Hi Everybody,
I think I've written a fairly decent implementation
for the DOMNodeList to provide real array access. Would anyone be
interested in taking a look at the code and basically checking my work? It
would be nice to be able to see it wind up in the codebase. I built against xerces v. 2.5 please e-mail if me for the source code. It is in a
zip file with the proper directory structure containing only the new files and
files that have changed.
Thanks,
Michael Williams
Shunra Software
Michael Williams
Shunra Software
Problem:
The DOMNode in xerces has a method called getChildNodes, which returns a DOMNodeList of child elements. This DOMNodeList basically provides a thin wrapper for the internal linked list, and is not efficient when doing element traversals, and direct array-type lookups with the DOMNodeList.item call.
The DOMNode in xerces has a method called getChildNodes, which returns a DOMNodeList of child elements. This DOMNodeList basically provides a thin wrapper for the internal linked list, and is not efficient when doing element traversals, and direct array-type lookups with the DOMNodeList.item call.
Solution:
The solution to this lies in creating a proper
implementation of the xerces DomNodeList class. We will extend this class
to implement the following method
virtual DOMNode *itemByTagNameNS(XMLSize_t
index, const XMLCh *namespaceURI, const XMLCh *localName) const {return
0;};
Retrieve an item in a specific collection by index, tag name, and namespace
Retrieve an item in a specific collection by index, tag name, and namespace
virtual XMLSize_t getLengthByTagNameNS(const XMLCh
*namespaceURI, const XMLCh *localName) const {return 0;};
Get the length of a specific collection by index, tag name, and namespace
Get the length of a specific collection by index, tag name, and namespace
virtual bool insertElementAtByTagNameNS(DOMNode *,
XMLSize_t index);
Insert an item into the list by index of the collection of elements with matching namespace URI and localname. Returns false if the index < 0 or greater than the number of elements of the appropriate type (namespace and element name match).
Insert an item into the list by index of the collection of elements with matching namespace URI and localname. Returns false if the index < 0 or greater than the number of elements of the appropriate type (namespace and element name match).
virtual DOMNode
*removeElementAtByTagNameNS(XMLSize_t index, const XMLCh *namespaceURI, const
XMLCh *localName)
Remove an element by index of the collection of elements with matching Namespace URI and localname. Returns the removed node upon success, or false if the index < 0 or greater than the number of elements of the appropriate type.
Remove an element by index of the collection of elements with matching Namespace URI and localname. Returns the removed node upon success, or false if the index < 0 or greater than the number of elements of the appropriate type.
virtual bool insertElementAt(DOMNode *, XMLSize_t
index) = 0;
Inserts an element into the list of child elements by index. Returns false if the index < 0 or greater than the number of child elements.
Inserts an element into the list of child elements by index. Returns false if the index < 0 or greater than the number of child elements.
virtual DOMNode *removeElementAt(XMLSize_t index) =
0;
Remove an element by index of the collection of elements with matching Namespace URI and localname. Returns the removed node upon success, or false if the index < 0 or greater than the number of child elements.
Remove an element by index of the collection of elements with matching Namespace URI and localname. Returns the removed node upon success, or false if the index < 0 or greater than the number of child elements.
Comments regarding element navigation:
All methods of navigating elements will probably
yield about the same level of performance, and linked list navigation or array
navigation can be mixed without any adverse performance effects.
Comments regarding element deletion and
insertion:
Choose one of the following three methods for
deleting and inserting children elements into an element, and for the same element, do not mix the methods. Otherwise performance will most likely
suffer.
1. Inserting and deleting by linked list methods
(original xerces methods)
2. Inserting and deleting into the vector of ALL children (not using namespace and nodename identifiers)
3. Inserting and deleting by NS and nodename.
2. Inserting and deleting into the vector of ALL children (not using namespace and nodename identifiers)
3. Inserting and deleting by NS and nodename.
The reason is that because algorithms to insert or
delete from a linked list can be very efficient, but then to try to find the
element to be deleted in an array will yield slow performance, because there is
no good way to know the array index of the element beforehand.
Also, the algorithms to partition an elements
children into a general child array, and arrays by namespace and element name,
will not yield good performance if these two sets of arrays (partitioned and
general) are both used in the same element for inserting and deleting
elements.
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