value_cast.hh

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#ifndef TYPELIB_VALUE_CAST_HH
#define TYPELIB_VALUE_CAST_HH

#include "value.hh"
#include "normalized_numerics.hh"

namespace Typelib
{
    template<typename T>
    class CastingVisitor : public ValueVisitor
    {
        bool m_found;
        T    m_value;

        bool visit_( typename normalized_numeric_type<T>::type& v)
        {
            m_value = v;
            m_found = true;
            return false;
        }
         
    public:
        CastingVisitor()
            : ValueVisitor(false), m_found(false), m_value() {};
        T& apply(Value v)
        {
            m_found = false;
            ValueVisitor::apply(v);
            if (!m_found)
                throw BadValueCast();

            return m_value;
        }
    };

    template<typename T>
    T& value_cast(Value v)
    {
        CastingVisitor<T> caster;
        return caster.apply(v);
    }

    template<typename T>
    T& value_cast(void* ptr, Type const& type)
    { return value_cast<T>(Value(ptr, type)); }
}

#endif