[fpc-devel] TAVLTree(avl_tree.pp) and "XML DOM" (dom.pp) thread safety issues
inoussa12 at gmail.com
Fri Dec 19 16:48:22 CET 2008
A discussion started a month or two ago about the thread safety issue
concerning XML DOM, issue due to avl_tree.pp implementation.
There were 3 propositions :
1 - Inoussa OUEDRAOGO :
Another proposition is to introduce a base avl class say TBaseAVLTree
that defines two abstract virtual methods "NewNode()" and "FreeNode()"
and then define :
- TAVLTree : that _do not_ use a node mem manager, then thread safe.
- TAVLManagedTree that uses a node mem manager provided in
The developer using this one is _aware_ of the thread
safety issue and can
then provide a thread safe node mem manager for an instance exposed
to more than one thread while using the default not thread safe node
mem manager for a thread local instance
2 - Marc Weustink :
I'm pro having a manged and an unmanaged avltree. One (big)
of the current implementation (with a shared node manager
for all trees)
is that you cannot add custom derived treenodes since they will be
released in the pool too.
Mattias Gärtner :
I think too, that we need a fast, lightweight tree and a slower, but
customizable tree. Something like TFPList and TList. One
methods and one with virtual methods and definable node class
3 - Sergei Gorelkin : I would like to vote for removing avl_tree
dependency from the DOM altogether
I would like to bring back the discussion hoping that this time a
definitive solution will be adopted.
No matter what solution will be choosed, a thread-safe implementation
of AVL tree is a must, IMHO.
PS : the discussions are at
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