Blowfish in Python?
tim_one at email.msn.com
Sun Feb 27 11:06:04 CET 2000
> speed was horrendous. >
> I think the main reason was the fact that I had to use _long ints_ for
> calculations, as the normal ints are signed, and apparently the bitwise
> operators do not work as advertised when bit32 is set (=number is
> negative). Or that's my theory anyway - my implementation worked with
> long's and did not work with ints.
Try to whittle this down. Negative ints are nothing special to the bitwise
ops, so if they "don't work as advertised" it would be a (very surprising!)
bug in the implementation. For example, here's the implementation of int &:
static PyObject *
register long a, b;
a = v->ob_ival;
b = w->ob_ival;
return PyInt_FromLong(a & b);
They're all like that -- they can't screw up unless C screws up.
> C implementations [of Blowfish] routinely go to megabytes/second level;
And are routinely highly optimized too. Once you get "&" to work <wink>,
one machine instruction in C is going to turn into a couple of function
calls in Python.
> my Python-with-longs implementation was kilobytes/second, to be precise,
> 2-10k/s depending on the machine.
Using ints will get you the biggest bang for the buck at this point, but
it's never going to be *fast* in pure Python 1.5.2.
not-implying-it-will-be-faster-in-later-versions-either<wink>-ly y'rs - tim
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