1 /**
2  * Copyright (c) 2020, 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 <climits>
20 #include <mutex>
21 #include <string>
22 #include <string_view>
23 #include <unordered_map>
24 
25 #include <android-base/thread_annotations.h>
26 #include <netdutils/DumpWriter.h>
27 
28 namespace android::net {
29 
30 // TODO: Add some way to update the stored experiment flags periodically.
31 // TODO: Refactor this class and make things easier. (e.g. remove string map.)
32 class Experiments {
33   public:
34     using GetExperimentFlagIntFunction = std::function<int(const std::string&, int)>;
35     static Experiments* getInstance();
36     int getFlag(std::string_view key, int defaultValue) const EXCLUDES(mMutex);
37     void update();
38     void dump(netdutils::DumpWriter& dw) const EXCLUDES(mMutex);
39 
40     Experiments(Experiments const&) = delete;
41     void operator=(Experiments const&) = delete;
42 
43   private:
44     explicit Experiments(GetExperimentFlagIntFunction getExperimentFlagIntFunction);
45     Experiments() = delete;
46     void updateInternal() EXCLUDES(mMutex);
47     mutable std::mutex mMutex;
48     std::unordered_map<std::string_view, int> mFlagsMapInt GUARDED_BY(mMutex);
49     // TODO: Migrate other experiment flags to here.
50     // (retry_count, retransmission_time_interval, dot_connect_timeout_ms)
51     static constexpr const char* const kExperimentFlagKeyList[] = {
52             "keep_listening_udp", "parallel_lookup", "parallel_lookup_sleep_time",
53             "sort_nameservers"};
54     // This value is used in updateInternal as the default value if any flags can't be found.
55     static constexpr int kFlagIntDefault = INT_MIN;
56     // For testing.
57     friend class ExperimentsTest;
58     const GetExperimentFlagIntFunction mGetExperimentFlagIntFunction;
59 };
60 
61 }  // namespace android::net
62