rtphashtable.h

Go to the documentation of this file.

/*

  This file is a part of JRTPLIB
  Copyright (c) 1999-2017 Jori Liesenborgs

  Contact: jori.liesenborgs@gmail.com

  This library was developed at the Expertise Centre for Digital Media
  (http://www.edm.uhasselt.be), a research center of the Hasselt University
  (http://www.uhasselt.be). The library is based upon work done for 
  my thesis at the School for Knowledge Technology (Belgium/The Netherlands).

  Permission is hereby granted, free of charge, to any person obtaining a
  copy of this software and associated documentation files (the "Software"),
  to deal in the Software without restriction, including without limitation
  the rights to use, copy, modify, merge, publish, distribute, sublicense,
  and/or sell copies of the Software, and to permit persons to whom the
  Software is furnished to do so, subject to the following conditions:

  The above copyright notice and this permission notice shall be included
  in all copies or substantial portions of the Software.

  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
  OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  IN THE SOFTWARE.

*/

#ifndef RTPHASHTABLE_H

#define RTPHASHTABLE_H

#include "rtperrors.h"
#include "rtpmemoryobject.h"

#ifdef RTPDEBUG
#include <iostream>
#endif // RTPDEBUG

namespace jrtplib
{

//template<class Element,int GetIndex(const Element &k),int hashsize>
template<class Element,class GetIndex,int hashsize>
class RTPHashTable : public RTPMemoryObject
{
public:
    RTPHashTable(RTPMemoryManager *mgr = 0, int memtype = RTPMEM_TYPE_OTHER);
    ~RTPHashTable()                     { Clear(); }

    void GotoFirstElement()                 { curhashelem = firsthashelem; }
    void GotoLastElement()                  { curhashelem = lasthashelem; }
    bool HasCurrentElement()                { return (curhashelem == 0)?false:true; }
    int DeleteCurrentElement();
    Element &GetCurrentElement()                { return curhashelem->GetElement(); }
    int GotoElement(const Element &e);
    bool HasElement(const Element &e);
    void GotoNextElement();
    void GotoPreviousElement();
    void Clear();

    int AddElement(const Element &elem);
    int DeleteElement(const Element &elem);

#ifdef RTPDEBUG
    void Dump();
#endif // RTPDEBUG
private:
    class HashElement
    {
    public:
        HashElement(const Element &e,int index):element(e) { hashprev = 0; hashnext = 0; listnext = 0; listprev = 0; hashindex = index; }
        int GetHashIndex()                      { return hashindex; }
        Element &GetElement()                       { return element; }
#ifdef RTPDEBUG
        void Dump()                         { std::cout << "\tHash index " << hashindex << " | Element " << element << std::endl; }
#endif // RTPDEBUG
    private:
        int hashindex;
        Element element;
    public:
        HashElement *hashprev,*hashnext;
        HashElement *listprev,*listnext;
    };

    HashElement *table[hashsize];
    HashElement *firsthashelem,*lasthashelem;
    HashElement *curhashelem;
#ifdef RTP_SUPPORT_MEMORYMANAGEMENT
    int memorytype;
#endif // RTP_SUPPORT_MEMORYMANAGEMENT
};

template<class Element,class GetIndex,int hashsize>
inline RTPHashTable<Element,GetIndex,hashsize>::RTPHashTable(RTPMemoryManager *mgr,int memtype) : RTPMemoryObject(mgr)
{
    JRTPLIB_UNUSED(memtype); // possibly unused

    for (int i = 0 ; i < hashsize ; i++)
        table[i] = 0;
    firsthashelem = 0;
    lasthashelem = 0;
#ifdef RTP_SUPPORT_MEMORYMANAGEMENT
    memorytype = memtype;
#endif // RTP_SUPPORT_MEMORYMANAGEMENT
}

template<class Element,class GetIndex,int hashsize>
inline int RTPHashTable<Element,GetIndex,hashsize>::DeleteCurrentElement()
{
    if (curhashelem)
    {
        HashElement *tmp1,*tmp2;
        int index;
        
        // First, relink elements in current hash bucket
        
        index = curhashelem->GetHashIndex();
        tmp1 = curhashelem->hashprev;
        tmp2 = curhashelem->hashnext;
        if (tmp1 == 0) // no previous element in hash bucket
        {
            table[index] = tmp2;
            if (tmp2 != 0)
                tmp2->hashprev = 0;
        }
        else // there is a previous element in the hash bucket
        {
            tmp1->hashnext = tmp2;
            if (tmp2 != 0)
                tmp2->hashprev = tmp1;
        }

        // Relink elements in list
        
        tmp1 = curhashelem->listprev;
        tmp2 = curhashelem->listnext;
        if (tmp1 == 0) // curhashelem is first in list
        {
            firsthashelem = tmp2;
            if (tmp2 != 0)
                tmp2->listprev = 0;
            else // curhashelem is also last in list
                lasthashelem = 0;   
        }
        else
        {
            tmp1->listnext = tmp2;
            if (tmp2 != 0)
                tmp2->listprev = tmp1;
            else // curhashelem is last in list
                lasthashelem = tmp1;
        }
        
        // finally, with everything being relinked, we can delete curhashelem
        RTPDelete(curhashelem,GetMemoryManager());
        curhashelem = tmp2; // Set to next element in the list
    }
    else
        return ERR_RTP_HASHTABLE_NOCURRENTELEMENT;
    return 0;
}

template<class Element,class GetIndex,int hashsize>
inline int RTPHashTable<Element,GetIndex,hashsize>::GotoElement(const Element &e)
{
    int index;
    bool found;
    
    index = GetIndex::GetIndex(e);
    if (index >= hashsize)
        return ERR_RTP_HASHTABLE_FUNCTIONRETURNEDINVALIDHASHINDEX;
    
    curhashelem = table[index]; 
    found = false;
    while(!found && curhashelem != 0)
    {
        if (curhashelem->GetElement() == e)
            found = true;
        else
            curhashelem = curhashelem->hashnext;
    }
    if (!found)
        return ERR_RTP_HASHTABLE_ELEMENTNOTFOUND;
    return 0;
}

template<class Element,class GetIndex,int hashsize>
inline bool RTPHashTable<Element,GetIndex,hashsize>::HasElement(const Element &e)
{
    int index;
    bool found;
    HashElement *tmp;
    
    index = GetIndex::GetIndex(e);
    if (index >= hashsize)
        return false;
    
    tmp = table[index]; 
    found = false;
    while(!found && tmp != 0)
    {
        if (tmp->GetElement() == e)
            found = true;
        else
            tmp = tmp->hashnext;
    }
    return found;
}

template<class Element,class GetIndex,int hashsize>
inline void RTPHashTable<Element,GetIndex,hashsize>::GotoNextElement()
{
    if (curhashelem)
        curhashelem = curhashelem->listnext;
}

template<class Element,class GetIndex,int hashsize>
inline void RTPHashTable<Element,GetIndex,hashsize>::GotoPreviousElement()
{
    if (curhashelem)
        curhashelem = curhashelem->listprev;
}

template<class Element,class GetIndex,int hashsize>
inline void RTPHashTable<Element,GetIndex,hashsize>::Clear()
{
    HashElement *tmp1,*tmp2;
    
    for (int i = 0 ; i < hashsize ; i++)
        table[i] = 0;
    
    tmp1 = firsthashelem;
    while (tmp1 != 0)
    {
        tmp2 = tmp1->listnext;
        RTPDelete(tmp1,GetMemoryManager());
        tmp1 = tmp2;
    }
    firsthashelem = 0;
    lasthashelem = 0;
}

template<class Element,class GetIndex,int hashsize>
inline int RTPHashTable<Element,GetIndex,hashsize>::AddElement(const Element &elem)
{
    int index;
    bool found;
    HashElement *e,*newelem;
    
    index = GetIndex::GetIndex(elem);
    if (index >= hashsize)
        return ERR_RTP_HASHTABLE_FUNCTIONRETURNEDINVALIDHASHINDEX;
    
    e = table[index];
    found = false;
    while(!found && e != 0)
    {
        if (e->GetElement() == elem)
            found = true;
        else
            e = e->hashnext;
    }
    if (found)
        return ERR_RTP_HASHTABLE_ELEMENTALREADYEXISTS;
    
    // Okay, the key doesn't exist, so we can add the new element in the hash table
    
    newelem = RTPNew(GetMemoryManager(),memorytype) HashElement(elem,index);
    if (newelem == 0)
        return ERR_RTP_OUTOFMEM;

    e = table[index];
    table[index] = newelem;
    newelem->hashnext = e;
    if (e != 0)
        e->hashprev = newelem;
    
    // Now, we still got to add it to the linked list
    
    if (firsthashelem == 0)
    {
        firsthashelem = newelem;
        lasthashelem = newelem;
    }
    else // there already are some elements in the list
    {
        lasthashelem->listnext = newelem;
        newelem->listprev = lasthashelem;
        lasthashelem = newelem;
    }
    return 0;
}

template<class Element,class GetIndex,int hashsize>
inline int RTPHashTable<Element,GetIndex,hashsize>::DeleteElement(const Element &elem)
{
    int status;

    status = GotoElement(elem);
    if (status < 0)
        return status;
    return DeleteCurrentElement();
}

#ifdef RTPDEBUG
template<class Element,class GetIndex,int hashsize>
inline void RTPHashTable<Element,GetIndex,hashsize>::Dump()
{
    HashElement *e;
    
    std::cout << "DUMPING TABLE CONTENTS:" << std::endl;
    for (int i = 0 ; i < hashsize ; i++)
    {
        e = table[i];
        while (e != 0)
        {
            e->Dump();
            e = e->hashnext;
        }
    }
    
    std::cout << "DUMPING LIST CONTENTS:" << std::endl;
    e = firsthashelem;
    while (e != 0)
    {
        e->Dump();
        e = e->listnext;
    }
}
#endif // RTPDEBUG

} // end namespace

#endif // RTPHASHTABLE_H