Re: [Boost-users] [Property Tree] Reading & Writing XML

Subject: Re: [Boost-users] [Property Tree] Reading & Writing XML
From: Sebastian Redl (sebastian.redl_at_[hidden])
Date: 2010-06-09 16:29:29

Brent Arias wrote:
>
> Regarding the write_xml routine used with the boost Property Tree, it
> evidently does not utilize the underlying RapidXML tool?  Said
> differently, is it true Property Tree relies on RapidXML for the
> reading step, but not the writing step?
>
Correct.
>
>   I ask because I may be swapping Property Tree’s dependence on
> RapidXML, for a Unicode branch of pugiXML
> <http://code.google.com/p/pugixml/source/browse/#svn/branches/unicode>
> instead, so that I get free conversions to-and-from UTF-16/UTF-8.  But
> if Property Tree does not use the underlying XML parser for the
> writing step, then I won’t get that free conversion when writing back
> to disk.
>
Correct. That said, if you have a wptree and imbue the output stream
with a utf8 codecvt facet, you get UTF-8 XML.
>
>  
>
> As for the read_xml func, is it also true that “twice” the memory is
> needed, because RapidXML will load a document into a DOM, and then the
> Property Tree will allocate more memory to convert the DOM content
> into its own format?
>
Sort of. Note, though, that RapidXML is an in-place parser, i.e. all the
string data of the nodes is represented by references into the original
XML code. (This is also why some things, like entity expansion, are not
really supported by RapidXML.) So you spend memory once for the input
text, a bit of memory for the nodes of the DOM, and then a lot of memory
on the property tree.

I have a feeling though that cases where this memory is a concern may
not be ideal use cases for proptree. At least that's not what I focus on
for proptree. But of course libraries get used for purposes not
originally intended by the author (or maintainer in my case) all the time.

Sebastian