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

**

** Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies).

** All rights reserved.

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

**

** This file is part of the documentation of the Qt Toolkit.

**

** $QT_BEGIN_LICENSE:FDL$

** Commercial Usage

** Licensees holding valid Qt Commercial licenses may use this file in

** accordance with the Qt Commercial License Agreement provided with the

** Software or, alternatively, in accordance with the terms contained in a

** written agreement between you and Nokia.

**

** GNU Free Documentation License

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

** Documentation License version 1.3 as published by the Free Software

** Foundation and appearing in the file included in the packaging of this

** file.

**

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

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

** $QT_END_LICENSE$

**

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

/*!

    \class QCache

    \brief The QCache class is a template class that provides a cache.

    \ingroup tools

    \ingroup shared

    \reentrant

    QCache\<Key, T\> defines a cache that stores objects of type T

    associated with keys of type Key. For example, here's the

    definition of a cache that stores objects of type Employee

    associated with an integer key:

    \snippet doc/src/snippets/code/doc_src_qcache.qdoc 0

    Here's how to insert an object in the cache:

    \snippet doc/src/snippets/code/doc_src_qcache.qdoc 1

    The advantage of using QCache over some other key-based data

    structure (such as QMap or QHash) is that QCache automatically

    takes ownership of the objects that are inserted into the cache and

    deletes them to make room for new objects, if necessary. When

    inserting an object into the cache, you can specify a \e{cost},

    which should bear some approximate relationship to the amount of

    memory taken by the object. When the sum of all objects' costs

    (totalCost()) exceeds the cache's limit (maxCost()), QCache starts

    deleting objects in the cache to keep under the limit, starting with

    less recently accessed objects.

    By default, QCache's maxCost() is 100. You can specify a

    different value in the QCache constructor:

    \snippet doc/src/snippets/code/doc_src_qcache.qdoc 2

    Each time you call insert(), you can specify a cost as third

    argument (after the key and a pointer to the object to insert).

    After the call, the inserted object is owned by the QCache, which

    may delete it at any time to make room for other objects.

    To look up objects in the cache, use object() or

    operator[](). This function looks up an object by its key, and

    returns either a pointer to the cached object (which is owned by

    the cache) or 0.

    If you want to remove an object from the cache for a particular key,

    call remove(). This will also delete the object. If you want to

    remove an object from the cache without the QCache deleting it, use

    take().

    \sa QPixmapCache, QHash, QMap

*/

/*! \fn QCache::QCache(int maxCost = 100)

    Constructs a cache whose contents will never have a total cost

    greater than \a maxCost.

*/

/*! \fn QCache::~QCache()

    Destroys the cache. Deletes all the objects in the cache.

*/

/*! \fn int QCache::maxCost() const

    Returns the maximum allowed total cost of the cache.

    \sa setMaxCost(), totalCost()

*/

/*! \fn void QCache::setMaxCost(int cost)

    Sets the maximum allowed total cost of the cache to \a cost. If

    the current total cost is greater than \a cost, some objects are

    deleted immediately.

    \sa maxCost(), totalCost()

*/

/*! \fn int QCache::totalCost() const

    Returns the total cost of the objects in the cache.

    This value is normally below maxCost(), but QCache makes an

    exception for Qt's \l{implicitly shared} classes. If a cached

    object shares its internal data with another instance, QCache may

    keep the object lying around, possibly contributing to making

    totalCost() larger than maxCost().

    \sa setMaxCost()

*/

/*! \fn int QCache::size() const

    Returns the number of objects in the cache.

    \sa isEmpty()

*/

/*! \fn int QCache::count() const

    Same as size().

*/

/*! \fn bool QCache::isEmpty() const

    Returns true if the cache contains no objects; otherwise

    returns false.

    \sa size()

*/

/*! \fn QList<Key> QCache::keys() const

    Returns a list of the keys in the cache.

*/

/*! \fn void QCache::clear();

    Deletes all the objects in the cache.

    \sa remove(), take()

*/

/*! \fn bool QCache::insert(const Key &key, T *object, int cost = 1)

    Inserts \a object into the cache with key \a key and

    associated cost \a cost. Any object with the same key already in

    the cache will be removed.

    After this call, \a object is owned by the QCache and may be

    deleted at any time. In particular, if \a cost is greater than

    maxCost(), the object will be deleted immediately.

    The function returns true if the object was inserted into the

    cache; otherwise it returns false.

    \sa take(), remove()

*/

/*! \fn T *QCache::object(const Key &key) const

    Returns the object associated with key \a key, or 0 if the key does

    not exist in the cache.

    \warning The returned object is owned by QCache and may be

    deleted at any time.

    \sa take(), remove()

*/

/*! \fn bool QCache::contains(const Key &key) const

    Returns true if the cache contains an object associated with key \a

    key; otherwise returns false.

    \sa take(), remove()

*/

/*! \fn T *QCache::operator[](const Key &key) const

    Returns the object associated with key \a key, or 0 if the key does

    not exist in the cache.

    This is the same as object().

    \warning The returned object is owned by QCache and may be

    deleted at any time.

*/

/*! \fn bool QCache::remove(const Key &key)

    Deletes the object associated with key \a key. Returns true if the

    object was found in the cache; otherwise returns false.

    \sa take(), clear()

*/

/*! \fn T *QCache::take(const Key &key)

    Takes the object associated with key \a key out of the cache

    without deleting it. Returns a pointer to the object taken out, or

    0 if the key does not exist in the cache.

    The ownership of the returned object is passed to the caller.

    \sa remove()

*/

/*!

    \fn QCache::QCache(int maxCost, int dummy)

    Use QCache(int) instead.

*/

/*!

    \fn T *QCache::find(const Key &key) const

    Use object() instead.

*/