geant4/source/intercoms/include/G4AnyMethod.hh

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//
// G4AnyMethod
//
// Class description:
//
// The G4AnyMethod class represents any object method.
// The class only holds a member pointer.

// See http://www.boost.org/libs/any for Documentation.
// Copyright Kevlin Henney, 2000, 2001, 2002. All rights reserved.
//
// Permission to use, copy, modify, and distribute this software for any
// purpose is hereby granted without fee, provided that this copyright and
// permissions notice appear in all copies and derivatives.
//
// This software is provided "as is" without express or implied warranty.
// What:  variant At boost::any
// who:   contributed by Kevlin Henney,
//        with features contributed and bugs found by
//        Ed Brey, Mark Rodgers, Peter Dimov, and James Curran
// when:  July 2001
// --------------------------------------------------------------------
#ifndef G4AnyMethod_hh
#define G4AnyMethod_hh 1

#include "G4Types.hh"

#include <functional>
#include <sstream>
#include <type_traits>

/** Bad Argument exception */
class G4BadArgument : public std::bad_cast
{
  public:
    G4BadArgument() = default;
    const char* what() const throw() override { return "G4BadArgument: failed operator()"; }
};

class G4AnyMethod
{
  public:
    G4AnyMethod() = default;

    template<class S, class T>
    G4AnyMethod(S (T::*f)())
    {
      fContent = new FuncRef<S, T>(f);
    }

    template<class S, class T, class A0>
    G4AnyMethod(S (T::*f)(A0)) : narg(1)
    {
      fContent = new FuncRef1<S, T, A0>(f);
    }

    template<class S, class T, class A0, class A1>
    G4AnyMethod(S (T::*f)(A0, A1)) : narg(2)
    {
      fContent = new FuncRef2<S, T, A0, A1>(f);
    }

    G4AnyMethod(const G4AnyMethod& other)
      : fContent(other.fContent != nullptr ? other.fContent->Clone() : nullptr), narg(other.narg)
    {}

    ~G4AnyMethod() { delete fContent; }

    G4AnyMethod& Swap(G4AnyMethod& rhs)
    {
      std::swap(fContent, rhs.fContent);
      std::swap(narg, rhs.narg);
      return *this;
    }

    template<class S, class T>
    G4AnyMethod& operator=(S (T::*f)())
    {
      G4AnyMethod(f).Swap(*this);
      narg = 0;
      return *this;
    }

    template<class S, class T, class A0>
    G4AnyMethod& operator=(S (T::*f)(A0))
    {
      G4AnyMethod(f).Swap(*this);
      narg = 1;
      return *this;
    }
    template<class S, class T, class A0, class A1>
    G4AnyMethod& operator=(S (T::*f)(A0, A1))
    {
      G4AnyMethod(f).Swap(*this);
      narg = 1;
      return *this;
    }

    G4AnyMethod& operator=(const G4AnyMethod& rhs)
    {
      G4AnyMethod(rhs).Swap(*this);
      narg = rhs.narg;
      return *this;
    }

    /** Query */

    G4bool Empty() const { return fContent == nullptr; }

    /** call operators */

    void operator()(void* obj) { fContent->operator()(obj); }
    void operator()(void* obj, const std::string& a0) { fContent->operator()(obj, a0); }

    /** Number of arguments */

    std::size_t NArg() const { return narg; }

    const std::type_info& ArgType(size_t n = 0) const
    {
      return fContent != nullptr ? fContent->ArgType(n) : typeid(void);
    }

  private:
    class Placeholder
    {
      public:
        Placeholder() = default;
        virtual ~Placeholder() = default;
        virtual Placeholder* Clone() const = 0;
        virtual void operator()(void*) = 0;
        virtual void operator()(void*, const std::string&) = 0;
        virtual const std::type_info& ArgType(size_t) const = 0;
    };

    template<class S, class T>
    struct FuncRef : public Placeholder
    {
        FuncRef(S (T::*f)()) : fRef(f) {}

        void operator()(void* obj) override { ((T*)obj->*fRef)(); }
        void operator()(void*, const std::string&) override { throw G4BadArgument(); }
        Placeholder* Clone() const override { return new FuncRef(fRef); }
        const std::type_info& ArgType(std::size_t) const override { return typeid(void); }
        S (T::*fRef)();
    };

    template<class S, class T, class A0>
    struct FuncRef1 : public Placeholder
    {
        using nakedA0 = std::remove_const_t<std::remove_reference_t<A0>>;

        FuncRef1(S (T::*f)(A0)) : fRef(f) {}

        void operator()(void*) override { throw G4BadArgument(); }
        void operator()(void* obj, const std::string& s0) override
        {
          nakedA0 a0;
          std::stringstream strs(s0);
          strs >> a0;
          ((T*)obj->*fRef)(a0);
        }
        Placeholder* Clone() const override { return new FuncRef1(fRef); }
        const std::type_info& ArgType(size_t) const override { return typeid(A0); }
        S (T::*fRef)(A0);
    };

    template<class S, class T, class A0, class A1>
    struct FuncRef2 : public Placeholder
    {
        using nakedA0 = std::remove_const_t<std::remove_reference_t<A0>>;
        using nakedA1 = std::remove_const_t<std::remove_reference_t<A1>>;

        FuncRef2(S (T::*f)(A0, A1)) : fRef(f) {}

        void operator()(void*) override { throw G4BadArgument(); }
        void operator()(void* obj, const std::string& s0) override
        {
          nakedA0 a0;
          nakedA1 a1;
          std::stringstream strs(s0);
          strs >> a0 >> a1;
          ((T*)obj->*fRef)(a0, a1);
        }
        Placeholder* Clone() const override { return new FuncRef2(fRef); }
        const std::type_info& ArgType(size_t i) const override
        {
          return i == 0 ? typeid(A0) : typeid(A1);
        }
        S (T::*fRef)(A0, A1);
    };

    Placeholder* fContent = nullptr;
    std::size_t narg = 0;
};

#endif