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diff --git a/cmds/statsd/src/state/StateTracker.h b/cmds/statsd/src/state/StateTracker.h
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+++ b/cmds/statsd/src/state/StateTracker.h
@@ -0,0 +1,94 @@
+/*
+ * 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.
+ */
+#pragma once
+
+#include <utils/RefBase.h>
+#include "HashableDimensionKey.h"
+#include "logd/LogEvent.h"
+
+#include "state/StateListener.h"
+
+#include <unordered_map>
+
+namespace android {
+namespace os {
+namespace statsd {
+
+class StateTracker : public virtual RefBase {
+public:
+    StateTracker(const int32_t atomId);
+
+    virtual ~StateTracker(){};
+
+    // Updates state map and notifies all listeners if a state change occurs.
+    // Checks if a state change has occurred by getting the state value from
+    // the log event and comparing the old and new states.
+    void onLogEvent(const LogEvent& event);
+
+    // Adds new listeners to set of StateListeners. If a listener is already
+    // registered, it is ignored.
+    void registerListener(wp<StateListener> listener);
+
+    void unregisterListener(wp<StateListener> listener);
+
+    // The output is a FieldValue object that has mStateField as the field and
+    // the original state value (found using the given query key) as the value.
+    //
+    // If the key isn't mapped to a state or the key size doesn't match the
+    // number of primary fields, the output value is set to kStateUnknown.
+    bool getStateValue(const HashableDimensionKey& queryKey, FieldValue* output) const;
+
+    inline int getListenersCount() const {
+        return mListeners.size();
+    }
+
+    const static int kStateUnknown = -1;
+
+private:
+    struct StateValueInfo {
+        int32_t state = kStateUnknown;  // state value
+        int count = 0;                  // nested count (only used for binary states)
+    };
+
+    Field mField;
+
+    // Maps primary key to state value info
+    std::unordered_map<HashableDimensionKey, StateValueInfo> mStateMap;
+
+    // Set of all StateListeners (objects listening for state changes)
+    std::set<wp<StateListener>> mListeners;
+
+    // Reset all state values in map to the given state.
+    void handleReset(const int64_t eventTimeNs, const FieldValue& newState);
+
+    // Clears the state value mapped to the given primary key by setting it to kStateUnknown.
+    void clearStateForPrimaryKey(const int64_t eventTimeNs, const HashableDimensionKey& primaryKey);
+
+    // Update the StateMap based on the received state value.
+    void updateStateForPrimaryKey(const int64_t eventTimeNs, const HashableDimensionKey& primaryKey,
+                                  const FieldValue& newState, const bool nested,
+                                  StateValueInfo* stateValueInfo);
+
+    // Notify registered state listeners of state change.
+    void notifyListeners(const int64_t eventTimeNs, const HashableDimensionKey& primaryKey,
+                         const FieldValue& oldState, const FieldValue& newState);
+};
+
+bool getStateFieldValueFromLogEvent(const LogEvent& event, FieldValue* output);
+
+}  // namespace statsd
+}  // namespace os
+}  // namespace android