/****************************************************************************

**

** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).

** All rights reserved.

** Contact: Nokia Corporation (qt-info@nokia.com)

**

** This file is part of the QtCore module of the Qt Toolkit.

**

** $QT_BEGIN_LICENSE:LGPL$

** No Commercial Usage

** This file contains pre-release code and may not be distributed.

** You may use this file in accordance with the terms and conditions

** contained in the Technology Preview License Agreement accompanying

** this package.

**

** GNU Lesser General Public License Usage

** Alternatively, this file may be used under the terms of the GNU Lesser

** General Public License version 2.1 as published by the Free Software

** Foundation and appearing in the file LICENSE.LGPL included in the

** packaging of this file.  Please review the following information to

** ensure the GNU Lesser General Public License version 2.1 requirements

** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.

**

** In addition, as a special exception, Nokia gives you certain additional

** rights.  These rights are described in the Nokia Qt LGPL Exception

** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.

**

** If you have questions regarding the use of this file, please contact

** Nokia at qt-info@nokia.com.

**

**

**

**

**

**

**

**

** $QT_END_LICENSE$

**

****************************************************************************/

#ifndef QCACHE_H

#define QCACHE_H

#include <QtCore/qhash.h>

QT_BEGIN_HEADER

QT_BEGIN_NAMESPACE

QT_MODULE(Core)

template <class Key, class T>

class QCache

{

    struct Node {

        inline Node() : keyPtr(0) {}

        inline Node(T *data, int cost)

            : keyPtr(0), t(data), c(cost), p(0), n(0) {}

        const Key *keyPtr; T *t; int c; Node *p,*n;

    };

    Node *f, *l;

    QHash<Key, Node> hash;

    void *unused;

    int mx, total;

    inline void unlink(Node &n) {

        if (n.p) n.p->n = n.n;

        if (n.n) n.n->p = n.p;

        if (l == &n) l = n.p;

        if (f == &n) f = n.n;

        total -= n.c;

        delete n.t;

        hash.remove(*n.keyPtr);

    }

    inline T *relink(const Key &key) {

        typename QHash<Key, Node>::iterator i = hash.find(key);

        if (typename QHash<Key, Node>::const_iterator(i) == hash.constEnd())

            return 0;

        Node &n = *i;

        if (f != &n) {

            if (n.p) n.p->n = n.n;

            if (n.n) n.n->p = n.p;

            if (l == &n) l = n.p;

            n.p = 0;

            n.n = f;

            f->p = &n;

            f = &n;

        }

        return n.t;

    }

    Q_DISABLE_COPY(QCache)

public:

    inline explicit QCache(int maxCost = 100);

#ifdef QT3_SUPPORT

    inline QT3_SUPPORT_CONSTRUCTOR QCache(int maxCost, int /* dummy */)

        : f(0), l(0), mx(maxCost), total(0) {}

#endif

    inline ~QCache() { clear(); }

    inline int maxCost() const { return mx; }

    void setMaxCost(int m);

    inline int totalCost() const { return total; }

    inline int size() const { return hash.size(); }

    inline int count() const { return hash.size(); }

    inline bool isEmpty() const { return hash.isEmpty(); }

    inline QList<Key> keys() const { return hash.keys(); }

    void clear();

    bool insert(const Key &key, T *object, int cost = 1);

    T *object(const Key &key) const;

    inline bool contains(const Key &key) const { return hash.contains(key); }

    T *operator[](const Key &key) const;

    bool remove(const Key &key);

    T *take(const Key &key);

private:

    void trim(int m);

#ifdef QT3_SUPPORT

    inline QT3_SUPPORT T *find(const Key &key) const { return object(key); }

#endif

};

template <class Key, class T>

inline QCache<Key, T>::QCache(int amaxCost)

    : f(0), l(0), unused(0), mx(amaxCost), total(0) {}

template <class Key, class T>

inline void QCache<Key,T>::clear()

{ while (f) { delete f->t; f = f->n; }

 hash.clear(); l = 0; total = 0; }

template <class Key, class T>

inline void QCache<Key,T>::setMaxCost(int m)

{ mx = m; trim(mx); }

template <class Key, class T>

inline T *QCache<Key,T>::object(const Key &key) const

{ return const_cast<QCache<Key,T>*>(this)->relink(key); }

template <class Key, class T>

inline T *QCache<Key,T>::operator[](const Key &key) const

{ return object(key); }

template <class Key, class T>

inline bool QCache<Key,T>::remove(const Key &key)

{

    typename QHash<Key, Node>::iterator i = hash.find(key);

    if (typename QHash<Key, Node>::const_iterator(i) == hash.constEnd()) {

        return false;

    } else {

        unlink(*i);

        return true;

    }

}

template <class Key, class T>

inline T *QCache<Key,T>::take(const Key &key)

{

    typename QHash<Key, Node>::iterator i = hash.find(key);

    if (i == hash.end())

        return 0;

    Node &n = *i;

    T *t = n.t;

    n.t = 0;

    unlink(n);

    return t;

}

template <class Key, class T>

bool QCache<Key,T>::insert(const Key &akey, T *aobject, int acost)

{

    remove(akey);

    if (acost > mx) {

        delete aobject;

        return false;

    }

    trim(mx - acost);

    Node sn(aobject, acost);

    typename QHash<Key, Node>::iterator i = hash.insert(akey, sn);

    total += acost;

    Node *n = &i.value();

    n->keyPtr = &i.key();

    if (f) f->p = n;

    n->n = f;

    f = n;

    if (!l) l = f;

    return true;

}

template <class Key, class T>

void QCache<Key,T>::trim(int m)

{

    Node *n = l;

    while (n && total > m) {

        Node *u = n;

        n = n->p;

        if (qIsDetached(*u->t))

            unlink(*u);

    }

}

QT_END_NAMESPACE

QT_END_HEADER

#endif // QCACHE_H