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>
Append(CollectionType & collection,T && arg)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>
Append(CollectionType & collection,T && arg,Args &&...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>
AssertType(Arg &&)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>
AssertType(Arg &&,Args &&...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
61