Convert.h

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/*
 *   ORXONOX - the hottest 3D action shooter ever to exist
 *                    > www.orxonox.net <
 *
 *
 *   License notice:
 *
 *   This program is free software; you can redistribute it and/or
 *   modify it under the terms of the GNU General Public License
 *   as published by the Free Software Foundation; either version 2
 *   of the License, or (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program; if not, write to the Free Software
 *   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 *
 *   Author:
 *      Reto Grieder
 *      Fabian 'x3n' Landau
 *      Benjamin Grauer
 *   Co-authors:
 *      ...
 */

#ifndef _Converter_H__
#define _Converter_H__

#include "UtilPrereqs.h"

#include <string>
#include <sstream>
#include <typeinfo>
#include <type_traits>
#include <loki/TypeManip.h>

#include "Output.h"

// disable warnings about possible loss of data
#ifdef ORXONOX_COMPILER_MSVC
#  pragma warning(push)
#  pragma warning(disable:4244)
#endif

namespace orxonox
{
    // No Conversion //

    template <class FromType, class ToType>
    struct ConverterFallback
    {
        ORX_FORCEINLINE static bool convert(ToType* /*output*/, const FromType& /*input*/)
        {
            orxout(internal_warning) << "Could not convert value of type " << typeid(FromType).name()
                                     << " to type " << typeid(ToType).name() << endl;
            return false;
        }
    };

    template <class FromType, class ToType>
    struct ConverterFallback<FromType*, ToType*>
    {
        ORX_FORCEINLINE static bool convert(ToType** output, FromType* const input)
        {
            ToType* temp = dynamic_cast<ToType*>(input);
            if (temp)
            {
                *output = temp;
                return true;
            }
            else
                return false;
        }
    };
}


// ConverterFallback //

template <class FromType, class ToType>
struct ConverterStringStream
{
    ORX_FORCEINLINE static bool convert(ToType* output, const FromType& input)
    {
        return orxonox::ConverterFallback<FromType, ToType>::convert(output, input);
    }
};


// OStream //

namespace fallbackTemplates
{
    template <class FromType>
    ORX_FORCEINLINE bool operator <<(std::ostream& outstream,  const FromType& input)
    {
        std::string temp;
        if (orxonox::ConverterFallback<FromType, std::string>::convert(&temp, input))
        {
            std::operator <<(outstream, temp);
            return true;
        }
        else
            return false;
    }
}

template <class FromType>
struct ConverterStringStream<FromType, std::string>
{
    ORX_FORCEINLINE static bool convert(std::string* output, const FromType& input)
    {
        using namespace fallbackTemplates;
        // this operator call only chooses fallbackTemplates::operator<<()
        // if there's no other fitting function
        std::ostringstream oss;
        // Note: std::ostream has operator!() to tell whether any error flag was set
        if (oss << input)
        {
            (*output) = oss.str();
            return true;
        }
        else
            return false;
    }
};


// IStream //

namespace fallbackTemplates
{
    template <class ToType>
    ORX_FORCEINLINE bool operator >>(std::istream& instream, ToType& output)
    {
        std::string input(static_cast<std::istringstream&>(instream).str());
        return orxonox::ConverterFallback<std::string, ToType>::convert(&output, input);
    }
}

template <class ToType>
struct ConverterStringStream<std::string, ToType>
{
    ORX_FORCEINLINE static bool convert(ToType* output, const std::string& input)
    {
        using namespace fallbackTemplates;
        // this operator call chooses fallbackTemplates::operator>>()
        // only if there's no other fitting function
        std::istringstream iss(input);
        // Note: std::istream has operator!() to tell whether any error flag was set
        if (iss >> (*output))
        {
            return true;
        }
        else
            return false;
    }
};

namespace orxonox
{
    // Implicit Cast //

    template <class FromType, class ToType>
    ORX_FORCEINLINE bool convertImplicitely(ToType* output, const FromType& input, Loki::Int2Type<false>)
    {
        return ConverterStringStream<FromType, ToType>::convert(output, input);
    }

    template <class FromType, class ToType>
    ORX_FORCEINLINE bool convertImplicitely(ToType* output, const FromType& input, Loki::Int2Type<true>)
    {
        (*output) = static_cast<ToType>(input);
        return true;
    }


    // ConverterExplicit Fallback //

    template <class FromType, class ToType>
    struct ConverterExplicit
    {
        static constexpr bool probe = std::is_convertible<FromType, ToType>::value;
        ORX_FORCEINLINE static bool convert(ToType* output, const FromType& input)
        {
            // Use the probe's value to delegate to the right function
            return convertImplicitely(output, input, Loki::Int2Type<probe>());
        }
    };


    // Public Functions //

    template <class FromType, class ToType>
    ORX_FORCEINLINE bool convertValue(ToType* output, const FromType& input)
    {
        return ConverterExplicit<FromType, ToType>::convert(output, input);
    }

    // Calls convertValue and returns true if the conversion was successful.
    // Otherwise the fallback is used.
    template<class FromType, class ToType>
    ORX_FORCEINLINE bool convertValue(ToType* output, const FromType& input, const ToType& fallback)
    {
        if (convertValue(output, input))
            return true;
        else
        {
            (*output) = fallback;
            return false;
        }
    }

    template<class FromType, class ToType>
    ORX_FORCEINLINE ToType getConvertedValue(const FromType& input, const ToType& fallback)
    {
        ToType output;
        convertValue(&output, input, fallback);
        return output;
    }

    template<class ToType, class FromType>
    ORX_FORCEINLINE ToType multi_cast(const FromType& input)
    {
        ToType output;
        convertValue(&output, input);
        return output;
    }

    // Special string conversions //

    template <class ToType>
    struct ConverterExplicit<const char*, ToType>
    {
        ORX_FORCEINLINE static bool convert(ToType* output, const char* input)
        {
            return convertValue<std::string, ToType>(output, input);
        }
    };

    template <>
    struct ConverterExplicit<char, std::string>
    {
        ORX_FORCEINLINE static bool convert(std::string* output, const char input)
        {
            *output = input;
            return true;
        }
    };
    template <>
    struct ConverterExplicit<unsigned char, std::string>
    {
        ORX_FORCEINLINE static bool convert(std::string* output, const unsigned char input)
        {
            *output = input;
            return true;
        }
    };
    template <>
    struct ConverterExplicit<std::string, char>
    {
        ORX_FORCEINLINE static bool convert(char* output, const std::string& input)
        {
            if (!input.empty())
                *output = input[0];
            else
                *output = '\0';
            return true;
        }
    };
    template <>
    struct ConverterExplicit<std::string, unsigned char>
    {
        ORX_FORCEINLINE static bool convert(unsigned char* output, const std::string& input)
        {
            if (!input.empty())
                *output = input[0];
            else
                *output = '\0';
            return true;
        }
    };


    template <>
    struct ConverterExplicit<bool, std::string>
    {
        ORX_FORCEINLINE static bool convert(std::string* output, const bool& input)
        {
            if (input)
              *output = "true";
            else
              *output = "false";
            return true;
        }
    };

    template <>
    struct _UtilExport ConverterExplicit<std::string, bool>
    {
        static bool convert(bool* output, const std::string& input);
    };
}

// Reinstate warnings
#ifdef ORXONOX_COMPILER_MSVC
#  pragma warning(pop)
#endif

#endif /* _Convert_H__ */