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- /**
- * Tencent is pleased to support the open source community by making Tars available.
- *
- * Copyright (C) 2016THL A29 Limited, a Tencent company. All rights reserved.
- *
- * Licensed under the BSD 3-Clause License (the "License"); you may not use this file except
- * in compliance with the License. You may obtain a copy of the License at
- *
- * https://opensource.org/licenses/BSD-3-Clause
- *
- * 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.
- */
- #ifndef _TARS_TYPE_LIST_H_
- #define _TARS_TYPE_LIST_H_
- namespace tars {
- namespace tl {
- template <typename... Types>
- struct TypeList {};
- // get the Nth type in a given type list.
- template <size_t N, typename List>
- struct TypeAtImpl;
- template <size_t N, typename T, typename... List>
- struct TypeAtImpl<N, TypeList<T, List...> >
- : TypeAtImpl<N-1, TypeList<List...> > {};
- template <typename T, typename... List>
- struct TypeAtImpl<0, TypeList<T, List...> > {
- using Type = T;
- };
- // throw error while empty list.
- template <> struct TypeAtImpl<0, TypeList<> > {};
- template <size_t N, typename... List>
- using TypeAt = typename TypeAtImpl<N, List...>::Type;
- // index of a type in a given type list.
- template <typename T, typename List>
- struct IndexOfImpl;
- template <typename T>
- struct IndexOfImpl<T, TypeList<> > {
- enum { value = -1 };
- };
- template <typename T, typename... List>
- struct IndexOfImpl<T, TypeList<T, List...> > {
- enum { value = 0 };
- };
- template <typename T, typename U, typename... List>
- struct IndexOfImpl<T, TypeList<U, List...> > {
- private:
- enum { temp = IndexOfImpl<T, TypeList<List...> >::value };
- public:
- enum { value = ((temp == -1) ? -1 : (1 + temp)) };
- };
- template <typename T, typename List>
- using IndexOf = IndexOfImpl<T, List>;
- // drop first N types in a given type list.
- template <size_t N, typename List>
- struct DropTypeListItemImpl;
- template <size_t N, typename T, typename... List>
- struct DropTypeListItemImpl<N, TypeList<T, List...> >
- : DropTypeListItemImpl<N-1, TypeList<List...> > {};
- template <typename T, typename... List>
- struct DropTypeListItemImpl<0, TypeList<T, List...> > {
- using Type = TypeList<T, List...>;
- };
- template <> struct DropTypeListItemImpl<0, TypeList<> > {
- using Type = TypeList<>;
- };
- template <size_t N, typename List>
- using DropTypeListItem = typename DropTypeListItemImpl<N, List>::Type;
- // take first N types in a given type list.
- template <size_t N, typename List, typename... TList>
- struct TakeTypeListItemImpl;
- template <size_t N, typename T, typename... List, typename... TList>
- struct TakeTypeListItemImpl<N, TypeList<T, List...>, TList...>
- : TakeTypeListItemImpl<N-1, TypeList<List...>, TList..., T> {};
- template <typename T, typename... List, typename... TList>
- struct TakeTypeListItemImpl<0, TypeList<T, List...>, TList...> {
- using Type = TypeList<TList...>;
- };
- template <typename... TList>
- struct TakeTypeListItemImpl<0, TypeList<>, TList...> {
- using Type = TypeList<TList...>;
- };
- template <size_t N, typename List>
- using TakeTypeListItem = typename TakeTypeListItemImpl<N, List>::Type;
- // concat type lists.
- template <typename List1, typename List2>
- struct ConcatTypeListImpl;
- template <typename... ListA, typename... ListB>
- struct ConcatTypeListImpl<TypeList<ListA...>, TypeList<ListB...> > {
- using Type = TypeList<ListA..., ListB...>;
- };
- template <typename List1, typename List2>
- using ConcatTypeList = typename ConcatTypeListImpl<List1, List2>::Type;
- } // end namespace tl(type list)
- } // end namespace tars
- #endif
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