[xml] xmlReaderForIO

[Minor Gordon <gordon zib de>]

Hello,

I am trying to use xmlReaderForIO() to read from some custom buffer 
structures.  I couldn't find any examples of this in the documentation, 
so I'm winging it.
Environment is MSVC7, with the pre-compiled DLLs.  A normal 
xmlReaderForFile works fine.

For the IO reader, I have:
xmlTextReaderPtr reader = 
xmlReaderForIO((xmlInputReadCallback)xmlReadBuffers,NULL,NULL,"sbns", 
NULL, 0);

which I've tried in several variations (giving an encoding "utf-8", 
makin a dummy close callback, passing an object in ioctx, etc.).  This 
is the variation I want.

The function xmlReadBuffers has the signature:
int xmlReadBuffers(void * context, char * buffer, int len)

When the program hits the first line (reader = ) it jumps into nowhere.  
Not exactly nowhere -- access violation at 0x00000010.  Like it's trying 
to access an element of an array that's actually a NULL pointer.
I don't think it's an environment problem, because the file reader works 
(so the DLLs are loading).

Is there something with the code?

Minor