Alc/polymorphism.h

   1 #ifndef POLYMORPHISM_H
   2 #define POLYMORPHISM_H
   3
   4 /* Macros to declare inheriting types, and to (down-)cast and up-cast. */
   5 #define DERIVE_FROM_TYPE(t)          t t##_parent
   6 #define STATIC_CAST(to, obj)         (&(obj)->to##_parent)
   7 #ifdef __GNUC__
   8 #define STATIC_UPCAST(to, from, obj) __extension__({                          \
   9     static_assert(__builtin_types_compatible_p(from, __typeof(*(obj))),       \
  10                   "Invalid upcast object from type");                         \
  11     (to*)((char*)(obj) - offsetof(to, from##_parent));                        \
  12 })
  13 #else
  14 #define STATIC_UPCAST(to, from, obj) ((to*)((char*)(obj) - offsetof(to, from##_parent)))
  15 #endif
  16
  17 /* Defines method forwards, which call the given parent's (T2's) implementation. */
  18 #define DECLARE_FORWARD(T1, T2, rettype, func)                                \
  19 rettype T1##_##func(T1 *obj)                                                  \
  20 { return T2##_##func(STATIC_CAST(T2, obj)); }
  21
  22 #define DECLARE_FORWARD1(T1, T2, rettype, func, argtype1)                     \
  23 rettype T1##_##func(T1 *obj, argtype1 a)                                      \
  24 { return T2##_##func(STATIC_CAST(T2, obj), a); }
  25
  26 #define DECLARE_FORWARD2(T1, T2, rettype, func, argtype1, argtype2)           \
  27 rettype T1##_##func(T1 *obj, argtype1 a, argtype2 b)                          \
  28 { return T2##_##func(STATIC_CAST(T2, obj), a, b); }
  29
  30 #define DECLARE_FORWARD3(T1, T2, rettype, func, argtype1, argtype2, argtype3) \
  31 rettype T1##_##func(T1 *obj, argtype1 a, argtype2 b, argtype3 c)              \
  32 { return T2##_##func(STATIC_CAST(T2, obj), a, b, c); }
  33
  34 /* Defines method thunks, functions that call to the child's method. */
  35 #define DECLARE_THUNK(T1, T2, rettype, func)                                  \
  36 static rettype T1##_##T2##_##func(T2 *obj)                                    \
  37 { return T1##_##func(STATIC_UPCAST(T1, T2, obj)); }
  38
  39 #define DECLARE_THUNK1(T1, T2, rettype, func, argtype1)                       \
  40 static rettype T1##_##T2##_##func(T2 *obj, argtype1 a)                        \
  41 { return T1##_##func(STATIC_UPCAST(T1, T2, obj), a); }
  42
  43 #define DECLARE_THUNK2(T1, T2, rettype, func, argtype1, argtype2)             \
  44 static rettype T1##_##T2##_##func(T2 *obj, argtype1 a, argtype2 b)            \
  45 { return T1##_##func(STATIC_UPCAST(T1, T2, obj), a, b); }
  46
  47 #define DECLARE_THUNK3(T1, T2, rettype, func, argtype1, argtype2, argtype3)   \
  48 static rettype T1##_##T2##_##func(T2 *obj, argtype1 a, argtype2 b, argtype3 c) \
  49 { return T1##_##func(STATIC_UPCAST(T1, T2, obj), a, b, c); }
  50
  51 #define DECLARE_THUNK4(T1, T2, rettype, func, argtype1, argtype2, argtype3, argtype4) \
  52 static rettype T1##_##T2##_##func(T2 *obj, argtype1 a, argtype2 b, argtype3 c, argtype4 d) \
  53 { return T1##_##func(STATIC_UPCAST(T1, T2, obj), a, b, c, d); }
  54
  55 /* Defines the default functions used to (de)allocate a polymorphic object. */
  56 #define DECLARE_DEFAULT_ALLOCATORS(T)                                         \
  57 static void* T##_New(size_t size) { return al_malloc(16, size); }             \
  58 static void T##_Delete(void *ptr) { al_free(ptr); }
  59
  60
  61 /* Helper to extract an argument list for virtual method calls. */
  62 #define EXTRACT_VCALL_ARGS(...)  __VA_ARGS__))
  63
  64 /* Call a "virtual" method on an object, with arguments. */
  65 #define V(obj, func)  ((obj)->vtbl->func((obj), EXTRACT_VCALL_ARGS
  66 /* Call a "virtual" method on an object, with no arguments. */
  67 #define V0(obj, func) ((obj)->vtbl->func((obj) EXTRACT_VCALL_ARGS
  68
  69
  70 /* Helper to extract an argument list for NEW_OBJ calls. */
  71 #define EXTRACT_NEW_ARGS(...)  __VA_ARGS__);                                  \
  72     }                                                                         \
  73 } while(0)
  74
  75 /* Allocate and construct an object, with arguments. */
  76 #define NEW_OBJ(_res, T) do {                                                 \
  77     _res = T##_New(sizeof(T));                                                \
  78     if(_res)                                                                  \
  79     {                                                                         \
  80         memset(_res, 0, sizeof(T));                                           \
  81         T##_Construct(_res, EXTRACT_NEW_ARGS
  82 /* Allocate and construct an object, with no arguments. */
  83 #define NEW_OBJ0(_res, T) do {                                                \
  84     _res = T##_New(sizeof(T));                                                \
  85     if(_res)                                                                  \
  86     {                                                                         \
  87         memset(_res, 0, sizeof(T));                                           \
  88         T##_Construct(_res EXTRACT_NEW_ARGS
  89
  90 /* Destructs and deallocate an object. */
  91 #define DELETE_OBJ(obj) do {                                                  \
  92     if((obj) != NULL)                                                         \
  93     {                                                                         \
  94         V0((obj),Destruct)();                                                 \
  95         V0((obj),Delete)();                                                   \
  96     }                                                                         \
  97 } while(0)
  98
  99
 100 /* Helper to get a type's vtable thunk for a child type. */
 101 #define GET_VTABLE2(T1, T2) (&(T1##_##T2##_vtable))
 102 /* Helper to set an object's vtable thunk for a child type. Used when constructing an object. */
 103 #define SET_VTABLE2(T1, T2, obj) (STATIC_CAST(T2, obj)->vtbl = GET_VTABLE2(T1, T2))
 104
 105 #endif /* POLYMORPHISM_H */