TSelector.cxx

Go to the documentation of this file.

// @(#)root/tree:$Id$
// Author: Rene Brun   05/02/97

/*************************************************************************
 * Copyright (C) 1995-2000, Rene Brun and Fons Rademakers.               *
 * All rights reserved.                                                  *
 *                                                                       *
 * For the licensing terms see $ROOTSYS/LICENSE.                         *
 * For the list of contributors see $ROOTSYS/README/CREDITS.             *
 *************************************************************************/

/** \class TSelector
\ingroup tree

A TSelector object is used by the TTree::Draw, TTree::Scan,
TTree::Process to navigate in a TTree and make selections.
It contains the following main methods:

- void TSelector::Init(TTree *t). Called every time a new TTree is
   attached.

- void TSelector::SlaveBegin(). Create e.g. histograms in this method.
  This method is called (with or without PROOF) before looping on the
  entries in the Tree. When using PROOF, this method is called on
  each worker node.

- void TSelector::Begin(). Mostly for backward compatibility; use
  SlaveBegin() instead. Both methods are called before looping on the
  entries in the Tree. When using PROOF, Begin() is called on the
  client only.

- Bool_t TSelector::Notify(). This method is called at the first entry
  of a new file in a chain.

- Bool_t TSelector::Process(Long64_t entry). This method is called
  to process an entry. It is the user's responsability to read
  the corresponding entry in memory (may be just a partial read).
  Once the entry is in memory one can apply a selection and if the
  entry is selected histograms can be filled. Processing stops
  when this function returns kFALSE. This function combines the
  next two functions in one, avoiding to have to maintain state
  in the class to communicate between these two functions.
  See WARNING below about entry.
  This method is used by PROOF.

- Bool_t TSelector::ProcessCut(Long64_t entry). This method is called
  before processing entry. It is the user's responsability to read
  the corresponding entry in memory (may be just a partial read).
  The function returns kTRUE if the entry must be processed,
  kFALSE otherwise. This method is obsolete, use Process().
  See WARNING below about entry.

- void TSelector::ProcessFill(Long64_t entry). This method is called
  for all selected entries. User fills histograms in this function.
  This method is obsolete, use Process().
  See WARNING below about entry.

- void TSelector::SlaveTerminate(). This method is called at the end of
  the loop on all PROOF worker nodes. In local mode this method is
  called on the client too.

- void TSelector::Terminate(). This method is called at the end of
  the loop on all entries. When using PROOF Terminate() is call on
  the client only. Typically one performs the fits on the produced
  histograms or write the histograms to file in this method.

__WARNING when a selector is used with a TChain:__

in the Process, ProcessCut, ProcessFill function, you must use
the pointer to the current Tree to call `GetEntry(entry)`.
entry is always the local entry number in the current tree.
Assuming that fChain is the pointer to the TChain being processed,
use `fChain->GetTree()->GetEntry(entry);`
*/

#include "TROOT.h"
#include "TSystem.h"
#include "TTree.h"
#include "TError.h"
#include "TSelector.h"
#include "TClass.h"
#include "TInterpreter.h"

ClassImp(TSelector);

////////////////////////////////////////////////////////////////////////////////
/// Default selector ctor.

TSelector::TSelector() : TObject()
{
   fStatus = 0;
   fAbort  = kContinue;
   fObject = 0;
   fInput  = 0;
   fOutput = new TSelectorList;
   fOutput->SetOwner();
}

////////////////////////////////////////////////////////////////////////////////
/// Selector destructor.

TSelector::~TSelector()
{
   delete fOutput;
}

////////////////////////////////////////////////////////////////////////////////
/// Abort processing. If what = kAbortProcess, the Process() loop will be
/// aborted. If what = kAbortFile, the current file in a chain will be
/// aborted and the processing will continue with the next file, if there
/// is no next file then Process() will be aborted. Abort() can also  be
/// called from Begin(), SlaveBegin(), Init() and Notify(). After abort
/// the SlaveTerminate() and Terminate() are always called. The abort flag
/// can be checked in these methods using GetAbort().

void TSelector::Abort(const char *why, EAbort what)
{
   fAbort = what;
   TString mess = "Abort";
   if (fAbort == kAbortProcess)
      mess = "AbortProcess";
   else if (fAbort == kAbortFile)
      mess = "AbortFile";

   Info(mess, "%s", why);
}

////////////////////////////////////////////////////////////////////////////////
/// The code in filename is loaded (interpreted or compiled, see below),
/// filename must contain a valid class implementation derived from TSelector.
///
/// If filename is of the form file.C, the file will be interpreted.
/// If filename is of the form file.C++, the file file.C will be compiled
/// and dynamically loaded. The corresponding binary file and shared
/// library will be deleted at the end of the function.
/// If filename is of the form file.C+, the file file.C will be compiled
/// and dynamically loaded. At next call, if file.C is older than file.o
/// and file.so, the file.C is not compiled, only file.so is loaded.
///
/// The static function returns a pointer to a TSelector object

TSelector *TSelector::GetSelector(const char *filename)
{
   // If the filename does not contain "." assume class is compiled in
   TString localname;
   Bool_t fromFile = kFALSE;
   if (strchr(filename, '.') != 0) {
      //Interpret/compile filename via CINT
      localname  = ".L ";
      localname += filename;
      gROOT->ProcessLine(localname);
      fromFile = kTRUE;
   }

   //loop on all classes known to CINT to find the class on filename
   //that derives from TSelector
   const char *basename = gSystem->BaseName(filename);
   if (!basename) {
      ::Error("TSelector::GetSelector","unable to determine the classname for file %s", filename);
      return 0;
   }
   TString aclicmode,args,io;
   localname = gSystem->SplitAclicMode(basename,aclicmode,args,io);
   if (localname.Last('.') != kNPOS)
      localname.Remove(localname.Last('.'));

   // if a file was not specified, try to load the class via the interpreter;
   // this returns 0 (== failure) in the case the class is already in memory
   // but does not have a dictionary, so we just raise a flag for better
   // diagnostic in the case the class is not found in the CINT ClassInfo table.
   Bool_t autoloaderr = kFALSE;
   if (!fromFile && gCling->AutoLoad(localname) != 1)
      autoloaderr = kTRUE;

   TClass *selCl = TClass::GetClass(localname);
   if (selCl) {
      // We have all we need.
      auto offset = selCl->GetBaseClassOffset(TSelector::Class());
      if (offset == -1) {
         // TSelector is not a based class.
         if (fromFile)
            ::Error("TSelector::GetSelector",
                    "The class %s in file %s does not derive from TSelector.", localname.Data(), filename);
         else if (autoloaderr)
            ::Error("TSelector::GetSelector", "class %s could not be loaded", filename);
         else
            ::Error("TSelector::GetSelector",
                    "class %s does not exist or does not derive from TSelector", filename);
         return 0;
      }
      char *result = (char*)selCl->New();
      // By adding offset, we support the case where TSelector is not the
      // "left-most" base class (i.e. offset != 0)
      return (TSelector*)(result+offset);

   } else {
      ClassInfo_t *cl = gCling->ClassInfo_Factory(localname);
      Bool_t ok = kFALSE;
      Bool_t nameFound = kFALSE;
      if (cl && gCling->ClassInfo_IsValid(cl)) {
         if (localname == gCling->ClassInfo_FullName(cl)) {
            nameFound = kTRUE;
            if (gCling->ClassInfo_IsBase(cl,"TSelector")) ok = kTRUE;
         }
      }
      if (!ok) {
         if (fromFile) {
            if (nameFound) {
               ::Error("TSelector::GetSelector",
                       "The class %s in file %s does not derive from TSelector.", localname.Data(), filename);
            } else {
               ::Error("TSelector::GetSelector",
                       "The file %s does not define a class named %s.", filename, localname.Data());
            }
         } else {
            if (autoloaderr)
               ::Error("TSelector::GetSelector", "class %s could not be loaded", filename);
            else
               ::Error("TSelector::GetSelector",
                       "class %s does not exist or does not derive from TSelector", filename);
         }
         gCling->ClassInfo_Delete(cl);
         return 0;
      }

      // we can now create an instance of the class
      TSelector *selector = (TSelector*)gCling->ClassInfo_New(cl);
      gCling->ClassInfo_Delete(cl);
      return selector;
   }
}

////////////////////////////////////////////////////////////////////////////////
/// Find out if this is a standard selection used for Draw actions
/// (either TSelectorDraw, TProofDraw or deriving from them).

Bool_t TSelector::IsStandardDraw(const char *selec)
{
   // Make sure we have a name
   if (!selec) {
      ::Info("TSelector::IsStandardDraw",
             "selector name undefined - do nothing");
      return kFALSE;
   }

   Bool_t stdselec = kFALSE;
   if (!strchr(selec, '.')) {
      if (strstr(selec, "TSelectorDraw")) {
         stdselec = kTRUE;
      } else {
         TClass *cl = TClass::GetClass(selec);
         if (cl && (cl->InheritsFrom("TProofDraw") ||
                    cl->InheritsFrom("TSelectorDraw")))
            stdselec = kTRUE;
      }
   }

   // We are done
   return stdselec;
}

////////////////////////////////////////////////////////////////////////////////
/// Imports the content of 'output' in the internal output list. Existing content
/// in the output list is discarded (unless found also in 'output').
/// In particular, if 'output' is nullptr or empty, reset the internal list.
/// On return, the content of 'output' is cleared to avoid double deletion issues.
/// (The caller is responsible of 'output' as container: its content is transferred
/// under the selector ownership).

void TSelector::ImportOutput(TList *output) {

   // Reset the list, if required
   if (!output || output->GetSize() <= 0) {
      fOutput->Delete();
      return;
   }

   TObject *o;

   // Remove from new list objects already existing locally
   TIter nxexo(fOutput);
   while ((o = nxexo())) {
      if (output->FindObject(o)) output->Remove(o);
   }

   // Transfer remaining objects
   TIter nxo(output);
   while ((o = nxo())) {
      fOutput->Add(o);
   }

   // Cleanup original list
   output->SetOwner(kFALSE);
   output->Clear("nodelete");

   // Done
   return;
}

Bool_t TSelector::ProcessCut(Long64_t /*entry*/)
{
   //    This method is called before processing entry. It is the user's responsability to read
   //    the corresponding entry in memory (may be just a partial read).
   //    The function returns kTRUE if the entry must be processed,
   //    kFALSE otherwise. This method is obsolete, use Process().
   //
   // WARNING when a selector is used with a TChain:
   //    in the Process, ProcessCut, ProcessFill function, you must use
   //    the pointer to the current Tree to call GetEntry(entry).
   //    entry is always the local entry number in the current tree.
   //    Assuming that fChain is the pointer to the TChain being processed,
   //    use fChain->GetTree()->GetEntry(entry);

   return kTRUE;
}

void TSelector::ProcessFill(Long64_t /*entry*/)
{
   // This method is called for all selected entries. User fills histograms
   // in this function.  This method is obsolete, use Process().
   //
   // WARNING when a selector is used with a TChain:
   //    in the Process, ProcessCut, ProcessFill function, you must use
   //    the pointer to the current Tree to call GetEntry(entry).
   //    entry is always the local entry number in the current tree.
   //    Assuming that fChain is the pointer to the TChain being processed,
   //    use fChain->GetTree()->GetEntry(entry);
}

Bool_t TSelector::Process(Long64_t /*entry*/) {
   // The Process() function is called for each entry in the tree (or possibly
   // keyed object in the case of PROOF) to be processed. The entry argument
   // specifies which entry in the currently loaded tree is to be processed.
   // It can be passed to either t01::GetEntry() or TBranch::GetEntry()
   // to read either all or the required parts of the data. When processing
   // keyed objects with PROOF, the object is already loaded and is available
   // via the fObject pointer.
   //
   // This function should contain the "body" of the analysis. It can contain
   // simple or elaborate selection criteria, run algorithms on the data
   // of the event and typically fill histograms.
   //
   // The processing can be stopped by calling Abort().
   //
   // Use fStatus to set the return value of TTree::Process().
   //
   // The return value is currently not used.

   return kFALSE;
}