class TKey: public TNamed

 TKey default constructor.

 copy constructor

 assignment operator

 TKey default constructor.

 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.

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

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

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

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

 method used in all TKey constructor to initialize basic data fields
 filepos is used to calculate correct version number of key
 if filepos==-1, end of file position is used

 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.

 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

 TKey default destructor.

 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()!

 Delete key buffer(s).

 Return cycle number associated to this key.

 Returns file to which key belong

 Returns the "KEEP" status.

 Encode key header into output buffer.

 This Hash function should redefine the default from TNamed.

 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.

 Check if object referenced by the key is a folder.

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

 List Key contents.

 Print key contents.

 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.

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

  NOTE:
  In case the class of this object derives from TObject but not
  as a first inheritance, one must cast the return value twice.
  Example1: Normal case:
      class MyClass : public TObject, public AnotherClass
   then on return, one can do:
    MyClass *obj = (MyClass*)key->ReadObj();

  Example2: Special case:
      class MyClass : public AnotherClass, public TObject
   then on return, one must do:
    MyClass *obj = dynamic_cast<MyClass*>(key->ReadObj());

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

 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.

  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  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:

     TClass *TopClass = TClass::GetClass("Top");
     Top *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.

 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.

 Decode input buffer.
 In some situation will add key to gDirectory ???

 Decode input buffer.

 Read the key structure from the file

 Set parent in key buffer.

 Return the size in bytes of the key header structure.
 Int_t nbytes = sizeof fNbytes;      4
             += sizeof(Version_t);   2
             += sizeof fObjlen;      4
             += sizeof fKeylen;      2
             += sizeof fCycle;       2
             += sizeof fSeekKey;     4 or 8
             += sizeof fSeekPdir;    4 or 8
              =                     22

 Stream a class object.

 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.

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

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