define SCM_VTABLE_FLAG_APPLICABLE (1L << 3) /* instances of this vtable are applicable? */
#define SCM_VTABLE_FLAG_SETTER_VTABLE (1L << 4) /* instances of this vtable are applicable-with-setter vtables? */
#define SCM_VTABLE_FLAG_SETTER (1L << 5) /* instances of this vtable are applicable-with-setters? */
#define SCM_VTABLE_FLAG_RESERVED_0 (1L << 6)
#define SCM_VTABLE_FLAG_RESERVED_1 (1L << 7)
#define SCM_VTABLE_FLAG_SMOB_0 (1L << 8)
#define SCM_VTABLE_FLAG_GOOPS_0 (1L << 9)
#define SCM_VTABLE_FLAG_GOOPS_1 (1L << 10)
#define SCM_VTABLE_FLAG_GOOPS_2 (1L << 11)
#define SCM_VTABLE_FLAG_GOOPS_3 (1L << 12)
#define SCM_VTABLE_FLAG_GOOPS_4 (1L << 13)
#define SCM_VTABLE_FLAG_RESERVED_2 (1L << 14)
#define SCM_VTABLE_FLAG_RESERVED_3 (1L << 15)
#define SCM_VTABLE_USER_FLAG_SHIFT 16

typedef void (*scm_t_struct_finalize) (SCM obj);

#define SCM_STRUCTP(X)  		(!SCM_IMP(X) && (SCM_TYP3(X) == scm_tc3_struct))
#define SCM_STRUCT_SLOTS(X) 		(SCM_CELL_OBJECT_LOC(X, 1))
#define SCM_STRUCT_SLOT_REF(X,I) 	(SCM_STRUCT_SLOTS (X)[(I)])
#define SCM_STRUCT_SLOT_SET(X,I,V) 	SCM_STRUCT_SLOTS (X)[(I)]=(V)
#define SCM_STRUCT_DATA(X) 		((scm_t_bits*)SCM_STRUCT_SLOTS (X))
#define SCM_STRUCT_DATA_REF(X,I) 	(SCM_STRUCT_DATA (X)[(I)])
#define SCM_STRUCT_DATA_SET(X,I,V) 	SCM_STRUCT_DATA (X)[(I)]=(V)

#define SCM_VALIDATE_STRUCT(pos, v) \
  SCM_MAKE_VALIDATE_MSG (pos, v, STRUCTP, "struct")
#define SCM_VALIDATE_VTABLE(pos, v) \
  do { \
    SCM_ASSERT (scm_is_true (scm_struct_vtable_p (v)), v, pos, FUNC_NAME); \
  } while (0)

/* The SCM_VTABLE_* macros assume that you're passing them a struct which is a
   valid vtable. */
#define SCM_VTABLE_LAYOUT(X)            (SCM_STRUCT_SLOT_REF ((X), scm_vtable_index_layout))
#define SCM_SET_VTABLE_LAYOUT(X,L)      (SCM_STRUCT_SLOT_SET ((X), scm_vtable_index_layout, L))
#define SCM_VTABLE_FLAGS(X)             (SCM_STRUCT_DATA_REF (X, scm_vtable_index_flags))
#define SCM_SET_VTABLE_FLAGS(X,F)       (SCM_STRUCT_DATA_REF (X, scm_vtable_index_flags) |= (F))
#define SCM_CLEAR_VTABLE_FLAGS(X,F)     (SCM_STRUCT_DATA_REF (X, scm_vtable_index_flags) &= (~(F)))
#define SCM_VTABLE_FLAG_IS_SET(X,F)     (SCM_STRUCT_DATA_REF (X, scm_vtable_index_flags) & (F))
#define SCM_VTABLE_INSTANCE_FINALIZER(X) ((scm_t_struct_finalize)SCM_STRUCT_DATA_REF (X, scm_vtable_index_instance_finalize))
#define SCM_SET_VTABLE_INSTANCE_FINALIZER(X,P) (SCM_STRUCT_DATA_SET (X, scm_vtable_index_instance_finalize, (scm_t_bits)(P)))
#define SCM_VTABLE_INSTANCE_PRINTER(X)  (SCM_STRUCT_SLOT_REF (X, scm_vtable_index_instance_printer))
#define SCM_SET_VTABLE_INSTANCE_PRINTER(X,P) (SCM_STRUCT_SLOT_SET (X, scm_vtable_index_instance_printer, (P)))
#define SCM_VTABLE_NAME(X)              (SCM_STRUCT_SLOT_REF (X, scm_vtable_index_name))
#define SCM_SET_VTABLE_NAME(X,V)        (SCM_STRUCT_SLOT_SET (X, scm_vtable_index_name, V))
#define SCM_VTABLE_SIZE(X)              (SCM_STRUCT_DATA_REF (X, scm_vtable_index_size))
#define SCM_VTABLE_UNBOXED_FIELDS(X)    ((uint32_t*) SCM_STRUCT_DATA_REF (X, scm_vtable_index_unboxed_fields))
#define SCM_VTABLE_FIELD_IS_UNBOXED(X,F) (SCM_VTABLE_UNBOXED_FIELDS (X)[(F)>>5]&(1U<<((F)&31)))

#define SCM_STRUCT_VTABLE(X)            (SCM_PACK (SCM_CELL_WORD_0 (X) - scm_tc3_struct))
#define SCM_STRUCT_LAYOUT(X) 	        (SCM_VTABLE_LAYOUT (SCM_STRUCT_VTABLE (X)))
#define SCM_STRUCT_SIZE(X) 	        (SCM_VTABLE_SIZE (SCM_STRUCT_VTABLE (X)))
#define SCM_STRUCT_PRINTER(X) 	        (SCM_VTABLE_INSTANCE_PRINTER (SCM_STRUCT_VTABLE (X)))
#define SCM_STRUCT_FINALIZER(X)         (SCM_VTABLE_INSTANCE_FINALIZER (SCM_STRUCT_VTABLE (X)))
#define SCM_STRUCT_VTABLE_FLAGS(X)      (SCM_VTABLE_FLAGS (SCM_STRUCT_VTABLE (X)))
#define SCM_STRUCT_VTABLE_FLAG_IS_SET(X,F) (SCM_VTABLE_FLAG_IS_SET (SCM_STRUCT_VTABLE (X), (F)))
#define SCM_STRUCT_FIELD_IS_UNBOXED(X,F) (SCM_VTABLE_FIELD_IS_UNBOXED (SCM_STRUCT_VTABLE (X), (F)))

#define SCM_STRUCT_APPLICABLE_P(X) 	(SCM_STRUCT_VTABLE_FLAG_IS_SET ((X), SCM_VTABLE_FLAG_APPLICABLE))
#define SCM_STRUCT_SETTER_P(X) 	        (SCM_STRUCT_VTABLE_FLAG_IS_SET ((X), SCM_VTABLE_FLAG_SETTER))
#define SCM_STRUCT_PROCEDURE(X) 	(SCM_STRUCT_SLOT_REF (X, scm_applicable_struct_index_procedure))
#define SCM_SET_STRUCT_PROCEDURE(X,P) 	(SCM_STRUCT_SLOT_SET (X, scm_applicable_struct_index_procedure, P))
#define SCM_STRUCT_SETTER(X)            (SCM_STRUCT_SLOT_REF (X, scm_applicable_struct_index_setter))
#define SCM_SET_STRUCT_SETTER(X,P) 	(SCM_STRUCT_SLOT_SET (X, scm_applicable_struct_index_setter, P))

SCM_API SCM scm_standard_vtable_vtable;
SCM_API SCM scm_applicable_struct_vtable_vtable;
SCM_API SCM scm_applicable_struct_with_setter_vtable_vtable;

