libcruft-util/types/traits.hpp

102 lines
3.4 KiB
C++

/*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
* Copyright 2012 Danny Robson <danny@nerdcruft.net>
*/
#ifndef __UTIL_TYPES_TRAITS_HPP
#define __UTIL_TYPES_TRAITS_HPP
#include <memory>
#include <type_traits>
//-----------------------------------------------------------------------------
template <typename T> struct is_dereferencable : std::false_type { };
template <typename T> struct is_dereferencable<T*> : std::true_type { };
template <typename T> struct is_dereferencable<std::unique_ptr<T>> : std::true_type { };
template <typename T> struct is_dereferencable<std::shared_ptr<T>> : std::true_type { };
template <typename T> struct is_dereferencable<std::weak_ptr<T>> : std::true_type { };
template <typename T> struct is_dereferencable<std::auto_ptr<T>> : std::true_type { };
template <typename T> struct dereferenced_type {
typedef typename std::enable_if<
std::is_pointer<T>::value,
std::remove_pointer<T>
>::type type;
};
//-----------------------------------------------------------------------------
template <typename T> struct dereferenced_type<std::unique_ptr<T>> { typedef T type; };
template <typename T> struct dereferenced_type<std::shared_ptr<T>> { typedef T type; };
template <typename T> struct dereferenced_type<std::weak_ptr<T>> { typedef T type; };
template <typename T> struct dereferenced_type<std::auto_ptr<T>> { typedef T type; };
///----------------------------------------------------------------------------
/// find the unsigned version of a type if one exists
template <typename T>
struct try_unsigned
{
typedef typename std::make_unsigned<T>::type type;
};
template <> struct try_unsigned<double> { typedef double type; };
template <> struct try_unsigned<float > { typedef float type; };
///----------------------------------------------------------------------------
/// find the signed version of a type if one exists
template <typename T>
struct try_signed
{
typedef typename std::make_signed<T>::type type;
};
template <> struct try_signed<double> { typedef double type; };
template <> struct try_signed<float > { typedef float type; };
///----------------------------------------------------------------------------
/// checks if a type can be converted in all cases without modification
template <typename T, typename U> struct is_lossless_cast : std::enable_if<
std::is_integral<T>::value &&
std::is_integral<U>::value &&
std::is_signed<T>::value == std::is_signed<U>::value &&
sizeof (T) <= sizeof (U),
std::true_type
>::value { };
//-----------------------------------------------------------------------------
template <typename T>
struct func_traits : public func_traits<decltype(&T::operator())>
{ };
template <typename C, typename R, typename ...Args>
struct func_traits<R(C::*)(Args...) const> {
typedef R return_type;
};
template <typename R, typename ...Args>
struct func_traits<R(Args...)> {
typedef R return_type;
};
#endif