[Libxmlplusplus-general] Node ownership

[murrayc t-online de (Murray Cumming)]

On Tue, 2003-02-04 at 08:21, Stefan Seefeld wrote:
> * decide who can create Nodes, 

Clearly libxml++ objects need to be able to create nodes. Maybe people
want to create nodes with normal C++ memory management too.

> who owns them if they are taken out of a document,

At the moment they are deleted if that happens.

>    etc. May be a 'Store' object may help...

So, let's list some possible solutions. For instance,

1. A boolean owned_by_libxml member variable.
  The libxml destroy callback would not destroy the C++ wrapper instance
if owned_by_libxml is false.
  Methods such as Node::add_child_node(Node*) would set the
owned_by_libxml to true and take ownership. This would be documented.
  Methods such as Node::remove_and_detach() would set the
owned_by_libxml and the Node should be deleted if it is never added to
something else with add_child_node().

2. Use of shared-reference-counting smartpointers everywhere. 
  The libxml destroy callback would just unref() the C++ wrapper
instance. It would be destroyed when the last smartpointer instance went
out of scope.
  I like this idea (I liked it when Xerces-C++ used it in the past), but
  - there might be complex circular-references issues, and
  - people might think it's slow or takes extra memory.

3. Implement reference-counting, as above, but make use of smartpointers
optional. Smartpointers would be necessary when copying parts of an XML
tree to another tree.


-- 
Murray Cumming
murray usa net
www.murrayc.com