text: /**
  ** @file mruby/boxing_nan.h - nan boxing mrb_value definition
  **
  ** See Copyright Notice in mruby.h
  */
  
  #ifndef MRUBY_BOXING_NAN_H
  #define MRUBY_BOXING_NAN_H
  
  #ifdef MRB_USE_FLOAT32
  # error ---->> MRB_NAN_BOXING and MRB_USE_FLOAT32 conflict <<----
  #endif
  
  #ifdef MRB_NO_FLOAT
  # error ---->> MRB_NAN_BOXING and MRB_NO_FLOAT conflict <<----
  #endif
  
  #define MRB_FIXNUM_MIN INT32_MIN
  #define MRB_FIXNUM_MAX INT32_MAX
  
  enum mrb_nanbox_tt_inline {
    MRB_NANBOX_TT_POINTER = 0,
    MRB_NANBOX_TT_INTEGER = 1,
    MRB_NANBOX_TT_SYMBOL = 2,
    MRB_NANBOX_TT_MISC = 3,
  };
  
  /* value representation by nan-boxing:
   *   float : SEEEEEEE EEEEFFFF FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF
   *   +/-inf: S1111111 11110000 00000000 00000000 00000000 00000000 00000000 00000000
   *   nan   : 01111111 11111000 00000000 00000000 00000000 00000000 00000000 00000000
   *   int   : 01111111 11111001 00000000 00000000 IIIIIIII IIIIIIII IIIIIIII IIIIIIII
   *   sym   : 01111111 11111110 00000000 00000000 SSSSSSSS SSSSSSSS SSSSSSSS SSSSSSSS
   *   misc  : 01111111 11111111 00000000 00000000 00000000 00000000 00TTTTTT 0000MMMM
   *   object: 01111111 11111100 PPPPPPPP PPPPPPPP PPPPPPPP PPPPPPPP PPPPPPPP PPPPPP00
   *   ptr   : 01111111 11111100 PPPPPPPP PPPPPPPP PPPPPPPP PPPPPPPP PPPPPPPP PPPPPP01
   * Stored as O = R + 0x8004000000000000, retrieved as R = O - 0x8004000000000000.
   * This makes pointers have all zeros in the top 32 bits.
   */
  typedef struct mrb_value {
    uint64_t u;
  } mrb_value;
  
  static inline mrb_float
  mrb_nan_boxing_value_float(mrb_value v)
  {
    union {
      mrb_float f;
      uint64_t u;
    } x;
    x.u = v.u - 0x8004000000000000;
    return x.f;
  }
  
  #define SET_FLOAT_VALUE(mrb,r,f) do { \
    union { \
      mrb_float f; \
      uint64_t u; \
    } float_uint_union; \
    if ((f) != (f)) { /* NaN */ \
      float_uint_union.u = 0x7ff8000000000000UL; \
    } \
    else { \
      float_uint_union.f = (f); \
    } \
    r.u = float_uint_union.u + 0x8004000000000000; \
  } while(0)
  
  #define mrb_float_p(o) (((uint64_t)((o).u)&0xfffc000000000000) != 0)
  
  struct RInteger {
    MRB_OBJECT_HEADER;
    mrb_int i;
  };
  
  #define mrb_nb_tt(o) ((((o).u>>48)&3))
  
  MRB_INLINE enum mrb_vtype
  mrb_type(mrb_value o)
  {
    if (mrb_float_p(o)) return MRB_TT_FLOAT;
  
    int64_t u = o.u;
    switch ((enum mrb_nanbox_tt_inline)((u >> 48) & 3)) {
    case MRB_NANBOX_TT_POINTER: {
      if (u == 0) return MRB_TT_FALSE;
      if (u & 1) return MRB_TT_CPTR;
      return ((struct RBasic*)(uintptr_t)u)->tt;
    }
    case MRB_NANBOX_TT_INTEGER:
      return MRB_TT_INTEGER;
    case MRB_NANBOX_TT_SYMBOL:
      return MRB_TT_SYMBOL;
    case MRB_NANBOX_TT_MISC:
      return (enum mrb_vtype)((o.u >> 8) & 0x1f);
    default:
      /* never happen */
      return MRB_TT_FLOAT;
    }
  }
  
  #define NANBOX_SET_MISC_VALUE(r,t,i) NANBOX_SET_VALUE(r, MRB_NANBOX_TT_MISC, ((t)<<8) | i)
  
  #define mrb_float(o) mrb_nan_boxing_value_float(o)
  #ifdef MRB_INT64
  /*
  #ifdef MRB_32BIT
  #define mrb_fixnum(o)  ((mrb_int)((intptr_t)0xffffffffffff&((o).u))|(((o).u & 0x800000000000)?0xffff000000000000:0))
  #else
  #define mrb_fixnum(o)  ((mrb_int)(int32_t)((o).u))
  #endif
  */
  
  #define mrb_fixnum(o)  ((mrb_int)(int32_t)((o).u))
  
  static inline mrb_int
  mrb_nan_boxing_value_int(mrb_value v)
  {
    uint64_t u = v.u;
    if (mrb_nb_tt(v)==MRB_NANBOX_TT_POINTER) {
      struct RInteger *p = (struct RInteger*)(uintptr_t)u;
      return p->i;
    }
    return mrb_fixnum(v);
  }
  #define mrb_integer(o) mrb_nan_boxing_value_int(o)
  #else
  #define mrb_fixnum(o)  ((mrb_int)(((uintptr_t)0xffffffff)&((o).u)))
  #define mrb_integer(o) mrb_fixnum(o)
  #endif
  #define mrb_symbol(o)  ((mrb_sym)((uintptr_t)0xffffffff)&((o).u))
  #define mrb_ptr(o)     ((void*)(uintptr_t)(o).u)
  #define mrb_cptr(o)    ((void*)(uintptr_t)(0xfffffffffffe&(o).u))
  
  #define NANBOX_SET_VALUE(o, tt, v) do { \
    (o).u = ((uint64_t)tt<<48) | ((uint64_t)(v)); \
  } while (0)
  
  #define SET_NIL_VALUE(r) ((r).u = 0)
  #define SET_FALSE_VALUE(r) NANBOX_SET_MISC_VALUE(r, MRB_TT_FALSE, 1)
  #define SET_TRUE_VALUE(r) NANBOX_SET_MISC_VALUE(r, MRB_TT_TRUE, 1)
  #define SET_BOOL_VALUE(r,b) NANBOX_SET_MISC_VALUE(r, (b) ? MRB_TT_TRUE : MRB_TT_FALSE, 1)
  #ifdef MRB_INT64
  MRB_API mrb_value mrb_boxing_int_value(struct mrb_state*, mrb_int);
  #define SET_INT_VALUE(mrb, r, n) ((r) = mrb_boxing_int_value(mrb, n))
  #else
  #define SET_INT_VALUE(mrb, r, n) SET_FIXNUM_VALUE(r, n)
  #endif
  #define SET_FIXNUM_VALUE(r,n) NANBOX_SET_VALUE(r, MRB_NANBOX_TT_INTEGER, (uint32_t)(n))
  #define SET_SYM_VALUE(r,v) NANBOX_SET_VALUE(r, MRB_NANBOX_TT_SYMBOL, (uint32_t)(v))
  #define SET_OBJ_VALUE(r,v) do {(r).u = (uint64_t)(uintptr_t)v;} while (0)
  #define SET_CPTR_VALUE(mrb,r,v) do {(r).u = ((uint64_t)(uintptr_t)v) | 1;} while (0)
  #define SET_UNDEF_VALUE(r) NANBOX_SET_MISC_VALUE(r, MRB_TT_UNDEF, 4)
  
  #define mrb_immediate_p(o) ((mrb_float_p(o) || mrb_nb_tt(o) != MRB_NANBOX_TT_POINTER) || (o).u == 0)
  #define mrb_nil_p(o)  ((o).u == 0)
  #define mrb_false_p(o) (mrb_type(o) == MRB_TT_FALSE || (o).u == 0)
  #define mrb_fixnum_p(o) (!mrb_float_p(o) && mrb_nb_tt(o)==MRB_NANBOX_TT_INTEGER)
  
  #endif  /* MRUBY_BOXING_NAN_H */
  