katie/src/core/tools/qcache.qdoc

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/*!
    \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.cpp 0

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

    \snippet doc/src/snippets/code/doc_src_qcache.cpp 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 number of all objects' costs
    exceeds the cache's limit (maxCost()), QCache starts deleting
    objects in the cache to keep under the limit, starting with the
    first object.

    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.cpp 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.
*/