TDirectoryFile.cxx

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// @(#)root/io:$Id$
// Author: Rene Brun   22/01/2007
 
/*************************************************************************
 * Copyright (C) 1995-2007, 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 TDirectoryFile
 \ingroup IO
 
 A ROOT file is structured in Directories (like a file system).
 Each Directory has a list of Keys (see TKeys) and a list of objects
 in memory. A Key is a small object that describes the type and location
 of a persistent object in a file. The persistent object may be a directory.
Begin_Macro
../../../tutorials/io/fildir.C
End_Macro
 The structure of a file is shown in TFile::TFile
*/
 
#include <iostream>
#include "Strlen.h"
#include "strlcpy.h"
#include "TDirectoryFile.h"
#include "TFile.h"
#include "TBufferFile.h"
#include "TBufferJSON.h"
#include "TMapFile.h"
#include "TClassTable.h"
#include "TInterpreter.h"
#include "THashList.h"
#include "TBrowser.h"
#include "TFree.h"
#include "TKey.h"
#include "TStreamerInfo.h"
#include "TROOT.h"
#include "TError.h"
#include "Bytes.h"
#include "TClass.h"
#include "TRegexp.h"
#include "TSystem.h"
#include "TStreamerElement.h"
#include "TProcessUUID.h"
#include "TVirtualMutex.h"
#include "TEmulatedCollectionProxy.h"
 
const UInt_t kIsBigFile = BIT(16);
const Int_t  kMaxLen = 2048;
 
ClassImp(TDirectoryFile);
 
 
////////////////////////////////////////////////////////////////////////////////
/// Default TDirectoryFile constructor
 
TDirectoryFile::TDirectoryFile()
{
   /// Intentionally placed here
   /// when TDirectoryFile() = default; used,  mac1014/cxx17 fails on some tests
   /// Problem with TObject::IsOnHeap() failing
}
 
 
////////////////////////////////////////////////////////////////////////////////
/// Create a new TDirectoryFile
///
///  A new directory with a name and a title is created in the current directory.
///  The directory header information is immediately saved on the file
///  A new key is added in the parent directory.
///  When this constructor is called from a class directly derived
///  from TDirectoryFile, the third argument, classname, MUST be specified.
///  In this case, classname must be the name of the derived class.
///
///  Note that the directory name cannot contain slashes.
 
TDirectoryFile::TDirectoryFile(const char *name, const char *title, Option_t *classname, TDirectory* initMotherDir)
{
   // We must not publish this objects to the list of RecursiveRemove (indirectly done
   // by 'Appending' this object to it's mother) before the object is completely
   // initialized.
   // However a better option would be to delay the publishing until the very end,
   // but it is currently done in the middle of the initialization (by Build which
   // is a public interface) ....
   R__LOCKGUARD(gROOTMutex);
 
   fName = name;
   fTitle = title;
 
   if (!initMotherDir) initMotherDir = gDirectory;
 
   if (strchr(name,'/')) {
      ::Error("TDirectoryFile","directory name (%s) cannot contain a slash", name);
      gDirectory = nullptr;
      return;
   }
   if (strlen(GetName()) == 0) {
      ::Error("TDirectoryFile","directory name cannot be \"\"");
      gDirectory = nullptr;
      return;
   }
 
   BuildDirectoryFile(initMotherDir ? initMotherDir->GetFile() : nullptr, initMotherDir);
 
   TDirectory* motherdir = GetMotherDir();
   TFile* f = TDirectoryFile::GetFile();
 
   if (!motherdir || !f) return;
   if (!f->IsWritable()) return; //*-* in case of a directory in memory
   if (motherdir->GetKey(name)) {
      Error("TDirectoryFile","An object with name %s exists already", name);
      return;
   }
   TClass *cl = nullptr;
   if (classname[0]) {
      cl = TClass::GetClass(classname);
      if (!cl) {
         Error("TDirectoryFile","Invalid class name: %s",classname);
         return;
      }
   } else {
      cl = TDirectoryFile::IsA();
   }
 
   fBufferSize  = 0;
   fWritable    = kTRUE;
 
   InitDirectoryFile(cl);
 
   fModified = kFALSE;
 
   // Temporarily redundant, see comment on lock early in the function.
   // R__LOCKGUARD(gROOTMutex);
   gROOT->GetUUIDs()->AddUUID(fUUID,this);
   // We should really be doing this now rather than in Build, see
   // comment at the start of the function.
   // if (initMotherDir && strlen(GetName()) != 0) initMotherDir->Append(this);
}
 
////////////////////////////////////////////////////////////////////////////////
/// Initialize the key associated with this directory (and the related
/// data members.
 
void TDirectoryFile::InitDirectoryFile(TClass *cl)
{
   TFile* f = GetFile(); // NOLINT: silence clang-tidy warnings
   if (f->IsBinary()) {
      if (!cl) {
         cl = IsA(); // NOLINT: silence clang-tidy warnings
      }
      TDirectory* motherdir = GetMotherDir();
      fSeekParent  = motherdir->GetSeekDir();
      Int_t nbytes = TDirectoryFile::Sizeof();
      TKey *key    = new TKey(fName,fTitle,cl,nbytes,motherdir);
      fNbytesName  = key->GetKeylen();
      fSeekDir     = key->GetSeekKey();
      if (fSeekDir == 0) return;
      char *buffer = key->GetBuffer();
      TDirectoryFile::FillBuffer(buffer);
      Int_t cycle = motherdir ? motherdir->AppendKey(key) : 0;
      key->WriteFile(cycle);
   } else {
      fSeekParent  = 0;
      fNbytesName  = 0;
      fSeekDir     = f->DirCreateEntry(this);
      if (fSeekDir == 0) return;
   }
 
}
 
////////////////////////////////////////////////////////////////////////////////
/// Destructor.
 
TDirectoryFile::~TDirectoryFile()
{
   if (fKeys) {
      fKeys->Delete("slow");
      SafeDelete(fKeys);
   }
 
   TDirectoryFile::CleanTargets();
 
   // Delete our content before we become somewhat invalid
   // since some those objects (TTree for example) needs information
   // from this object.  Note that on some platform after the end
   // of the body (i.e. thus during ~TDirectory which is also
   // contains this code) the execution of 'this->GetFile()' fails
   // to return the 'proper' value (because it uses the wrong
   // virtual function).
   if (fList) {
      fList->Delete("slow");
      SafeDelete(fList);
   }
 
   if (gDebug) {
      Info("~TDirectoryFile", "dtor called for %s", GetName());
   }
}
 
////////////////////////////////////////////////////////////////////////////////
/// Append object to this directory.
///
/// If replace is true:
///   remove any existing objects with the same same (if the name is not ""
 
void TDirectoryFile::Append(TObject *obj, Bool_t replace /* = kFALSE */)
{
   if (!obj || !fList) return;
 
   TDirectory::Append(obj,replace);
 
   if (!fMother) return;
   if (fMother->IsA() == TMapFile::Class()) {
      TMapFile *mfile = (TMapFile*)fMother;
      mfile->Add(obj);
   }
}
 
////////////////////////////////////////////////////////////////////////////////
/// Insert key in the linked list of keys of this directory.
 
Int_t TDirectoryFile::AppendKey(TKey *key)
{
   if (!fKeys) {
      Error("AppendKey","TDirectoryFile not initialized yet.");
      return 0;
   }
 
   fModified = kTRUE;
 
   key->SetMotherDir(this);
 
   // This is a fast hash lookup in case the key does not already exist
   TKey *oldkey = (TKey*)fKeys->FindObject(key->GetName());
   if (!oldkey) {
      fKeys->Add(key);
      return 1;
   }
 
   // If the key name already exists we have to make a scan for it
   // and insert the new key ahead of the current one
   TObjLink *lnk = fKeys->FirstLink();
   while (lnk) {
      oldkey = (TKey*)lnk->GetObject();
      if (!strcmp(oldkey->GetName(), key->GetName()))
         break;
      lnk = lnk->Next();
   }
 
   fKeys->AddBefore(lnk, key);
   return oldkey->GetCycle() + 1;
}
 
////////////////////////////////////////////////////////////////////////////////
/// Browse the content of the directory.
 
void TDirectoryFile::Browse(TBrowser *b)
{
   TString name;
 
   if (b) {
      TObject *obj = nullptr;
      TIter nextin(fList);
      TKey *key = nullptr, *keyo = nullptr;
      TIter next(fKeys);
 
      cd();
 
      //Add objects that are only in memory
      while ((obj = nextin())) {
         if (fKeys->FindObject(obj->GetName())) continue;
         b->Add(obj, obj->GetName());
      }
 
      //Add keys
      while ((key = (TKey *) next())) {
         int skip = 0;
         if (!keyo || (keyo && strcmp(keyo->GetName(), key->GetName()))) {
            skip = 0;
            obj = fList->FindObject(key->GetName());
 
            if (obj) {
               b->Add(obj, obj->GetName());
               if (obj->IsFolder() && !obj->InheritsFrom("TTree"))
                  skip = 1;
            }
         }
 
         if (!skip) {
            name.Form("%s;%d", key->GetName(), key->GetCycle());
            b->Add(key, name);
         }
 
         keyo = key;
      }
   }
}
 
////////////////////////////////////////////////////////////////////////////////
/// Initialise directory to defaults.
 
void TDirectoryFile::BuildDirectoryFile(TFile* motherFile, TDirectory* motherDir)
{
   // If directory is created via default ctor (when dir is read from file)
   // don't add it here to the directory since its name is not yet known.
   // It will be added to the directory in TKey::ReadObj().
 
   if (motherDir && strlen(GetName()) != 0) motherDir->Append(this);
 
   fModified   = kTRUE;
   fWritable   = kFALSE;
   fDatimeC.Set();
   fDatimeM.Set();
   fNbytesKeys = 0;
   fSeekDir    = 0;
   fSeekParent = 0;
   fSeekKeys   = 0;
   fList       = new THashList(100,50);
   fKeys       = new THashList(100,50);
   fList->UseRWLock();
   fMother     = motherDir;
   fFile       = motherFile ? motherFile : TFile::CurrentFile();
   SetBit(kCanDelete);
}
 
////////////////////////////////////////////////////////////////////////////////
/// Change current directory to "this" directory.
///
/// Returns kTRUE in case of success.
 
Bool_t TDirectoryFile::cd()
{
   Bool_t ok = TDirectory::cd();
   if (ok)
      TFile::CurrentFile() = fFile;
   return ok;
}
 
////////////////////////////////////////////////////////////////////////////////
/// Change current directory the directory described by the path if given one.
/// change the current directory to "path". The absolute path syntax is:
///
///     file.root:/dir1/dir2
///
/// where file.root is the file and /dir1/dir2 the desired subdirectory
/// in the file. Relative syntax is relative to "this" directory. E.g:
/// ../aa. Returns kTRUE in case of success.
 
Bool_t TDirectoryFile::cd(const char *path)
{
   Bool_t ok = TDirectory::cd(path);
   if (ok)
      TFile::CurrentFile() = fFile;
   return ok;
}
 
////////////////////////////////////////////////////////////////////////////////
/// Clean the pointers to this object (gDirectory, TContext, etc.)
 
void TDirectoryFile::CleanTargets()
{
   // After CleanTargets either gFile was changed appropriately
   // by a cd() or needs to be set to zero.
   if (gFile == this) {
      gFile = nullptr;
   }
 
   TDirectory::CleanTargets();
}
 
////////////////////////////////////////////////////////////////////////////////
/// Make a clone of an object using the Streamer facility.
///
/// If the object derives from TNamed, this function is called
/// by TNamed::Clone. TNamed::Clone uses the optional argument newname to set
/// a new name to the newly created object.
///
/// If autoadd is true and if the object class has a
/// DirectoryAutoAdd function, it will be called at the end of the
/// function with the parameter gDirectory.  This usually means that
/// the object will be appended to the current ROOT directory.
 
TObject *TDirectoryFile::CloneObject(const TObject *obj, Bool_t autoadd /* = kTRUE */)
{
   // if no default ctor return immediately (error issued by New())
   char *pobj = (char*)obj->IsA()->New();
   if (!pobj) return nullptr;
 
   Int_t baseOffset = obj->IsA()->GetBaseClassOffset(TObject::Class());
   if (baseOffset==-1) {
      // cl does not inherit from TObject.
      // Since this is not supported in this function, the only reason we could reach this code
      // is because something is screwed up in the ROOT code.
      Fatal("CloneObject","Incorrect detection of the inheritance from TObject for class %s.\n",
            obj->IsA()->GetName());
   }
   TObject *newobj = (TObject*)(pobj+baseOffset);
 
   //create a buffer where the object will be streamed
   {
      // NOTE: do we still need to make this change to gFile?
      // NOTE: This can not be 'gDirectory=0' as at least roofit expect gDirectory to not be null
      // during the streaming ....
      TFile *filsav = gFile;
      gFile = nullptr;
      const Int_t bufsize = 10000;
      TBufferFile buffer(TBuffer::kWrite,bufsize);
      buffer.MapObject(obj);  //register obj in map to handle self reference
      {
         Bool_t isRef = obj->TestBit(kIsReferenced);
         ((TObject*)obj)->ResetBit(kIsReferenced);
 
         ((TObject*)obj)->Streamer(buffer);
 
         if (isRef) ((TObject*)obj)->SetBit(kIsReferenced);
      }
 
      // read new object from buffer
      buffer.SetReadMode();
      buffer.ResetMap();
      buffer.SetBufferOffset(0);
      buffer.MapObject(newobj);  //register obj in map to handle self reference
      newobj->Streamer(buffer);
      newobj->ResetBit(kIsReferenced);
      newobj->ResetBit(kCanDelete);
      gFile = filsav;
   }
 
   if (autoadd) {
      ROOT::DirAutoAdd_t func = obj->IsA()->GetDirectoryAutoAdd();
      if (func) {
         func(newobj,this);
      }
   }
   return newobj;
}
 
////////////////////////////////////////////////////////////////////////////////
/// Scan the memory lists of all files for an object with name
 
TObject *TDirectoryFile::FindObjectAnyFile(const char *name) const
{
   TFile *f;
   R__LOCKGUARD(gROOTMutex);
   TIter next(gROOT->GetListOfFiles());
   while ((f = (TFile*)next())) {
      TObject *obj = f->GetList()->FindObject(name);
      if (obj) return obj;
   }
   return nullptr;
}
 
////////////////////////////////////////////////////////////////////////////////
/// Find a directory named "apath".
///
/// It apath is null or empty, returns "this" directory.
/// Otherwise use the name "apath" to find a directory.
/// The absolute path syntax is:
///
///     file.root:/dir1/dir2
///
/// where file.root is the file and /dir1/dir2 the desired subdirectory
/// in the file. Relative syntax is relative to "this" directory. E.g:
/// ../aa.
/// Returns 0 in case path does not exist.
/// If printError is true, use Error with 'funcname' to issue an error message.
 
TDirectory *TDirectoryFile::GetDirectory(const char *apath,
                                         Bool_t printError, const char *funcname)
{
   Int_t nch = 0;
   if (apath) nch = strlen(apath);
   if (!nch) {
      return this;
   }
 
   if (funcname==0 || strlen(funcname)==0) funcname = "GetDirectory";
 
   TDirectory *result = this;
 
   char *path = new char[nch+1]; path[0] = 0;
   if (nch) strlcpy(path,apath,nch+1);
   char *s = (char*)strchr(path, ':');
   if (s) {
      *s = '\0';
      R__LOCKGUARD(gROOTMutex);
      TDirectory *f = (TDirectory *)gROOT->GetListOfFiles()->FindObject(path);
      // Check if this is a duplicate (2nd opening) on this file and prefer
      // this file.
      if (GetFile()) {
         auto url = GetFile()->GetEndpointUrl();
         if (f && 0 == url->Compare(f->GetFile()->GetEndpointUrl())) {
            result = GetDirectory(s+1,printError,funcname);
            delete [] path;
            return result;
         }
      }
      if (!f && !strcmp(gROOT->GetName(), path)) f = gROOT;
      if (s) *s = ':';
      if (f) {
         result = f;
         if (s && *(s+1)) result = f->GetDirectory(s+1,printError,funcname);
         delete [] path; return result;
      } else {
         if (printError) Error(funcname, "No such file %s", path);
         delete [] path; return nullptr;
      }
   }
 
   // path starts with a slash (assumes current file)
   if (path[0] == '/') {
      TDirectory *td = fFile;
      if (!fFile) td = gROOT;
      result = td->GetDirectory(path+1,printError,funcname);
      delete [] path; return result;
   }
 
   TDirectoryFile *obj;
   char *slash = (char*)strchr(path,'/');
   if (!slash) {                     // we are at the lowest level
      if (!strcmp(path, "..")) {
         result = GetMotherDir();
         delete [] path; return result;
      }
      GetObject(path,obj);
      if (!obj) {
         if (printError) Error(funcname,"Unknown directory %s", path);
         delete [] path; return nullptr;
      }
 
      delete [] path; return obj;
   }
 
   TString subdir(path);
   slash = (char*)strchr(subdir.Data(),'/');
   *slash = 0;
   //Get object with path from current directory/file
   if (!strcmp(subdir, "..")) {
      TDirectory* mom = GetMotherDir();
      if (mom)
         result = mom->GetDirectory(slash+1,printError,funcname);
      delete [] path; return result;
   }
   GetObject(subdir,obj);
   if (!obj) {
      if (printError) Error(funcname,"Unknown directory %s", subdir.Data());
      delete [] path; return nullptr;
   }
 
   result = ((TDirectory*)obj)->GetDirectory(slash+1,printError,funcname);
   delete [] path; return result;
}
 
////////////////////////////////////////////////////////////////////////////////
/// Delete all objects from memory and directory structure itself.
 
void TDirectoryFile::Close(Option_t *option)
{
   if (!fList || !fSeekDir) {
      return;
   }
 
   // Save the directory key list and header
   Save();
 
   Bool_t nodelete = option ? (!strcmp(option, "nodelete") ? kTRUE : kFALSE) : kFALSE;
 
   if (!nodelete) {
      Bool_t fast = kTRUE;
      TObjLink *lnk = fList->FirstLink();
      while (lnk) {
         if (lnk->GetObject()->IsA() == TDirectoryFile::Class()) {fast = kFALSE;break;}
         lnk = lnk->Next();
      }
      // Delete objects from directory list, this in turn, recursively closes all
      // sub-directories (that were allocated on the heap)
      // if this dir contains subdirs, we must use the slow option for Delete!
      // we must avoid "slow" as much as possible, in particular Delete("slow")
      // with a large number of objects (eg >10^5) would take for ever.
      {
         if (fast) fList->Delete();
         else      fList->Delete("slow");
      }
   }
 
   // Delete keys from key list (but don't delete the list header)
   if (fKeys) {
      fKeys->Delete("slow");
   }
 
   TDirectoryFile::CleanTargets();
}
 
////////////////////////////////////////////////////////////////////////////////
/// Delete Objects or/and keys in the current directory.
/// 
/// \param[in] namecycle Encodes the name and cycle of the objects to delete in
/// the current directory (e.g. the top directory of a TFile)
///   - <em>namecycle</em> has the format <em>name;cycle</em>.
///   - <em>namecycle</em>="" is same as <em>namecycle</em>="T*"
///   - <em>name</em>="*" means all objects, use "T*" to also delete subdirectories
///   - <em>cycle</em>="*" means all cycles (memory and keys)
///   - <em>cycle</em>="" or <em>cycle</em>="9999" ==> apply to a memory object
///   - When <em>name</em>="*"" use "T*" to delete subdirectories also
///
/// To delete one directory, you must specify the directory cycle,
/// eg.  file.Delete("dir1;1");
///
/// Examples:
/// | Pattern | Description |
/// |---------|-------------|
/// |   foo   | delete object named foo in memory |
/// |   foo*  | delete all objects with a name starting with foo |
/// |   foo;1 | delete cycle 1 of foo on file |
/// |   foo;* | delete all cycles of foo on file and also from memory |
/// |   *;2   | delete all objects on file having the cycle 2 |
/// |   *;*   | delete all objects from memory and file |
/// |   T*;*  | delete all objects from memory and file and all subdirectories |
///
/// \note For some objects, this method, which is used e.g. by rootrm,
/// properly deletes the specified cycles of the object, but does not free any ‘dependent’
/// data records (unless it is a TDirectoryFile). In other words, in these cases, Delete
/// does not free all subdata records, but rather orphans them, ie. the file size is not
/// reduced, and there is later no option to shrink it nor recover the disappeared ‘dependent’
/// items. For example, deleting a TTree does not free up space from the directory since the
/// underlying basket records are not recursively deleted. If this is wanted, one can call
/// TTree::Delete("all") before calling TDirectoryFile::Delete(); file size won't
/// shrink either, but more space will be left open for overwriting with other objects.
/// See also Purge() documentation. A workaround to reduce filesize is to clone all
/// objects (excluding those to be deleted) into a new TFile.
///
/// ## WARNING
/// If the key to be deleted contains special characters ("+","^","?", etc
/// that have a special meaning for the regular expression parser (see TRegexp)
/// then you must specify 2 backslash characters to escape the regular expression.
/// For example, if the key to be deleted is namecycle = "C++", you must call
///
///     mydir.Delete("C\\+\\+"));
///
 
void TDirectoryFile::Delete(const char *namecycle)
{
   if (gDebug)
     Info("Delete","Call for this = %s namecycle = %s",
               GetName(), (namecycle ? namecycle : "null"));
 
   TDirectory::TContext ctxt(this);
   Short_t  cycle;
   char     name[kMaxLen];
   const char *nmcy = (namecycle) ? namecycle : "";
   DecodeNameCycle(nmcy, name, cycle, kMaxLen);
 
   Int_t deleteall    = 0;
   Int_t deletetree   = 0;
   if(strcmp(name,"*") == 0)   deleteall = 1;
   if(strcmp(name,"*T") == 0){ deleteall = 1; deletetree = 1;}
   if(strcmp(name,"T*") == 0){ deleteall = 1; deletetree = 1;}
   if(namecycle==0 || !namecycle[0]){ deleteall = 1; deletetree = 1;}
   TRegexp re(name,kTRUE);
   TString s;
   Int_t deleteOK = 0;
 
//*-*---------------------Case of Object in memory---------------------
//                        ========================
   if (cycle >= 9999 ) {
      TNamed *idcur;
      TIter   next(fList);
      while ((idcur = (TNamed *) next())) {
         deleteOK = 0;
         s = idcur->GetName();
         if (deleteall || s.Index(re) != kNPOS) {
            deleteOK = 1;
            if (idcur->IsA() == TDirectoryFile::Class()) {
               deleteOK = 2;
               if (!deletetree && deleteall) deleteOK = 0;
            }
         }
         if (deleteOK != 0) {
            fList->Remove(idcur);
            if (deleteOK==2) {
               // read subdirectories to correctly delete them
               if (deletetree)
                  ((TDirectory*) idcur)->ReadAll("dirs");
               idcur->Delete(deletetree ? "T*;*" : "*");
               delete idcur;
            } else
               idcur->Delete(name);
         }
      }
//      if (deleteOK == 2) {
//         Info("Delete","Dir:%lx %s", fList->FindObject(name), name);
//         delete fList->FindObject(name); //deleting a TDirectory
//      }
   }
//*-*---------------------Case of Key---------------------
//                        ===========
   if (cycle != 9999 ) {
      if (IsWritable()) {
         TKey *key;
         TIter nextkey(GetListOfKeys());
         while ((key = (TKey *) nextkey())) {
            deleteOK = 0;
            s = key->GetName();
            if (deleteall || s.Index(re) != kNPOS) {
               if (cycle == key->GetCycle()) deleteOK = 1;
               if (cycle > 9999) deleteOK = 1;
               //if (!strcmp(key->GetClassName(),"TDirectory")) {
               if (strstr(key->GetClassName(),"TDirectory")) {
                  deleteOK = 2;
                  if (!deletetree && deleteall) deleteOK = 0;
                  if (cycle == key->GetCycle()) deleteOK = 2;
               }
            }
            if (deleteOK) {
               if (deleteOK==2) {
                  // read directory with subdirectories to correctly delete and free key structure
                  TDirectory* dir = GetDirectory(key->GetName(), kTRUE, "Delete");
                  if (dir!=0) {
                     dir->Delete("T*;*");
                     fList->Remove(dir);
                     delete dir;
                  }
               }
 
               key->Delete();
               fKeys->Remove(key);
               fModified = kTRUE;
               delete key;
            }
         }
         TFile* f = GetFile();
         if (fModified && (f!=0)) {
            WriteKeys();            //*-* Write new keys structure
            WriteDirHeader();       //*-* Write new directory header
            f->WriteFree();     //*-* Write new free segments list
            f->WriteHeader();   //*-* Write new file header
         }
      }
   }
}
 
////////////////////////////////////////////////////////////////////////////////
/// Encode directory header into output buffer
 
void TDirectoryFile::FillBuffer(char *&buffer)
{
   Version_t version = TDirectoryFile::Class_Version();
   if (fSeekDir > TFile::kStartBigFile ||
       fSeekParent > TFile::kStartBigFile ||
       fSeekKeys > TFile::kStartBigFile )
   {
      // One of the address is larger than 2GB we need to use longer onfile
      // integer, thus we increase the version number.
      // Note that fSeekDir and fSeekKey are not necessarily correlated, if
      // some object are 'removed' from the file and the holes are reused.
      version += 1000;
   }
   tobuf(buffer, version);
   const bool reproducible = TestBit(TFile::kReproducible) || (fFile && fFile->TestBit(TFile::kReproducible));
   if (reproducible) {
      TDatime((UInt_t) 1).FillBuffer(buffer);
      TDatime((UInt_t) 1).FillBuffer(buffer);
   } else {
      fDatimeC.FillBuffer(buffer);
      fDatimeM.FillBuffer(buffer);
   }
   tobuf(buffer, fNbytesKeys);
   tobuf(buffer, fNbytesName);
   if (version > 1000) {
      tobuf(buffer, fSeekDir);
      tobuf(buffer, fSeekParent);
      tobuf(buffer, fSeekKeys);
   } else {
      tobuf(buffer, (Int_t)fSeekDir);
      tobuf(buffer, (Int_t)fSeekParent);
      tobuf(buffer, (Int_t)fSeekKeys);
   }
   if (reproducible)
      TUUID("00000000-0000-0000-0000-000000000000").FillBuffer(buffer);
   else
      fUUID.FillBuffer(buffer);
   if (fFile && fFile->GetVersion() < 40000) return;
   if (version <=1000) for (Int_t i=0;i<3;i++) tobuf(buffer,Int_t(0));
}
 
////////////////////////////////////////////////////////////////////////////////
/// Find key with name `keyname` in the current directory.
/// `keyname` may be of the form name;cycle.
/// See GetKey() for details on the semantics of this form.
 
TKey *TDirectoryFile::FindKey(const char *keyname) const
{
   Short_t  cycle;
   char     name[kMaxLen];
 
   DecodeNameCycle(keyname, name, cycle, kMaxLen);
   return GetKey(name,cycle);
}
 
////////////////////////////////////////////////////////////////////////////////
/// Find key with name `keyname` in the current directory or
/// its subdirectories.
/// `keyname` may be of the form name;cycle.
/// See GetKey() for details on the semantics of this form.
///
/// NOTE: that If a key is found, the directory containing the key becomes
/// the current directory
 
TKey *TDirectoryFile::FindKeyAny(const char *keyname) const
{
   TDirectory *dirsav = gDirectory;
   Short_t  cycle;
   char     name[kMaxLen];
 
   DecodeNameCycle(keyname, name, cycle, kMaxLen);
 
   auto listOfKeys = dynamic_cast<THashList *>(GetListOfKeys());
   if (!listOfKeys) {
      Error("FindKeyAny", "Unexpected type of TDirectoryFile::fKeys!");
      return nullptr;
   }
 
   if (const TList *keyList = listOfKeys->GetListForObject(name)) {
      for (auto key: TRangeDynCast<TKey>(*keyList)) {
         if (key && !strcmp(key->GetName(), name)
             && (cycle == 9999 || cycle >= key->GetCycle())) {
            const_cast<TDirectoryFile*>(this)->cd(); // may be we should not make cd ???
            return key;
         }
      }
   }
 
   //try with subdirectories
   TIter next(GetListOfKeys());
   TKey *key;
   while ((key = (TKey *) next())) {
      //if (!strcmp(key->GetClassName(),"TDirectory")) {
      if (strstr(key->GetClassName(),"TDirectory")) {
         TDirectory* subdir =
             const_cast<TDirectoryFile*>(this)->GetDirectory(key->GetName(), kTRUE, "FindKeyAny");
         TKey *k = subdir ? subdir->FindKeyAny(keyname) : nullptr;
         if (k) return k;
      }
   }
   if (dirsav) dirsav->cd();
   return nullptr;
}
 
////////////////////////////////////////////////////////////////////////////////
/// Find object by name in the list of memory objects of the current
/// directory or its sub-directories.
///
/// After this call the current directory is not changed.
/// To automatically set the current directory where the object is found,
/// use FindKeyAny(aname)->ReadObj().
 
TObject *TDirectoryFile::FindObjectAny(const char *aname) const
{
   //object may be already in the list of objects in memory
   TObject *obj = TDirectory::FindObjectAny(aname);
   if (obj) return obj;
 
   TDirectory *dirsav = gDirectory;
   Short_t  cycle;
   char     name[kMaxLen];
 
   DecodeNameCycle(aname, name, cycle, kMaxLen);
 
   auto listOfKeys = dynamic_cast<THashList *>(GetListOfKeys());
   if (!listOfKeys) {
      Error("FindObjectAny", "Unexpected type of TDirectoryFile::fKeys!");
      return nullptr;
   }
 
   if (const TList *keyList = listOfKeys->GetListForObject(name)) {
      for (auto key: TRangeDynCast<TKey>(*keyList)) {
         if (key && !strcmp(key->GetName(), name)
             && (cycle == 9999 || cycle >= key->GetCycle())) {
            return key->ReadObj();
         }
      }
   }
 
   //try with subdirectories
   TIter next(GetListOfKeys());
   TKey *key;
   while ((key = (TKey *) next())) {
      //if (!strcmp(key->GetClassName(),"TDirectory")) {
      if (strstr(key->GetClassName(),"TDirectory")) {
         TDirectory* subdir =
           ((TDirectory*)this)->GetDirectory(key->GetName(), kTRUE, "FindKeyAny");
         TKey *k = subdir ? subdir->FindKeyAny(aname) : nullptr;
         if (k) { if (dirsav) dirsav->cd(); return k->ReadObj();}
      }
   }
   if (dirsav) dirsav->cd();
   return nullptr;
}
 
////////////////////////////////////////////////////////////////////////////////
/// Return pointer to object identified by namecycle.
///
/// Properties:
///   - namecycle has the format name;cycle
///   - name  = * is illegal, cycle = * is illegal
///   - cycle = "" or cycle = 9999 ==> apply to a memory object
///
/// Examples:
/// | %Pattern | Explanation |
/// |----------|-------------|
/// |   foo    | get object named foo in memory if object is not in memory, try with highest cycle from file |
/// |   foo;1  | get cycle 1 of foo on file |
///
/// The retrieved object should in principle derive from TObject.
/// If not, the function TDirectoryFile::Get<T> should be called.
/// However, this function will still work for a non-TObject, provided that
/// the calling application cast the return type to the correct type (which
/// is the actual type of the object).
///
/// ### The Get<T> Method
/// The method Get<T> offers better protection and avoids the need for any
/// cast:
/// ~~~{.cpp}
/// auto objPtr = directory->Get<MyClass>("some object");
/// if (objPtr) { ... the object exist and inherits from MyClass ... }
/// ~~~
///
/// ### Very important note about inheritance
/// In case the class of this object derives from TObject but not
/// as a first inheritance, one must use dynamic_cast<>().
///
/// #### Example 1 - Normal case:
///
///     class MyClass : public TObject, public AnotherClass
///
/// then on return, one can adopt a C style cast:
///
///     auto objPtr = (MyClass*)directory->Get("some object of MyClass");
///
/// #### Example 2 - Special case:
///
///     class MyClass : public AnotherClass, public TObject
///
/// then on return, one must do:
///
///     auto objPtr = dynamic_cast<MyClass*>(directory->Get("some object of MyClass"));
///
/// Of course, dynamic_cast<> can also be used in the example 1.
///
 
TObject *TDirectoryFile::Get(const char *namecycle)
{
   Short_t  cycle;
   char     name[kMaxLen];
 
   DecodeNameCycle(namecycle, name, cycle, kMaxLen);
   Int_t nch = strlen(name);
   for (Int_t i = nch-1; i > 0; i--) {
      if (name[i] == '/') {
         name[i] = 0;
         TDirectory* dirToSearch=GetDirectory(name);
         const char *subnamecycle = namecycle + i + 1;
         name[i] = '/';
         return dirToSearch?dirToSearch->Get(subnamecycle):0;
      }
   }
   const char *namobj = name;
 
//*-*---------------------Case of Object in memory---------------------
//                        ========================
   TObject *idcur = fList ? fList->FindObject(namobj) : nullptr;
   if (idcur) {
      if (idcur==this && strlen(namobj)!=0) {
         // The object has the same name has the directory and
         // that's what we picked-up!  We just need to ignore
         // it ...
         idcur = nullptr;
      } else if (cycle == 9999) {
         return idcur;
      } else {
         if (idcur->InheritsFrom(TCollection::Class()))
            idcur->Delete();  // delete also list elements
         delete idcur;
         idcur = nullptr;
      }
   }
 
//*-*---------------------Case of Key---------------------
//                        ===========
   auto listOfKeys = dynamic_cast<THashList *>(GetListOfKeys());
   if (!listOfKeys) {
      Error("Get", "Unexpected type of TDirectoryFile::fKeys!");
      return nullptr;
   }
 
   if (const TList *keyList = listOfKeys->GetListForObject(namobj)) {
      for (auto key: TRangeDynCast<TKey>(*keyList)) {
         if (key && !strcmp(key->GetName(), namobj)
             && (cycle == 9999 || cycle == key->GetCycle())) {
            TDirectory::TContext ctxt(this);
            return key->ReadObj();
         }
      }
   }
 
   return nullptr;
}
 
////////////////////////////////////////////////////////////////////////////////
/// Return pointer to object identified by namecycle.
///
/// The returned object may or may not derive from TObject.
///
///   - namecycle has the format name;cycle
///   - name  = * is illegal, cycle = * is illegal
///   - cycle = "" or cycle = 9999 ==> apply to a memory object
///
/// ## Very important note
/// The calling application must cast the returned object to
/// the final type, e.g.
///
///   auto objPtr = (MyClass*)directory->GetObject("some object of MyClass");
 
void *TDirectoryFile::GetObjectUnchecked(const char *namecycle)
{
   return GetObjectChecked(namecycle,(TClass*)nullptr);
}
 
////////////////////////////////////////////////////////////////////////////////
/// See documentation of TDirectoryFile::GetObjectCheck(const char *namecycle, const TClass *cl)
 
void *TDirectoryFile::GetObjectChecked(const char *namecycle, const char* classname)
{
   return GetObjectChecked(namecycle,TClass::GetClass(classname));
}
 
 
////////////////////////////////////////////////////////////////////////////////
/// Return pointer to object identified by namecycle if and only if the actual
/// object is a type suitable to be stored as a pointer to a "expectedClass"
/// If expectedClass is null, no check is performed.
///
///   - namecycle has the format name;cycle
///   - name  = * is illegal, cycle = * is illegal
///   - cycle = "" or cycle = 9999 ==> apply to a memory object
///
/// ### Very important note
/// The calling application must cast the returned pointer to
/// the type described by the 2 arguments (i.e. cl):
///
/// auto objPtr = (MyClass*)directory->GetObjectChecked("some object of MyClass","MyClass"));
///
/// Note: We recommend using the method TDirectoryFile::Get<T>:
/// ~~~{.cpp}
/// auto objPtr = directory->Get<MyClass>("some object inheriting from MyClass");
/// if (objPtr) { ... we found what we are looking for ... }
/// ~~~
 
void *TDirectoryFile::GetObjectChecked(const char *namecycle, const TClass* expectedClass)
{
 
   // If the name is invalid, issue an error message and return a nullptr
   if (!namecycle || '\0' == namecycle[0]) {
      Error("GetObjectChecked", "The provided key name is invalid.");
      return nullptr;
   }
 
   Short_t  cycle;
   char     name[kMaxLen];
 
   DecodeNameCycle(namecycle, name, cycle, kMaxLen);
   Int_t nch = strlen(name);
   for (Int_t i = nch-1; i > 0; i--) {
      if (name[i] == '/') {
         name[i] = 0;
         TDirectory* dirToSearch=GetDirectory(name);
         const char *subnamecycle = namecycle + i + 1;
         name[i] = '/';
         if (dirToSearch) {
            return dirToSearch->GetObjectChecked(subnamecycle, expectedClass);
         } else {
            return nullptr;
         }
      }
   }
   const char *namobj = name;
 
//*-*---------------------Case of Object in memory---------------------
//                        ========================
   if (expectedClass==0 || expectedClass->IsTObject()) {
      TObject *objcur = fList ? fList->FindObject(namobj) : nullptr;
      if (objcur) {
         if (objcur==this && strlen(namobj)!=0) {
            // The object has the same name has the directory and
            // that's what we picked-up!  We just need to ignore
            // it ...
            objcur = nullptr;
         } else if (cycle == 9999) {
            // Check type
            if (expectedClass && objcur->IsA()->GetBaseClassOffset(expectedClass) == -1) return nullptr;
            else return objcur;
         } else {
            if (objcur->InheritsFrom(TCollection::Class()))
               objcur->Delete();  // delete also list elements
            delete objcur;
            objcur = nullptr;
         }
      }
   }
 
//*-*---------------------Case of Key---------------------
//                        ===========
   auto listOfKeys = dynamic_cast<THashList *>(GetListOfKeys());
   if (!listOfKeys) {
      Error("GetObjectChecked", "Unexpected type of TDirectoryFile::fKeys!");
      return nullptr;
   }
 
   if (const TList *keyList = listOfKeys->GetListForObject(namobj)) {
      for (auto key: TRangeDynCast<TKey>(*keyList)) {
         if (key && !strcmp(key->GetName(), namobj)
             && (cycle == 9999 || cycle == key->GetCycle())) {
            TDirectory::TContext ctxt(this);
            return key->ReadObjectAny(expectedClass);
         }
      }
   }
 
   return nullptr;
}
 
////////////////////////////////////////////////////////////////////////////////
/// Return the buffer size to create new TKeys.
///
/// If the stored fBufferSize is null, the value returned is the average
/// buffer size of objects in the file so far.
 
Int_t TDirectoryFile::GetBufferSize() const
{
   if (fBufferSize <= 0) return fFile->GetBestBuffer();
   else                  return fBufferSize;
}
 
 
////////////////////////////////////////////////////////////////////////////////
/// Return pointer to key with name,cycle. If no key exists with the specified
/// cycle, returns the key with the highest cycle that is lower than the requested cycle.
///
///  if cycle = 9999 returns highest cycle
 
TKey *TDirectoryFile::GetKey(const char *name, Short_t cycle) const
{
   if (!fKeys) return nullptr;
 
   auto listOfKeys = dynamic_cast<THashList *>(GetListOfKeys());
   if (!listOfKeys) {
      Error("GetKey", "Unexpected type of TDirectoryFile::fKeys!");
      return nullptr;
   }
 
   if (const TList *keyList = listOfKeys->GetListForObject(name)) {
      for (auto key: TRangeDynCast<TKey>(*keyList)) {
         if (key && !strcmp(key->GetName(), name)
             && (cycle == 9999 || cycle >= key->GetCycle())) {
            return key;
         }
      }
   }
 
   return nullptr;
}
 
////////////////////////////////////////////////////////////////////////////////
/// List Directory contents
///
/// Indentation is used to identify the directory tree
/// Subdirectories are listed first, then objects in memory, then objects on the file
///
/// The option can has the following format: <b>`[-d |-m][<regexp>]`</b>
/// Options:
///   - -d: only list objects in the file
///   - -m: only list objects in memory
///  The `<regexp>` will be used to match the name of the objects.
///  By default memory and disk objects are listed.
 
void TDirectoryFile::ls(Option_t *option) const
{
   TROOT::IndentLevel();
   std::cout <<ClassName()<<"*\t\t"<<GetName()<<"\t"<<GetTitle()<<std::endl;
   TROOT::IncreaseDirLevel();
 
   TString opta = option;
   TString opt  = opta.Strip(TString::kBoth);
   Bool_t memobj  = kTRUE;
   Bool_t diskobj = kTRUE;
   TString reg;
   if (opt.BeginsWith("-m")) {
      diskobj = kFALSE;
      if (opt.Length() > 2) {
         reg = opt(2,opt.Length());
      }
   } else if (opt.BeginsWith("-d")) {
      memobj  = kFALSE;
      if (opt.Length() > 2) {
         reg = opt(2,opt.Length());
      }
   } else if (!opt.IsNull()) {
      reg = opt;
   }
 
   TRegexp re(reg, kTRUE);
 
   if (memobj) {
      TObject *obj;
      TIter nextobj(fList);
      while ((obj = (TObject *) nextobj())) {
         TString s = obj->GetName();
         if (!reg.IsNull() && s.Index(re) == kNPOS)
            continue;
         obj->ls(option);            //*-* Loop on all the objects in memory
      }
   }
 
   if (diskobj && fKeys) {
      //*-* Loop on all the keys
      for (TObjLink *lnk = fKeys->FirstLink(); lnk != nullptr; lnk = lnk->Next()) {
         TKey *key = (TKey*)lnk->GetObject();
         TString s = key->GetName();
         if (!reg.IsNull() && s.Index(re) == kNPOS)
            continue;
         bool first = (lnk->Prev() == nullptr) || (s != lnk->Prev()->GetObject()->GetName());
         bool hasbackup = (lnk->Next() != nullptr) && (s == lnk->Next()->GetObject()->GetName());
         if (first)
            if (hasbackup)
               key->ls(true);
            else
               key->ls();
         else
            key->ls(false);
      }
   }
   TROOT::DecreaseDirLevel();
}
 
////////////////////////////////////////////////////////////////////////////////
/// Interface to TFile::Open
 
TFile *TDirectoryFile::OpenFile(const char *name, Option_t *option,const char *ftitle, Int_t compress, Int_t netopt)
{
   return TFile::Open(name,option,ftitle,compress,netopt);
 
}
 
////////////////////////////////////////////////////////////////////////////////
/// Create a sub-directory "a" or a hierarchy of sub-directories "a/b/c/...".
///
/// @param name the name or hierarchy of the subdirectory ("a" or "a/b/c")
/// @param title the title
/// @param returnExistingDirectory if key-name is already existing, the returned
/// value points to preexisting sub-directory if true and to `nullptr` if false.
/// @return a pointer to the created sub-directory, not to the top sub-directory
/// of the hierarchy (in the above example, the returned TDirectory * points
/// to "c"). In case of an error, it returns `nullptr`. In case of a preexisting
/// sub-directory (hierarchy) with the requested name, the return value depends
/// on the parameter returnExistingDirectory.
 
TDirectory *TDirectoryFile::mkdir(const char *name, const char *title, Bool_t returnExistingDirectory)
{
   if (!name || !title || !name[0]) return nullptr;
   if (!title[0]) title = name;
   if (GetKey(name)) {
      if (returnExistingDirectory)
         return (TDirectoryFile*) GetDirectory(name);
      else {
        Error("mkdir","An object with name %s exists already",name);
        return nullptr;
      }
   }
   if (const char *slash = strchr(name,'/')) {
      TString workname(name, Long_t(slash-name));
      TDirectoryFile *tmpdir = nullptr;
      GetObject(workname.Data(), tmpdir);
      if (!tmpdir) {
         tmpdir = (TDirectoryFile*)mkdir(workname.Data(),title);
         if (!tmpdir) return nullptr;
      }
      return tmpdir->mkdir(slash + 1);
   }
 
   TDirectory::TContext ctxt(this);
 
   return new TDirectoryFile(name, title, "", this);
}
 
////////////////////////////////////////////////////////////////////////////////
/// Purge lowest key cycles in a directory.
///
/// By default, only the highest cycle of a key is kept. Keys for which
/// the "KEEP" flag has been set are not removed. See TKey::Keep().
/// NOTE: This does not reduce the size of a TFile--
/// the space is simply freed up to be overwritten.
 
void TDirectoryFile::Purge(Short_t)
{
   if (!IsWritable()) return;
 
   TDirectory::TContext ctxt(this);
 
   TKey  *key;
   TIter  prev(GetListOfKeys(), kIterBackward);
 
   while ((key = (TKey*)prev())) {      // reverse loop on keys
      TKey *keyprev = (TKey*)GetListOfKeys()->Before(key);
      if (!keyprev) break;
      if (key->GetKeep() == 0) {
         if (strcmp(key->GetName(), keyprev->GetName()) == 0) {
            key->Delete(); // Remove from the file.
            delete key;    // Remove from memory.
         }
      }
   }
   TFile *f = GetFile();
   if (fModified && f) {
      WriteKeys();                   // Write new keys structure
      WriteDirHeader();              // Write new directory header
      f->WriteFree();                // Write new free segments list
      f->WriteHeader();              // Write new file header
   }
}
 
////////////////////////////////////////////////////////////////////////////////
/// Read objects from a ROOT file directory into memory.
///
/// If an object is already in memory, the memory copy is deleted
/// and the object is again read from the file.
/// If opt=="dirs", only subdirectories will be read
/// If opt=="dirs*" complete directory tree will be read
 
void TDirectoryFile::ReadAll(Option_t* opt)
{
   TDirectory::TContext ctxt(this);
 
   TKey *key;
   TIter next(GetListOfKeys());
 
   Bool_t readdirs = ((opt!=0) && ((strcmp(opt,"dirs")==0) || (strcmp(opt,"dirs*")==0)));
 
   if (readdirs)
      while ((key = (TKey *) next())) {
 
         //if (strcmp(key->GetClassName(),"TDirectory")!=0) continue;
         if (strstr(key->GetClassName(),"TDirectory")==0) continue;
 
         TDirectory *dir = GetDirectory(key->GetName(), kTRUE, "ReadAll");
 
         if ((dir!=0) && (strcmp(opt,"dirs*")==0)) dir->ReadAll("dirs*");
      }
   else
      while ((key = (TKey *) next())) {
         TObject *thing = GetList()->FindObject(key->GetName());
         if (thing) { delete thing; }
         key->ReadObj();
      }
}
 
////////////////////////////////////////////////////////////////////////////////
/// Read the linked list of keys.
///
/// Every directory has a linked list (fKeys). This linked list has been
/// written on the file via WriteKeys as a single data record.
///
/// It is interesting to call this function in the following situation.
/// Assume another process1 is connecting this directory in Update mode
///   - Process1 is adding/updating objects in this directory
///   - You want to see the latest status from process1.
/// Example Process1:
/// ~~~{.cpp}
/// obj1.Write();
/// obj2.Write();
/// gDirectory->SaveSelf();
/// ~~~
///
/// Example Process2:
/// ~~~{.cpp}
/// gDirectory->ReadKeys();
/// obj1->Draw();
/// ~~~
/// This is an efficient way (without opening/closing files) to view
/// the latest updates of a file being modified by another process
/// as it is typically the case in a data acquisition system.
 
Int_t TDirectoryFile::ReadKeys(Bool_t forceRead)
{
   if (!fFile || !fKeys) return 0;
 
   if (!fFile->IsBinary())
      return fFile->DirReadKeys(this);
 
   TDirectory::TContext ctxt(this);
 
   char *buffer;
   if (forceRead) {
      fKeys->Delete();
      //In case directory was updated by another process, read new
      //position for the keys
      Int_t nbytes = fNbytesName + TDirectoryFile::Sizeof();
      char *header = new char[nbytes];
      buffer       = header;
      fFile->Seek(fSeekDir);
      if ( fFile->ReadBuffer(buffer,nbytes) ) {
         // ReadBuffer return kTRUE in case of failure.
         delete [] header;
         return 0;
      }
      buffer += fNbytesName;
      Version_t versiondir;
      frombuf(buffer,&versiondir);
      fDatimeC.ReadBuffer(buffer);
      fDatimeM.ReadBuffer(buffer);
      frombuf(buffer, &fNbytesKeys);
      frombuf(buffer, &fNbytesName);
      if (versiondir > 1000) {
         frombuf(buffer, &fSeekDir);
         frombuf(buffer, &fSeekParent);
         frombuf(buffer, &fSeekKeys);
      } else {
         Int_t sdir,sparent,skeys;
         frombuf(buffer, &sdir);    fSeekDir    = (Long64_t)sdir;
         frombuf(buffer, &sparent); fSeekParent = (Long64_t)sparent;
         frombuf(buffer, &skeys);   fSeekKeys   = (Long64_t)skeys;
      }
      delete [] header;
   }
 
   Int_t nkeys = 0;
   Long64_t fsize = fFile->GetSize();
   if ( fSeekKeys >  0) {
      TKey *headerkey    = new TKey(fSeekKeys, fNbytesKeys, this);
      headerkey->ReadFile();
      buffer = headerkey->GetBuffer();
      headerkey->ReadKeyBuffer(buffer);
 
      TKey *key;
      frombuf(buffer, &nkeys);
      for (Int_t i = 0; i < nkeys; i++) {
         key = new TKey(this);
         key->ReadKeyBuffer(buffer);
         if (key->GetSeekKey() < 64 || key->GetSeekKey() > fsize) {
            Error("ReadKeys","reading illegal key, exiting after %d keys",i);
            fKeys->Remove(key);
            nkeys = i;
            break;
         }
         if (key->GetSeekPdir() < 64 || key->GetSeekPdir() > fsize) {
            Error("ReadKeys","reading illegal key, exiting after %d keys",i);
            fKeys->Remove(key);
            nkeys = i;
            break;
         }
         fKeys->Add(key);
      }
      delete headerkey;
   }
 
   return nkeys;
}
 
 
////////////////////////////////////////////////////////////////////////////////
/// Read object with keyname from the current directory
///
/// Read contents of object with specified name from the current directory.
/// First the key with keyname is searched in the current directory,
/// next the key buffer is deserialized into the object.
/// The object must have been created before via the default constructor.
/// See TObject::Write().
 
Int_t TDirectoryFile::ReadTObject(TObject *obj, const char *keyname)
{
   if (!fFile) { Error("ReadTObject","No file open"); return 0; }
   auto listOfKeys = dynamic_cast<THashList *>(GetListOfKeys());
   if (!listOfKeys) {
      Error("ReadTObject", "Unexpected type of TDirectoryFile::fKeys!");
      return 0;
   }
 
   if (const TList *keyList = listOfKeys->GetListForObject(keyname)) {
      for (auto key: TRangeDynCast<TKey>(*keyList)) {
         if (key && !strcmp(key->GetName(), keyname) ) {
            return key->Read(obj);
         }
      }
   }
 
   Error("ReadTObject","Key not found");
   return 0;
}
 
////////////////////////////////////////////////////////////////////////////////
/// Reset the TDirectory after its content has been merged into another
/// Directory.
///
/// This returns the TDirectoryFile object back to its state
/// before any data has been written to the file.
/// The object in the in-memory list are assumed to also have been reset.
 
void TDirectoryFile::ResetAfterMerge(TFileMergeInfo *info)
{
   // There is nothing to reset in the base class (TDirectory) since
   // we do want to key the list of in-memory object as is.
   fModified = kFALSE;
   // Does not change: fWritable
   fDatimeC.Set();
   fDatimeM.Set();
   fNbytesKeys = 0; // updated when the keys are written
   fNbytesName = 0; // updated by Init
   // Does not change (user customization): fBufferSize;
   fSeekDir = 0;    // updated by Init
   fSeekParent = 0; // updated by Init
   fSeekKeys = 0;   // updated by Init
   // Does not change: fFile
   TKey *key = fKeys ? (TKey*)fKeys->FindObject(fName) : nullptr;
   TClass *cl = IsA();
   if (key) {
      cl = TClass::GetClass(key->GetClassName());
   }
   // NOTE: We should check that the content is really mergeable and in
   // the in-mmeory list, before deleting the keys.
   if (fKeys) {
      fKeys->Delete("slow");
   }
 
   InitDirectoryFile(cl);
 
   // Do the same with the sub-directories.
   TIter   next(GetList());
   TObject *idcur;
   while ((idcur = next())) {
      if (idcur->IsA() == TDirectoryFile::Class()) {
         ((TDirectoryFile*)idcur)->ResetAfterMerge(info);
      }
   }
 
}
 
////////////////////////////////////////////////////////////////////////////////
/// Removes subdirectory from the directory
///
/// When directory is deleted, all keys in all subdirectories will be
/// read first and deleted from file (if exists)
/// Equivalent call is Delete("name;*");
 
void TDirectoryFile::rmdir(const char *name)
{
   if (!name || (*name==0)) return;
 
   TString mask(name);
   mask += ";*";
   Delete(mask);
}
 
////////////////////////////////////////////////////////////////////////////////
/// Save recursively all directory keys and headers
 
void TDirectoryFile::Save()
{
   TDirectory::TContext ctxt(this);
 
   SaveSelf();
 
   // recursively save all sub-directories
   if (fList && fList->FirstLink()) {
      auto lnk = fList->FirstLink()->shared_from_this();
      while (lnk) {
         TObject *idcur = lnk->GetObject();
         if (TDirectoryFile *dir = dynamic_cast<TDirectoryFile *>(idcur)) {
            dir->Save();
         }
         lnk = lnk->NextSP();
      }
   }
}
 
////////////////////////////////////////////////////////////////////////////////
/// Save object in filename.
///
/// If filename is `nullptr` or "", a file with "<objectname>.root" is created.
/// The name of the key is the object name.
/// By default new file will be created. Using option "a", one can append object
/// to the existing ROOT file.
/// If the operation is successful, it returns the number of bytes written to the file
/// otherwise it returns 0.
/// By default a message is printed. Use option "q" to not print the message.
/// If filename contains ".json" extension, JSON representation of the object
/// will be created and saved in the text file. Such file can be used in
/// JavaScript ROOT (https://root.cern/js/) to display object in web browser
/// When creating JSON file, option string may contain compression level from 0 to 3 (default 0)
 
Int_t TDirectoryFile::SaveObjectAs(const TObject *obj, const char *filename, Option_t *option) const
{
   // option can contain single letter args: "a" for append, "q" for quiet in any combinations
 
   if (!obj) return 0;
   TString fname, opt = option;
   if (filename && *filename)
      fname = filename;
   else
      fname.Form("%s.root", obj->GetName());
   opt.ToLower();
 
   Int_t nbytes = 0;
   if (fname.Index(".json") > 0) {
      nbytes = TBufferJSON::ExportToFile(fname, obj, option);
   } else {
      TContext ctxt; // The TFile::Open will change the current directory.
      auto *local = TFile::Open(fname.Data(), opt.Contains("a") ? "update" : "recreate");
      if (!local) return 0;
      nbytes = obj->Write();
      delete local;
   }
   if (!opt.Contains("q") && !gSystem->AccessPathName(fname.Data()))
      obj->Info("SaveAs", "ROOT file %s has been created", fname.Data());
   return nbytes;
}
 
////////////////////////////////////////////////////////////////////////////////
/// Save Directory keys and header
///
/// If the directory has been modified (fModified set), write the keys
/// and the directory header. This function assumes the cd is correctly set.
///
/// It is recommended to use this function in the following situation:
/// Assume a process1 using a directory in Update mode
///   - New objects or modified objects have been written to the directory.
///   - You do not want to close the file.
///   - You want your changes be visible from another process2 already connected
///     to this directory in read mode.
///   - Call this function.
///   - In process2, use TDirectoryFile::ReadKeys to refresh the directory.
 
void TDirectoryFile::SaveSelf(Bool_t force)
{
   if (IsWritable() && (fModified || force) && fFile) {
      Bool_t dowrite = kTRUE;
      if (fFile->GetListOfFree())
        dowrite = fFile->GetListOfFree()->First() != nullptr;
      if (dowrite) {
         TDirectory *dirsav = gDirectory;
         if (dirsav != this) cd();
         WriteKeys();          //*-*- Write keys record
         WriteDirHeader();     //*-*- Update directory record
         if (dirsav && dirsav != this) dirsav->cd();
      }
   }
}
 
////////////////////////////////////////////////////////////////////////////////
/// Set the default buffer size when creating new TKeys.
///
/// See also TDirectoryFile::GetBufferSize
 
void TDirectoryFile::SetBufferSize(Int_t bufsize)
{
   fBufferSize = bufsize;
}
 
////////////////////////////////////////////////////////////////////////////////
/// Find the action to be executed in the dictionary of the parent class
/// and store the corresponding exec number into fBits.
///
/// This function searches a data member in the class of parent with an
/// offset corresponding to this.
/// If a comment "TEXEC:" is found in the comment field of the data member,
/// the function stores the exec identifier of the exec statement
/// following this keyword.
 
void TDirectoryFile::SetTRefAction(TObject *ref, TObject *parent)
{
   Int_t offset = (char*)ref - (char*)parent;
   TClass *cl = parent->IsA();
   cl->BuildRealData(parent);
   TStreamerInfo *info = (TStreamerInfo*)cl->GetStreamerInfo();
   TIter next(info->GetElements());
   TStreamerElement *element;
   while((element = (TStreamerElement*)next())) {
      if (element->GetOffset() != offset) continue;
      Int_t execid = element->GetExecID();
      if (execid > 0) ref->SetBit(execid << 8);
      return;
   }
}
 
////////////////////////////////////////////////////////////////////////////////
///  Set the new value of fWritable recursively
 
void TDirectoryFile::SetWritable(Bool_t writable)
{
   TDirectory::TContext ctxt(this);
 
   fWritable = writable;
 
   // recursively set all sub-directories
   if (fList) {
      TObject *idcur;
      TIter    next(fList);
      while ((idcur = next())) {
         if (idcur->InheritsFrom(TDirectoryFile::Class())) {
            TDirectoryFile *dir = (TDirectoryFile*)idcur;
            dir->SetWritable(writable);
         }
      }
   }
}
 
 
////////////////////////////////////////////////////////////////////////////////
/// Return the size in bytes of the directory header
 
Int_t TDirectoryFile::Sizeof() const
{
   Int_t nbytes = 22;
 
   nbytes     += fDatimeC.Sizeof();
   nbytes     += fDatimeM.Sizeof();
   nbytes     += fUUID.Sizeof();
    //assume that the file may be above 2 Gbytes if file version is > 4
   if (fFile && fFile->GetVersion() >= 40000) nbytes += 12;
   return nbytes;
}
 
 
////////////////////////////////////////////////////////////////////////////////
/// Stream a class object
 
void TDirectoryFile::Streamer(TBuffer &b)
{
   Version_t v,version;
   if (b.IsReading()) {
      BuildDirectoryFile((TFile*)b.GetParent(), nullptr);
      if (fFile && fFile->IsWritable()) fWritable = kTRUE;
 
      if (fFile && !fFile->IsBinary()) {
         Version_t R__v = b.ReadVersion(0, 0);
 
         TClass* dirclass = (R__v < 5) ? TDirectory::Class() : TDirectoryFile::Class();
 
         b.ClassBegin(dirclass, R__v);
 
         TString sbuf;
 
         b.ClassMember("CreateTime","TString");
         sbuf.Streamer(b);
         TDatime timeC(sbuf.Data());
         fDatimeC = timeC;
 
         b.ClassMember("ModifyTime","TString");
         sbuf.Streamer(b);
         TDatime timeM(sbuf.Data());
         fDatimeM = timeM;
 
         b.ClassMember("UUID","TString");
         sbuf.Streamer(b);
         TUUID id(sbuf.Data());
         fUUID = id;
 
         b.ClassEnd(dirclass);
 
         fSeekKeys = 0; // read keys later in the TKeySQL class
      } else {
         b >> version;
         fDatimeC.Streamer(b);
         fDatimeM.Streamer(b);
         b >> fNbytesKeys;
         b >> fNbytesName;
         if (version > 1000) {
            SetBit(kIsBigFile);
            b >> fSeekDir;
            b >> fSeekParent;
            b >> fSeekKeys;
         } else {
            Int_t sdir,sparent,skeys;
            b >> sdir;    fSeekDir    = (Long64_t)sdir;
            b >> sparent; fSeekParent = (Long64_t)sparent;
            b >> skeys;   fSeekKeys   = (Long64_t)skeys;
         }
         v = version%1000;
         if (v == 2) {
            fUUID.StreamerV1(b);
         } else if (v > 2) {
            fUUID.Streamer(b);
         }
      }
      fList->UseRWLock();
      R__LOCKGUARD(gROOTMutex);
      gROOT->GetUUIDs()->AddUUID(fUUID,this);
      if (fSeekKeys) ReadKeys();
   } else {
      if (fFile && !fFile->IsBinary()) {
         b.WriteVersion(TDirectoryFile::Class());
 
         TString sbuf;
 
         b.ClassBegin(TDirectoryFile::Class());
 
         b.ClassMember("CreateTime","TString");
         sbuf = fDatimeC.AsSQLString();
         sbuf.Streamer(b);
 
         b.ClassMember("ModifyTime","TString");
         fDatimeM.Set();
         sbuf = fDatimeM.AsSQLString();
         sbuf.Streamer(b);
 
         b.ClassMember("UUID","TString");
         sbuf = fUUID.AsString();
         sbuf.Streamer(b);
 
         b.ClassEnd(TDirectoryFile::Class());
      } else {
         version = TDirectoryFile::Class_Version();
         if (fFile && fFile->GetEND() > TFile::kStartBigFile) version += 1000;
         b << version;
         fDatimeC.Streamer(b);
         fDatimeM.Streamer(b);
         b << fNbytesKeys;
         b << fNbytesName;
         if (version > 1000) {
            b << fSeekDir;
            b << fSeekParent;
            b << fSeekKeys;
         } else {
            b << (Int_t)fSeekDir;
            b << (Int_t)fSeekParent;
            b << (Int_t)fSeekKeys;
         }
         fUUID.Streamer(b);
         if (version <=1000) for (Int_t i=0;i<3;i++) b << Int_t(0);
      }
   }
}
 
////////////////////////////////////////////////////////////////////////////////
/// Write all objects in memory to disk.
///
/// Loop on all objects in memory (including subdirectories).
/// A new key is created in the keys linked list for each object.
/// For allowed options see TObject::Write().
/// The directory header info is rewritten on the directory header record.
 
Int_t TDirectoryFile::Write(const char *, Int_t opt, Int_t bufsize)
{
   if (!IsWritable()) return 0;
   TDirectory::TContext ctxt(this);
 
   // Loop on all objects (including subdirs)
   TIter next(fList);
   TObject *obj;
   Int_t nbytes = 0;
   while ((obj=next())) {
      nbytes += obj->Write(0,opt,bufsize);
   }
   if (R__likely(!(opt & kOnlyPrepStep)))
      SaveSelf(kTRUE);   // force save itself
 
   return nbytes;
}
 
////////////////////////////////////////////////////////////////////////////////
/// One can not save a const TDirectory object.
 
Int_t TDirectoryFile::Write(const char *n, Int_t opt, Int_t bufsize) const
{
   Error("Write const","A const TDirectory object should not be saved. We try to proceed anyway.");
   return const_cast<TDirectoryFile*>(this)->Write(n, opt, bufsize);
}
 
////////////////////////////////////////////////////////////////////////////////
/// Write object obj to this directory.
///
/// The data structure corresponding to this object is serialized.
/// The corresponding buffer is written to this directory
/// with an associated key with name "name".
///
/// Writing an object to a file involves the following steps:
///   - Creation of a support TKey object in the directory. The TKey object
/// creates a TBuffer object.
///   - The TBuffer object is filled via the class::Streamer function.
///   - If the file is compressed (default) a second buffer is created to hold
/// the compressed buffer.
///   - Reservation of the corresponding space in the file by looking in the
/// TFree list of free blocks of the file.
///   - The buffer is written to the file.
///
/// By default, the buffersize will be taken from the average buffer size
/// of all objects written to the current file so far.
/// Use TDirectoryFile::SetBufferSize to force a given buffer size.
///
/// If a name is specified, it will be the name of the key.
/// If name is not given, the name of the key will be the name as returned
/// by obj->GetName().
///
/// The option can be a combination of:
///   - "SingleKey"
///   - "Overwrite"
///   - "WriteDelete"
/// Using the "Overwrite" option a previous key with the same name is
/// overwritten. The previous key is deleted before writing the new object.
/// Using the "WriteDelete" option a previous key with the same name is
/// deleted only after the new object has been written. This option
/// is safer than kOverwrite but it is slower.
/// The "SingleKey" option is only used by TCollection::Write() to write
/// a container with a single key instead of each object in the container
/// with its own key.
/// An object is read from this directory via TDirectoryFile::Get.
/// The function returns the total number of bytes written to the directory.
/// It returns 0 if the object cannot be written.
///
/// WARNING: avoid special characters like '^','$','.' in the name as they
/// are used by the regular expression parser (see TRegexp).
 
Int_t TDirectoryFile::WriteTObject(const TObject *obj, const char *name, Option_t *option, Int_t bufsize)
{
   TDirectory::TContext ctxt(this);
 
   if (fFile==0) {
      const char *objname = "no name specified";
      if (name) objname = name;
      else if (obj) objname = obj->GetName();
      Error("WriteTObject","The current directory (%s) is not associated with a file. The object (%s) has not been written.",GetName(),objname);
      return 0;
   }
 
   if (!fFile->IsWritable()) {
      if (!fFile->TestBit(TFile::kWriteError)) {
         // Do not print the error if the file already had a SysError.
         Error("WriteTObject","Directory %s is not writable", fFile->GetName());
      }
      return 0;
   }
 
   if (!obj) return 0;
 
   TString opt = option;
   opt.ToLower();
 
   TKey *key=0, *oldkey=0;
   Int_t bsize = GetBufferSize();
   if (bufsize > 0) bsize = bufsize;
 
   const char *oname;
   if (name && *name)
      oname = name;
   else
      oname = obj->GetName();
 
   // Remove trailing blanks in object name
   Int_t nch = strlen(oname);
   char *newName = nullptr;
   if (nch && oname[nch-1] == ' ') {
      Warning("WriteTObject", "The key name '%s' will be stored in file without the trailing blanks.", obj->GetName());
      // See https://github.com/root-project/root/issues/17003
      newName = new char[nch+1];
      strlcpy(newName,oname,nch+1);
      for (Int_t i=0;i<nch;i++) {
         if (newName[nch-i-1] != ' ') break;
         newName[nch-i-1] = 0;
      }
      oname = newName;
   }
 
   if (opt.Contains("overwrite")) {
      //One must use GetKey. FindObject would return the lowest cycle of the key!
      //key = (TKey*)gDirectory->GetListOfKeys()->FindObject(oname);
      key = GetKey(oname);
      if (key) {
         key->Delete();
         delete key;
      }
   }
   if (opt.Contains("writedelete")) {
      oldkey = GetKey(oname);
   }
   key = fFile->CreateKey(this, obj, oname, bsize);
   if (newName) delete [] newName;
 
   if (!key->GetSeekKey()) {
      fKeys->Remove(key);
      delete key;
      if (bufsize) fFile->SetBufferSize(bufsize);
      return 0;
   }
   fFile->SumBuffer(key->GetObjlen());
   Int_t nbytes = key->WriteFile(0);
   if (fFile->TestBit(TFile::kWriteError)) {
      if (bufsize) fFile->SetBufferSize(bufsize);
      return 0;
   }
   if (oldkey) {
      oldkey->Delete();
      delete oldkey;
   }
   if (bufsize) fFile->SetBufferSize(bufsize);
 
   return nbytes;
}
 
////////////////////////////////////////////////////////////////////////////////
/// Write object from pointer of class classname in this directory.
///
/// obj may not derive from TObject. See TDirectoryFile::WriteTObject for comments
///
/// ## Very important note
/// The value passed as 'obj' needs to be from a pointer to the type described by classname.
/// For example:
/// ~~~{.cpp}
/// TopClass *top;
/// BottomClass *bottom;
/// top = bottom;
/// ~~~
/// you can do:
/// ~~~{.cpp}
/// directory->WriteObjectAny(top,"top","name of object");
/// directory->WriteObjectAny(bottom,"bottom","name of object");
/// ~~~
/// <b>BUT YOU CAN NOT DO</b> the following since it will fail with multiple inheritance:
/// ~~~{.cpp}
/// directory->WriteObjectAny(top,"bottom","name of object");
/// ~~~
/// We <b>STRONGLY</b> recommend to use
/// ~~~{.cpp}
/// TopClass *top = ....;
/// directory->WriteObject(top,"name of object")
/// ~~~
/// See also remarks in TDirectoryFile::WriteTObject
 
Int_t TDirectoryFile::WriteObjectAny(const void *obj, const char *classname, const char *name, Option_t *option, Int_t bufsize)
{
   TClass *cl = TClass::GetClass(classname);
   if (!cl) {
      TObject *info_obj = *(TObject**)obj;
      TVirtualStreamerInfo *info = dynamic_cast<TVirtualStreamerInfo*>(info_obj);
      if (!info) {
         Error("WriteObjectAny","Unknown class: %s",classname);
         return 0;
      } else {
         cl = info->GetClass();
      }
   }
   return WriteObjectAny(obj,cl,name,option,bufsize);
}
 
////////////////////////////////////////////////////////////////////////////////
/// Write object of class with dictionary cl in this directory.
///
/// obj may not derive from TObject
/// To get the TClass* cl pointer, one can use
///
///     TClass *cl = TClass::GetClass("classname");
///
/// An alternative is to call the function WriteObjectAny above.
/// see TDirectoryFile::WriteTObject for comments
 
Int_t TDirectoryFile::WriteObjectAny(const void *obj, const TClass *cl, const char *name, Option_t *option, Int_t bufsize)
{
   TDirectory::TContext ctxt(this);
 
   if (!fFile) return 0;
 
   if (!cl) {
      Error("WriteObject","Unknown type for %s, it can not be written.",name);
      return 0;
   }
 
   if (!fFile->IsWritable()) {
      if (!fFile->TestBit(TFile::kWriteError)) {
         // Do not print the error if the file already had a SysError.
         Error("WriteObject","File %s is not writable", fFile->GetName());
      }
      return 0;
   }
 
   if (!obj) return 0;
 
   const char *className = cl->GetName();
   const char *oname;
   if (name && *name)
      oname = name;
   else
      oname = className;
 
   if (cl && cl->GetCollectionProxy() && dynamic_cast<TEmulatedCollectionProxy*>(cl->GetCollectionProxy())) {
      Error("WriteObjectAny",
            "The class requested (%s) for the key name \"%s\""
            " is an instance of an stl collection and does not have a compiled CollectionProxy."
            " Please generate the dictionary for this collection (%s). No data will be written.",
            className, oname, className);
      return 0;
   }
 
   TKey *key, *oldkey = nullptr;
   Int_t bsize = GetBufferSize();
   if (bufsize > 0) bsize = bufsize;
 
   TString opt = option;
   opt.ToLower();
 
   // Remove trailing blanks in object name
   Int_t nch = strlen(oname);
   char *newName = nullptr;
   if (nch && oname[nch-1] == ' ') {
      newName = new char[nch+1];
      strlcpy(newName,oname,nch+1);
      for (Int_t i=0;i<nch;i++) {
         if (newName[nch-i-1] != ' ') break;
         newName[nch-i-1] = 0;
      }
      oname = newName;
   }
 
   if (opt.Contains("overwrite")) {
      //One must use GetKey. FindObject would return the lowest cycle of the key!
      //key = (TKey*)gDirectory->GetListOfKeys()->FindObject(oname);
      key = GetKey(oname);
      if (key) {
         key->Delete();
         delete key;
      }
   }
   if (opt.Contains("writedelete")) {
      oldkey = GetKey(oname);
   }
   key = fFile->CreateKey(this, obj, cl, oname, bsize);
   if (newName) delete [] newName;
 
   if (!key->GetSeekKey()) {
      fKeys->Remove(key);
      delete key;
      return 0;
   }
   fFile->SumBuffer(key->GetObjlen());
   Int_t nbytes = key->WriteFile(0);
   if (fFile->TestBit(TFile::kWriteError)) return 0;
 
   if (oldkey) {
      oldkey->Delete();
      delete oldkey;
   }
 
   return nbytes;
}
 
////////////////////////////////////////////////////////////////////////////////
/// Overwrite the Directory header record.
 
void TDirectoryFile::WriteDirHeader()
{
   TFile* f = GetFile();
   if (!f) return;
 
   if (!f->IsBinary()) {
      fDatimeM.Set();
      f->DirWriteHeader(this);
      return;
   }
 
   Int_t nbytes  = TDirectoryFile::Sizeof();  //Warning ! TFile has a Sizeof()
   char *header = new char[nbytes];
   char *buffer = header;
   fDatimeM.Set();
   TDirectoryFile::FillBuffer(buffer);
   Long64_t pointer = fSeekDir + fNbytesName; // do not overwrite the name/title part
   fModified     = kFALSE;
   f->Seek(pointer);
   f->WriteBuffer(header, nbytes);
   if (f->MustFlush()) f->Flush();
   delete [] header;
}
 
////////////////////////////////////////////////////////////////////////////////
/// Write Keys linked list on the file.
///
///  The linked list of keys (fKeys) is written as a single data record
 
void TDirectoryFile::WriteKeys()
{
   TFile* f = GetFile();
   if (!f) return;
 
   if (!f->IsBinary()) {
      f->DirWriteKeys(this);
      return;
   }
 
//*-* Delete the old keys structure if it exists
   if (fSeekKeys != 0) {
      f->MakeFree(fSeekKeys, fSeekKeys + fNbytesKeys -1);
   }
//*-* Write new keys record
   TIter next(fKeys);
   TKey *key;
   Int_t nkeys  = fKeys->GetSize();
   Int_t nbytes = sizeof nkeys;          //*-* Compute size of all keys
   if (f->GetEND() > TFile::kStartBigFile) nbytes += 8;
   while ((key = (TKey*)next())) {
      nbytes += key->Sizeof();
   }
   TKey *headerkey  = new TKey(fName,fTitle,IsA(),nbytes,this);
   if (headerkey->GetSeekKey() == 0) {
      delete headerkey;
      return;
   }
   char *buffer = headerkey->GetBuffer();
   next.Reset();
   tobuf(buffer, nkeys);
   while ((key = (TKey*)next())) {
      key->FillBuffer(buffer);
   }
 
   fSeekKeys     = headerkey->GetSeekKey();
   fNbytesKeys   = headerkey->GetNbytes();
   headerkey->WriteFile();
   delete headerkey;
}