src/implicit_cast.cpp

   1 // Copyright (c) 2003 Daniel Wallin and Arvid Norberg
   2
   3 // Permission is hereby granted, free of charge, to any person obtaining a
   4 // copy of this software and associated documentation files (the "Software"),
   5 // to deal in the Software without restriction, including without limitation
   6 // the rights to use, copy, modify, merge, publish, distribute, sublicense,
   7 // and/or sell copies of the Software, and to permit persons to whom the
   8 // Software is furnished to do so, subject to the following conditions:
   9
  10 // The above copyright notice and this permission notice shall be included
  11 // in all copies or substantial portions of the Software.
  12
  13 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
  14 // ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
  15 // TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
  16 // PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
  17 // SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR
  18 // ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
  19 // ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  20 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE
  21 // OR OTHER DEALINGS IN THE SOFTWARE.
  22
  23 #include <luabind/lua_include.hpp>
  24
  25 #include <luabind/luabind.hpp>
  26 #include <luabind/detail/implicit_cast.hpp>
  27
  28 namespace luabind { namespace detail {
  29
  30     // returns -1 if there exists no implicit cast from the given class_rep
  31     // to T. If there exists an implicit cast to T, the number of steps times
  32     // 2 is returned and pointer_offset is filled with the number of bytes
  33     // the pointer have to be offseted to perform the cast the reason why we
  34     // return the number of cast-steps times two, instead of just the number
  35     // of steps is to be consistent with the function matchers. They have to
  36     // give one matching-point extra to match const functions. There may be
  37     // two functions that match their parameters exactly, but there is one
  38     // const function and one non-const function, then (if the this-pointer
  39     // is non-const) both functions will match. To avoid amiguaties, the const
  40     // version will get one penalty point to make the match-selector select
  41     // the non-const version. If the this-pointer is const, there's no
  42     // problem, since the non-const function will not match at all.
  43
  44     int implicit_cast(
  45         class_rep const* crep
  46       , LUABIND_TYPE_INFO const& type_id
  47       , int& pointer_offset)
  48     {
  49         int offset = 0;
  50         if (LUABIND_TYPE_INFO_EQUAL(crep->type(), type_id)) return 0;
  51
  52         for (std::vector<class_rep::base_info>::const_iterator i =
  53             crep->bases().begin(); i != crep->bases().end(); ++i)
  54         {
  55             int steps = implicit_cast(i->base, type_id, offset);
  56             pointer_offset = offset + i->pointer_offset;
  57             if (steps >= 0) return steps + 2;
  58         }
  59         return -1;
  60     }
  61 }}
  62