[xslt] How do I stop I/O?

[David Hyatt <hyatt apple com>]

The problem I was running into is that I/O still occurs if I try to 
stop I/O this way...

static int matchFunc(const char* URI)
{
    return 1; // Match everything.
}

static void* openFunc(const char * URI) {
    return NULL; // Don't ever allow the open.
}


....

xmlRegisterInputCallbacks(matchFunc, openFunc, NULL, NULL);

========

In the case of imported/included stylesheets, my match/open functions 
get called, but if I return NULL from the openFunc, it looks like 
libxslt goes ahead and reads the file itself anyway.  This may become a 
non-issue once I start using the docLoaderFunc, but I'd still like a 
bulletproof way of guaranteeing that libxml isn't doing any I/O.

dave