rtpkeyhashtable.h

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/*

 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 RTPKEYHASHTABLE_H

#define RTPKEYHASHTABLE_H

#include "rtpconfig.h"
#include "rtperrors.h"

namespace qrtplib
{

template<class Key, class Element, class GetIndex, int hashsize>
class RTPKeyHashTable
{
public:
    RTPKeyHashTable();
    ~RTPKeyHashTable()
    {
        Clear();
    }

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

    int AddElement(const Key &k, const Element &elem);
    int DeleteElement(const Key &k);

private:
    class HashElement
    {
    public:
        HashElement(const Key &k, const Element &e, int index) :
                key(k), element(e)
        {
            hashprev = 0;
            hashnext = 0;
            listnext = 0;
            listprev = 0;
            hashindex = index;
        }
        int GetHashIndex()
        {
            return hashindex;
        }
        Key &GetKey()
        {
            return key;
        }
        Element &GetElement()
        {
            return element;
        }

    private:
        int hashindex;
        Key key;
        Element element;
    public:
        HashElement *hashprev, *hashnext;
        HashElement *listprev, *listnext;
    };

    HashElement *table[hashsize];
    HashElement *firsthashelem, *lasthashelem;
    HashElement *curhashelem;
};

template<class Key, class Element, class GetIndex, int hashsize>
inline RTPKeyHashTable<Key, Element, GetIndex, hashsize>::RTPKeyHashTable()
{
    for (int i = 0; i < hashsize; i++)
        table[i] = 0;
    firsthashelem = 0;
    lasthashelem = 0;
}

template<class Key, class Element, class GetIndex, int hashsize>
inline int RTPKeyHashTable<Key, 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
        delete curhashelem;
        curhashelem = tmp2; // Set to next element in list
    }
    else
        return ERR_RTP_KEYHASHTABLE_NOCURRENTELEMENT;
    return 0;
}

template<class Key, class Element, class GetIndex, int hashsize>
inline int RTPKeyHashTable<Key, Element, GetIndex, hashsize>::GotoElement(const Key &k)
{
    int index;
    bool found;

    index = GetIndex::GetIndex(k);
    if (index >= hashsize)
        return ERR_RTP_KEYHASHTABLE_FUNCTIONRETURNEDINVALIDHASHINDEX;

    curhashelem = table[index];
    found = false;
    while (!found && curhashelem != 0)
    {
        if (curhashelem->GetKey() == k)
            found = true;
        else
            curhashelem = curhashelem->hashnext;
    }
    if (!found)
        return ERR_RTP_KEYHASHTABLE_KEYNOTFOUND;
    return 0;
}

template<class Key, class Element, class GetIndex, int hashsize>
inline bool RTPKeyHashTable<Key, Element, GetIndex, hashsize>::HasElement(const Key &k)
{
    int index;
    bool found;
    HashElement *tmp;

    index = GetIndex::GetIndex(k);
    if (index >= hashsize)
        return false;

    tmp = table[index];
    found = false;
    while (!found && tmp != 0)
    {
        if (tmp->GetKey() == k)
            found = true;
        else
            tmp = tmp->hashnext;
    }
    return found;
}

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

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

template<class Key, class Element, class GetIndex, int hashsize>
inline void RTPKeyHashTable<Key, 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;
        delete tmp1;
        tmp1 = tmp2;
    }
    firsthashelem = 0;
    lasthashelem = 0;
}

template<class Key, class Element, class GetIndex, int hashsize>
inline int RTPKeyHashTable<Key, Element, GetIndex, hashsize>::AddElement(const Key &k, const Element &elem)
{
    int index;
    bool found;
    HashElement *e, *newelem;

    index = GetIndex::GetIndex(k);
    if (index >= hashsize)
        return ERR_RTP_KEYHASHTABLE_FUNCTIONRETURNEDINVALIDHASHINDEX;

    e = table[index];
    found = false;
    while (!found && e != 0)
    {
        if (e->GetKey() == k)
            found = true;
        else
            e = e->hashnext;
    }
    if (found)
        return ERR_RTP_KEYHASHTABLE_KEYALREADYEXISTS;

    // Okay, the key doesn't exist, so we can add the new element in the hash table

    newelem = new HashElement(k, elem, index);

    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 Key, class Element, class GetIndex, int hashsize>
inline int RTPKeyHashTable<Key, Element, GetIndex, hashsize>::DeleteElement(const Key &k)
{
    int status;

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

} // end namespace

#endif // RTPKEYHASHTABLE_H