power/stats: Add default implementation

Bug: 181592995
Test: atest VtsHalPowerStatsTargetTest
Change-Id: I87ea4974f857ebd126b80a45c7d7403307bceb03
diff --git a/power/stats/aidl/default/FakeStateResidencyDataProvider.h b/power/stats/aidl/default/FakeStateResidencyDataProvider.h
new file mode 100644
index 0000000..2eeab61
--- /dev/null
+++ b/power/stats/aidl/default/FakeStateResidencyDataProvider.h
@@ -0,0 +1,87 @@
+/*
+ * Copyright (C) 2021 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+#include <PowerStats.h>
+
+#include <random>
+
+namespace aidl {
+namespace android {
+namespace hardware {
+namespace power {
+namespace stats {
+
+class FakeStateResidencyDataProvider : public PowerStats::IStateResidencyDataProvider {
+  public:
+    FakeStateResidencyDataProvider(const std::string& name, std::vector<State> states)
+        : mName(name), mStates(states) {
+        for (const auto& state : mStates) {
+            StateResidency r;
+            r.id = state.id;
+            r.totalTimeInStateMs = 0;
+            r.totalStateEntryCount = 0;
+            r.lastEntryTimestampMs = 0;
+            mResidencies.push_back(r);
+        }
+    }
+    ~FakeStateResidencyDataProvider() = default;
+
+    // Methods from PowerStats::IStateResidencyDataProvider
+    bool getStateResidencies(
+            std::unordered_map<std::string, std::vector<StateResidency>>* residencies) override {
+        for (auto& residency : mResidencies) {
+            mFakeStateResidency.update(&residency);
+        }
+
+        residencies->emplace(mName, mResidencies);
+        return true;
+    }
+
+    std::unordered_map<std::string, std::vector<State>> getInfo() override {
+        return {{mName, mStates}};
+    }
+
+  private:
+    class FakeStateResidency {
+      public:
+        FakeStateResidency() : mDistribution(1, 100) {}
+        void update(StateResidency* residency) {
+            // generates number in the range 1..100
+            auto randNum = std::bind(mDistribution, mGenerator);
+
+            residency->totalTimeInStateMs += randNum() * 100;
+            residency->totalStateEntryCount += randNum();
+            residency->lastEntryTimestampMs += randNum() * 100;
+        }
+
+      private:
+        std::default_random_engine mGenerator;
+        std::uniform_int_distribution<int> mDistribution;
+    };
+
+    const std::string mName;
+    const std::vector<State> mStates;
+    FakeStateResidency mFakeStateResidency;
+    std::vector<StateResidency> mResidencies;
+};
+
+}  // namespace stats
+}  // namespace power
+}  // namespace hardware
+}  // namespace android
+}  // namespace aidl
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