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Diffstat (limited to 'src/corelib/tools/qcache.qdoc')
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diff --git a/src/corelib/tools/qcache.qdoc b/src/corelib/tools/qcache.qdoc new file mode 100644 index 0000000..4c008fa --- /dev/null +++ b/src/corelib/tools/qcache.qdoc @@ -0,0 +1,244 @@ +/**************************************************************************** +** +** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies). +** Contact: Nokia Corporation (qt-info@nokia.com) +** +** This file is part of the documentation 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 either Technology Preview License Agreement or the +** Beta Release License Agreement. +** +** 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 1.0, included in the file LGPL_EXCEPTION.txt in this +** package. +** +** GNU General Public License Usage +** Alternatively, this file may be used under the terms of the GNU +** General Public License version 3.0 as published by the Free Software +** Foundation and appearing in the file LICENSE.GPL included in the +** packaging of this file. Please review the following information to +** ensure the GNU General Public License version 3.0 requirements will be +** met: http://www.gnu.org/copyleft/gpl.html. +** +** If you are unsure which license is appropriate for your use, please +** contact the sales department at http://qt.nokia.com/contact. +** $QT_END_LICENSE$ +** +****************************************************************************/ + +/*! + \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. +*/ |