Q3AsciiCache Class Reference
[Qt3Support module]

Detailed Description

The Q3AsciiCache class is a template class that provides a cache based on char* keys.

Q3AsciiCache is implemented as a template class. Define a template instance Q3AsciiCache<X> to create a cache that operates on pointers to X (X*).

A cache is a least recently used (LRU) list of cache items. The cache items are accessed via char* keys. For Unicode keys use the Q3Cache template instead, which uses QString keys. A Q3Cache has the same performace as a Q3AsciiCache.

Each cache item has a cost. The sum of item costs, totalCost(), will not exceed 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.

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) tells the cache to delete items that are removed. The default is to not delete items when then 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 Q3PtrCollection::newItem() for the item to be inserted. Inherit a cache and reimplement newItem() if you want deep copies.

When removing a cache item the virtual function Q3PtrCollection::deleteItem() is called. Its default implementation in Q3AsciiCache is to delete the item if auto-deletion is enabled.

There is a Q3AsciiCacheIterator which may be used to traverse the items in the cache in arbitrary order.

See also Q3AsciiCacheIterator, Q3Cache, and Q3IntCache.

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