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.

core/base/utils/CbmFileUtils.cxx

+#include "CbmFileUtils.h"
+
+#include "FairLogger.h"  // for LOG, info and error
+
+#include "TArchiveFile.h"  // for TArchiveFile
+#include "TFile.h"         // for TFile
+#include "TObjArray.h"
+
+#include <string>      // for string, find, substr
+#include <sys/stat.h>  // for stcuct stat
+
+
+namespace Cbm {
+  namespace File {
+    bool IsRootFile(std::string filename) {
+      // Currently plain root files and root files stored in a zip file are supported.
+      // The destiction between the two is a "#" in the filename string  which separates the
+      // name of the zip file from the name of the root file which is inside the zip file.
+      // In case the filename contains a hash (e.g. multi.zip#file.root) the hash
+      // separates the name of a zipfile (multi.zip) which contains the real root file
+      // (file.root).
+      // This nameing convention (e.g. multi.zip#file.root) is sed by ROOT.
+
+      // If a filename string contains a hash "#"
+      // split the string at the # in the name of the zipfile and
+      // the name of the contained root file.
+      std::string checkFilename {""};
+      std::string membername {""};
+      std::size_t found = filename.find("#");
+      if (found != std::string::npos) {
+        checkFilename = filename.substr(0, found);
+        membername    = filename.substr(found + 1);
+      } else {
+        checkFilename = filename;
+      }
+
+      bool wasfound = kFALSE;
+
+      // Check if the file exist
+      // In case of a root file contained in a zip archive check if the zip file
+      // exist
+      struct stat buffer;
+      if (stat(checkFilename.c_str(), &buffer) == 0) {
+        wasfound = kTRUE;
+      } else {
+        wasfound = kFALSE;
+        LOG(error) << "Input File " << checkFilename << " not found";
+      }
+
+      // In case of a zip archive check if the archive contains the root file
+      if (membername.compare("") != 0) {
+        TFile* fzip = TFile::Open(checkFilename.c_str());
+        if (fzip->IsOpen()) {
+          TArchiveFile* archive = fzip->GetArchive();
+          if (archive) {
+            TObjArray* members = archive->GetMembers();
+            if (members->FindObject(membername.c_str()) == 0) {
+              LOG(error) << "File " << membername << " not found in zipfile "
+                         << checkFilename;
+              wasfound = kFALSE;
+            } else {
+              LOG(info) << "File " << membername << " found in zipfile "
+                        << checkFilename;
+              wasfound = kTRUE;
+            }
+          } else {
+            LOG(error) << "Zipfile " << checkFilename
+                       << " does not contain an archive";
+            wasfound = kFALSE;
+          }
+          fzip->Close();
+          delete fzip;
+        } else {
+          LOG(error) << "Could not open zipfile " << checkFilename;
+          wasfound = kFALSE;
+        }
+      } else {
+        TFile* rootfile = TFile::Open(checkFilename.c_str());
+        if (rootfile->IsOpen()) {
+          LOG(info) << "File " << checkFilename << " is a ROOT file.";
+          wasfound = kTRUE;
+        } else {
+          LOG(error) << "File " << checkFilename << " is no ROOT file.";
+          wasfound = kFALSE;
+        }
+        rootfile->Close();
+        delete rootfile;
+      }
+
+      return wasfound;
+    }
+  }  // namespace File
+}  // namespace Cbm