1/*
2 * Copyright (C) 2017 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#include <tuple>
18
19namespace utility {
20
21namespace detail {
22// Helper class to generate the HIDL synchronous callback
23template <class... ResultStore>
24class ReturnIn {
25 public:
26    // Provide to the constructor the variables where the output parameters must be copied
27    // TODO: take pointers to match google output parameter style ?
28    ReturnIn(ResultStore&... ts) : results(ts...) {}
29    // Synchronous callback
30    template <class... Results>
31    void operator() (Results&&...results) {
32        set(std::forward<Results>(results)...);
33    }
34 private:
35    // Recursively set all output parameters
36    template <class Head, class... Tail>
37    void set(Head&& head, Tail&&... tail) {
38        std::get<sizeof...(ResultStore) - sizeof...(Tail) - 1>(results)
39                  = std::forward<Head>(head);
40        set(tail...);
41    }
42    // Trivial case
43    void set() {}
44
45    // All variables to set are stored here
46    std::tuple<ResultStore&...> results;
47};
48} // namespace detail
49
50// Generate the HIDL synchronous callback with a copy policy
51// Input: the variables (lvalue reference) where to save the return values
52// Output: the callback to provide to a HIDL call with a synchronous callback
53// The output parameters *will be copied* do not use this function if you have
54// a zero copy policy
55template <class... ResultStore>
56detail::ReturnIn<ResultStore...> returnIn(ResultStore&... ts) { return {ts...};}
57
58}
59