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** QCache and QCacheIterator class documentation
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/*****************************************************************************
  QCache documentation
 *****************************************************************************/

// BEING REVISED: ettrich
/*!
  \class QCache

  \brief The QCache class is a template class that provides a cache based on QString keys.

  \ingroup collection
  \ingroup tools

  \important autoDelete setAutoDelete

  A cache is a least recently used (LRU) list of cache items.  Each
  cache item has a key and a certain cost. The sum of item costs,
  totalCost(), never exceeds the maximum cache cost, maxCost(). If
  inserting a new item would cause the total cost to exceed the
  maximum cost, the least recently used items in the cache are
  removed.

  QCache is a template class. QCache\<X\> defines a cache that
  operates on pointers to X, or X*.

  Apart from insert(), by far the most important function is find()
  (which also exists as operator[]()).  This function looks up an item,
  returns it, and by default marks it as being the most recently used
  item.

  There are also methods to remove() or take() an object from the
  cache.  Calling setAutoDelete(TRUE) for a cache tells it to delete
  items that are removed.  The default is to not delete items when
  they are removed (i.e., remove() and take() are equivalent).

  When inserting an item into the cache, only the pointer is copied, not
  the item itself. This is called a shallow copy. It is possible to make the
  cache copy all of the item's data (known as a deep copy) when an
  item is inserted.  insert() calls the virtual function
  QPtrCollection::newItem() for the item to be inserted.
  Inherit a cache and reimplement it if you want deep copies.

  When removing a cache item, the virtual function
  QPtrCollection::deleteItem() is called.  The default implementation
  deletes the item if auto-deletion is enabled, and does nothing
  otherwise.

  There is a QCacheIterator that can be used to traverse the
  items in the cache in arbitrary order.

  In QCache, the cache items are accessed via \l QString keys, which
  are Unicode strings.  If you want to use non-Unicode, plain 8-bit \c
  char* keys, use the QAsciiCache template.  A QCache has the same
  performace as a QAsciiCache.

  \sa QCacheIterator, QAsciiCache, QIntCache
*/

/*!
  \fn QCache::QCache( const QCache<type> &c )

  \internal

  Do not use. A QCache cannot be copied. Calls qFatal() in debug version.
*/


/*!
  \fn QCache::QCache( int maxCost, int size, bool caseSensitive )

  Constructs a cache whose contents will never have a total cost
  greater than \a maxCost and which is expected to contain less than
  \a size items.

  \a size is actually the size of an internal hash array; it's usually
  best to make it a prime number and at least 50% bigger than the largest
  expected number of items in the cache.

  Each inserted item has an associated cost.  When inserting a new
  item, if the total cost of all items in the cache will exceed \a
  maxCost, the cache will start throwing out the older (least recently
  used) items until there is enough room for the new item to be
  inserted.

  If \a caseSensitive is TRUE (the default), the cache keys are case
  sensitive; if it is FALSE, they are case-insensitive.
  Case-insensitive comparison includes all letters in Unicode.
*/

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

  Removes all items from the cache and destroys it.
  All iterators that access this cache will be reset.
*/

/*!
  \fn QCache<type>& QCache::operator=( const QCache<type> &c )

  \internal

  Do not use. A QCache cannot be copied. Calls qFatal() in debug version.
*/

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

  Returns the maximum allowed total cost of the cache.
  \sa setMaxCost() totalCost()
*/

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

  Returns the total cost of the items in the cache.  This is an
  integer in the range 0 to maxCost().

  \sa setMaxCost()
*/

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

  Sets the maximum allowed total cost of the cache to \a m.  If the
  current total cost is greater than \a m, some items are deleted
  immediately.

  \sa maxCost() totalCost()
*/

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

  Returns the number of items in the cache.

  \sa totalCost()
*/

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

  Returns the size of the hash array used to implement the cache.
  This should be a bit bigger than count() is likely to be.
*/

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

  Returns TRUE if the cache is empty, or FALSE if there is at least one
  object in it.
*/

/*!
  \fn bool QCache::insert( const QString &k, const type *d, int c, int p )

  Inserts the item \a d into the cache with key \a k and cost \a
  c. Returns TRUE if it is successful and FALSE if it fails.

  The cache's size is limited, and if the total cost is too high,
  QCache will remove old, least recently used items until there is room
  for this new item.

  The parameter \a p is internal and should be left at the default
  value (0).

  \warning If this function returns FALSE you must delete \a d
  yourself.  Additionally, be very careful about using \a d after
  calling this function because any other insertions into the cache, from
  anywhere in the application or within Qt itself, could cause the
  object to be discarded from the cache and the pointer to become
  invalid.
*/

/*!
  \fn bool QCache::remove( const QString &k )

  Removes the item associated with \a k, and returns TRUE if the item
  was present in the cache or FALSE if it was not.

  The item is deleted if auto-deletion has been enabled, i.e., you have
  called setAutoDelete(TRUE).

  If there are two or more items with equal keys, the one that
  was inserted last is removed.

  All iterators that refer to the removed item are set to point to the
  next item in the cache's traversal order.

  \sa take(), clear()
*/

/*!
  \fn type *QCache::take( const QString &k )

  Takes the item associated with \a k out of the cache without
  deleting it and returns a pointer to the item taken out, or null if
  the key does not exist in the cache.

  If there are two or more items with equal keys, the one that
  was inserted last is taken.

  All iterators that refer to the taken item are set to point to the
  next item in the cache's traversal order.

  \sa remove(), clear()
*/

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

  Removes all items from the cache and deletes them if auto-deletion
  has been enabled.

  All cache iterators that operate this on cache are reset.

  \sa remove() take()
*/

/*!
  \fn type *QCache::find( const QString &k, bool ref ) const

  Returns the item associated with key \a k, or null if the key does not
  exist in the cache.  If \a ref is TRUE (the default), the item is
  moved to the front of the least recently used list.

  If there are two or more items with equal keys, the one that
  was inserted last is returned.
*/

/*!
  \fn type *QCache::operator[]( const QString &k ) const

  Returns the item associated with key \a k, or null if \a k does not
  exist in the cache, and moves the item to the front of the least
  recently used list.

  If there are two or more items with equal keys, the one that
  was inserted last is returned.

  This is the same as find( k, TRUE ).

  \sa find()
*/

/*!
  \fn void QCache::statistics() const

  A debug-only utility function. Prints out cache usage, hit/miss, and
  distribution information using qDebug(). This function does nothing
  in the release library.
*/

/*****************************************************************************
  QCacheIterator documentation
 *****************************************************************************/

/*!
  \class QCacheIterator qcache.h
  \brief The QCacheIterator class provides an iterator for QCache collections.

  \ingroup collection
  \ingroup tools

  Note that the traversal order is arbitrary; you are not guaranteed
  any particular order.  If new objects are inserted into the cache
  while the iterator is active, the iterator may or may not see them.

  Multiple iterators are completely independent, even when they
  operate on the same QCache. QCache updates all iterators that refer
  an item when that item is removed.

  QCacheIterator provides an operator++(), and an operator+=() to
  traverse the cache. The current() and currentKey() functions are used
  to access the current cache item and its key. The atFirst() and
  atLast() return TRUE if the iterator points to the first or last item
  in the cache respectively. The isEmpty() function returns TRUE if the
  cache is empty, and count() returns the number of items in the cache.

  Note that atFirst() and atLast() refer to the iterator's arbitrary
  ordering, not to the cache's internal least recently used list.

  \sa QCache
*/

/*!
  \fn QCacheIterator::QCacheIterator( const QCache<type> &cache )

  Constructs an iterator for \a cache.  The current iterator item is
  set to point to the first item in the \a cache.
*/

/*!
  \fn QCacheIterator::QCacheIterator (const QCacheIterator<type> & ci)

  Constructs an iterator for the same cache as \a ci.  The new
  iterator starts at the same item as ci.current(), but moves
  independently from there on.
*/

/*!
  \fn QCacheIterator<type>& QCacheIterator::operator=( const QCacheIterator<type> &ci )

  Makes this an iterator for the same cache as \a ci.  The new
  iterator starts at the same item as ci.current(), but moves
  independently thereafter.
*/

/*!
  \fn uint QCacheIterator::count() const

  Returns the number of items in the cache on which this iterator operates.
  \sa isEmpty()
*/

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

  Returns TRUE if the cache is empty, i.e. count() == 0; otherwise
  it returns FALSE.  \sa count()
*/

/*!
  \fn bool QCacheIterator::atFirst() const

  Returns TRUE if the iterator points to the first item in the
  cache. Note that this refers to the iterator's arbitrary ordering,
  not to the cache's internal least recently used list.

  \sa toFirst(), atLast()
*/

/*!
  \fn bool QCacheIterator::atLast() const

  Returns TRUE if the iterator points to the last item in the
  cache. Note that this refers to the iterator's arbitrary ordering,
  not to the cache's internal least recently used list.

  \sa toLast(), atFirst()
*/

/*!
  \fn type *QCacheIterator::toFirst()

  Sets the iterator to point to the first item in the cache and
  returns a pointer to the item.

  Sets the iterator to null and returns null if the cache is empty.

  \sa toLast() isEmpty()
*/

/*!
  \fn type *QCacheIterator::toLast()

  Sets the iterator to point to the last item in the cache and
  returns a pointer to the item.

  Sets the iterator to null and returns null if the cache is empty.

  \sa toFirst() isEmpty()
*/

/*!
  \fn QCacheIterator::operator type *() const

  Cast operator. Returns a pointer to the current iterator item.
  Same as current().

*/

/*!
  \fn type *QCacheIterator::current() const

  Returns a pointer to the current iterator item.
*/

/*!
  \fn QString QCacheIterator::currentKey() const

  Returns the key for the current iterator item.
*/

/*!
  \fn type *QCacheIterator::operator()()

  Makes the succeeding item current and returns the original current
  item.

  If the current iterator item was the last item in the cache or if it
  was null, null is returned.
*/

/*!
  \fn type *QCacheIterator::operator+=( uint jump )

  Returns the item \a jump positions after the current item, or null if
  it is beyond the last item.  Makes this the current item.
*/

/*!
  \fn type *QCacheIterator::operator-=( uint jump )

  Returns the item \a jump positions before the current item, or null if
  it is before the first item.  Makes this the current item.
*/

/*!
  \fn type *QCacheIterator::operator++()

  Prefix++ makes the iterator point to the item just after
  current() and makes that the new current item for the iterator.  If
  current() was the last item, operator++() returns 0.
*/

/*!
  \fn type *QCacheIterator::operator--()

  Prefix-- makes the iterator point to the item just before
  current() and makes that the new current item for the iterator.  If
  current() was the first item, operator--() returns 0.
*/