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Reference Guide
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TKey Class Reference

Book space in a file, create I/O buffers, to fill them, (un)compress them.

The TKey class includes functions to book space in a file, to create I/O buffers, to fill these buffers, to compress/uncompress data buffers. Before saving (making persistent) an object in a file, a key must be created. The key structure contains all the information to uniquely identify a persistent object in a file.

Data Member Explanation
fNbytes Number of bytes for the compressed object and key.
fObjlen Length of uncompressed object.
fDatime Date/Time when the object was written.
fKeylen Number of bytes for the key structure.
fCycle Cycle number of the object.
fSeekKey Address of the object on file (points to fNbytes). This is a redundant information used to cross-check the data base integrity.
fSeekPdir Pointer to the directory supporting this object.
fClassName Object class name.
fName Name of the object.
fTitle Title of the object.

In the 16 highest bits of fSeekPdir is encoded a pid offset. This offset is to be added to the pid index stored in the TRef object and the referenced TObject.

The TKey class is used by ROOT to:

The structure of a file is shown in TFile::TFile. The structure of a directory is shown in TDirectoryFile::TDirectoryFile. The TKey class is used by the TBasket class. See also TTree.

Definition at line 24 of file TKey.h.

Public Member Functions

 TKey ()
 TKey default constructor. More...
 
 TKey (TDirectory *motherDir)
 TKey default constructor. More...
 
 TKey (TDirectory *motherDir, const TKey &orig, UShort_t pidOffset)
 Copy a TKey from its original directory to the new 'motherDir'. More...
 
 TKey (const char *name, const char *title, const TClass *cl, Int_t nbytes, TDirectory *motherDir)
 Create a TKey object with the specified name, title for the given class. More...
 
 TKey (const TString &name, const TString &title, const TClass *cl, Int_t nbytes, TDirectory *motherDir)
 Create a TKey object with the specified name, title for the given class. More...
 
 TKey (const TObject *obj, const char *name, Int_t bufsize, TDirectory *motherDir)
 Create a TKey object for a TObject* and fill output buffer. More...
 
 TKey (const void *obj, const TClass *cl, const char *name, Int_t bufsize, TDirectory *motherDir)
 Create a TKey object for any object obj of class cl d and fill output buffer. More...
 
 TKey (Long64_t pointer, Int_t nbytes, TDirectory *motherDir=0)
 Create a TKey object to read keys. More...
 
virtual ~TKey ()
 TKey default destructor. More...
 
virtual void Browse (TBrowser *b)
 Read object from disk and call its Browse() method. More...
 
virtual void Delete (Option_t *option="")
 Delete an object from the file. More...
 
virtual void DeleteBuffer ()
 Delete key buffer(s). More...
 
virtual void FillBuffer (char *&buffer)
 Encode key header into output buffer. More...
 
virtual char * GetBuffer () const
 
TBufferGetBufferRef () const
 
virtual const char * GetClassName () const
 
Short_t GetCycle () const
 Return cycle number associated to this key. More...
 
const TDatimeGetDatime () const
 
TFileGetFile () const
 Returns file to which key belong. More...
 
virtual const char * GetIconName () const
 Title can keep 32x32 xpm thumbnail/icon of the parent object. More...
 
Short_t GetKeep () const
 Returns the "KEEP" status. More...
 
Int_t GetKeylen () const
 
TDirectoryGetMotherDir () const
 
Int_t GetNbytes () const
 
Int_t GetObjlen () const
 
virtual Long64_t GetSeekKey () const
 
virtual Long64_t GetSeekPdir () const
 
virtual const char * GetTitle () const
 Returns title (title can contain 32x32 xpm thumbnail/icon). More...
 
Int_t GetVersion () const
 
virtual void IncrementPidOffset (UShort_t offset)
 Increment fPidOffset by 'offset'. More...
 
Bool_t IsFolder () const
 Check if object referenced by the key is a folder. More...
 
virtual void Keep ()
 Set the "KEEP" status. More...
 
virtual void ls (Option_t *option="") const
 List Key contents. More...
 
virtual void Print (Option_t *option="") const
 Print key contents. More...
 
virtual Int_t Read (TObject *obj)
 To read an object from the file. More...
 
virtual void ReadBuffer (char *&buffer)
 Decode input buffer. More...
 
virtual Bool_t ReadFile ()
 Read the key structure from the file. More...
 
void ReadKeyBuffer (char *&buffer)
 Decode input buffer. More...
 
virtual TObjectReadObj ()
 To read a TObject* from the file. More...
 
template<typename T >
T * ReadObject ()
 To read an object (non deriving from TObject) from the file. More...
 
virtual voidReadObjectAny (const TClass *expectedClass)
 To read an object (non deriving from TObject) from the file. More...
 
virtual TObjectReadObjWithBuffer (char *bufferRead)
 To read a TObject* from bufferRead. More...
 
virtual void SetBuffer ()
 
void SetMotherDir (TDirectory *dir)
 
virtual void SetParent (const TObject *parent)
 Set parent in key buffer. More...
 
virtual Int_t Sizeof () const
 Return the size in bytes of the key header structure. More...
 
virtual Int_t WriteFile (Int_t cycle=1, TFile *f=0)
 Write the encoded object supported by this key. More...
 
- Public Member Functions inherited from TNamed
 TNamed ()
 
 TNamed (const char *name, const char *title)
 
 TNamed (const TString &name, const TString &title)
 
 TNamed (const TNamed &named)
 TNamed copy ctor. More...
 
virtual ~TNamed ()
 TNamed destructor. More...
 
virtual void Clear (Option_t *option="")
 Set name and title to empty strings (""). More...
 
virtual TObjectClone (const char *newname="") const
 Make a clone of an object using the Streamer facility. More...
 
virtual Int_t Compare (const TObject *obj) const
 Compare two TNamed objects. More...
 
virtual void Copy (TObject &named) const
 Copy this to obj. More...
 
virtual const char * GetName () const
 Returns name of object. More...
 
virtual ULong_t Hash () const
 Return hash value for this object. More...
 
virtual Bool_t IsSortable () const
 
TNamedoperator= (const TNamed &rhs)
 TNamed assignment operator. More...
 
virtual void SetName (const char *name)
 Set the name of the TNamed. More...
 
virtual void SetNameTitle (const char *name, const char *title)
 Set all the TNamed parameters (name and title). More...
 
virtual void SetTitle (const char *title="")
 Set the title of the TNamed. More...
 
- Public Member Functions inherited from TObject
 TObject ()
 TObject constructor. More...
 
 TObject (const TObject &object)
 TObject copy ctor. More...
 
virtual ~TObject ()
 TObject destructor. More...
 
void AbstractMethod (const char *method) const
 Use this method to implement an "abstract" method that you don't want to leave purely abstract. More...
 
virtual void AppendPad (Option_t *option="")
 Append graphics object to current pad. More...
 
ULong_t CheckedHash ()
 Checked and record whether for this class has a consistent Hash/RecursiveRemove setup (*) and then return the regular Hash value for this object. More...
 
virtual const char * ClassName () const
 Returns name of class to which the object belongs. More...
 
virtual Int_t DistancetoPrimitive (Int_t px, Int_t py)
 Computes distance from point (px,py) to the object. More...
 
virtual void Draw (Option_t *option="")
 Default Draw method for all objects. More...
 
virtual void DrawClass () const
 Draw class inheritance tree of the class to which this object belongs. More...
 
virtual TObjectDrawClone (Option_t *option="") const
 Draw a clone of this object in the current selected pad for instance with: gROOT->SetSelectedPad(gPad). More...
 
virtual void Dump () const
 Dump contents of object on stdout. More...
 
virtual void Error (const char *method, const char *msgfmt,...) const
 Issue error message. More...
 
virtual void Execute (const char *method, const char *params, Int_t *error=0)
 Execute method on this object with the given parameter string, e.g. More...
 
virtual void Execute (TMethod *method, TObjArray *params, Int_t *error=0)
 Execute method on this object with parameters stored in the TObjArray. More...
 
virtual void ExecuteEvent (Int_t event, Int_t px, Int_t py)
 Execute action corresponding to an event at (px,py). More...
 
virtual void Fatal (const char *method, const char *msgfmt,...) const
 Issue fatal error message. More...
 
virtual TObjectFindObject (const char *name) const
 Must be redefined in derived classes. More...
 
virtual TObjectFindObject (const TObject *obj) const
 Must be redefined in derived classes. More...
 
virtual Option_tGetDrawOption () const
 Get option used by the graphics system to draw this object. More...
 
virtual char * GetObjectInfo (Int_t px, Int_t py) const
 Returns string containing info about the object at position (px,py). More...
 
virtual Option_tGetOption () const
 
virtual UInt_t GetUniqueID () const
 Return the unique object id. More...
 
virtual Bool_t HandleTimer (TTimer *timer)
 Execute action in response of a timer timing out. More...
 
Bool_t HasInconsistentHash () const
 Return true is the type of this object is known to have an inconsistent setup for Hash and RecursiveRemove (i.e. More...
 
virtual void Info (const char *method, const char *msgfmt,...) const
 Issue info message. More...
 
virtual Bool_t InheritsFrom (const char *classname) const
 Returns kTRUE if object inherits from class "classname". More...
 
virtual Bool_t InheritsFrom (const TClass *cl) const
 Returns kTRUE if object inherits from TClass cl. More...
 
virtual void Inspect () const
 Dump contents of this object in a graphics canvas. More...
 
void InvertBit (UInt_t f)
 
virtual Bool_t IsEqual (const TObject *obj) const
 Default equal comparison (objects are equal if they have the same address in memory). More...
 
R__ALWAYS_INLINE Bool_t IsOnHeap () const
 
R__ALWAYS_INLINE Bool_t IsZombie () const
 
void MayNotUse (const char *method) const
 Use this method to signal that a method (defined in a base class) may not be called in a derived class (in principle against good design since a child class should not provide less functionality than its parent, however, sometimes it is necessary). More...
 
virtual Bool_t Notify ()
 This method must be overridden to handle object notification. More...
 
void Obsolete (const char *method, const char *asOfVers, const char *removedFromVers) const
 Use this method to declare a method obsolete. More...
 
void operator delete (void *ptr)
 Operator delete. More...
 
void operator delete[] (void *ptr)
 Operator delete []. More...
 
voidoperator new (size_t sz)
 
voidoperator new (size_t sz, void *vp)
 
voidoperator new[] (size_t sz)
 
voidoperator new[] (size_t sz, void *vp)
 
TObjectoperator= (const TObject &rhs)
 TObject assignment operator. More...
 
virtual void Paint (Option_t *option="")
 This method must be overridden if a class wants to paint itself. More...
 
virtual void Pop ()
 Pop on object drawn in a pad to the top of the display list. More...
 
virtual void RecursiveRemove (TObject *obj)
 Recursively remove this object from a list. More...
 
void ResetBit (UInt_t f)
 
virtual void SaveAs (const char *filename="", Option_t *option="") const
 Save this object in the file specified by filename. More...
 
virtual void SavePrimitive (std::ostream &out, Option_t *option="")
 Save a primitive as a C++ statement(s) on output stream "out". More...
 
void SetBit (UInt_t f, Bool_t set)
 Set or unset the user status bits as specified in f. More...
 
void SetBit (UInt_t f)
 
virtual void SetDrawOption (Option_t *option="")
 Set drawing option for object. More...
 
virtual void SetUniqueID (UInt_t uid)
 Set the unique object id. More...
 
virtual void SysError (const char *method, const char *msgfmt,...) const
 Issue system error message. More...
 
R__ALWAYS_INLINE Bool_t TestBit (UInt_t f) const
 
Int_t TestBits (UInt_t f) const
 
virtual void UseCurrentStyle ()
 Set current style settings in this object This function is called when either TCanvas::UseCurrentStyle or TROOT::ForceStyle have been invoked. More...
 
virtual void Warning (const char *method, const char *msgfmt,...) const
 Issue warning message. More...
 
virtual Int_t Write (const char *name=0, Int_t option=0, Int_t bufsize=0)
 Write this object to the current directory. More...
 
virtual Int_t Write (const char *name=0, Int_t option=0, Int_t bufsize=0) const
 Write this object to the current directory. More...
 

Protected Member Functions

void Build (TDirectory *motherDir, const char *classname, Long64_t filepos)
 Method used in all TKey constructor to initialize basic data fields. More...
 
virtual void Create (Int_t nbytes, TFile *f=0)
 Create a TKey object of specified size. More...
 
virtual Int_t Read (const char *name)
 Read contents of object with specified name from the current directory. More...
 
virtual void Reset ()
 Reset the key as it had not been 'filled' yet. More...
 
virtual Int_t WriteFileKeepBuffer (TFile *f=0)
 Write the encoded object supported by this key. More...
 
- Protected Member Functions inherited from TObject
virtual void DoError (int level, const char *location, const char *fmt, va_list va) const
 Interface to ErrorHandler (protected). More...
 
void MakeZombie ()
 

Protected Attributes

char * fBuffer
 Object buffer. More...
 
TBufferfBufferRef
 Pointer to the TBuffer object. More...
 
TString fClassName
 Object Class name. More...
 
Short_t fCycle
 Cycle number. More...
 
TDatime fDatime
 Date/Time of insertion in file. More...
 
Short_t fKeylen
 Number of bytes for the key itself. More...
 
Int_t fLeft
 Number of bytes left in current segment. More...
 
TDirectoryfMotherDir
 !pointer to mother directory More...
 
Int_t fNbytes
 Number of bytes for the object on file. More...
 
Int_t fObjlen
 Length of uncompressed object in bytes. More...
 
UShort_t fPidOffset
 !Offset to be added to the pid index in this key/buffer. This is actually saved in the high bits of fSeekPdir More...
 
Long64_t fSeekKey
 Location of object on file. More...
 
Long64_t fSeekPdir
 Location of parent directory on file. More...
 
Int_t fVersion
 Key version identifier. More...
 
- Protected Attributes inherited from TNamed
TString fName
 
TString fTitle
 

Private Types

enum  EStatusBits { kIsDirectoryFile = BIT(14) }
 

Private Member Functions

 TKey (const TKey &)
 
TKeyoperator= (const TKey &)
 

Additional Inherited Members

- Public Types inherited from TObject
enum  {
  kIsOnHeap = 0x01000000, kNotDeleted = 0x02000000, kZombie = 0x04000000, kInconsistent = 0x08000000,
  kBitMask = 0x00ffffff
}
 
enum  { kSingleKey = BIT(0), kOverwrite = BIT(1), kWriteDelete = BIT(2) }
 
enum  EDeprecatedStatusBits { kObjInCanvas = BIT(3) }
 
enum  EStatusBits {
  kCanDelete = BIT(0), kMustCleanup = BIT(3), kIsReferenced = BIT(4), kHasUUID = BIT(5),
  kCannotPick = BIT(6), kNoContextMenu = BIT(8), kInvalidObject = BIT(13)
}
 
- Static Public Member Functions inherited from TObject
static Long_t GetDtorOnly ()
 Return destructor only flag. More...
 
static Bool_t GetObjectStat ()
 Get status of object stat flag. More...
 
static void SetDtorOnly (void *obj)
 Set destructor only flag. More...
 
static void SetObjectStat (Bool_t stat)
 Turn on/off tracking of objects in the TObjectTable. More...
 

#include <TKey.h>

Inheritance diagram for TKey:
[legend]

Member Enumeration Documentation

◆ EStatusBits

enum TKey::EStatusBits
private
Enumerator
kIsDirectoryFile 

Definition at line 27 of file TKey.h.

Constructor & Destructor Documentation

◆ TKey() [1/9]

TKey::TKey ( const TKey )
private

◆ TKey() [2/9]

TKey::TKey ( )

TKey default constructor.

Definition at line 92 of file TKey.cxx.

◆ TKey() [3/9]

TKey::TKey ( TDirectory motherDir)

TKey default constructor.

Definition at line 104 of file TKey.cxx.

◆ TKey() [4/9]

TKey::TKey ( TDirectory motherDir,
const TKey orig,
UShort_t  pidOffset 
)

Copy a TKey from its original directory to the new 'motherDir'.

Definition at line 116 of file TKey.cxx.

◆ TKey() [5/9]

TKey::TKey ( const char *  name,
const char *  title,
const TClass cl,
Int_t  nbytes,
TDirectory motherDir 
)

Create a TKey object with the specified name, title for the given class.

WARNING: in name avoid special characters like '^','$','.' that are used by the regular expression parser (see TRegexp).

Definition at line 196 of file TKey.cxx.

◆ TKey() [6/9]

TKey::TKey ( const TString name,
const TString title,
const TClass cl,
Int_t  nbytes,
TDirectory motherDir 
)

Create a TKey object with the specified name, title for the given class.

WARNING: in name avoid special characters like '^','$','.' that are used by the regular expression parser (see TRegexp).

Definition at line 212 of file TKey.cxx.

◆ TKey() [7/9]

TKey::TKey ( const TObject obj,
const char *  name,
Int_t  bufsize,
TDirectory motherDir 
)

Create a TKey object for a TObject* and fill output buffer.

WARNING: in name avoid special characters like '^','$','.' that are used by the regular expression parser (see TRegexp).

Definition at line 228 of file TKey.cxx.

◆ TKey() [8/9]

TKey::TKey ( const void obj,
const TClass cl,
const char *  name,
Int_t  bufsize,
TDirectory motherDir 
)

Create a TKey object for any object obj of class cl d and fill output buffer.

WARNING: in name avoid special characters like '^','$','.' that are used by the regular expression parser (see TRegexp).

Definition at line 301 of file TKey.cxx.

◆ TKey() [9/9]

TKey::TKey ( Long64_t  pointer,
Int_t  nbytes,
TDirectory motherDir = 0 
)

Create a TKey object to read keys.

Constructor called by TDirectoryFile::ReadKeys and by TFile::TFile. A TKey object is created to read the keys structure itself.

Definition at line 180 of file TKey.cxx.

◆ ~TKey()

TKey::~TKey ( )
virtual

TKey default destructor.

Definition at line 520 of file TKey.cxx.

Member Function Documentation

◆ Browse()

void TKey::Browse ( TBrowser b)
virtual

Read object from disk and call its Browse() method.

If object with same name already exist in memory delete it (like TDirectoryFile::Get() is doing), except when the key references a folder in which case we don't want to re-read the folder object since it might contain new objects not yet saved.

Reimplemented from TObject.

Definition at line 426 of file TKey.cxx.

◆ Build()

void TKey::Build ( TDirectory motherDir,
const char *  classname,
Long64_t  filepos 
)
protected

Method used in all TKey constructor to initialize basic data fields.

The member filepos is used to calculate correct version number of key if filepos==-1, end of file position is used.

Definition at line 391 of file TKey.cxx.

◆ Create()

void TKey::Create ( Int_t  nbytes,
TFile externFile = 0 
)
protectedvirtual

Create a TKey object of specified size.

If externFile!=0, key will be allocated in specified file, otherwise file of mother directory will be used.

Definition at line 458 of file TKey.cxx.

◆ Delete()

void TKey::Delete ( Option_t option = "")
virtual

Delete an object from the file.

Note: the key is not deleted. You still have to call "delete key". This is different from the behaviour of TObject::Delete()!

Reimplemented from TObject.

Reimplemented in TKeySQL, and TKeyXML.

Definition at line 534 of file TKey.cxx.

◆ DeleteBuffer()

void TKey::DeleteBuffer ( )
virtual

Delete key buffer(s).

Reimplemented in TKeySQL, and TKeyXML.

Definition at line 546 of file TKey.cxx.

◆ FillBuffer()

void TKey::FillBuffer ( char *&  buffer)
virtual

Encode key header into output buffer.

Reimplemented from TNamed.

Reimplemented in TKeySQL, and TKeyXML.

Definition at line 588 of file TKey.cxx.

◆ GetBuffer()

virtual char* TKey::GetBuffer ( ) const
inlinevirtual

Reimplemented in TKeySQL, and TKeyXML.

Definition at line 74 of file TKey.h.

◆ GetBufferRef()

TBuffer* TKey::GetBufferRef ( ) const
inline

Definition at line 75 of file TKey.h.

◆ GetClassName()

virtual const char* TKey::GetClassName ( ) const
inlinevirtual

Definition at line 71 of file TKey.h.

◆ GetCycle()

Short_t TKey::GetCycle ( ) const

Return cycle number associated to this key.

Definition at line 564 of file TKey.cxx.

◆ GetDatime()

const TDatime& TKey::GetDatime ( ) const
inline

Definition at line 77 of file TKey.h.

◆ GetFile()

TFile * TKey::GetFile ( ) const

Returns file to which key belong.

Definition at line 572 of file TKey.cxx.

◆ GetIconName()

const char * TKey::GetIconName ( ) const
virtual

Title can keep 32x32 xpm thumbnail/icon of the parent object.

Reimplemented from TObject.

Definition at line 1509 of file TKey.cxx.

◆ GetKeep()

Short_t TKey::GetKeep ( ) const

Returns the "KEEP" status.

Definition at line 580 of file TKey.cxx.

◆ GetKeylen()

Int_t TKey::GetKeylen ( ) const
inline

Definition at line 80 of file TKey.h.

◆ GetMotherDir()

TDirectory* TKey::GetMotherDir ( ) const
inline

Definition at line 81 of file TKey.h.

◆ GetNbytes()

Int_t TKey::GetNbytes ( ) const
inline

Definition at line 82 of file TKey.h.

◆ GetObjlen()

Int_t TKey::GetObjlen ( ) const
inline

Definition at line 83 of file TKey.h.

◆ GetSeekKey()

virtual Long64_t TKey::GetSeekKey ( ) const
inlinevirtual

Reimplemented in TKeySQL, and TKeyXML.

Definition at line 85 of file TKey.h.

◆ GetSeekPdir()

virtual Long64_t TKey::GetSeekPdir ( ) const
inlinevirtual

Reimplemented in TKeySQL, and TKeyXML.

Definition at line 86 of file TKey.h.

◆ GetTitle()

const char * TKey::GetTitle ( ) const
virtual

Returns title (title can contain 32x32 xpm thumbnail/icon).

Reimplemented from TNamed.

Definition at line 1517 of file TKey.cxx.

◆ GetVersion()

Int_t TKey::GetVersion ( ) const
inline

Definition at line 84 of file TKey.h.

◆ IncrementPidOffset()

void TKey::IncrementPidOffset ( UShort_t  offset)
virtual

Increment fPidOffset by 'offset'.

This offset is used when a key (or basket) is transfered from one file to the other. In this case the TRef and TObject might have stored a pid index (to retrieve TProcessIDs) which refered to their order on the original file, the fPidOffset is to be added to those values to correctly find the TProcessID. This fPidOffset needs to be increment if the key/basket is copied and need to be zero for new key/basket.

Definition at line 634 of file TKey.cxx.

◆ IsFolder()

Bool_t TKey::IsFolder ( ) const
virtual

Check if object referenced by the key is a folder.

Reimplemented from TObject.

Definition at line 648 of file TKey.cxx.

◆ Keep()

void TKey::Keep ( )
virtual

Set the "KEEP" status.

When the KEEP flag is set to 1 the object cannot be purged.

Reimplemented in TKeySQL, and TKeyXML.

Definition at line 669 of file TKey.cxx.

◆ ls()

void TKey::ls ( Option_t option = "") const
virtual

List Key contents.

Reimplemented from TNamed.

Definition at line 677 of file TKey.cxx.

◆ operator=()

TKey& TKey::operator= ( const TKey )
private

◆ Print()

void TKey::Print ( Option_t option = "") const
virtual

Print key contents.

Reimplemented from TNamed.

Definition at line 686 of file TKey.cxx.

◆ Read() [1/2]

virtual Int_t TKey::Read ( const char *  name)
inlineprotectedvirtual

Read contents of object with specified name from the current directory.

First the key with the given name 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().

Reimplemented from TObject.

Reimplemented in TKeyXML, and TKeySQL.

Definition at line 49 of file TKey.h.

◆ Read() [2/2]

Int_t TKey::Read ( TObject obj)
virtual

To read an object from the file.

The object associated to this key is read from the file into memory. Before invoking this function, obj has been created via the default constructor.

Reimplemented in TKeySQL, and TKeyXML.

Definition at line 1138 of file TKey.cxx.

◆ ReadBuffer()

void TKey::ReadBuffer ( char *&  buffer)
virtual

Decode input buffer.

In some situation will add key to gDirectory.

Reimplemented in TKeySQL, and TKeyXML.

Definition at line 1198 of file TKey.cxx.

◆ ReadFile()

Bool_t TKey::ReadFile ( )
virtual

Read the key structure from the file.

Reimplemented in TKeySQL, and TKeyXML.

Definition at line 1253 of file TKey.cxx.

◆ ReadKeyBuffer()

void TKey::ReadKeyBuffer ( char *&  buffer)

Decode input buffer.

Definition at line 1210 of file TKey.cxx.

◆ ReadObj()

TObject * TKey::ReadObj ( )
virtual

To read a TObject* from the file.

The object associated to this key is read from the file into memory Once the key structure is read (via Streamer) the class identifier of the object is known. Using the class identifier we find the TClass object for this class. A TClass object contains a full description (i.e. dictionary) of the associated class. In particular the TClass object can create a new object of the class type it describes. This new object now calls its Streamer function to rebuilt itself.

Use TKey::ReadObjectAny to read any object non-derived from TObject

Note

A C style cast can only be used in the case where the final class of this object derives from TObject as a first inheritance, otherwise one must use a dynamic_cast.

Example1: simplified case

class MyClass : public TObject, public AnotherClass then on return, one get away with using: MyClass obj = (MyClass)key->ReadObj();

Example2: Usual case (recommended unless performance is critical)

MyClass obj = dynamic_cast<MyClass>(key->ReadObj()); which support also the more complex inheritance like: class MyClass : public AnotherClass, public TObject

Of course, dynamic_cast<> can also be used in the example 1.

Reimplemented in TKeySQL, and TKeyXML.

Definition at line 722 of file TKey.cxx.

◆ ReadObject()

template<typename T >
T* TKey::ReadObject ( )
inline

To read an object (non deriving from TObject) from the file.

This is more user friendly version of TKey::ReadObjectAny. See TKey::ReadObjectAny for more details.

Definition at line 98 of file TKey.h.

◆ ReadObjectAny()

void * TKey::ReadObjectAny ( const TClass expectedClass)
virtual

To read an object (non deriving from TObject) from the file.

If expectedClass is not null, we checked that that actual class of the object stored is suitable to be stored in a pointer pointing to an object of class 'expectedClass'. We also adjust the value of the returned address so that it is suitable to be cast (C-Style) a pointer pointing to an object of class 'expectedClass'.

So for example if the class Bottom inherits from Top and the object stored is of type Bottom you can safely do:

auto TopClass = TClass::GetClass("Top");
auto ptr = (Top*) key->ReadObjectAny( TopClass );
if (ptr==0) printError("the object stored in the key is not of the expected type\n");

The object associated to this key is read from the file into memory. Once the key structure is read (via Streamer) the class identifier of the object is known. Using the class identifier we find the TClass object for this class. A TClass object contains a full description (i.e. dictionary) of the associated class. In particular the TClass object can create a new object of the class type it describes. This new object now calls its Streamer function to rebuilt itself.

Reimplemented in TKeySQL, and TKeyXML.

Definition at line 1000 of file TKey.cxx.

◆ ReadObjWithBuffer()

TObject * TKey::ReadObjWithBuffer ( char *  bufferRead)
virtual

To read a TObject* from bufferRead.

This function is identical to TKey::ReadObj, but it reads directly from bufferRead instead of reading from a file. The object associated to this key is read from the buffer into memory Using the class identifier we find the TClass object for this class. A TClass object contains a full description (i.e. dictionary) of the associated class. In particular the TClass object can create a new object of the class type it describes. This new object now calls its Streamer function to rebuilt itself.

Note

This function is called only internally by ROOT classes. Although being public it is not supposed to be used outside ROOT. If used, you must make sure that the bufferRead is large enough to accomodate the object being read.

Reimplemented in TKeySQL, and TKeyXML.

Definition at line 864 of file TKey.cxx.

◆ Reset()

void TKey::Reset ( void  )
protectedvirtual

Reset the key as it had not been 'filled' yet.

Reimplemented in TBasket, and TBasketSQL.

Definition at line 1290 of file TKey.cxx.

◆ SetBuffer()

virtual void TKey::SetBuffer ( )
inlinevirtual

Reimplemented in TKeySQL, and TKeyXML.

Definition at line 105 of file TKey.h.

◆ SetMotherDir()

void TKey::SetMotherDir ( TDirectory dir)
inline

Definition at line 107 of file TKey.h.

◆ SetParent()

void TKey::SetParent ( const TObject parent)
virtual

Set parent in key buffer.

Definition at line 1282 of file TKey.cxx.

◆ Sizeof()

Int_t TKey::Sizeof ( ) const
virtual

Return the size in bytes of the key header structure.

An explaination about the nbytes (Int_t nbytes) variable used in the function. The size of fSeekKey and fSeekPdir is 8 instead of 4 if version is greater than 1000.

Component Sizeof
fNbytes 4
sizeof(Version_t) 2
fObjlen 4
fKeylen 2
fCycle 2
fSeekKey 4 or 8
fSeekPdir 4 or 8
TOTAL 22

Reimplemented from TNamed.

Definition at line 1324 of file TKey.cxx.

◆ WriteFile()

Int_t TKey::WriteFile ( Int_t  cycle = 1,
TFile f = 0 
)
virtual

Write the encoded object supported by this key.

The function returns the number of bytes committed to the file. If a write error occurs, the number of bytes returned is -1.

Reimplemented in TKeySQL, and TKeyXML.

Definition at line 1435 of file TKey.cxx.

◆ WriteFileKeepBuffer()

Int_t TKey::WriteFileKeepBuffer ( TFile f = 0)
protectedvirtual

Write the encoded object supported by this key.

The function returns the number of bytes committed to the file. If a write error occurs, the number of bytes returned is -1.

Definition at line 1476 of file TKey.cxx.

Member Data Documentation

◆ fBuffer

char* TKey::fBuffer
protected

Object buffer.

Definition at line 44 of file TKey.h.

◆ fBufferRef

TBuffer* TKey::fBufferRef
protected

Pointer to the TBuffer object.

Definition at line 45 of file TKey.h.

◆ fClassName

TString TKey::fClassName
protected

Object Class name.

Definition at line 42 of file TKey.h.

◆ fCycle

Short_t TKey::fCycle
protected

Cycle number.

Definition at line 39 of file TKey.h.

◆ fDatime

TDatime TKey::fDatime
protected

Date/Time of insertion in file.

Definition at line 37 of file TKey.h.

◆ fKeylen

Short_t TKey::fKeylen
protected

Number of bytes for the key itself.

Definition at line 38 of file TKey.h.

◆ fLeft

Int_t TKey::fLeft
protected

Number of bytes left in current segment.

Definition at line 43 of file TKey.h.

◆ fMotherDir

TDirectory* TKey::fMotherDir
protected

!pointer to mother directory

Definition at line 47 of file TKey.h.

◆ fNbytes

Int_t TKey::fNbytes
protected

Number of bytes for the object on file.

Definition at line 35 of file TKey.h.

◆ fObjlen

Int_t TKey::fObjlen
protected

Length of uncompressed object in bytes.

Definition at line 36 of file TKey.h.

◆ fPidOffset

UShort_t TKey::fPidOffset
protected

!Offset to be added to the pid index in this key/buffer. This is actually saved in the high bits of fSeekPdir

Definition at line 46 of file TKey.h.

◆ fSeekKey

Long64_t TKey::fSeekKey
protected

Location of object on file.

Definition at line 40 of file TKey.h.

◆ fSeekPdir

Long64_t TKey::fSeekPdir
protected

Location of parent directory on file.

Definition at line 41 of file TKey.h.

◆ fVersion

Int_t TKey::fVersion
protected

Key version identifier.

Definition at line 34 of file TKey.h.

Libraries for TKey:
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The documentation for this class was generated from the following files: