Also, depending on the use-case, binascii.crc32 might also work fine:
https://docs.python.org/2/library/binascii.html#binascii.crc32
import binascii
def calc_crc(data):
return binascii.crc32(data)
Much simpler.
Chris
On Tue, Sep 2, 2014 at 11:24 AM, Peter Otten <__pete...@web.de> wrote:
> dream4s...@gmail.com wrote:
>
> > I have trouble to implement crc algorithm in python 3.3
> >
> > c version work perfect. I try to use bytes, int and c_types without any
> > success can some who help me:
>
> ctypes is for interfacing with C; don't use it in regular code.
>
> > c version:
> >
> > unsigned short calc_crc(const void *p_dat, int l_dat){
> > unsigned char *dat_ptr;
> > int loopc;
> > unsigned short crc_dat;
> > unsigned char c_work;
> >
> > dat_ptr = (unsigned char*)p_dat;
> > crc_dat = 0x0000;
> > for (; l_dat > 0; l_dat--)
> > {
> > c_work = *(dat_ptr++);
> > for (loopc = 0; loopc < 8; loopc++)
> > {
> > if ((((unsigned char )(crc_dat & 0x0001)) ^
> > (c_work & 0x01)) == 0x01)
> > {
> > crc_dat >>=1 ;
> > crc_dat ^=0x8408;
> > } else {
> > crc_dat >>=1;
> >
> > }
> > c_work >>=1;
> > }
> > }
> > return(crc_dat);
> > }
>
> A near-literal translation would be:
>
> def calc_crc(data):
> crc = 0
> for work in data:
> for i in range(8):
> if (crc & 1) ^ (work & 1):
> crc >>= 1
> crc ^= 0x8408
> else:
> crc >>= 1
> work >>= 1
> return crc
>
> I don't see any operation where the "unboundedness" of Python's integer
> type
> could be a problem -- but no guarantees.
>
> --
> https://mail.python.org/mailman/listinfo/python-list
>
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