ChaiScript/include/chaiscript/dispatchkit/any.hpp

// This file is distributed under the BSD License.
// See "license.txt" for details.
// Copyright 2009-2012, Jonathan Turner (jonathan@emptycrate.com)
// and Jason Turner (jason@emptycrate.com)
// http://www.chaiscript.com

#ifndef CHAISCRIPT_ANY_HPP_
#define CHAISCRIPT_ANY_HPP_

#include <utility>

namespace chaiscript {
  namespace detail {
    namespace exception {
      /// \brief Thrown in the event that an Any cannot be cast to the desired type
      ///
      /// It is used internally during function dispatch.
      ///
      /// \sa chaiscript::detail::Any
      class bad_any_cast : public std::bad_cast {
      public:
        /// \brief Description of what error occurred
        const char *what() const noexcept override { return "bad any cast"; }
      };
    } // namespace exception

    class Any {
    private:
      struct Data {
        constexpr explicit Data(const std::type_info &t_type) noexcept
            : m_type(t_type) {
        }

        Data &operator=(const Data &) = delete;

        virtual ~Data() noexcept = default;

        virtual void *data() noexcept = 0;

        const std::type_info &type() const noexcept { return m_type; }

        virtual std::unique_ptr<Data> clone() const = 0;
        const std::type_info &m_type;
      };

      template<typename T>
      struct Data_Impl : Data {
        explicit Data_Impl(T t_type)
            : Data(typeid(T))
            , m_data(std::move(t_type)) {
        }

        void *data() noexcept override { return &m_data; }

        std::unique_ptr<Data> clone() const override { return std::make_unique<Data_Impl<T>>(m_data); }

        Data_Impl &operator=(const Data_Impl &) = delete;

        T m_data;
      };

      std::unique_ptr<Data> m_data;

    public:
      // construct/copy/destruct
      constexpr Any() noexcept = default;
      Any(Any &&) noexcept = default;
      Any &operator=(Any &&t_any) = default;

      Any(const Any &t_any)
          : m_data(t_any.empty() ? nullptr : t_any.m_data->clone()) {
      }

      template<typename ValueType, typename = std::enable_if_t<!std::is_same_v<Any, std::decay_t<ValueType>>>>
      explicit Any(ValueType &&t_value)
          : m_data(std::make_unique<Data_Impl<std::decay_t<ValueType>>>(std::forward<ValueType>(t_value))) {
      }

      Any &operator=(const Any &t_any) {
        Any copy(t_any);
        swap(copy);
        return *this;
      }

      template<typename ToType>
      ToType &cast() const {
        if (m_data && typeid(ToType) == m_data->type()) {
          return *static_cast<ToType *>(m_data->data());
        } else {
          throw chaiscript::detail::exception::bad_any_cast();
        }
      }

      // modifiers
      Any &swap(Any &t_other) {
        std::swap(t_other.m_data, m_data);
        return *this;
      }

      // queries
      bool empty() const noexcept { return !static_cast<bool>(m_data); }

      const std::type_info &type() const noexcept {
        if (m_data) {
          return m_data->type();
        } else {
          return typeid(void);
        }
      }
    };

  } // namespace detail
} // namespace chaiscript

#endif