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470 lines
14 KiB
470 lines
14 KiB
/****************************************************************************
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**
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** QCache and QCacheIterator class documentation
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**
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** Copyright (C) 1992-2008 Trolltech ASA. All rights reserved.
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**
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** This file is part of the TQt GUI Toolkit.
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**
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** This file may be used under the terms of the GNU General
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** Public License versions 2.0 or 3.0 as published by the Free
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** Software Foundation and appearing in the files LICENSE.GPL2
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** and LICENSE.GPL3 included in the packaging of this file.
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** Alternatively you may (at your option) use any later version
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** of the GNU General Public License if such license has been
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** publicly approved by Trolltech ASA (or its successors, if any)
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** and the KDE Free TQt Foundation.
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**
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** Please review the following information to ensure GNU General
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** Public Licensing requirements will be met:
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** http://trolltech.com/products/qt/licenses/licensing/opensource/.
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** If you are unsure which license is appropriate for your use, please
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** review the following information:
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** http://trolltech.com/products/qt/licenses/licensing/licensingoverview
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** or contact the sales department at sales@trolltech.com.
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**
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** This file may be used under the terms of the Q Public License as
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** defined by Trolltech ASA and appearing in the file LICENSE.QPL
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** included in the packaging of this file. Licensees holding valid Qt
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** Commercial licenses may use this file in accordance with the Qt
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** Commercial License Agreement provided with the Software.
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**
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** This file is provided "AS IS" with NO WARRANTY OF ANY KIND,
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** INCLUDING THE WARRANTIES OF DESIGN, MERCHANTABILITY AND FITNESS FOR
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** A PARTICULAR PURPOSE. Trolltech reserves all rights not granted
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** herein.
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**
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**********************************************************************/
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/*****************************************************************************
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QCache documentation
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*****************************************************************************/
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/*!
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\class QCache
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\brief The QCache class is a template class that provides a cache based on TQString keys.
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\ingroup collection
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\ingroup tools
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\important autoDelete setAutoDelete
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A cache is a least recently used (LRU) list of cache items. Each
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cache item has a key and a certain cost. The sum of item costs,
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totalCost(), never exceeds the maximum cache cost, maxCost(). If
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inserting a new item would cause the total cost to exceed the
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maximum cost, the least recently used items in the cache are
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removed.
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QCache is a template class. QCache\<X\> defines a cache that
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operates on pointers to X, or X*.
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Apart from insert(), by far the most important function is find()
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(which also exists as operator[]()). This function looks up an
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item, returns it, and by default marks it as being the most
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recently used item.
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There are also methods to remove() or take() an object from the
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cache. Calling setAutoDelete(TRUE) for a cache tells it to delete
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items that are removed. The default is to not delete items when
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they are removed (i.e., remove() and take() are equivalent).
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When inserting an item into the cache, only the pointer is copied,
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not the item itself. This is called a shallow copy. It is possible
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to make the cache copy all of the item's data (known as a deep
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copy) when an item is inserted. insert() calls the virtual
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function QPtrCollection::newItem() for the item to be inserted.
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Inherit a cache and reimplement newItem() if you want deep copies.
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When removing a cache item, the virtual function
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QPtrCollection::deleteItem() is called. The default
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implementation deletes the item if auto-deletion is enabled, and
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does nothing otherwise.
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There is a QCacheIterator that can be used to traverse the items
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in the cache in arbitrary order.
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In QCache, the cache items are accessed via \l TQString keys, which
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are Unicode strings. If you want to use non-Unicode, plain 8-bit
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\c char* keys, use the QAsciiCache template. A QCache has the
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same performance as a QAsciiCache.
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\sa QCacheIterator, QAsciiCache, QIntCache
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*/
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/*!
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\fn QCache::QCache( const QCache<type> &c )
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\internal
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Do not use. A QCache cannot be copied. Calls tqFatal() in debug version.
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*/
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/*!
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\fn QCache::QCache( int maxCost, int size, bool caseSensitive )
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Constructs a cache whose contents will never have a total cost
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greater than \a maxCost and which is expected to contain less than
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\a size items.
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\a size is actually the size of an internal hash array; it's
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usually best to make it a prime number and at least 50% bigger
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than the largest expected number of items in the cache.
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Each inserted item has an associated cost. When inserting a new
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item, if the total cost of all items in the cache will exceed \a
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maxCost, the cache will start throwing out the older (least
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recently used) items until there is enough room for the new item
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to be inserted.
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If \a caseSensitive is TRUE (the default), the cache keys are case
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sensitive; if it is FALSE, they are case-insensitive.
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Case-insensitive comparison considers all Unicode letters.
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*/
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/*!
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\fn QCache::~QCache()
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Removes all items from the cache and destroys it. All iterators
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that access this cache will be reset.
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*/
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/*!
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\fn QCache<type>& QCache::operator=( const QCache<type> &c )
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\internal
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Do not use. A QCache cannot be copied. Calls tqFatal() in debug version.
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*/
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/*!
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\fn int QCache::maxCost() const
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Returns the maximum allowed total cost of the cache.
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\sa setMaxCost() totalCost()
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*/
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/*!
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\fn int QCache::totalCost() const
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Returns the total cost of the items in the cache. This is an
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integer in the range 0 to maxCost().
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\sa setMaxCost()
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*/
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/*!
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\fn void QCache::setMaxCost( int m )
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Sets the maximum allowed total cost of the cache to \a m. If the
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current total cost is greater than \a m, some items are deleted
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immediately.
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\sa maxCost() totalCost()
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*/
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/*!
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\fn uint QCache::count() const
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Returns the number of items in the cache.
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\sa totalCost()
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*/
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/*!
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\fn uint QCache::size() const
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Returns the size of the hash array used to implement the cache.
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This should be a bit bigger than count() is likely to be.
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*/
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/*!
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\fn bool QCache::isEmpty() const
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Returns TRUE if the cache is empty; otherwise returns FALSE.
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*/
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/*!
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\fn bool QCache::insert( const TQString &k, const type *d, int c, int p )
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Inserts the item \a d into the cache with key \a k and associated
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cost, \a c. Returns TRUE if it is successfully inserted; otherwise
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returns FALSE.
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The cache's size is limited, and if the total cost is too high,
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QCache will remove old, least recently used items until there is
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room for this new item.
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The parameter \a p is internal and should be left at the default
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value (0).
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\warning If this function returns FALSE (which could happen, e.g.
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if the cost of this item alone exceeds maxCost()) you must delete
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\a d yourself. Additionally, be very careful about using \a d
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after calling this function because any other insertions into the
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cache, from anywhere in the application or within TQt itself, could
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cause the object to be discarded from the cache and the pointer to
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become invalid.
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*/
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/*!
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\fn bool QCache::remove( const TQString &k )
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Removes the item associated with \a k, and returns TRUE if the
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item was present in the cache; otherwise returns FALSE.
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The item is deleted if auto-deletion has been enabled, i.e., if
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you have called setAutoDelete(TRUE).
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If there are two or more items with equal keys, the one that was
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inserted last is removed.
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All iterators that refer to the removed item are set to point to
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the next item in the cache's traversal order.
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\sa take(), clear()
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*/
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/*!
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\fn type *QCache::take( const TQString &k )
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Takes the item associated with \a k out of the cache without
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deleting it, and returns a pointer to the item taken out, or 0
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if the key does not exist in the cache.
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If there are two or more items with equal keys, the one that was
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inserted last is taken.
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All iterators that refer to the taken item are set to point to the
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next item in the cache's traversal order.
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\sa remove(), clear()
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*/
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/*!
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\fn void QCache::clear()
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Removes all items from the cache and deletes them if auto-deletion
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has been enabled.
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All cache iterators that operate this on cache are reset.
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\sa remove() take()
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*/
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/*!
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\fn type *QCache::find( const TQString &k, bool ref ) const
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Returns the item associated with key \a k, or 0 if the key does
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not exist in the cache. If \a ref is TRUE (the default), the item
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is moved to the front of the least recently used list.
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If there are two or more items with equal keys, the one that was
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inserted last is returned.
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*/
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/*!
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\fn type *QCache::operator[]( const TQString &k ) const
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Returns the item associated with key \a k, or 0 if \a k does not
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exist in the cache, and moves the item to the front of the least
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recently used list.
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If there are two or more items with equal keys, the one that was
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inserted last is returned.
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This is the same as find( k, TRUE ).
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\sa find()
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*/
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/*!
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\fn void QCache::statistics() const
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A debug-only utility function. Prints out cache usage, hit/miss,
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and distribution information using tqDebug(). This function does
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nothing in the release library.
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*/
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/*****************************************************************************
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QCacheIterator documentation
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*****************************************************************************/
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/*!
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\class QCacheIterator ntqcache.h
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\brief The QCacheIterator class provides an iterator for QCache collections.
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\ingroup collection
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\ingroup tools
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Note that the traversal order is arbitrary; you are not guaranteed
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any particular order. If new objects are inserted into the cache
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while the iterator is active, the iterator may or may not see
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them.
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Multiple iterators are completely independent, even when they
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operate on the same QCache. QCache updates all iterators that
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refer an item when that item is removed.
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QCacheIterator provides an operator++(), and an operator+=() to
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traverse the cache. The current() and currentKey() functions are
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used to access the current cache item and its key. The atFirst()
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and atLast() return TRUE if the iterator points to the first or
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last item in the cache respectively. The isEmpty() function
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returns TRUE if the cache is empty, and count() returns the number
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of items in the cache.
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Note that atFirst() and atLast() refer to the iterator's arbitrary
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ordering, not to the cache's internal least recently used list.
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\sa QCache
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*/
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/*!
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\fn QCacheIterator::QCacheIterator( const QCache<type> &cache )
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Constructs an iterator for \a cache. The current iterator item is
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set to point to the first item in the \a cache.
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*/
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/*!
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\fn QCacheIterator::QCacheIterator (const QCacheIterator<type> & ci)
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Constructs an iterator for the same cache as \a ci. The new
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iterator starts at the same item as ci.current(), but moves
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independently from there on.
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*/
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/*!
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\fn QCacheIterator<type>& QCacheIterator::operator=( const QCacheIterator<type> &ci )
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Makes this an iterator for the same cache as \a ci. The new
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iterator starts at the same item as ci.current(), but moves
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independently thereafter.
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*/
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/*!
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\fn uint QCacheIterator::count() const
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Returns the number of items in the cache on which this iterator
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operates.
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\sa isEmpty()
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*/
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/*!
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\fn bool QCacheIterator::isEmpty() const
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Returns TRUE if the cache is empty, i.e. count() == 0; otherwise
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it returns FALSE.
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\sa count()
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*/
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/*!
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\fn bool QCacheIterator::atFirst() const
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Returns TRUE if the iterator points to the first item in the
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cache; otherwise returns FALSE. Note that this refers to the
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iterator's arbitrary ordering, not to the cache's internal least
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recently used list.
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\sa toFirst(), atLast()
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*/
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/*!
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\fn bool QCacheIterator::atLast() const
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Returns TRUE if the iterator points to the last item in the cache;
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otherwise returns FALSE. Note that this refers to the iterator's
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arbitrary ordering, not to the cache's internal least recently
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used list.
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\sa toLast(), atFirst()
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*/
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/*!
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\fn type *QCacheIterator::toFirst()
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Sets the iterator to point to the first item in the cache and
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returns a pointer to the item.
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Sets the iterator to 0 and returns 0 if the cache is empty.
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\sa toLast() isEmpty()
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*/
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/*!
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\fn type *QCacheIterator::toLast()
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Sets the iterator to point to the last item in the cache and
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returns a pointer to the item.
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Sets the iterator to 0 and returns 0 if the cache is empty.
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\sa toFirst() isEmpty()
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*/
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/*!
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\fn QCacheIterator::operator type *() const
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Cast operator. Returns a pointer to the current iterator item.
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Same as current().
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*/
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/*!
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\fn type *QCacheIterator::current() const
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Returns a pointer to the current iterator item.
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*/
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/*!
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\fn TQString QCacheIterator::currentKey() const
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Returns the key for the current iterator item.
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*/
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/*!
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\fn type *QCacheIterator::operator()()
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Makes the succeeding item current and returns the original current
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item.
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If the current iterator item was the last item in the cache or if
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it was 0, 0 is returned.
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*/
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/*!
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\fn type *QCacheIterator::operator+=( uint jump )
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Returns the item \a jump positions after the current item, or 0 if
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it is beyond the last item. Makes this the current item.
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*/
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/*!
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\fn type *QCacheIterator::operator-=( uint jump )
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Returns the item \a jump positions before the current item, or 0
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if it is before the first item. Makes this the current item.
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*/
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/*!
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\fn type *QCacheIterator::operator++()
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Prefix++ makes the iterator point to the item just after current()
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and makes that the new current item for the iterator. If current()
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was the last item, operator++() returns 0.
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*/
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/*!
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\fn type *QCacheIterator::operator--()
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Prefix-- makes the iterator point to the item just before
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current() and makes that the new current item for the iterator. If
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current() was the first item, operator--() returns 0.
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*/
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