any.h

/*
 *  Copyright (C) 2004-2021 Edward F. Valeev
 *
 *  This file is part of Libint.
 *
 *  Libint is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU Lesser General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  (at your option) any later version.
 *
 *  Libint 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 Lesser General Public License for more details.
 *
 *  You should have received a copy of the GNU Lesser General Public License
 *  along with Libint.  If not, see <http://www.gnu.org/licenses/>.
 *
 */
 
#ifndef _libint2_include_libint2_util_any_h_
#define _libint2_include_libint2_util_any_h_
 
#include <type_traits>
#include <utility>
#include <typeinfo>
#include <string>
#include <cassert>
 
// Include C++17 any header, if available AND functional
#if __cplusplus >= 201703L
// macos < 10.14 do not have any_cast in their libc++
# include <ciso646>  // see https://stackoverflow.com/a/31658120
# if defined(_LIBCPP_VERSION) && defined(__APPLE__)
#  include <Availability.h>
#  ifdef __MAC_OS_X_VERSION_MIN_ALLOWED
#   if __MAC_OS_X_VERSION_MIN_ALLOWED >= 10140
#    define LIBINT_HAS_CXX17_ANY
#   endif  //  10.14 or later
#  endif  // have macos version
# else // libc++ on macos
#  define LIBINT_HAS_CXX17_ANY
# endif  // libc++ on macos
#endif  // c++17
 
#ifdef LIBINT_HAS_CXX17_ANY
# include <any>
#endif
 
namespace libint2 {
 
// prefer std::any, if available
#ifdef LIBINT_HAS_CXX17_ANY
using std::any;
using std::any_cast;
using std::bad_any_cast;
#else
 
namespace detail {
// true if decayed T is Base, or is derived from it
template <typename Base, typename T>
using disable_if_same_or_derived = typename std::enable_if<
    !std::is_base_of<Base, typename std::decay<T>::type>::value>::type;
};
 
class any {
 public:
  // this is constexpr in the standard
  any() : impl_(nullptr) {}
  any(const any& other) : impl_(other.impl_->clone()) {}
  any(any&& other) = default;
  template <typename ValueType,
            typename = detail::disable_if_same_or_derived<any, ValueType> >
  any(ValueType&& value)
      : impl_(new impl<typename std::decay<ValueType>::type>(
            std::forward<ValueType>(value))) {}
  ~any() = default;
 
  any& operator=( const any& rhs ) {
    impl_ = decltype(impl_)(rhs.impl_->clone());
    return *this;
  }
  any& operator=( any&& rhs ) {
    impl_ = std::move(rhs.impl_);
    return *this;
  }
  template <typename ValueType,
            typename = detail::disable_if_same_or_derived<any, ValueType> >
  any& operator=(ValueType&& rhs) {
    impl_ = decltype(impl_)(new impl<typename std::decay<ValueType>::type>(
        std::forward<ValueType>(rhs)));
    return *this;
  }
 
  template< class ValueType, class... Args >
  typename std::decay<ValueType>::type& emplace( Args&&... args ) {
    reset();
    impl_ = new impl<typename std::decay<ValueType>::type> (
        std::forward<Args>(args)...);
    return (impl_->cast_static<typename std::decay<ValueType>::type>()->value);
  }
  template< class ValueType, class U, class... Args >
  typename std::decay<ValueType>::type& emplace( std::initializer_list<U> il, Args&&... args ) {
    reset();
    impl_ = new impl<typename std::decay<ValueType>::type> (il,
        std::forward<Args>(args)...);
    return (impl_->cast_static<typename std::decay<ValueType>::type>()->value);
  }
 
  void reset() { impl_.reset(); }
 
  void swap(any& other) {
    std::swap(impl_, other.impl_);
  }
 
  bool has_value() const {
    return static_cast<bool>(impl_);
  }
 
  const std::type_info& type() const {
    if (has_value())
      return impl_->type();
    else
      return typeid(void);
  }
 
 private:
  template <typename T> struct impl;
 
  struct impl_base {
    virtual ~impl_base() {}
    virtual impl_base* clone() const = 0;
 
    virtual const std::type_info& type() const = 0;
 
    // static if NDEBUG is defined, dynamic otherwise
    template <typename T> impl<T>* cast() {
#ifndef NDEBUG
        return this->cast_static<T>();
#else
        return dynamic_cast<impl<T>*>(this);
#endif
    }
    // static always
    template <typename T> impl<T>* cast_static() {
      return static_cast<impl<T>*>(this);
    }
  };
  template <typename T>
  struct impl : public impl_base {
    template <typename U> explicit impl(U&& v) : value(std::forward<U>(v)) {}
    impl_base* clone() const override {
      return new impl{value};
    }
 
    const std::type_info& type() const override {
      return typeid(T);
    }
 
    T value;
  };
 
  template<typename ValueType>
  friend typename std::decay<ValueType>::type* any_cast(any* operand);
  template<typename ValueType>
  friend const typename std::decay<ValueType>::type* any_cast(const any* operand);
 
  template <typename ValueType>
  typename std::decay<ValueType>::type* value_ptr() {
    return &(impl_->cast_static<typename std::decay<ValueType>::type>()->value);
  }
 
  template <typename ValueType>
  const typename std::decay<ValueType>::type* value_ptr() const {
    return &(impl_->cast_static<typename std::decay<ValueType>::type>()->value);
  }
 
  std::unique_ptr<impl_base> impl_;
};
 
class bad_any_cast : public std::bad_cast {
 public:
  bad_any_cast() = default;
  virtual ~bad_any_cast() {}
  virtual const char* what() const noexcept {
    return "Bad any_cast";
  }
};
 
template<typename ValueType>
typename std::decay<ValueType>::type* any_cast(any* operand) {
  if (operand->type() == typeid(typename std::decay<ValueType>::type))
    return operand->value_ptr<typename std::decay<ValueType>::type>();
  else
    return nullptr;
}
 
template<typename ValueType>
const typename std::decay<ValueType>::type* any_cast(const any* operand) {
  if (operand->type() == typeid(typename std::decay<ValueType>::type))
    return operand->value_ptr<typename std::decay<ValueType>::type>();
  else
    return nullptr;
}
 
template <typename ValueType>
ValueType any_cast(const any& operand) {
  const auto* cast_ptr =
      any_cast<typename std::decay<ValueType>::type>(&operand);
  if (cast_ptr != nullptr) return *cast_ptr;
  throw bad_any_cast();
}
 
template <typename ValueType>
ValueType any_cast(any& operand) {
  auto* cast_ptr = any_cast<typename std::decay<ValueType>::type>(&operand);
  if (cast_ptr != nullptr) return *cast_ptr;
  throw bad_any_cast();
}
#endif  // C++17
 
} // namespace libint2
 
#endif // header guard