llskiplist.h

Go to the documentation of this file.

#ifndef LL_LLSKIPLIST_H
#define LL_LLSKIPLIST_H

#include "llrand.h"

// NOTA BENE: Insert first needs to be < NOT <=
// Binary depth must be >= 2
template <class DATA_TYPE, S32 BINARY_DEPTH = 10>
class LLSkipList
{
public:
        typedef BOOL (*compare)(const DATA_TYPE& first, const DATA_TYPE& second);
        typedef compare insert_func;
        typedef compare equals_func;

        void init();

        // basic constructor
        LLSkipList();

        // basic constructor including sorter
        LLSkipList(insert_func insert_first, equals_func equals);
        ~LLSkipList();

        inline void setInsertFirst(insert_func insert_first);
        inline void setEquals(equals_func equals);

        inline BOOL addData(const DATA_TYPE& data);
        inline BOOL checkData(const DATA_TYPE& data);

        // returns number of items in the list
        inline S32 getLength() const; // NOT a constant time operation, traverses entire list!

        inline BOOL moveData(const DATA_TYPE& data, LLSkipList *newlist);

        inline BOOL removeData(const DATA_TYPE& data);

        // remove all nodes from the list but do not delete data
        inline void removeAllNodes();

        // place mCurrentp on first node
        inline void resetList();

        // return the data currently pointed to, set mCurentOperatingp to that node and bump mCurrentp
        inline DATA_TYPE getCurrentData();

        // same as getCurrentData() but a more intuitive name for the operation
        inline DATA_TYPE getNextData();

        // remove the Node at mCurentOperatingp
        // leave mCurrentp and mCurentOperatingp on the next entry
        inline void removeCurrentData();

        // reset the list and return the data currently pointed to, set mCurentOperatingp to that node and bump mCurrentp
        inline DATA_TYPE getFirstData();

        class LLSkipNode
        {
        public:
                LLSkipNode()
                :       mData(0)
                {
                        S32 i;
                        for (i = 0; i < BINARY_DEPTH; i++)
                        {
                                mForward[i] = NULL;
                        }
                }

                LLSkipNode(DATA_TYPE data)
                        : mData(data)
                {
                        S32 i;
                        for (i = 0; i < BINARY_DEPTH; i++)
                        {
                                mForward[i] = NULL;
                        }
                }

                ~LLSkipNode()
                {
                }

                DATA_TYPE                                       mData;
                LLSkipNode                                      *mForward[BINARY_DEPTH];

        private:
                // Disallow copying of LLSkipNodes by not implementing these methods.
                LLSkipNode(const LLSkipNode &);
                LLSkipNode &operator=(const LLSkipNode &);
        };

        static BOOL defaultEquals(const DATA_TYPE& first, const DATA_TYPE& second)
        {
                return first == second;
        }

private:
        LLSkipNode                                      mHead;
        LLSkipNode                                      *mUpdate[BINARY_DEPTH];
        LLSkipNode                                      *mCurrentp;
        LLSkipNode                                      *mCurrentOperatingp;
        S32                                                     mLevel;
        insert_func mInsertFirst;
        equals_func mEquals;

private:
        // Disallow copying of LLSkipNodes by not implementing these methods.
        LLSkipList(const LLSkipList &);
        LLSkipList &operator=(const LLSkipList &);
};


//
// Implementation
//


// Binary depth must be >= 2
template <class DATA_TYPE, S32 BINARY_DEPTH>
inline void LLSkipList<DATA_TYPE, BINARY_DEPTH>::init()
{
        S32 i;
        for (i = 0; i < BINARY_DEPTH; i++)
        {
                mHead.mForward[i] = NULL;
                mUpdate[i] = NULL;
        }
        mLevel = 1;
        mCurrentp = *(mHead.mForward);
        mCurrentOperatingp = *(mHead.mForward);
}


// basic constructor
template <class DATA_TYPE, S32 BINARY_DEPTH>
inline LLSkipList<DATA_TYPE, BINARY_DEPTH>::LLSkipList()
:       mInsertFirst(NULL), 
        mEquals(defaultEquals)
{
        init();
}

// basic constructor including sorter
template <class DATA_TYPE, S32 BINARY_DEPTH>
inline LLSkipList<DATA_TYPE, BINARY_DEPTH>::LLSkipList(insert_func insert,
                                                                                                           equals_func equals)
:       mInsertFirst(insert), 
        mEquals(equals)
{
        init();
}

template <class DATA_TYPE, S32 BINARY_DEPTH>
inline LLSkipList<DATA_TYPE, BINARY_DEPTH>::~LLSkipList()
{
        removeAllNodes();
}

template <class DATA_TYPE, S32 BINARY_DEPTH>
inline void LLSkipList<DATA_TYPE, BINARY_DEPTH>::setInsertFirst(insert_func insert_first)
{
        mInsertFirst = insert_first;
}

template <class DATA_TYPE, S32 BINARY_DEPTH>
inline void LLSkipList<DATA_TYPE, BINARY_DEPTH>::setEquals(equals_func equals)
{
        mEquals = equals;
}

template <class DATA_TYPE, S32 BINARY_DEPTH>
inline BOOL LLSkipList<DATA_TYPE, BINARY_DEPTH>::addData(const DATA_TYPE& data)
{
        S32                     level;
        LLSkipNode      *current = &mHead;
        LLSkipNode      *temp;
        // find the pointer one in front of the one we want
        if (mInsertFirst)
        {
                for (level = mLevel - 1; level >= 0; level--)
                {
                        temp = *(current->mForward + level);
                        while (  (temp)
                                   &&(mInsertFirst(temp->mData, data)))
                        {
                                current = temp;
                                temp = *(current->mForward + level);
                        }
                        *(mUpdate + level) = current;
                }
        }
        else
        {
                for (level = mLevel - 1; level >= 0; level--)
                {
                        temp = *(current->mForward + level);
                        while (  (temp)
                                   &&(temp->mData < data))
                        {
                                current = temp;
                                temp = *(current->mForward + level);
                        }
                        *(mUpdate + level) = current;
                }
        }
        // we're now just in front of where we want to be . . . take one step forward
        current = *current->mForward;

        // now add the new node
        S32 newlevel;
        for (newlevel = 1; newlevel <= mLevel && newlevel < BINARY_DEPTH; newlevel++)
        {
                if (ll_frand() < 0.5f)
                        break;
        }

        LLSkipNode *snode = new LLSkipNode(data);

        if (newlevel > mLevel)
        {
                mHead.mForward[mLevel] = NULL;
                mUpdate[mLevel] = &mHead;
                mLevel = newlevel;
        }

        for (level = 0; level < newlevel; level++)
        {
                snode->mForward[level] = mUpdate[level]->mForward[level];
                mUpdate[level]->mForward[level] = snode;
        }
        return TRUE;
}

template <class DATA_TYPE, S32 BINARY_DEPTH>
inline BOOL LLSkipList<DATA_TYPE, BINARY_DEPTH>::checkData(const DATA_TYPE& data)
{
        S32                     level;
        LLSkipNode      *current = &mHead;
        LLSkipNode      *temp;
        // find the pointer one in front of the one we want
        if (mInsertFirst)
        {
                for (level = mLevel - 1; level >= 0; level--)
                {
                        temp = *(current->mForward + level);
                        while (  (temp)
                                   &&(mInsertFirst(temp->mData, data)))
                        {
                                current = temp;
                                temp = *(current->mForward + level);
                        }
                        *(mUpdate + level) = current;
                }
        }
        else
        {
                for (level = mLevel - 1; level >= 0; level--)
                {
                        temp = *(current->mForward + level);
                        while (  (temp)
                                   &&(temp->mData < data))
                        {
                                current = temp;
                                temp = *(current->mForward + level);
                        }
                        *(mUpdate + level) = current;
                }
        }
        // we're now just in front of where we want to be . . . take one step forward
        current = *current->mForward;


        if (current)
        {
                return mEquals(current->mData, data);
        }

        return FALSE;
}

// returns number of items in the list
template <class DATA_TYPE, S32 BINARY_DEPTH>
inline S32 LLSkipList<DATA_TYPE, BINARY_DEPTH>::getLength() const
{
        U32     length = 0;
        for (LLSkipNode* temp = *(mHead.mForward); temp != NULL; temp = temp->mForward[0])
        {
                length++;
        }
        return length;
}


template <class DATA_TYPE, S32 BINARY_DEPTH>
inline BOOL LLSkipList<DATA_TYPE, BINARY_DEPTH>::moveData(const DATA_TYPE& data, LLSkipList *newlist)
{
        BOOL removed = removeData(data);
        BOOL added = newlist->addData(data);
        return removed && added;
}


template <class DATA_TYPE, S32 BINARY_DEPTH>
inline BOOL LLSkipList<DATA_TYPE, BINARY_DEPTH>::removeData(const DATA_TYPE& data)
{
        S32                     level;
        LLSkipNode      *current = &mHead;
        LLSkipNode      *temp;
        // find the pointer one in front of the one we want
        if (mInsertFirst)
        {
                for (level = mLevel - 1; level >= 0; level--)
                {
                        temp = *(current->mForward + level);
                        while (  (temp)
                                   &&(mInsertFirst(temp->mData, data)))
                        {
                                current = temp;
                                temp = *(current->mForward + level);
                        }
                        *(mUpdate + level) = current;
                }
        }
        else
        {
                for (level = mLevel - 1; level >= 0; level--)
                {
                        temp = *(current->mForward + level);
                        while (  (temp)
                                   &&(temp->mData < data))
                        {
                                current = temp;
                                temp = *(current->mForward + level);
                        }
                        *(mUpdate + level) = current;
                }
        }
        // we're now just in front of where we want to be . . . take one step forward
        current = *current->mForward;


        if (!current)
        {
                // empty list or beyond the end!
                return FALSE;
        }

        // is this the one we want?
        if (!mEquals(current->mData, data))
        {
                // nope!
                return FALSE;
        }
        else
        {
                // do we need to fix current or currentop?
                if (current == mCurrentp)
                {
                        mCurrentp = current->mForward[0];
                }

                if (current == mCurrentOperatingp)
                {
                        mCurrentOperatingp = current->mForward[0];
                }
                // yes it is!  change pointers as required
                for (level = 0; level < mLevel; level++)
                {
                        if (mUpdate[level]->mForward[level] != current)
                        {
                                // cool, we've fixed all the pointers!
                                break;
                        }
                        mUpdate[level]->mForward[level] = current->mForward[level];
                }

                // clean up cuurent
                delete current;

                // clean up mHead
                while (  (mLevel > 1)
                           &&(!mHead.mForward[mLevel - 1]))
                {
                        mLevel--;
                }
        }
        return TRUE;
}

// remove all nodes from the list but do not delete data
template <class DATA_TYPE, S32 BINARY_DEPTH>
inline void LLSkipList<DATA_TYPE, BINARY_DEPTH>::removeAllNodes()
{
        LLSkipNode *temp;
        // reset mCurrentp
        mCurrentp = *(mHead.mForward);

        while (mCurrentp)
        {
                temp = mCurrentp->mForward[0];
                delete mCurrentp;
                mCurrentp = temp;
        }

        S32 i;
        for (i = 0; i < BINARY_DEPTH; i++)
        {
                mHead.mForward[i] = NULL;
                mUpdate[i] = NULL;
        }

        mCurrentp = *(mHead.mForward);
        mCurrentOperatingp = *(mHead.mForward);
}

// place mCurrentp on first node
template <class DATA_TYPE, S32 BINARY_DEPTH>
inline void LLSkipList<DATA_TYPE, BINARY_DEPTH>::resetList()
{
        mCurrentp = *(mHead.mForward);
        mCurrentOperatingp = *(mHead.mForward);
}

// return the data currently pointed to, set mCurentOperatingp to that node and bump mCurrentp
template <class DATA_TYPE, S32 BINARY_DEPTH>
inline DATA_TYPE LLSkipList<DATA_TYPE, BINARY_DEPTH>::getCurrentData()
{
        if (mCurrentp)
        {
                mCurrentOperatingp = mCurrentp;
                mCurrentp = mCurrentp->mForward[0];
                return mCurrentOperatingp->mData;
        }
        else
        {
                //return NULL;          // causes compile warning
                return (DATA_TYPE)0;                    // equivalent, but no warning
        }
}

// same as getCurrentData() but a more intuitive name for the operation
template <class DATA_TYPE, S32 BINARY_DEPTH>
inline DATA_TYPE LLSkipList<DATA_TYPE, BINARY_DEPTH>::getNextData()
{
        if (mCurrentp)
        {
                mCurrentOperatingp = mCurrentp;
                mCurrentp = mCurrentp->mForward[0];
                return mCurrentOperatingp->mData;
        }
        else
        {
                //return NULL;          // causes compile warning
                return (DATA_TYPE)0;                    // equivalent, but no warning
        }
}

// remove the Node at mCurentOperatingp
// leave mCurrentp and mCurentOperatingp on the next entry
template <class DATA_TYPE, S32 BINARY_DEPTH>
inline void LLSkipList<DATA_TYPE, BINARY_DEPTH>::removeCurrentData()
{
        if (mCurrentOperatingp)
        {
                removeData(mCurrentOperatingp->mData);
        }
}

// reset the list and return the data currently pointed to, set mCurentOperatingp to that node and bump mCurrentp
template <class DATA_TYPE, S32 BINARY_DEPTH>
inline DATA_TYPE LLSkipList<DATA_TYPE, BINARY_DEPTH>::getFirstData()
{
        mCurrentp = *(mHead.mForward);
        mCurrentOperatingp = *(mHead.mForward);
        if (mCurrentp)
        {
                mCurrentOperatingp = mCurrentp;
                mCurrentp = mCurrentp->mForward[0];
                return mCurrentOperatingp->mData;
        }
        else
        {
                //return NULL;          // causes compile warning
                return (DATA_TYPE)0;                    // equivalent, but no warning
        }
}


#endif

---