#53655: Improve speed of DOMNode::C14N() on large XML documents #12278
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…ents The XPath query is in accordance to spec [1]. However, we can do it in a simpler way. We can use a custom callback function instead of a linear search in XPath to check if a node is visible. Note that comment nodes are handled internally by libxml2 already, so we do not need to differentiate between node types. The callback will do an upwards traversal of the tree until the root of the canonicalization is reached. In practice this will speed up the application a lot. [1] https://www.w3.org/TR/2001/REC-xml-c14n-20010315 section 2.1
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https://bugs.php.net/bug.php?id=53655
The XPath query is in accordance to spec [1]. However, we can do it in a
simpler way. We can use a custom callback function instead of a linear
search in XPath to check if a node is visible. Note that comment nodes
are handled internally by libxml2 already, so we do not need to
differentiate between node types. The callback will do an upwards
traversal of the tree until the root of the canonicalization is reached.
In practice this will speed up the application a lot.
[1] https://www.w3.org/TR/2001/REC-xml-c14n-20010315 section 2.1
This can make processing easily 100 times faster for a large document. I generated some random XML documents with https://codebeautify.org/generate-random-xml: https://gist.github.com/nielsdos/369813d1b1c5c146a6fd7992b8ddbc28
file.xml: before -> after:
random.xml: 0.159s -> 0.004s
large.xml: 1.256s -> 0.008s
There's another speed-up I could do by replacing the linear search with a search in a HashTable, that's orthogonal to this but also a smaller time save. That's important for the cases that do use a nodeset. something to do as a follow-up probably.