lib/c++/orb.cc

   1 #include <System.h>
   2
   3 namespace System {
   4         namespace RunTime {
   5                 // This function could be made to do a binary search if we can
   6                 // manage to somehow sort the IFaceTables...
   7
   8                 uintptr_t downcast(::System::_i_Object *obj,
   9                                    const unsigned long *new_guid)
  10                 {
  11                         if (!obj)
  12                                 return 0;
  13
  14                         void unsupported_long_size();
  15
  16                         if (sizeof(long) != 4 && sizeof(long) != 8)
  17                                 unsupported_long_size();
  18
  19                         IFaceTable *tbl = obj->info->concrete_IFaceTable;
  20                         unsigned long new_guid_first = *new_guid;
  21
  22                         // This doesn't use guids_equal(), as that would eliminate the
  23                         // ability to cache the first word of new_guid.  The compiler
  24                         // *might* do it anyway, but this code was written before
  25                         // guids_equal existed, and I don't want to risk removing an
  26                         // optimization by changing it now without testing how GCC
  27                         // behaves.
  28
  29                         do {
  30                                 if (*tbl->guid == new_guid_first &&
  31                                     tbl->guid[1] == new_guid[1] &&
  32                                     (sizeof(long) == 8 ||
  33                                      (tbl->guid[2] == new_guid[2] &&
  34                                       tbl->guid[3] == new_guid[3])))
  35                                         break;
  36
  37                                 tbl++;
  38                         } while (tbl->guid);
  39
  40                         uintptr_t ptr = reinterpret_cast<uintptr_t>(obj);
  41
  42                         ptr += obj->info->concrete;
  43                         ptr += tbl->offset;
  44
  45                         return ptr;
  46                 };
  47
  48                 unsigned long get_pc()
  49                 {
  50                         return reinterpret_cast<unsigned long>(__builtin_return_address(0));
  51                 }
  52         }
  53 }