argtype2 b, argtype3 c, argtype4 d) \
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{ return T1##_##func(STATIC_UPCAST(T1, T2, obj), a, b, c, d); }
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/* Defines the default functions used to (de)allocate a polymorphic object. */
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#define DECLARE_DEFAULT_ALLOCATORS(T) \
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static void* T##_New(size_t size) { return al_malloc(16, size); } \
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static void T##_Delete(void *ptr) { al_free(ptr); }
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/* Helper to extract an argument list for virtual method calls. */
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#define EXTRACT_VCALL_ARGS(...) __VA_ARGS__))
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/* Call a "virtual" method on an object, with arguments. */
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#define V(obj, func) ((obj)->vtbl->func((obj), EXTRACT_VCALL_ARGS
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/* Call a "virtual" method on an object, with no arguments. */
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#define V0(obj, func) ((obj)->vtbl->func((obj) EXTRACT_VCALL_ARGS
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/* Helper to extract an argument list for NEW_OBJ calls. */
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#define EXTRACT_NEW_ARGS(...) __VA_ARGS__); \
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} \
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} while(0)
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/* Allocate and construct an object, with arguments. */
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#define NEW_OBJ(_res, T) do { \
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_res = T##_New(sizeof(T)); \
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if(_res) \
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{ \
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memset(_res, 0, sizeof(T)); \
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T##_Construct(_res, EXTRACT_NEW_ARGS
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/* Allocate and construct an object, with no arguments. */
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#define NEW_OBJ0(_res, T) do { \
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_res = T##_New(sizeof(T)); \
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if(_res) \
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{ \
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memset(_res, 0, sizeof(T)); \
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T##_Construct(_res EXTRACT_NEW_ARGS
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/* Destructs and deallocate an object. */
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#define DELETE_OBJ(obj) do { \
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if((obj) != NULL) \
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{ \
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V0((obj),Destruct)(); \
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V0((obj),Delete)(); \
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} \
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} while(0)
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/* Helper to get a type's vtable thunk for a child type. */
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#define GET_VTABLE2(T1, T2) (&(T1##_##T2##_vtable))
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/* Helper to set an object's vtable thunk for a child type. Used when constructing an object. */
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#define SET_VTABLE2(T1, T2, obj) (STATIC_CAST(T2, obj)->vtbl = GET_VTABLE2(T1, T2))
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#endif /* POLYMORPHISM_H */
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