On Oct 2, 2010, at 5:10 AM, Kurt Sutter wrote:
> Sorry to be obtuse, but it may be that I am overlooking something. Presently,
> we have calls such as
>
> n = PyNumber_Float(obj)
> s = PyString_AsString(obj)
>
> I understand that I would need to generate #defines for all those names, such
> as PyNumber_Float to map them to some table. I would have to initialize that
> table in a big for loop that goes through another table containing the name
> of each function (e.g. "PyNumber_Float". The loop then looks each name up
> with dlsym and initializes the table.
>
> Or can this be done more elegantly?
Declare function pointers:
typeof(PyNumber_Float) *pPyNumber_Float;
typeof(PyString_AsString) * pPyString_AsString;
This can be table-ized with a macro:
#define DOFUNC(f) typeof(f) *p##f
DOFUNC(PyNumber_Float);
DOFUNC(PyString_AsString);
// ...
#undef DOFUNC
During initialization, dynamically load the Python framework with dlopen().
Then, load the function pointers by looking up the symbols:
pPyNumber_Float = dlsym(handle, "PyNumber_Float");
pPyString_AsString = dlsym(handle, "PyString_AsString");
This can be table-ized with a macro:
#define DOFUNC(f) do { if (!(p##f = dlsym(handle, #f))) { \
fprintf(stderr, "Failed to load %s\n", #f); \
goto bail; \
} while (0)
DOFUNC(PyNumber_Float);
DOFUNC(PyString_AsString);
// ...
#undef DOFUNC
Notice that the table within the definitions of DOFUNC is identical in both
cases. So, you can extract it to a separate file and #include it between the
DOFUNC #define and #undef:
#define DOFUNC(f) /* whatever */
#include "PythonFunctionDoFuncs.h"
#undef DOFUNC
That way there's just the one table for both purposes.
Then, you have two choices. 1) Throughout your code, call the functions with
the function pointers. This basically entails prepending a "p" to all the
function names. 2) Use macros to do this for you:
#define PyNumber_Float pPyNumber_Float
#define PyString_AsString pPyString_AsString
I can't think of a technique to table-ize the above. There may be one that I'm
forgetting, but I don't think so. Still, that's just two places to touch for
each Python function you use.
If you want to get fancier, you could have a single file which just lists the
Python functions you use, one per line. Then, a script would generate both the
PythonFunctionDoFuncs.h and a PythonFunctionRedefines.h (with the above macro
definitions) from that list.
Regards,
Ken
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