Seperate LatencyStatistics from InputReader

Test: atest LatencyStatisticsTest
Change-Id: I22a39cd5bef7fa9180bc1ee1fd9478a2cf872e83
diff --git a/include/input/LatencyStatistics.h b/include/input/LatencyStatistics.h
new file mode 100644
index 0000000..bd86266
--- /dev/null
+++ b/include/input/LatencyStatistics.h
@@ -0,0 +1,59 @@
+/*
+ * Copyright (C) 2019 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.
+ */
+
+#ifndef _UI_INPUT_STATISTICS_H
+#define _UI_INPUT_STATISTICS_H
+
+#include <android-base/chrono_utils.h>
+
+#include <stddef.h>
+
+namespace android {
+
+class LatencyStatistics {
+private:
+    /* Minimum sample recorded */
+    float mMin;
+    /* Maximum sample recorded */
+    float mMax;
+    /* Sum of all samples recorded */
+    float mSum;
+    /* Sum of all the squares of samples recorded */
+    float mSum2;
+    /* Count of all samples recorded */
+    size_t mCount;
+    /* The last time statistics were reported */
+    std::chrono::steady_clock::time_point mLastReportTime;
+    /* Statistics Report Frequency */
+    const std::chrono::seconds mReportPeriod;
+
+public:
+    LatencyStatistics(std::chrono::seconds period);
+
+    void addValue(float);
+    void reset();
+    bool shouldReport();
+
+    float getMean();
+    float getMin();
+    float getMax();
+    float getStDev();
+    size_t getCount();
+};
+
+} // namespace android
+
+#endif // _UI_INPUT_STATISTICS_H