Fix sensor uuid, retrofit recent event logger

Fix an issue that causes uuid field not being initialzed in
sensorservice.

MostRecentEventLogger in sensorservice is migrated to use RingBuffer
instead of a custom circular buffer. This is expected to improve
readability and maintainability of code.

Dumpsys print format is retouched to offer more information in easier
to read format.

Bug: 28305085

Change-Id: I190e43350b60a22a9fccb92a95d6eab06a471560
diff --git a/services/sensorservice/RecentEventLogger.h b/services/sensorservice/RecentEventLogger.h
new file mode 100644
index 0000000..4f9bc4a
--- /dev/null
+++ b/services/sensorservice/RecentEventLogger.h
@@ -0,0 +1,68 @@
+/*
+ * Copyright (C) 2016 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 ANDROID_SENSOR_SERVICE_UTIL_RECENT_EVENT_LOGGER_H
+#define ANDROID_SENSOR_SERVICE_UTIL_RECENT_EVENT_LOGGER_H
+
+#include "RingBuffer.h"
+#include "SensorServiceUtils.h"
+
+#include <hardware/sensors.h>
+#include <utils/String8.h>
+
+#include <mutex>
+
+namespace android {
+namespace SensorServiceUtil {
+
+// A circular buffer that record the last N events of a sensor type for debugging. The size of this
+// buffer depends on sensor type and is controlled by logSizeBySensorType(). The last N events
+// generated from the sensor are stored in this buffer.  The buffer is NOT cleared when the sensor
+// unregisters and as a result very old data in the dumpsys output can be seen, which is an intended
+// behavior.
+class RecentEventLogger : public Dumpable {
+public:
+    RecentEventLogger(int sensorType);
+    void addEvent(const sensors_event_t& event);
+    bool populateLastEvent(sensors_event_t *event) const;
+    bool isEmpty() const;
+    virtual ~RecentEventLogger() {}
+
+    // Dumpable interface
+    virtual std::string dump() const override;
+
+protected:
+    struct SensorEventLog {
+        SensorEventLog(const sensors_event_t& e);
+        timespec mWallTime;
+        sensors_event_t mEvent;
+    };
+
+    const int mSensorType;
+    const size_t mEventSize;
+
+    mutable std::mutex mLock;
+    RingBuffer<SensorEventLog> mRecentEvents;
+
+private:
+    static size_t logSizeBySensorType(int sensorType);
+};
+
+} // namespace SensorServiceUtil
+} // namespace android;
+
+#endif // ANDROID_SENSOR_SERVICE_UTIL_RECENT_EVENT_LOGGER_H
+