TFile

class TFile : public TDirectory

    private:

      TFile TFile(TFile&)
       void operator=(TFile&)

    protected:

                void Init(Bool_t create)
       virtual Int_t SysClose(Int_t fd)
       virtual Int_t SysOpen(char* pathname, Int_t flags, UInt_t mode)
       virtual Int_t SysRead(Int_t fd, void* buf, Int_t len)
      virtual Seek_t SysSeek(Int_t fd, Seek_t offset, Int_t whence)
       virtual Int_t SysSync(Int_t fd)
       virtual Int_t SysWrite(Int_t fd, void* buf, Int_t len)

    public:

                  TFile TFile()
                  TFile TFile(Text_t* fname, Option_t* option, Text_t* ftitle, Int_t compress = 1)
           virtual void ~TFile()
                TClass* Class()
           virtual void Close(Option_t* option)
           virtual void Copy(TObject&)
           virtual void Delete(Text_t* namecycle)
           virtual void Draw(Option_t* option)
           virtual void FillBuffer(char*& buffer)
           virtual void Flush()
                  Int_t GetBestBuffer()
               Double_t GetBytesRead()
               Double_t GetBytesWritten()
                Float_t GetCompressionFactor()
                  Int_t GetCompressionLevel()
         virtual Seek_t GetEND()
                  Int_t GetFd()
               Double_t GetFileBytesRead()
               Double_t GetFileBytesWritten()
                 TList* GetListOfFree()
          virtual Int_t GetNfree()
      virtual Option_t* GetOption()
                  Int_t GetVersion()
        virtual TClass* IsA()
         virtual Bool_t IsOpen()
           virtual void ls(Option_t* option)
           virtual void MakeFree(Seek_t first, Seek_t last)
           virtual void Map()
                 TFile* Open(Text_t* name, Option_t* option, Text_t* ftitle, Int_t compress = 1)
           virtual void Paint(Option_t* option)
           virtual void Print(Option_t* option)
         virtual Bool_t ReadBuffer(char* buf, int len)
           virtual void ReadFree()
           virtual void Recover()
           virtual void Seek(Seek_t offset, TFile::ERelativeTo pos = kBeg)
           virtual void SetCompressionLevel(Int_t level = 1)
           virtual void SetEND(Seek_t last)
                   void SetFileBytesRead(Double_t bytes = 0)
                   void SetFileBytesWritten(Double_t bytes = 0)
           virtual void SetOption(Option_t* option = >)
           virtual void ShowMembers(TMemberInspector& insp, char* parent)
          virtual Int_t Sizeof()
           virtual void Streamer(TBuffer& b)
                   void SumBuffer(Int_t bufsize)
           virtual void Write(Text_t* name = 0, Int_t opt = 0, Int_t bufsiz = 0)
         virtual Bool_t WriteBuffer(char* buf, int len)
           virtual void WriteFree()
           virtual void WriteHeader()

  Data Members

    protected:

                    Int_t fD            File descriptor
                   Seek_t fBEGIN        First used byte in file
                   Seek_t fEND          Last used byte in file
                    Int_t fVersion      File format version
                    Int_t fCompress     (=1 file is compressed, 0 otherwise)
                  TString fOption       File options
                   Char_t fUnits        Number of bytes for file pointers
                   Seek_t fSeekFree     Location on disk of free segments structure
                    Int_t fNbytesFree   Number of bytes for free segments structure
                    Int_t fWritten      Number of objects written so far
                 Double_t fSumBuffer    Sum of buffer sizes of objects written so far
                 Double_t fSum2Buffer   Sum of squares of buffer sizes of objects written so far
                   TList* fFree         Free segments linked list table
                 Double_t fBytesWrite   Number of bytes written to this file
                 Double_t fBytesRead    Number of bytes read from this file
          static Double_t fgBytesWrite  Number of bytes written by all TFile objects
          static Double_t fgBytesRead   Number of bytes read by all TFile objects
       static const Int_t kBegin        
      static const Char_t kUnits        

    public:

      static const TFile::ERelativeTo kBeg  
      static const TFile::ERelativeTo kCur  
      static const TFile::ERelativeTo kEnd  

See also

TNetFile, TRFIOFile, TWebFile

Class Description

*-*-*-*-*-*-*-*-*-*-*-*File default Constructor*-*-*-*-*-*-*-*-*-*-*-*-*-*-*
*-*                    ========================

*-*-*-*-*-*-*-*-*-*-*-*File Constructor*-*--*-*-*-*-*-*-*-*-*-*-*-*-*-*-*
*-*                    ================
  If Option = NEW or CREATE   create a new file and open it for writing,
                              if the file already exists the file is
                              not opened.
            = RECREATE        create a new file, if the file already
                              exists it will be overwritten.
            = UPDATE          open an existing file for writing.
            = READ            open an existing file for reading.
  Use IsOpen() to check if the file is opened successfuly.

  The parameter name is used to identify the file in the current job
    name may be different in a job writing the file and another job
    reading/writing the file.
  When the file is created, the name of the file seen from the file system
    is fname. It is recommended to specify fname as "file.root"
    The suffix root will be used by object browsers to automatically
    identify ROOT files.
  The title of the file (ftitle) will be shown by the ROOT browsers.

  A ROOT file (like a Unix file system) may contain objects and
    directories. There are no restrictions for the number of levels
    of directories.

  A ROOT file is designed such that one can write in the file in pure
    sequential mode (case of BATCH jobs). In this case, the file may be
    read sequentially again without using the file index written
    at the end of the file. In case of a job crash, all the information
    on the file is therefore protected.
  A ROOT file can be used interactively. In this case, one has the
    possibility to delete existing objects and add new ones.
  When an object is deleted from the file, the freed space is added
  into the FREE linked list (lFree). The FREE list consists of a chain
  of consecutive free segments on the file. At the same time, the first
  4 bytes of the freed record on the file are overwritten by GAPSIZE
  where GAPSIZE = -(Number of bytes occupied by the record).

  compress = 0 objects written to this file will not be compressed.
  compress = 1 minimal compression level but fast.
  ....
  compress = 9 maximal compression level but slow.

  Note that the compression level may be changed at any time.
  The new compression level will only apply to newly written objects.
  The function TFile::Map shows the compression factor
  for each object written to this file.
  The function TFile::GetCompressionFactor returns the global
  compression factor for this file.

  A ROOT file is a suite of consecutive data records with the following
    format (see also the TKey class);
 TKey ---------------------
      byte 1->4  Nbytes    = Length of compressed object (in bytes)
           5->6  Version   = TKey version identifier
           7->10 ObjLen    = Length of uncompressed object
          11->14 Datime    = Date and time when object was written to file
          15->16 KeyLen    = Length of the key structure (in bytes)
          17->18 Cycle     = Cycle of key
          19->22 SeekKey   = Pointer to record itself (consistency check)
          23->26 SeekPdir  = Pointer to directory header
          27->27 lname     = Number of bytes in the class name
          28->.. ClassName = Object Class Name
          ..->.. lname     = Number of bytes in the object name
          ..->.. Name      = lName bytes with the name of the object
          ..->.. lTitle    = Number of bytes in the object title
          ..->.. Title     = Title of the object
          -----> DATA      = Data bytes associated to the object

  The first data record starts at byte fBEGIN (currently set to kBegin)
  Bytes 1->kBegin contain the file description:
       byte  1->4  "root"      = Root file identifier
             5->8  fVersion    = File format version
             9->12 fBEGIN      = Pointer to first data record
            13->16 fEND        = Pointer to first free word at the EOF
            17->20 fSeekFree   = Pointer to FREE data record
            21->24 fNbytesFree = Number of bytes in FREE data record
            25->28 nfree       = Number of free data records
            29->32 fNbytesName = Number of bytes in TNamed at creation time
            33->33 fUnits      = Number of bytes for file pointers
            34->37 fCompress   = Zip compression level

/*

*/


  The structure of a directory is shown in TDirectory::TDirectory

*-*-*-*-*-*-*-*-*-*-*-*File destructor*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*
*-*                    ===============

 Initialize a TFile object.

*-*-*-*-*-*-*-*-*-*-*-*Close a file*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*
*-*                    ============

*-*-*-*-*-*-*-*-*-*-*-*-*Delete object namecycle*-*-*-*-*-*-*-*-*-*-*-*-*-*
*-*                      =======================
  namecycle identifies an object in the top directory of the file
   namecycle has the format name;cycle
   name  = * means all
   cycle = * means all cycles (memory and keys)
   cycle = "" or cycle = 9999 ==> apply to a memory object
   When name=* use T* to delete subdirectories also

   examples:
     foo   : delete object named foo in memory
     foo;1 : delete cycle 1 of foo on file
     foo;* : delete all cycles of foo on disk 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

*-*-*-*-*-*-*-*-*-*-*-*Fill Graphics Structure and Paint-*-*-*-*-*-*-*-*-*-*
*-*                    =================================
 Loop on all objects (memory or file) and all subdirectories

 Synchornize a file's in-core and on-disk states.

*-*-*-*-*-*-*-*-*-*-*-*Encode file output buffer*-*-*-*-*-*-*
*-*                    =========================
 The file output buffer contains only the FREE data record

*-*-*-*-*-*-*-*Return the best buffer size of objects on this file*-*-*-*-*-*
*-*            ===================================================

  The best buffer size is estimated based on the current mean value
  and standard deviation of all objects written so far to this file.
  Returns mean value + one standard deviation.

*-*-*-*-*-*-*-*-*-*Return the file compression factor*-*-*-*-*-*-*-*-*-*
*-*                =================================

  Add total number of compressed/uncompressed bytes for each key.
  return ratio of the two.

*-*-*-*-*-*-*-*-*-*-*-*List File contents*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*
*-*                    ==================
  Indentation is used to identify the file tree
  Subdirectories are listed first
  then objects in memory
  then objects on the file

 Returns kTRUE in case file is open and kFALSE if file is not open.

*-*-*-*-*-*-*-*-*-*-*-*Mark unused bytes on the file*-*-*-*-*-*-*-*-*-*-*
*-*                    =============================
  The list of free segments is in the lFree linked list
  When an object is deleted from the file, the freed space is added
  into the FREE linked list (lFree). The FREE list consists of a chain
  of consecutive free segments on the file. At the same time, the first
  4 bytes of the freed record on the file are overwritten by GAPSIZE
  where GAPSIZE = -(Number of bytes occupied by the record).

*-*-*-*-*-*-*-*-*-*List the contents of a file sequentially*-*-*-*-*-*
*-*                ========================================

  For each logical record found, it prints
     Date/Time  Record_Adress Logical_Record_Length  ClassName  CompressionFactor

  Example of output
  960122/105933  At:64        N=160       TFile
  960122/105933  At:224       N=402       TH1F           CX = 2.09
  960122/105934  At:626       N=1369      TH2F           CX = 5.57
  960122/105934  At:1995      N=1761      TProfile       CX = 1.63
  960122/105936  At:3756      N=181640    THN            CX = 1.10
  960122/105936  At:185396    N=326       TFile
  960122/105936  At:185722    N=98        TFile

*-*-*-*-*-*-*-*-*-*-*-*Paint all objects in the file*-*-*-*-*-*-*-*-*-*-*
*-*                    =============================

*-*-*-*-*-*-*-*-*-*-*-*Print all objects in the file*-*-*-*-*-*-*-*-*-*-*
*-*                    =============================

 Read a buffer from the file. This is the basic low level read operation.
 Returns kTRUE in case of failure.

*-*-*-*-*-*-*-*-*-*-*-*-*Read the FREE linked list*-*-*-*-*-*-*-*-*-*-*-*-*
*-*                      =========================
  Every file has a linked list (fFree) of free segments
  This linked list has been written on the file via WriteFree
  as a single data record

*-*-*-*-*-*-*-*-*Attempt to recover file if not correctly closed*-*-*-*-*
*-*              ===============================================

 Seek to a specific position in the file. Pos it either kBeg, kCur or kEnd.

*-*-*-*-*-*-*-*-*-*Set level of compression for this file*-*-*-*-*-*-*-*
*-*                ======================================

  level = 0 objects written to this file will not be compressed.
  level = 1 minimal compression level but fast.
  ....
  level = 9 maximal compression level but slow.

  Note that the compression level may be changed at any time.
  The new compression level will only apply to newly written objects.
  The function TFile::Map shows the compression factor
  for each object written to this file.
  The function TFile::GetCompressionFactor returns the global
  compression factor for this file.

*-*-*-*-*-*-*Return the size in bytes of the file header-*-*-*-*-*-*-*-*
*-*          ===========================================

 Stream a TFile object.

*-*-*-*-*Increment statistics for buffer sizes of objects in this file*-*-*
*-*      =============================================================

*-*-*-*-*-*-*-*-*-*Write memory objects to this file*-*-*-*-*-*-*-*-*-*
*-*                =================================
  Loop on all objects in memory (including subdirectories).
  A new key is created in the KEYS linked list for each object.
  The list of keys is then saved on the file (via WriteKeys)
  as a single data record.
  For values of opt see TObject::Write().
  The directory header info is rewritten on the directory header record.
  The linked list of FREE segments is written.
  The file header is written (bytes 1->fBEGIN).

 Write a buffer to the file. This is the basic low level write operation.
 Returns kTRUE in case of failure.

*-*-*-*-*-*-*-*-*-*-*-*Write FREE linked list on the file *-*-*-*-*-*-*-*
*-*                    ==================================
  The linked list of FREE segments (fFree) is written as a single data
  record

*-*-*-*-*-*-*-*-*-*-*-*Write File Header*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*
*-*                    =================

 Static member function allowing the creation/opening of either a
 TFile, TNetFile, TWebFile or a TRFIOFile. The returned type of TFile
 depends on the file name. If the file starts with "root:" a TNetFile
 object will be returned, with "http:" a TWebFile, with "rfio:" a
 TRFIOFile and with "file:" or the default a local TFile. However,
 before opening a file via TNetFile a check is made to see if the URL
 specifies a local file. If that is the case the file will be opened
 via a normal TFile. To force the opening of a local file via a
 TNetFile use either TNetFile directly or specify as host "localhost".

 Interface to system open. All arguments like in "man 2 open".

 Interface to system close. All arguments like in "man 2 close".

 Interface to system read. All arguments like in "man 2 read".

 Interface to system write. All arguments like in "man 2 write".

 Interface to system lseek. All arguments like in "man 2 lseek"
 except that the offset and return value are Long_t to be able to
 handle 64 bit file systems.

 Interface to system fsync. All arguments like in "man 2 fsync".

Inline Functions

               void operator=(TFile&)
               void Copy(TObject&)
              Int_t GetCompressionLevel()
             Seek_t GetEND()
              Int_t GetFd()
             TList* GetListOfFree()
              Int_t GetNfree()
          Option_t* GetOption()
           Double_t GetBytesRead()
           Double_t GetBytesWritten()
              Int_t GetVersion()
               void SetEND(Seek_t last)
               void SetOption(Option_t* option = >)
            TClass* Class()
            TClass* IsA()
               void ShowMembers(TMemberInspector& insp, char* parent)