On Tue, 6 Feb 2007, Johan Geldenhuys wrote:
> I'm not a C++ expert at all and I would like to find out if somebody can
> explain to me how the statement below can be done in Python?
>
> """
> _uint16 ComCRC16(_uint8 val, _uint16 crc)
> {
> _uint8 i;
> _uint16 cval;
>
> for (i=0;i<8;i++)
> {
> if (((crc & 0x0001)^(val & 0x0001))!= 0) crc = (crc >> 1)^
> CCITT_POLY;
> else crc >>= 1;
> val >>= 1;
> }
> return crc
> }
>
> """
I agree with Kent that you might want to see if someone has done this work
already. Still, a translation of the above should be fairly
straightforward. We do have right shifts, and bitwise operators:
############
>>> (42 >> 1)
21
############
The bit pattern of 42 is shifted to the right by one place: in effect,
doing a division by 2.
We also have XORs and bitwise ANDs:
############
>>> (12345678 ^ 0xdeadbeef)
<stdin>:1: FutureWarning: hex/oct constants > sys.maxint will return
positive values in Python 2.4 and up
-569253983
>>>
>>> (12345678 ^ 0xdeadbeef) ^ 0xdeadbeef
<stdin>:1: FutureWarning: hex/oct constants > sys.maxint will return
positive values in Python 2.4 and up
12345678
############
What problems do you have in translating the C++ code to the equivalent
Python code?
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