1 files changed, 90 insertions, 0 deletions
diff --git a/libs/input/LatencyStatistics.cpp b/libs/input/LatencyStatistics.cpp
new file mode 100644
index 0000000000..394da22a62
--- /dev/null
+++ b/libs/input/LatencyStatistics.cpp
@@ -0,0 +1,90 @@
+/*
+ * 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.
+ */
+
+#include <input/LatencyStatistics.h>
+
+#include <android-base/chrono_utils.h>
+
+#include <cmath>
+#include <limits>
+
+namespace android {
+
+LatencyStatistics::LatencyStatistics(std::chrono::seconds period) : mReportPeriod(period) {
+    reset();
+}
+
+/**
+ * Add a raw value to the statistics
+ */
+void LatencyStatistics::addValue(float value) {
+    if (value < mMin) {
+        mMin = value;
+    }
+    if (value > mMax) {
+        mMax = value;
+    }
+    mSum += value;
+    mSum2 += value * value;
+    mCount++;
+}
+
+/**
+ * Get the mean. Should not be called if no samples have been added.
+ */
+float LatencyStatistics::getMean() {
+    return mSum / mCount;
+}
+
+/**
+ * Get the standard deviation. Should not be called if no samples have been added.
+ */
+float LatencyStatistics::getStDev() {
+    float mean = getMean();
+    return sqrt(mSum2 / mCount - mean * mean);
+}
+
+float LatencyStatistics::getMin() {
+    return mMin;
+}
+
+float LatencyStatistics::getMax() {
+    return mMax;
+}
+
+size_t LatencyStatistics::getCount() {
+    return mCount;
+}
+
+/**
+ * Reset internal state. The variable 'when' is the time when the data collection started.
+ * Call this to start a new data collection window.
+ */
+void LatencyStatistics::reset() {
+    mMax = std::numeric_limits<float>::lowest();
+    mMin = std::numeric_limits<float>::max();
+    mSum = 0;
+    mSum2 = 0;
+    mCount = 0;
+    mLastReportTime = std::chrono::steady_clock::now();
+}
+
+bool LatencyStatistics::shouldReport() {
+    std::chrono::duration timeSinceReport = std::chrono::steady_clock::now() - mLastReportTime;
+    return mCount != 0 && timeSinceReport >= mReportPeriod;
+}
+
+} // namespace android