Josh Gao | c50f38f | 2019-01-07 19:16:21 -0800 | [diff] [blame^] | 1 | /* |
| 2 | * Copyright (C) 2019 The Android Open Source Project |
| 3 | * |
| 4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | * you may not use this file except in compliance with the License. |
| 6 | * You may obtain a copy of the License at |
| 7 | * |
| 8 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | * |
| 10 | * Unless required by applicable law or agreed to in writing, software |
| 11 | * distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | * See the License for the specific language governing permissions and |
| 14 | * limitations under the License. |
| 15 | */ |
| 16 | |
| 17 | #pragma once |
| 18 | |
| 19 | #include <utility> |
| 20 | |
| 21 | namespace android { |
| 22 | namespace base { |
| 23 | |
| 24 | // Helpers for converting a variadic template parameter pack to a homogeneous collection. |
| 25 | // Parameters must be implictly convertible to the contained type (including via move/copy ctors). |
| 26 | // |
| 27 | // Use as follows: |
| 28 | // |
| 29 | // template <typename... Args> |
| 30 | // std::vector<int> CreateVector(Args&&... args) { |
| 31 | // std::vector<int> result; |
| 32 | // Append(result, std::forward<Args>(args)...); |
| 33 | // return result; |
| 34 | // } |
| 35 | template <typename CollectionType, typename T> |
| 36 | void Append(CollectionType& collection, T&& arg) { |
| 37 | collection.push_back(std::forward<T>(arg)); |
| 38 | } |
| 39 | |
| 40 | template <typename CollectionType, typename T, typename... Args> |
| 41 | void Append(CollectionType& collection, T&& arg, Args&&... args) { |
| 42 | collection.push_back(std::forward<T>(arg)); |
| 43 | return Append(collection, std::forward<Args>(args)...); |
| 44 | } |
| 45 | |
| 46 | // Assert that all of the arguments in a variadic template parameter pack are of a given type |
| 47 | // after std::decay. |
| 48 | template <typename T, typename Arg, typename... Args> |
| 49 | void AssertType(Arg&&) { |
| 50 | static_assert(std::is_same<T, typename std::decay<Arg>::type>::value); |
| 51 | } |
| 52 | |
| 53 | template <typename T, typename Arg, typename... Args> |
| 54 | void AssertType(Arg&&, Args&&... args) { |
| 55 | static_assert(std::is_same<T, typename std::decay<Arg>::type>::value); |
| 56 | AssertType<T>(std::forward<Args>(args)...); |
| 57 | } |
| 58 | |
| 59 | } // namespace base |
| 60 | } // namespace android |