conversions.h

来自「cpptcl library for ns2」· C头文件 代码 · 共 102 行

//
// Copyright (C) 2004-2006, Maciej Sobczak
//
// Permission to copy, use, modify, sell and distribute this software
// is granted provided this copyright notice appears in all copies.
// This software is provided "as is" without express or implied
// warranty, and with no claim as to its suitability for any purpose.
//

// Note: this file is not supposed to be a stand-alone header


// helper functor for converting Tcl objects to the given type
// (it is a struct instead of function,
// because I need to partially specialize it)

template <typename T>
struct tcl_cast;

template <typename T>
struct tcl_cast<T*>
{
     static T * from(Tcl_Interp *, Tcl_Obj *obj)
     {
          std::string s(Tcl_GetString(obj));
          if (s.size() == 0)
          {
               throw tcl_error("Expected pointer value, got empty string.");
          }

          if (s[0] != 'p')
          {
               throw tcl_error("Expected pointer value.");
          }

          std::istringstream ss(s);
          char dummy;
          void *p;
          ss >> dummy >> p;

          return static_cast<T*>(p);
     }
};

// the following partial specialization is to strip reference
// (it returns a temporary object of the underlying type, which
// can be bound to the const-ref parameter of the actual function)

template <typename T>
struct tcl_cast<T const &>
{
     static T from(Tcl_Interp *interp, Tcl_Obj *obj)
     {
          return tcl_cast<T>::from(interp, obj);
     }
};


// the following specializations are implemented

template <>
struct tcl_cast<int>
{
     static int from(Tcl_Interp *, Tcl_Obj *);
};

template <>
struct tcl_cast<long>
{
     static long from(Tcl_Interp *, Tcl_Obj *);
};

template <>
struct tcl_cast<bool>
{
     static bool from(Tcl_Interp *, Tcl_Obj *);
};

template <>
struct tcl_cast<double>
{
     static double from(Tcl_Interp *, Tcl_Obj *);
};

template <>
struct tcl_cast<std::string>
{
     static std::string from(Tcl_Interp *, Tcl_Obj *);
};

template <>
struct tcl_cast<char const *>
{
     static char const * from(Tcl_Interp *, Tcl_Obj *);
};

template <>
struct tcl_cast<object>
{
     static object from(Tcl_Interp *, Tcl_Obj *);
};