src/gromacs/options/valueconverter.h

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  35 /*! \libinternal \file
  36  * \brief
  37  * Provides gmx::OptionValueConverterSimple.
  38  *
  39  * \author Teemu Murtola <teemu.murtola@gmail.com>
  40  * \ingroup module_options
  41  */
  42 #ifndef GMX_OPTIONS_VALUECONVERTER_H
  43 #define GMX_OPTIONS_VALUECONVERTER_H
  44
  45 #include <functional>
  46 #include <map>
  47 #include <typeindex>
  48
  49 #include "gromacs/utility/exceptions.h"
  50 #include "gromacs/utility/variant.h"
  51
  52 namespace gmx
  53 {
  54
  55 /*! \libinternal \brief
  56  * Helper for converting from Variant to a given type.
  57  *
  58  * \tparam OutType  Type this converter converts to.
  59  *
  60  * Default-constructed converter only supports identity mapping from the a
  61  * Variant holding `OutType`.  To add support for additional input types,
  62  * provide conversion functions with addConverter().  To use a non-identity
  63  * mapping for an `OutType` -> `OutType` conversion, provide an alternative
  64  * conversion from `OutType` with addConverter().
  65  *
  66  * \inlibraryapi
  67  * \ingroup module_options
  68  */
  69 template <typename OutType>
  70 class OptionValueConverterSimple
  71 {
  72     public:
  73         /*! \brief
  74          * Converts a Variant value to the output type.
  75          *
  76          * \returns  Converted value.
  77          * \throws InvalidInputError If the input Variant has a type that is
  78          *     not recognized by any conversion.
  79          */
  80         OutType convert(const Variant &value) const
  81         {
  82             std::type_index type(value.type());
  83             auto            iter = converters_.find(type);
  84             if (iter == converters_.end())
  85             {
  86                 if (value.isType<OutType>())
  87                 {
  88                     return value.cast<OutType>();
  89                 }
  90                 GMX_THROW(InvalidInputError("Invalid type of value"));
  91             }
  92             return iter->second(value);
  93         }
  94
  95         /*! \brief
  96          * Adds a supported conversion.
  97          *
  98          * \tparam InType  Type to convert from.
  99          * \param  func    Function to convert from `InType` to `OutType`.
 100          */
 101         template <typename InType>
 102         void addConverter(std::function<OutType(const InType &)> func)
 103         {
 104             converters_[std::type_index(typeid(InType))] =
 105                 [func] (const Variant &value)
 106                 {
 107                     return func(value.cast<InType>());
 108                 };
 109         }
 110         /*! \brief
 111          * Adds a supported conversion from a type that can be directly cast.
 112          *
 113          * \tparam InType  Type to convert from with a simple cast.
 114          */
 115         template <typename InType>
 116         void addCastConversion()
 117         {
 118             converters_[std::type_index(typeid(InType))] =
 119                 [] (const Variant &value)
 120                 {
 121                     return static_cast<OutType>(value.cast<InType>());
 122                 };
 123         }
 124
 125     private:
 126         typedef std::function<OutType(const Variant &value)> ConversionFunction;
 127
 128         std::map<std::type_index, ConversionFunction> converters_;
 129 };
 130
 131 } // namespace gmx
 132
 133 #endif