#if UINTPTR_MAX == 0xffffffff
#define UPB_SIZE(size32, size64) size32
#else
#define UPB_SIZE(size32, size64) size64
#endif

#define UPB_FIELD_AT(msg, fieldtype, offset) \
  *(fieldtype*)((const char*)(msg) + offset)

#define UPB_READ_ONEOF(msg, fieldtype, offset, case_offset, case_val, default) \
  UPB_FIELD_AT(msg, int, case_offset) == case_val                              \
      ? UPB_FIELD_AT(msg, fieldtype, offset)                                   \
      : default

#define UPB_WRITE_ONEOF(msg, fieldtype, offset, value, case_offset, case_val) \
  UPB_FIELD_AT(msg, int, case_offset) = case_val;                             \
  UPB_FIELD_AT(msg, fieldtype, offset) = value;