added few new functionality in buffer

include/core/processor/processor_base.h

@@ -60,6 +60,10 @@ public:
 
     T selectFirstBefore(const TimeStamp& _time_stamp, const Scalar& _time_tolerance);
 
+    T selectFirst();
+
+    T selectLast();
+
     /**\brief Buffer size
     *
     */
@@ -444,6 +448,28 @@ T Buffer<T>::selectFirstBefore(const TimeStamp& _time_stamp, const Scalar& _time
 
 }
 
+template <typename T>
+T Buffer<T>::selectFirst()
+{
+    // There is no element
+    if (container_.empty())
+         return nullptr;
+
+    // Returning first map element
+    return container_.begin()->second;
+}
+
+template <typename T>
+T Buffer<T>::selectLast()
+{
+    // There is no element
+    if (container_.empty())
+         return nullptr;
+
+    // Returning last map element
+    return container_.rbegin()->second;
+}
+
 template <typename T>
 void Buffer<T>::add(const TimeStamp& _time_stamp, const T& _element)
 {