CWE-ou-minkata/Sources/Plasma/NucleusLib/pnUtils/Private/pnUtSkipList.h

/*==LICENSE==*

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*==LICENSE==*/
/*****************************************************************************
*
*   $/Plasma20/Sources/Plasma/NucleusLib/pnUtils/Private/pnUtSkipList.h
*   
***/

#ifdef PLASMA20_SOURCES_PLASMA_NUCLEUSLIB_PNUTILS_PRIVATE_PNUTSKIPLIST_H
#error "Header $/Plasma20/Sources/Plasma/NucleusLib/pnUtils/Private/pnUtSkipList.h included more than once"
#endif
#define PLASMA20_SOURCES_PLASMA_NUCLEUSLIB_PNUTILS_PRIVATE_PNUTSKIPLIST_H


/*****************************************************************************
*
*   Macros
*
***/

#define SKIPLIST(type, keyType, keyField, cmp)      TSkipList< type, keyType, offsetof(type, keyField), cmp >
#define SKIPLIST_NUMERIC(type, keyType, keyField)   SKIPLIST(type, keyType, keyField, TSkipListNumericCmp<keyType>)
#define SKIPLIST_STRING(type, keyType, keyField)    SKIPLIST(type, keyType, keyField, TSkipListStringCmp<keyType>)
#define SKIPLIST_STRINGI(type, keyType, keyField)   SKIPLIST(type, keyType, keyField, TSkipListStringCmpI<keyType>)



/*****************************************************************************
*
*   Typedefs
*
***/

typedef void * SkipListTag;


/*****************************************************************************
*
*   Comparers
*
***/


template<class K>
class TSkipListNumericCmp {
public:
    static bool Eq (const K & a, const K & b) { return a == b; }
    static bool Lt (const K & a, const K & b) { return a < b;  }
};

template<class K>
class TSkipListStringCmp {
public:
    static bool Eq (const K & a, const K & b) { return StrCmp(a, b, (unsigned)-1) == 0; }
    static bool Lt (const K & a, const K & b) { return StrCmp(a, b, (unsigned)-1) < 0;  }
};

template<class K>
class TSkipListStringCmpI {
public:
    static bool Eq (const K & a, const K & b) { return StrCmpI(a, b, (unsigned)-1) == 0; }
    static bool Lt (const K & a, const K & b) { return StrCmpI(a, b, (unsigned)-1) < 0;  }
};


/*****************************************************************************
*
*   TSkipList
*
***/

template<class T, class K, unsigned keyOffset, class Cmp>
class TSkipList {
private:
    enum { kMaxLevels = 32 };

    template<class T2, class K2>
    struct TNode {
        const K2 *     key;
        T2 *           object;
        unsigned      level;
        TNode<T2, K2> * prev;
        TNode<T2, K2> * next[1];      // variable size array
    };
    typedef TNode<T,K> Node;

    unsigned    m_level;
    Node *      m_head;
    Node *      m_stop;
    unsigned    m_randomBits;
    unsigned    m_randomsLeft;

    Node *      AllocNode (unsigned levels);
    void        FreeNode (Node * node);
    unsigned    RandomLevel ();

public:
    inline TSkipList ();
    inline ~TSkipList ();
    inline void Clear ();
    inline void Delete (T * object);
    inline T *  Find (const K & key, SkipListTag * tag = nil) const;
    inline T *  FindNext (SkipListTag * tag) const;
    inline T *  Head (SkipListTag * tag) const;
    inline T *  Next (SkipListTag * tag) const;
    inline T *  Prev (SkipListTag * tag) const;
    inline T *  Tail (SkipListTag * tag) const;
    inline void Link (T * object);
    inline void Unlink (T * object);
    inline void Unlink (SkipListTag * tag);
    inline void UnlinkAll ();
    
    #ifdef HS_DEBUGGING
    inline void Print () const;
    #endif
};


/*****************************************************************************
*
*   TSkipList private member functions
*
***/

//============================================================================
template<class T, class K, unsigned keyOffset, class Cmp>
typename TSkipList<T,K,keyOffset,Cmp>::Node* TSkipList<T,K,keyOffset,Cmp>::AllocNode (unsigned level) {

    unsigned size = offsetof(Node, next) + (level + 1) * sizeof(Node);
    Node * node = (Node *)malloc(size);
    node->level = level;
    return node;
}

//============================================================================
template<class T, class K, unsigned keyOffset, class Cmp>
void TSkipList<T,K,keyOffset,Cmp>::FreeNode (TNode<T,K> * node) {

    free(node);
}

//============================================================================
template<class T, class K, unsigned keyOffset, class Cmp>
unsigned TSkipList<T,K,keyOffset,Cmp>::RandomLevel () {

    unsigned level = 0;
    unsigned bits  = 0;

    while (!bits) {
        bits = m_randomBits % 4;
        if (!bits)
            ++level;
        m_randomBits >>= 2;
        m_randomsLeft -= 2;
        if (!m_randomsLeft) {
            m_randomBits  = RandUnsigned();
            m_randomsLeft = 30;
        }
    }

    return level;
}


/*****************************************************************************
*
*   TSkipList public member functions
*
***/

//============================================================================
template<class T, class K, unsigned keyOffset, class Cmp>
TSkipList<T,K,keyOffset,Cmp>::TSkipList () {

    m_level       = 0; 
    m_head        = AllocNode(kMaxLevels);
    m_stop        = AllocNode(0);
    m_randomBits  = RandUnsigned();
    m_randomsLeft = 30;

    // Initialize header and stop skip node pointers
    m_stop->prev    = m_head;
    m_stop->object  = nil;
    m_stop->next[0] = nil;
    m_head->object  = nil;
    for (unsigned index = 0; index < kMaxLevels; ++index)
        m_head->next[index] = m_stop;
}

//============================================================================
template<class T, class K, unsigned keyOffset, class Cmp>
TSkipList<T,K,keyOffset,Cmp>::~TSkipList () {

    UnlinkAll();
    ASSERT(m_stop->prev == m_head);
    FreeNode(m_head);
    FreeNode(m_stop);
}

//============================================================================
template<class T, class K, unsigned keyOffset, class Cmp>
void TSkipList<T,K,keyOffset,Cmp>::Clear () {

    Node * ptr = m_head->next[0];
    while (ptr != m_stop) {
        Node * next = ptr->next[0];
        delete ptr->object;
        FreeNode(ptr);
        ptr = next;
    }

    m_stop->prev = m_head;
    for (unsigned index = 0; index < kMaxLevels; ++index)
        m_head->next[index] = m_stop;
    m_level = 0;
}

//============================================================================
template<class T, class K, unsigned keyOffset, class Cmp>
void TSkipList<T,K,keyOffset,Cmp>::Delete (T * object) {

    Unlink(object);
    delete object;
}

//============================================================================
template<class T, class K, unsigned keyOffset, class Cmp>
T * TSkipList<T,K,keyOffset,Cmp>::Find (const K & key, SkipListTag * tag) const {

    Node * node = m_head;

    m_stop->key = &key;
    for (int level = (int)m_level; level >= 0; --level)
        while (Cmp::Lt(*node->next[level]->key, key))
            node = node->next[level];

    node = node->next[0];
    if (node != m_stop && Cmp::Eq(*node->key, *m_stop->key)) {
        if (tag)
            *tag = node;
        return node->object;
    }
    else {
        if (tag)
            *tag = nil;
        return nil;
    }
}

//============================================================================
template<class T, class K, unsigned keyOffset, class Cmp>
T * TSkipList<T,K,keyOffset,Cmp>::FindNext (SkipListTag * tag) const {

    Node * node = (Node *)*tag;

    m_stop->key = node->key;
    for (int level = (int)node->level; level >= 0; --level)
        while (Cmp::Lt(*node->next[level]->key, *m_stop->key))
            node = node->next[level];

    node = node->next[0];
    if (node != m_stop && Cmp::Eq(*node->key, *m_stop->key)) {
        *tag = node;
        return node->object;
    }
    else {
        *tag = nil;
        return nil;
    }
}

//============================================================================
template<class T, class K, unsigned keyOffset, class Cmp>
T * TSkipList<T,K,keyOffset,Cmp>::Head (SkipListTag * tag) const {

    ASSERT(tag);
    Node * first = m_head->next[0];
    if (first == m_stop) {
        *tag = nil;
        return nil;
    }

    *tag = first;
    return first->object;
}

//============================================================================
template<class T, class K, unsigned keyOffset, class Cmp>
T * TSkipList<T,K,keyOffset,Cmp>::Next (SkipListTag * tag) const {

    ASSERT(tag);
    Node * node = (Node *)*tag;
    ASSERT(node);
    if (node->next[0] == m_stop) {
        *tag = nil;
        return nil;
    }

    *tag = node->next[0];
    return node->next[0]->object;
}

//============================================================================
template<class T, class K, unsigned keyOffset, class Cmp>
T * TSkipList<T,K,keyOffset,Cmp>::Prev (SkipListTag * tag) const {

    ASSERT(tag);
    Node * node = (Node *)*tag;
    ASSERT(node);
    if (node->prev == m_head) {
        *tag = nil;
        return nil;
    }

    *tag = node->prev;
    return node->prev->object;
}

//============================================================================
template<class T, class K, unsigned keyOffset, class Cmp>
T * TSkipList<T,K,keyOffset,Cmp>::Tail (SkipListTag * tag) const {

    ASSERT(tag);
    Node * last = m_stop->prev;
    if (last == m_head) {
        *tag = nil;
        return nil;
    }

    *tag = last;
    return last->object;
}

//============================================================================
template<class T, class K, unsigned keyOffset, class Cmp>
void TSkipList<T,K,keyOffset,Cmp>::Link (T * object) {

    const K * key = (const K *)((const uint8_t *)object + keyOffset);

    // Find the node's insertion point
    m_stop->key = key;
    Node * update[kMaxLevels];
    Node * node = m_head;
    for (int level = (int)m_level; level >= 0; --level) {
        while (Cmp::Lt(*node->next[level]->key, *key))
            node = node->next[level];
        update[level] = node;
    }
    node = node->next[0];

    {
        // Select a level for the skip node
        unsigned newLevel = RandomLevel();
        if (newLevel > m_level) {
            if (m_level < kMaxLevels - 1) {
                newLevel         = ++m_level;
                update[newLevel] = m_head;
            }
            else
                newLevel = m_level;
        }

        // Create the node and insert it into the skip list
        Node * node  = AllocNode(newLevel);
        node->key    = key;
        node->object = object;
        for (unsigned level = newLevel; level >= 1; --level) {
            node->next[level] = update[level]->next[level];
            update[level]->next[level] = node;
        }
        node->prev               = update[0];
        node->next[0]            = update[0]->next[0];
        update[0]->next[0]->prev = node;
        update[0]->next[0]       = node;
    }
}

//============================================================================
template<class T, class K, unsigned keyOffset, class Cmp>
void TSkipList<T,K,keyOffset,Cmp>::Unlink (T * object) {

    const K * key = (const K *)((const uint8_t *)object + keyOffset);

    Node * node = m_head;
    Node * update[kMaxLevels];
    int    level = m_level;

    for (;;) {  
        // Find the node being unlinked
        m_stop->key = key;
        for (; level >= 0; --level) {
            while (Cmp::Lt(*node->next[level]->key, *key))
                node = node->next[level];
            update[level] = node;
        }
        node = node->next[0];

        // Node wasn't found so do nothing
        if (*node->key != *key || node == m_stop)
            return;
            
        if (node->object == object)
            break;
    }
    
    // Update all links
    for (level = m_level; level >= 1; --level) {
        if (update[level]->next[level] != node)
            continue;
        update[level]->next[level] = node->next[level];
    }
    ASSERT(update[0]->next[0] == node);
    node->next[0]->prev = update[0];
    update[0]->next[0]  = node->next[0];

    // Update header
    while (m_level && m_head->next[m_level] == m_stop)
        --m_level;

    FreeNode(node);
}

//============================================================================
template<class T, class K, unsigned keyOffset, class Cmp>
void TSkipList<T,K,keyOffset,Cmp>::UnlinkAll () {

    Node * ptr = m_head->next[0];
    while (ptr != m_stop) {
        Node * next = ptr->next[0];
        FreeNode(ptr);
        ptr = next;
    }

    m_stop->prev = m_head;
    for (unsigned index = 0; index < kMaxLevels; ++index)
        m_head->next[index] = m_stop;
    m_level = 0;
}