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.
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