THashList


class description - source file - inheritance tree

class THashList : public TList


    public:
THashList THashList(Int_t capacity = TCollection::kInitHashTableCapacity, Int_t rehash = 0) THashList THashList(TObject* parent, Int_t capacity = TCollection::kInitHashTableCapacity, Int_t rehash = 0) virtual void ~THashList() virtual void AddAfter(TObjLink* after, TObject* obj) virtual void AddAfter(TObject* after, TObject* obj) virtual void AddAt(TObject* obj, Int_t idx) virtual void AddBefore(TObject* before, TObject* obj) virtual void AddBefore(TObjLink* before, TObject* obj) virtual void AddFirst(TObject* obj, Option_t* opt) virtual void AddFirst(TObject* obj) virtual void AddLast(TObject* obj) virtual void AddLast(TObject* obj, Option_t* opt) Float_t AverageCollisions() const TClass* Class() virtual void Clear(Option_t* option) virtual void Delete(Option_t* option) virtual TObject* FindObject(TObject* obj) const virtual TObject* FindObject(const char* name) const virtual TClass* IsA() const void Rehash(Int_t newCapacity) virtual TObject* Remove(TObjLink* lnk) virtual TObject* Remove(TObject* obj) virtual void ShowMembers(TMemberInspector& insp, char* parent) virtual void Streamer(TBuffer& b)

Data Members

protected:
THashTable* fTable Hashtable used for quick lookup of objects

Class Description

                                                                      
 THashList                                                            
                                                                      
 THashList implements a hybrid collection class consisting of a       
 hash table and a list to store TObject's. The hash table is used for 
 quick access and lookup of objects while the list allows the objects 
 to be ordered. 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.                                  

/*

*/

                                                                      


THashList(Int_t capacity, Int_t rehash)
 Create a THashList object. Capacity is the initial hashtable capacity
 (i.e. number of slots), by default kInitHashTableCapacity = 17, and
 rehash 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 rehash
 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 rehash=0 the table will
 NOT automatically be rehashed. Use Rehash() for manual rehashing.

THashList(TObject *parent, Int_t capacity, Int_t rehash) : TList(parent)
 Create a THashList object. Capacity is the initial hashtable capacity
 (i.e. number of slots), by default kInitHashTableCapacity = 17, and
 rehash 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 rehash
 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 rehash=0 the table will
 NOT automatically be rehashed. Use Rehash() for manual rehashing.

~THashList()
 Delete a hashlist. All objects will be removed from the list before the
 list will be deleted.

void AddFirst(TObject *obj)
 Add object at the beginning of the list.

void AddFirst(TObject *obj, Option_t *opt)
 Add object at the beginning of the list and also store option.
 Storing an option is useful when one wants to change the behaviour
 of an object a little without having to create a complete new
 copy of the object. This feature is used, for example, by the Draw()
 method. It allows the same object to be drawn in different ways.

void AddLast(TObject *obj)
 Add object at the end of the list.

void AddLast(TObject *obj, Option_t *opt)
 Add object at the end of the list and also store option.
 Storing an option is useful when one wants to change the behaviour
 of an object a little without having to create a complete new
 copy of the object. This feature is used, for example, by the Draw()
 method. It allows the same object to be drawn in different ways.

void AddBefore(TObject *before, TObject *obj)
 Insert object before object before in the list.

void AddBefore(TObjLink *before, TObject *obj)
 Insert object before object before in the list.

void AddAfter(TObject *after, TObject *obj)
 Insert object after object after in the list.

void AddAfter(TObjLink *after, TObject *obj)
 Insert object after object after in the list.

void AddAt(TObject *obj, Int_t idx)
 Insert object at location idx in the list.

Float_t AverageCollisions() const
 Return the average collision rate. The higher the number the longer
 the linked lists in the hashtable, the slower the lookup. If the number
 is high, or lookup noticeably too slow, perfrom a Rehash().

void Clear(Option_t *option)
 Remove all objects from the list. Does not delete the objects.

void Delete(Option_t *option)
 Remove all objects from the list AND delete all heap based objects.

TObject* FindObject(const char *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).

void Rehash(Int_t newCapacity)
 Rehash the hashlist. 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.

TObject* Remove(TObject *obj)
 Remove object from the list.

TObject* Remove(TObjLink *lnk)
 Remove object via its objlink from the list.



Inline Functions


            TClass* Class()
            TClass* IsA() const
               void ShowMembers(TMemberInspector& insp, char* parent)
               void Streamer(TBuffer& b)


Author: Fons Rademakers 10/08/95
Last update: 2.23/12 26/01/2000 09.57.11 by Rene Brun
Copyright (c) 1995-1999, The ROOT System, All rights reserved. *


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