class TFileIter: public TListIter

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;
   }

 }