TFileIter

Class Description

                                                                       
 Class to iterate (read / write ) the events written to TFile.         
 The event is supposed to assign an unique ID in form of               
                                                                       
  TKey <event Id> ::= eventName "." run_number "." event_number        
                                                                       
 and stored as the TKey name of the object written                     
                                                                       
        ///////        //////////      ////////        ///////     

 void TestFileIter(){
 // This macros tests the various methods of TFileIter class.
   gSystem->Load("libTable");

   //First create simple ROOT file
   TDataSet *ds = new TDataSet("event");
   TObject *nextObject = 0;
   TRandom run;
   TRandom event;
   {
     TFileIter outSet("test.root","RECREATE");
     UInt_t totalEvent = 10;
     UInt_t runNumber  = 20010301;
     Int_t i=0;
     Int_t j=0;
     for (;j < 10;j++) {
       for (i = 1;i<totalEvent;i++) {
         outSet.NextEventPut(ds,UInt_t(i),UInt_t(runNumber+j+10*run.Rndm()-5));
       }
     }
   }
   printf(" ----------------------> TFile has been created <--------------------\n");
   TFile *f = new TFile("test.root");
   TFileIter readObj(f);
   // the number of the object available directly from "MyDataSet.root"
   Int_t size = readObj.TotalKeys();
   printf(" The total number of the objects: %d\n",size);

   //-----------------------------------------------------------------------
   // Loop over all objects, read them in to memory one by one

   printf(" -- > Loop over all objects, read them in to memory one by one < -- \n");
   for( readObj = 0; int(readObj) < size; ++readObj){
       nextObject = *readObj;
       printf(" %d bytes of the object \"%s\" of class \"%s\" written with TKey \"%s\"  has been read from file\n"
                ,readObj.GetObjlen()
                ,nextObject->GetName()
                ,nextObject->IsA()->GetName()
                ,(const char *)readObj
             );
       delete nextObject;
  }
 //-----------------------------------------------------------------------
 //  Now loop over all objects in inverse order
  printf(" -- > Now loop over all objects in inverse order < -- \n");
  for( readObj = size-1; (int)readObj >= 0; --readObj)
  {
       nextObject = *readObj;
       if (nextObject) {
          printf(" Object \"%s\" of class \"%s\" written with TKey \"%s\"  has been read from file\n"
                 ,nextObject->GetName()
                 , nextObject->IsA()->GetName()
                 ,(const char *)readObj
                );
         delete nextObject;
      } else {
        printf("Error reading file by index\n");
      }
  }
 //-----------------------------------------------------------------------
 // Loop over the objects starting from the object with the key name "event.02.01"
   printf(" -- > Loop over the objects starting from the object with the key name \"event.02.01\" < -- \n");
   for( readObj = "event.02.01"; (const char *)readObj != 0; ++readObj){
       nextObject = *readObj;
       printf(" Object \"%s\" of class \"%s\" written with Tkey \"%s\"  has been read from file\n"
               , nextObject->GetName()
               , nextObject->IsA()->GetName()
               , (const char *)readObj
             );
       delete nextObject;
   }

   printf(" -- > Loop over the objects starting from the 86-th object" < -- \n");
   for( readObj = (const char *)(readObj = 86); (const char *)readObj != 0; ++readObj){
       nextObject = *readObj;
       printf(" Object \"%s\" of class \"%s\" written with Tkey \"%s\"  has been read from file\n"
               , nextObject->GetName()
               , nextObject->IsA()->GetName()
               , (const char *)readObj
             );
       delete nextObject;
   }

 }
-----------------------------------------------------------------------

TFileIter(const char *name, Option_t *option, const char *ftitle , Int_t compress, Int_t /*netopt*/)

{
 Open ROOT TFile by the name provided;
 This TFile is to be deleted by the TFileIter alone
if (name && name[0]) {
fOwnTFile = kTRUE;
 Map a special file system to rfio
   /hpss/in2p3.fr/group/atlas/cppm/data/genz
   #setenv HPSSIN bnlhpss:/home/atlasgen/evgen
 #example for castor:   /castor/cern.ch/user/p/paniccia/evgen
fRootFile = TFile::Open(MapName(name),option,ftitle,compress);
Initialize();
}
}

__________________________________________________________________________
TFileIter::TFileIter(const TFileIter &dst) : TListIter()
,fRootFile(dst.fRootFile)
,fEventName(dst.fEventName), fRunNumber(dst.fRunNumber)
,fEventNumber(dst.fRunNumber),
fCursorPosition(-1),  fOwnTFile(dst.fOwnTFile)
{
 Copy stor can be used with the "read only" files only.

TString MapName(const char *name, const char *localSystemKey,const char *mountedFileSystemKey)

 --------------------------------------------------------------------------------------
 MapName(const char *name, const char *localSystemKey,const char *mountedFileSystemKey)
 --------------------------------------------------------------------------------------
 Substitute the logical name with the real one if any
 1. add a line into system.rootrc or ~/.rootrc or ./.rootrc

  TFileIter.ForeignFileMap  mapFile // the name of the file
 to map the local name
 to the global file service

  If this line is omitted then TFileIter class seeks for
  the default mapping file in the current directory "io.config"

TFileIter

class TFileIter : public TListIter

Data Members

Class Description