Re: [boost] [xml] Brainstorming / Request for Comments, Suggestions, Opinions ...

From: Nils Springob (nils.springob_at_[hidden])
Date: 2006-09-07 12:13:13

Hi ,

Perhaps you can get some additional ideas from my xml lib, it's not 
finished yet, but it already works. You can download it here:

http://download.nicai-systems.com/xmlpp/xmlpp.tar.gz

I am using my library to transmit data over a tcp stream (wrapped in an 
std::istream and an std::ostream), load and store measurement data and 
for handling configuration data in xml-files.
I wrote a class generator which generates derived xml element nodes. The 
generator itself uses the library, and generates it's own source code ;-)

I started developing an xml-library for c++ because the existing 
libraries did not fit my taste. I think they are written for other 
languages than c++: DOM and SAX are good and nice for java and .net 
applications. Libxml is to big, and TinyXml supports only the DOM 
interface...

When I use xml, I can ensure that everything is coded in UTF-8, so it 
would be possible to work with char based std::streams and std::strings, 
and if the file would be coded in "real Unicode", there would be the 
possibility to use the wchar based classes.

My design of the library has 3 different layers:

The requirements for the fist (tag based) layer were (demo1):
  - Compatibility with std::istream and std::ostream
  - Extremely lightweight, not a huge xml framework...

The requirements for the second layer were (demo2):
  - Access to an element tree, which may contain a whole xml document or 
a part of it.
  - The parser can load the whole document, or a single element with or 
without it's contents.

The requirement for the third layer were (demo3 and xclassgen):
  - Access to the elements of the tree by derived classes which can be 
automatically generated by an xml:schema definition file.

The current limitations of the library are:
- no encoding support, but UTF-8 can be handled with std::string
- no namespaces, but it should be possible to change this...
- the automatic generation of the derived classes needs at the moment a 
special xml definition file, it does not work with the xml:schema file

Loading an xml document is always done by a pull parser based on an 
std::istream, pushing will be handled by using a thread wrapped around 
the pull parser (so there is no need to use an self made stack....)

std::ifstream in("test.xml");
xml::ixmlstream xin(in);
while(true)
{
   xml::node n = xin.getNextNode();
   if (n==0) break;
   handle(n);
   delete n;
}

Regards,
Nils