As part of some django usage I need to get some ReportLab C extensions into a
state where they can be safely used with mod_python.
Unfortunately we have C code that seems incompatible with mod_python and I'm
looking for ways to improve the situation.
Basically the main things that are wrong are all privately cached copies of
python variables. This sample code
static PyObject *_pdfmetrics_fonts = NULL;
static PyObject *_pdfmetrics_ffar = NULL;
..........
if(!_pdfmetrics_fonts){
res = PyImport_ImportModule("reportlab.pdfbase.pdfmetrics");
if(!res) ERROR_EXIT();
_o1 = _GetAttrString(res,"_fonts");
if(!_o1) ERROR_EXIT();
_o2 = _GetAttrString(res,"findFontAndRegister");
if(!_o2) ERROR_EXIT();
_pdfmetrics_fonts = _o1;
_pdfmetrics_ffar = _o2;
Py_DECREF(res); _o1 = _o2 = res = NULL;
}
if((res = PyObject_GetItem(_pdfmetrics_fonts,fontName))) return res;
...........
illustrates the general problem. If called first by interpreter A I'll get the
values from interpreter A. When later called by interpreter B I'll be using the
wrong values and _pdfmetrics_ffar can alter the wrong interpreter's data.
The functions themselves are fairly small, but may be called many times so
they're worth speeding up.
Is there a simple/cheap way for C code to cache these sorts of module level
globals on a per interpreter basis? Is there even a way to tell which
interpreter I'm being called in?
Anything too costly will probably bust any speedup. Luckily I don't think we
have too many of these cached variables so it's possible we may be able to get
away with just dropping the caching for some and eliminating others.
--
Robin Becker
--
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