manes/dyncast.cpp

   1 /* Quarn OS
   2  *
   3  * dynamic_cast<>
   4  *
   5  * Copyright (C) 2009 Pawel Dziepak
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License as published by
   9  * the Free Software Foundation; either version 2 of the License, or
  10  * (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License along
  18  * with this program; if not, write to the Free Software Foundation, Inc.,
  19  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  */
  22
  23 #include "manes/error.h"
  24 #include "typeinfo"
  25
  26 typedef signed int ptrdiff_t;
  27 using namespace __cxxabiv1;
  28 typedef unsigned int cpu_word;
  29 extern "C" void *__dynamic_cast(const void *src_ptr,
  30                                 const __class_type_info *src_type,
  31                                 const __class_type_info *dst_type,
  32                                 ptrdiff_t src2dst) {
  33         /* Get real source type information */
  34         const int **src = (const int **)src_ptr;
  35         const std::type_info *ti = (const std::type_info*)((*src)[-1]);
  36
  37         /* Get base */
  38         void *pointer = (void*)src_ptr;
  39         void *old_ptr = (void*)src_ptr;
  40
  41         if (!ti->__do_upcast(src_type, &old_ptr))
  42                 return (void*)0;
  43
  44         pointer = (void*)((cpu_word)pointer + (cpu_word)src_ptr - (cpu_word)old_ptr);
  45
  46         /* Upcast */
  47         if (ti->__do_upcast(dst_type, &pointer))
  48                 return (void*)pointer;
  49         else
  50                 return (void*)0;
  51 }
  52
  53