1 /**
2  * Copyright (c) 2021, 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 #ifndef CPP_LIBSYSFSMONITOR_SRC_SYSFSMONITOR_H_
18 #define CPP_LIBSYSFSMONITOR_SRC_SYSFSMONITOR_H_
19 
20 #include <android-base/result.h>
21 #include <android-base/unique_fd.h>
22 #include <utils/RefBase.h>
23 
24 #include <functional>
25 #include <string>
26 #include <unordered_set>
27 
28 namespace android {
29 namespace automotive {
30 
31 using CallbackFunc = ::std::function<void(const std::vector<int32_t>&)>;
32 
33 /**
34  * SysfsMonitor monitors sysfs file changes and invokes the registered callback when there is a
35  * change at the sysfs files to monitor.
36  */
37 class SysfsMonitor final : public RefBase {
38 public:
39     // Initializes SysfsMonitor instance.
40     android::base::Result<void> init(CallbackFunc callback);
41     // Releases resources used for monitoring.
42     android::base::Result<void> release();
43     // Registers a sysfs file to monitor.
44     android::base::Result<void> registerFd(int32_t fd);
45     // Unregisters a sysfs file to monitor.
46     android::base::Result<void> unregisterFd(int32_t fd);
47     // Starts observing sysfs file changes.
48     android::base::Result<void> observe();
49 
50 private:
51     android::base::unique_fd mEpollFd;
52     std::unordered_set<int32_t> mMonitoringFds;
53     CallbackFunc mCallback;
54 };
55 
56 }  // namespace automotive
57 }  // namespace android
58 
59 #endif  // CPP_LIBSYSFSMONITOR_SRC_SYSFSMONITOR_H_
60