Fix leak from HepPDT::HeavyIonUnknownID

HepPDT::HeavyIonUnknownID creates a new particle in the case the
HepPDT does not know of that particle by default. However, nothing
deletes that particle. This code wraps HeavyIonUnknownID and does
a thread safe cache of the particle in order to delete it later.

SimGeneral/HepPDTESSource/BuildFile.xml

@@ -1,3 +1,4 @@
 <use   name="FWCore/ParameterSet"/>
 <use   name="SimGeneral/HepPDTRecord"/>
+<use   name="tbb"/>
 <flags   EDM_PLUGIN="1"/>

SimGeneral/HepPDTESSource/src/HepPDTESSource.cc

@@ -1,5 +1,28 @@
 #include "SimGeneral/HepPDTESSource/interface/HepPDTESSource.h"
 #include "HepPDT/HeavyIonUnknownID.hh"
+#include "tbb/concurrent_unordered_map.h"
+
+namespace {
+
+  class CachingHeavyIonUnknownID : public HepPDT::ProcessUnknownID {
+    HepPDT::ParticleData  * processUnknownID( HepPDT::ParticleID id, 
+                                              const HepPDT::ParticleDataTable & table) final {
+      auto find = idToParticleMap_.find(id.pid());
+      if(find != idToParticleMap_.end()) {
+        return find->second.get();
+      }
+
+      //HeavyIonUnknownID constructs a new particle but does not delete it
+      // we need to do that ourselves
+      return idToParticleMap_.emplace( id.pid(), std::unique_ptr<HepPDT::ParticleData>{ wrapped_.callProcessUnknownID(id, table) } ).first->second.get();
+
+    }
+
+    HepPDT::HeavyIonUnknownID wrapped_;
+    tbb::concurrent_unordered_map<int, std::unique_ptr<HepPDT::ParticleData>> idToParticleMap_;
+  };
+
+}
 
 HepPDTESSource::HepPDTESSource( const edm::ParameterSet& cfg ) :
   pdtFileName( cfg.getParameter<edm::FileInPath>( "pdtFileName" ) ) {
@@ -13,7 +36,7 @@ HepPDTESSource::~HepPDTESSource() {
 HepPDTESSource::ReturnType
 HepPDTESSource::produce( const PDTRecord & iRecord ) {
   using namespace edm::es;
-  auto pdt = std::make_unique<PDT>( "PDG table" , new HepPDT::HeavyIonUnknownID );
+  auto pdt = std::make_unique<PDT>( "PDG table" , new CachingHeavyIonUnknownID );
   std::ifstream pdtFile( pdtFileName.fullPath().c_str() );
   if( ! pdtFile ) 
     throw cms::Exception( "FileNotFound", "can't open pdt file" )