MCKinematicsReader: Allow to use with Hit/Kinematics file

This allows to fetch a track when one is just given
an eventID + trackID (in a hit).

Steer/include/Steer/MCKinematicsReader.h

@@ -23,32 +23,54 @@ namespace steer
 class MCKinematicsReader
 {
  public:
+  enum class Mode {
+    kDigiContext,
+    kMCKine
+  };
+
   /// default constructor
   MCKinematicsReader() = default;
 
-  /// constructor taking context and auto-initializing
-  MCKinematicsReader(std::string_view filename)
+  /// constructor taking a name and mode (either kDigiContext or kMCKine)
+  /// In case of "context", the name is the filename of the digitization context.
+  /// In case of MCKine mode, the name is the "prefix" referencing a single simulation production.
+  /// The default mode is kDigiContext.
+  MCKinematicsReader(std::string_view name, Mode mode = Mode::kDigiContext)
   {
-    init(filename);
+    if (mode == Mode::kMCKine) {
+      initFromKinematics(name);
+    } else if (mode == Mode::kDigiContext) {
+      initFromDigitContext(name);
+    }
   }
 
   /// inits the reader from a digitization context
   /// returns true if successful
-  bool init(std::string_view filename);
+  bool initFromDigitContext(std::string_view filename);
+
+  /// inits the reader from a simple kinematics file
+  bool initFromKinematics(std::string_view filename);
 
   bool isInitialized() const { return mInitialized; }
 
   /// query an MC track given a basic label object
   /// returns nullptr if no track was found
   MCTrack const* getTrack(o2::MCCompLabel const&) const;
 
-  /// query an MC track given a basic label object
+  /// query an MC track given source, event, track IDs
   /// returns nullptr if no track was found
   MCTrack const* getTrack(int source, int event, int track) const;
 
+  /// query an MC track given event, track IDs
+  /// returns nullptr if no track was found
+  MCTrack const* getTrack(int event, int track) const;
+
   /// variant returning all tracks for source and event at once
   std::vector<MCTrack> const& getTracks(int source, int event) const;
 
+  /// variant returning all tracks for source and event at once
+  std::vector<MCTrack> const& getTracks(int event) const;
+
   /// get all primaries for a certain event
 
   /// get all secondaries of the given label
@@ -85,6 +107,11 @@ inline MCTrack const* MCKinematicsReader::getTrack(int source, int event, int tr
   return &mTracks[source][event][track];
 }
 
+inline MCTrack const* MCKinematicsReader::getTrack(int event, int track) const
+{
+  return getTrack(0, event, track);
+}
+
 inline std::vector<MCTrack> const& MCKinematicsReader::getTracks(int source, int event) const
 {
   if (mTracks[source].size() == 0) {
@@ -93,5 +120,10 @@ inline std::vector<MCTrack> const& MCKinematicsReader::getTracks(int source, int
   return mTracks[source][event];
 }
 
+inline std::vector<MCTrack> const& MCKinematicsReader::getTracks(int event) const
+{
+  return getTracks(0, event);
+}
+
 } // namespace steer
 } // namespace o2

Steer/src/MCKinematicsReader.cxx

@@ -8,6 +8,7 @@
 // granted to it by virtue of its status as an Intergovernmental Organization
 // or submit itself to any jurisdiction.
 
+#include "DetectorsCommonDataFormats/NameConf.h"
 #include "Steer/MCKinematicsReader.h"
 #include <TChain.h>
 #include <vector>
@@ -34,8 +35,13 @@ void MCKinematicsReader::loadTracksForSource(int source) const
   }
 }
 
-bool MCKinematicsReader::init(std::string_view name)
+bool MCKinematicsReader::initFromDigitContext(std::string_view name)
 {
+  if (mInitialized) {
+    LOG(INFO) << "MCKinematicsReader already initialized; doing nothing";
+    return false;
+  }
+
   auto context = DigitizationContext::loadFromFile(name);
   if (!context) {
     return false;
@@ -54,3 +60,17 @@ bool MCKinematicsReader::init(std::string_view name)
 
   return true;
 }
+
+bool MCKinematicsReader::initFromKinematics(std::string_view name)
+{
+  if (mInitialized) {
+    LOG(INFO) << "MCKinematicsReader already initialized; doing nothing";
+    return false;
+  }
+  mInputChains.emplace_back(new TChain("o2sim"));
+  mInputChains.back()->AddFile(o2::base::NameConf::getMCKinematicsFileName(name.data()).c_str());
+  mTracks.resize(1);
+  mInitialized = true;
+
+  return true;
+}