Add new class that represent a time stamp

Fixing issues from review by @fwinkl

Further review fixes


Former-commit-id: 09eeaa92

Trigger/TrigTools/TrigTimeAlgs/TrigTimeAlgs/TrigTimeStamp.h

+/*
+  Copyright (C) 2002-2018 CERN for the benefit of the ATLAS collaboration
+*/
+
+#ifndef TrigTimeAlgs_TrigTimeStamp_h
+#define TrigTimeAlgs_TrigTimeStamp_h
+
+
+#include <chrono>
+#include "SGTools/CLASS_DEF.h"
+/**
+ * utility class to measure time duration in AthenaMT
+ * The pattern when it is useful: 
+ * AlgA tags the beginning of the time period
+ *AlgA::execute() { 
+ * timeStampHandle.record( std::move( std::make_unique<TrigTimeStamp>() ) ); }
+ *
+ * AlgB obtains the duration since the start tagged in AlgA:
+ * AlgB::execute() { 
+ *  double duration = timeStampHandle.cptr().milisecondsSince();  }
+ **/
+class TrigTimeStamp {
+public:
+  typedef std::chrono::high_resolution_clock::time_point stamp_type;
+
+  TrigTimeStamp()
+    : m_stamp( std::chrono::high_resolution_clock::now() ) {}
+
+  /**
+   * time duration between now and when the time stamp was created
+   **/
+  double millisecondsSince() const; 
+
+  /**
+   * Obtain the stamp value.
+   **/
+  stamp_type get() const { return m_stamp; }
+private:
+  stamp_type m_stamp;
+};
+
+
+
+CLASS_DEF( TrigTimeStamp , 262409323 , 1 )
+
+#endif  // TrigTimeAlgs_TrigTimeStamp_h
+

Trigger/TrigTools/TrigTimeAlgs/src/TrigTimeStamp.cxx

+/*
+  Copyright (C) 2002-2018 CERN for the benefit of the ATLAS collaboration
+*/
+
+#include "TrigTimeAlgs/TrigTimeStamp.h"
+
+double TrigTimeStamp::millisecondsSince() const { 
+  return std::chrono::duration_cast<std::chrono::microseconds>( std::chrono::high_resolution_clock::now() - m_stamp ).count();
+}