Re: Problem with the Streamer function of a class derived from TDirectory...

Hi,

I have installed 5.18/00 (I was using 5.14/00e before) and I have derived my class from TDirectoryFile. The code of my class is now the following:

#include "Rtypes.h"
#include "TObject.h"
#include "TDirectoryFile.h"

class QMyDir: public TDirectoryFile
{
  public:
    QMyDir():TDirectoryFile(){}

    QMyDir(const QMyDir& newqds):TDirectoryFile(){}

    QMyDir(const char *name, const char *title, TDirectory* motherDir = 0):TDirectoryFile(name,title,"QMyDir",motherDir){}

    virtual ~QMyDir(){}

    QMyDir& operator=(const QMyDir &rhs){fprintf(stderr,"Warning: TDirectoryFile::operator= cannot be called from derived class QMyDir\n"); return *this;}

  private:

    ClassDef(QMyDir,1) //QSigEx Data Structure Class };

I still get an error when I try to load the instance from the file. I have stored and have tried to load the instance using the code I have shown in my previous email. Here is the error I get:

_file0->Get("dir")
Error in <TBufferFile::ReadBuffer2>: class: TUUID, attempting to access a wrong version: 127, object skipped at offset 87 Error in <TFile::ReadBuffer>: error reading all requested bytes from file file.root, got 0 of 2687036
(class TObject*)0x8345fa8

Thank you
Pierre-Luc Drouin

Rene Brun wrote:
> Pierre-Luc,
>
> Instead of TDirectory, you should derive from TDirectoryFile. In
> version 5.16, TDirectory
> became an abstract interface. See 5.16 Release Notes at:
> http://root.cern.ch/root/Version516.news.html
>
> Rene Brun
>
> Pierre-Luc Drouin wrote:
>> Hi,
>>
>> I have derived a class from TDirectory and I am trying to store and
>> retrieve an instance of this class to/from a ROOT file.
>>
>> I am using the autogenerated Streamer function and when I call
>> TDirectory
>> <http://root.cern.ch/root/html514/src/TDirectory.cxx.html#OUS8P>(const
>> char *name, const char *title, Option_t
>> <http://root.cern.ch/root/html514/ListOfTypes.html#Option_t>
>> *classname, TDirectory
>> <http://root.cern.ch/root/html514/TDirectory.html>* initMotherDir)
>> from the constructor of my class, I set classname to the name of my
>> class.
>>
>> I do not get any warning/error message when I Write the instance in
>> the root file, but I get the following error when I try to load the
>> instance using TFile::Get:
>>
>> Error in <TBuffer::ReadVersion>: Could not find the StreamerInfo with
>> a checksum of 0 for the class "TUUID" in file.root.
>> Error in <TBuffer::CheckByteCount>: object of class TUUID read too
>> few bytes: 22 instead of 898023151
>> Error in <TBuffer::CheckByteCount>: Byte count probably corrupted
>> around buffer position 85:
>> 898023151 for a possible maximum of 17
>> SysError in <TFile::Seek>: cannot seek to position 60235645022633984
>> in file file.root, retpos=-1 (Invalid argument)
>> Error in <TFile::ReadBuffer>: error reading all requested bytes from
>> file file.root, got 186 of 2687036
>>
>> Here is the code of a class that allows to reproduce the problem:
>>
>> class QMyDir: public TDirectory
>> {
>> public:
>> QMyDir():TDirectory(){}
>>
>> QMyDir(const QMyDir& newqds):TDirectory(){*this=newqds; }
>>
>> QMyDir(const char *name, const char *title, TDirectory* motherDir
>> = 0):TDirectory(name,title,"QMyDir",motherDir){}
>>
>> virtual ~QMyDir(){}
>>
>> QMyDir& operator=(const QMyDir &rhs){fprintf(stderr,"Warning:
>> TDirectory::operator= function is private and cannot be called by
>> derived class QMyDir\n"); return *this;}
>>
>> private:
>>
>> ClassDef(QMyDir,1) //QSigEx Data Structure Class
>> };
>>
>> Here is the code of the autogenerated Streamer function:
>>
>> void QMyDir::Streamer(TBuffer &R__b)
>> {
>> // Stream an object of class QMyDir.
>>
>> UInt_t R__s, R__c;
>> if (R__b.IsReading()) {
>> Version_t R__v = R__b.ReadVersion(&R__s, &R__c); if (R__v) { }
>> TDirectory::Streamer(R__b);
>> R__b.CheckByteCount(R__s, R__c, QMyDir::IsA());
>> } else {
>> R__c = R__b.WriteVersion(QMyDir::IsA(), kTRUE);
>> TDirectory::Streamer(R__b);
>> R__b.SetByteCount(R__c, kTRUE);
>> } }
>>
>> Now how I get the error in CINT:
>>
>> root [0] TFile file("file.root","recreate")
>> root [1] QMyDir* dir=new QMyDir("dir","dir")
>> root [2] file.ls()
>> TFile** file.root
>> TFile* file.root
>> QMyDir* dir dir
>> KEY: QMyDir dir;1 dir
>> root [3] file.Write()
>> (Int_t)0
>> root [4] file.Close()
>> root [5] .q
>>
>> root [0] TFile file("file.root","read")
>> root [1] file.ls()
>> TFile** file.root
>> TFile* file.root
>> KEY: QMyDir dir;1 dir
>> root [2] QMyDir *dir=file.Get("dir")
>> Error in <TBuffer::ReadVersion>: Could not find the StreamerInfo with
>> a checksum of 0 for the class "TUUID" in file.root.
>> Error in <TBuffer::CheckByteCount>: object of class TUUID read too
>> few bytes: 22 instead of 898023151
>> Error in <TBuffer::CheckByteCount>: Byte count probably corrupted
>> around buffer position 85:
>> 898023151 for a possible maximum of 17
>> SysError in <TFile::Seek>: cannot seek to position 60235645022633984
>> in file file.root, retpos=-1 (Invalid argument)
>> Error in <TFile::ReadBuffer>: error reading all requested bytes from
>> file file.root, got 186 of 2687036
>>
>>
>> Thanks!
>> Pierre-Luc Drouin
>>
>>
>
Received on Tue Mar 18 2008 - 16:27:34 CET