[Expat-discuss] Re: Feedback on pre-release snapshot

[Reid Spencer]

Attempt #2 .. looks like the list doesn't like signed messages ...

On Sat, 2005-01-29 at 00:45, Reid Spencer wrote:
Hi,

I've been using expat for a while, but pretty silent about it. You asked
for some feedback before the 2.0 release. In general, expat is working
very well for me. I really only have a few small items to report:

1. Documentation inconsistency (see patch). The "Overview" section
   states that the XML_EndNamespaceDeclHandler callback is called
   *before* the corresponding XML_EndElementHandler is called. This
   doesn't make sense because the namespace can't go out of scope
   before an end tag in that namespace is processed. Fortunately, the
   "Reference" section correctly states the EndNamespaceDeclHandler
   callback as coming after the EndElementHandler. The patch just
   corrects the documentation.

2. I would prepare a patch for this, but its somewhat controversial and
   requires an API change. So, I thought it would be better to ask 
   first. The issue has to do with XML_ParserCreate_MM and the 
   XML_Memory_Handling_Suite structure. The memory handling callback 
   functions, as defined in the structure, have no way of knowing for 
   which parser (and thus its user data) memory is being allocated. This
   makes it *really hard* to write a thread safe pooled memory parsing
   system because the memory handling functions can't know which pool
   of memory to act upon. In my particular case, I'm using the Apache
   Portable Runtime's pooled memory handling functions but there's no
   way to pass the pool to the expat memory handling functions. I would
   like to see each of these functions take an additional argument which
   is the user data of the parser into which the functions were
   installed. This shouldn't be too hard to implement since all the
   calls to the memory hanlding routines are done via macros in expat.

3. There's no way to avoid copying data with memory mapped files. If you
   use XML_Parse, it copies the provided input calling XML_GetBuffer
   itself. Alternatively you can call XML_GetBuffer yourself and call
   XML_ParseBuffer. That's fine for files read from a file descriptor. 
   However, its not much help with an mmap'd file where I have the
   entire file in memory and I want expat to swallow it whole without
   any copying at all. I haven't found a way to do this. Is there some
   reason expat can't parse the provided buffer without copying it
   first?

4. It would be handy if the XML_ExternalEntityRefHandler callback was
   passed the user data of the XML_Parser invoking it.

Other than the above, I've had no issues with expat 1.95.8 on Fedora
Core 2 compiled with GCC 3.4.3.

Reid Spencer
XPS Project
http://x-p-s.net/