fptr.hpp

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/*
 * Copyright (c) 2002 Shane Beasley
 *
 * Permission is hereby granted, free of charge, to any person
 * obtaining a copy of this software and associated documentation
 * files (the "Software"), to deal in the Software without restriction,
 * including without limitation the rights to use, copy, modify, merge,
 * publish, distribute, sublicense, and/or sell copies of the Software,
 * and to permit persons to whom the Software is furnished to do so,
 * subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
 * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

#ifndef ELOI_FPTR_HPP_20030604T2158
#define ELOI_FPTR_HPP_20030604T2158

#include <typeinfo>

namespace eloi {

  //////////////////////////////////////////////////////////////////////

  //! Typeless function pointer.
  template <typename VoidFP>
  class unchecked_fptr_T {
  public:
    typedef VoidFP voidfp_type;

    //! Construct a null unchecked function pointer.
    unchecked_fptr_T () : myPointer(0) { }

    //! Construct an unchecked function pointer.
    template <typename T>
    unchecked_fptr_T (T p)
      : myPointer(reinterpret_cast<voidfp_type>(p)) {
    }

    //! Convert this unchecked function pointer to the appropriate type.
    template <typename To, typename V>
    friend To fptr_cast (const unchecked_fptr_T<V> &rhs);

  private:
    voidfp_type myPointer;
  };

  template <typename To, typename V>
  To fptr_cast (const unchecked_fptr_T<V> &rhs) {
    return reinterpret_cast<To>(rhs.myPointer);
  }

  //////////////////////////////////////////////////////////////////////

  //! Typeless function pointer which uses RTTI to guarantee safety.
  template <typename VoidFP>
  class checked_fptr_T {
  public:
    typedef VoidFP voidfp_type;

    //! Construct a null checked function pointer.
    checked_fptr_T () : myInfo(&typeid(voidfp_type)) { }

    //! Construct a checked function pointer.
    template <typename T>
    checked_fptr_T (T p) : myPointer(p), myInfo(&typeid(p)) { }

    //! Convert this unchecked function pointer to the appropriate type.
    //! @throw  std::bad_cast  Conversion to inappropriate type requested.
    template <typename To, typename V>
    friend To fptr_cast (const checked_fptr_T<V> &rhs);

  private:
    unchecked_fptr_T<voidfp_type> myPointer;
    const std::type_info *myInfo;
  };

  template <typename To, typename V>
  To fptr_cast (const checked_fptr_T<V> &rhs) {
    if (typeid(To) != *rhs.myInfo) throw std::bad_cast();
    return fptr_cast<To>(rhs.myPointer);
  }

  //////////////////////////////////////////////////////////////////////

  class T_;
  typedef unchecked_fptr_T<void (*) ()> unchecked_fptr;
  typedef unchecked_fptr_T<void (T_::*) ()> unchecked_mem_fptr;
  typedef checked_fptr_T<void (*) ()> checked_fptr;
  typedef checked_fptr_T<void (T_::*) ()> checked_mem_fptr;

  //////////////////////////////////////////////////////////////////////

}

#endif