THashTable
class description - source file - inheritance tree
private:
Int_t GetHashValue(TObject* obj)
Int_t GetHashValue(TString& s)
Int_t GetHashValue(char* str)
public:
THashTable THashTable(Int_t capacity = TCollection::kInitHashTableCapacity, Int_t rehash = 0)
virtual void ~THashTable()
virtual void Add(TObject* obj)
Float_t AverageCollisions()
TClass* Class()
virtual void Clear(Option_t* option)
Int_t Collisions(char* name)
Int_t Collisions(TObject* obj)
virtual void Delete(Option_t* option)
virtual TObject* FindObject(Text_t* name)
virtual TObject* FindObject(TObject* obj)
virtual Int_t GetSize()
virtual TClass* IsA()
virtual TIterator* MakeIterator(Bool_t dir = kIterForward)
void Rehash(Int_t newCapacity, Bool_t checkObjValidity = kTRUE)
virtual TObject* Remove(TObject* obj)
virtual void ShowMembers(TMemberInspector& insp, char* parent)
virtual void Streamer(TBuffer& b)
private:
TList** fCont Hash table (table of lists)
Int_t fEntries Number of objects in table
Int_t fUsedSlots Number of used slots
Int_t fRehashLevel Average collision rate which triggers rehash
THashTable
THashTable implements a hash table to store TObject's. The hash
value is calculated using the value returned by the TObject's
Hash() function. Each class inheriting from TObject can override
Hash() as it sees fit.
THashTable does not preserve the insertion order of the objects.
If the insertion order is important AND fast retrieval is needed
use THashList instead.
/*
*/
THashTable(Int_t capacity, Int_t rehashlevel)
Create a THashTable object. Capacity is the initial hashtable capacity
(i.e. number of slots), by default kInitHashTableCapacity = 17, and
rehashlevel is the value at which a rehash will be triggered. I.e. when
the average size of the linked lists at a slot becomes longer than
rehashlevel then the hashtable will be resized and refilled to reduce
the collision rate to about 1. The higher the collision rate, i.e. the
longer the linked lists, the longer lookup will take. If rehashlevel=0
the table will NOT automatically be rehashed. Use Rehash() for manual
rehashing.
~THashTable()
Delete a hashtable. All objects will be removed from the table before the
table will be deleted.
void Add(TObject *obj)
Add object to the hash table. Its position in the table will be
determined by the value returned by its Hash() function.
void Clear(Option_t *option)
Remove all objects from the table. Does not delete the objects.
Int_t Collisions(const char *name) const
Returns the number of collisions for an object with a certain name
(i.e. number of objects in same slot in the hash table, i.e. length
of linked list).
Int_t Collisions(TObject *obj) const
Returns the number of collisions for an object (i.e. number of objects
in same slot in the hash table, i.e. length of linked list).
void Delete(Option_t *)
Remove all objects from the table AND delete all heap based objects.
TObject* FindObject(const Text_t *name) const
Find object using its name. Uses the hash value returned by the
TString::Hash() after converting name to a TString.
TObject* FindObject(TObject *obj) const
Find object using its hash value (returned by its Hash() member).
TIterator* MakeIterator(Bool_t dir) const
Returns a hash table iterator.
void Rehash(Int_t newCapacity, Bool_t checkObjValidity)
Rehash the hashtable. If the collision rate becomes too high (i.e.
the average size of the linked lists become too long) then lookup
efficiency decreases since relatively long lists have to be searched
every time. To improve performance rehash the hashtable. This resizes
the table to newCapacity slots and refills the table. Use
AverageCollisions() to check if you need to rehash. Set checkObjValidity
to kFALSE if you know that all objects in the table are still valid
(i.e. have not been deleted from the system in the meanwhile).
TObject* Remove(TObject *obj)
Remove object from the hashtable.
Inline Functions
Int_t GetHashValue(TObject* obj)
Int_t GetHashValue(TString& s)
Int_t GetHashValue(char* str)
Float_t AverageCollisions()
Int_t GetSize()
TClass* Class()
TClass* IsA()
void ShowMembers(TMemberInspector& insp, char* parent)
void Streamer(TBuffer& b)
Author: Fons Rademakers 27/09/95
Last update: 2.22/07 05/07/99 18.54.36 by Fons Rademakers
Copyright (c) 1995-1999, The ROOT System, All rights reserved. *
ROOT page - Class index - Top of the page
This page has been automatically generated. If you have any comments or suggestions about the page layout send a mail to ROOT support, or contact the developers with any questions or problems regarding ROOT.