Allow as input ROOT file from ZIP archives

Since the size of a single PLUTO file is very small the preferred storage solution for them is to store a large number of them in a archive. ROOT is able to handle ROOT files stored in a ZIP archive so the file handling in the class was adapted for the ZIP file usage.

sim/transport/generators/CbmPlutoGenerator.cxx

@@ -179,12 +179,26 @@ void CbmPlutoGenerator::CloseInput() {
 // ------------------------------------------------------------------------
 
 void CbmPlutoGenerator::CheckFileExist(std::string filename) {
+
+  // Extract the filename of the zip file in case the real root file
+  // is packed into a zip file. The delimiter between the two file
+  // names is a hash (#).
+  // For the time being we don't check if the root file really exist in
+  // the zip file since we don't know how to do the check
+  std::string checkFilename {""};
+  std::size_t found = filename.find("#");
+  if (found != std::string::npos) {
+    checkFilename = filename.substr(0, found);
+  } else {
+    checkFilename = filename;
+  }
+
   struct stat buffer;
-  if (stat(filename.c_str(), &buffer) == 0) {
+  if (stat(checkFilename.c_str(), &buffer) == 0) {
     LOG(info) << "CbmPlutoGenerator: Add file " << filename
               << " to input chain";
   } else {
-    LOG(fatal) << "Input File " << filename << " not found";
+    LOG(fatal) << "Input File " << checkFilename << " not found";
   }
 }