Protect FT decoding from misordered links

FT/FTDAQ/src/FTRawBankDecoder.cpp

@@ -71,6 +71,7 @@ private:
   ServiceHandle<IDataProviderSvc> m_dataSvc{this, "DataService", "DetectorDataSvc", "The detector data service"};
 
   mutable Gaudi::Accumulators::MsgCounter<MSG::ERROR> m_misordered{this, "Misordered large cluster"};
+  mutable Gaudi::Accumulators::MsgCounter<MSG::ERROR> m_misorderedLinks{this, "Misordered links"};
   mutable Gaudi::Accumulators::MsgCounter<MSG::ERROR> m_corrupt1{
       this, "Possibly corrupt data (type 1). Ignoring the cluster."};
   mutable Gaudi::Accumulators::MsgCounter<MSG::ERROR> m_corrupt2{
@@ -115,6 +116,11 @@ private:
       "misordered",
       "Misordered large clusters;iLink",
       {FTRawBank::BankProperties::NbLinksMax, -0.5, static_cast<float>( FTRawBank::BankProperties::NbLinksMax ) - 0.5}};
+  mutable Gaudi::Accumulators::Histogram<1, Gaudi::Accumulators::atomicity::full, float> m_misorderedLinks_hist{
+      this,
+      "misorderedLinks",
+      "Misordered link index;iLink",
+      {FTRawBank::BankProperties::NbLinksMax, -0.5, static_cast<float>( FTRawBank::BankProperties::NbLinksMax ) - 0.5}};
   mutable Gaudi::Accumulators::Histogram<1, Gaudi::Accumulators::atomicity::full, float> m_corruptCluster1_hist{
       this,
       "corrupt_cluster1",
@@ -646,6 +652,13 @@ FTLiteClusters FTRawBankDecoder::decode( const EventContext& evtCtx, LHCb::RawBa
           clusters = clusters.subspan( 1 );
           continue;
         }
+        if ( localLinkIndex < lastLink ) {
+          // LoH: this has happened in April 2024 because of bit flips. Allen!1546
+          ++m_misorderedLinks;
+          ++m_misorderedLinks_hist[iRow * FTRawBank::BankProperties::NbLinksPerBank + localLinkIndex];
+          clusters = clusters.subspan( 1 );
+          continue;
+        }
         if ( localLinkIndex == lastLink && channelInSiPM <= lastChannel ) {
           ++m_misordered;
           ++m_misordered_hist[iRow * FTRawBank::BankProperties::NbLinksPerBank + localLinkIndex];