crc_CRCCCITT.py

from PyCRC.CRCCCITT import CRCCCITT
from PyCRC.CRC32 import CRC32
from PyCRC.CRC16 import CRC16
from PyCRC.CRC16DNP import CRC16DNP
from PyCRC.CRC16Kermit import CRC16Kermit
from PyCRC.CRC16SICK import CRC16SICK

src = [
#    'surface_galaxy.bmp',
    'surface_01_red_arron.bmp'
]


def crc16_ccitt_direct(crc, data):
    msb = crc >> 8
    lsb = crc & 255
    for c in data:
        # x = ord(c) ^ msb
        x = c ^ msb
        x ^= (x >> 4)
        msb = (lsb ^ (x >> 3) ^ (x << 4)) & 255
        lsb = (x ^ (x << 5)) & 255
    return (msb << 8) + lsb

POLYNOMIAL = 0x11021
PRESET = 0

def _initial(c):
    crc = 0
    c = c << 8
    for j in range(8):
        if (crc ^ c) & 0x8000:
            crc = (crc << 1) ^ POLYNOMIAL
        else:
            crc = crc << 1
        c = c << 1
    return crc

def _update_crc(crc, c, _tab):
    cc = 0xff & c

    tmp = (crc >> 8) ^ cc
    crc = (crc << 8) ^ _tab[tmp & 0xff]
    crc = crc & 0xffff
#    print (crc)

    return crc

def calc_manu(bs, present = PRESET):
    '''
    x^16+x^12+x^5+1

    unsigned short crc16(const unsigned char* data_p, unsigned char length)
    {
        unsigned char x;
        unsigned short crc = 0xFFFF;

        while (length--)
        {
            x = crc >> 8 ^ *data_p++;
            x ^= x>>4;
            crc = (crc << 8) ^ ((unsigned short)(x << 12)) ^ ((unsigned short)(x <<5)) ^ ((unsigned short)x);
        }
        return crc;
    }
    '''
    # return crc16_ccitt_direct(0, bs)
    _tab = [ _initial(i) for i in range(256) ]
    crc = present
    for b in bs:
        crc = _update_crc(crc, b, _tab)
    return crc

# bs = [0x0,0x1,0x2,0x3,0x4,0x5]

bimage = open(src[0], 'rb').read(90000)
print(src[0] + ": " +str(len(bimage)))
print("CRCCCITT: " + hex(CRCCCITT().calculate(bimage)))
print("manu: " +hex(calc_manu(bimage)))
print("FFFF: " +hex(calc_manu(bimage, present = 0xFFFF)))


bs = '123456'.encode('utf-8')
print(str(bs) + ": " +str(len(bs)))
print("CRCCCITT: " + hex(CRCCCITT().calculate(bs)))
print("manu: " +hex(calc_manu(bs)))
print("FFFF: " +hex(calc_manu(bs, present = 0xFFFF)))

# print("CRCCCITT" + hex(CRCCCITT().calculate(bs)))
# for s in src:
#     bs = open(s, 'rb').read(90000)
#     # print(len(bs))
#     print(s + ": " +hex(CRCCCITT().calculate(bs)))
#     print("manu: " +hex(calc_manu(bs)))
#     print("CRC32:" + hex(CRCCCITT().calculate(bs)))
#     print("CRC16:" + hex(CRC16().calculate(s)))
#     print("CRC16DNP:" + hex(CRC16DNP().calculate(s)))
#     print("CRC16Kermit:" + hex(CRC16Kermit().calculate(s)))
#     print("CRC16SICK:" + hex(CRC16SICK().calculate(s)))

'''
surface_01_red_arron.bmp: 86454
CRCCCITT: 0x2d2f
manu: 0x2d2f
FFFF: 0x9c92
b'123456': 6
CRCCCITT: 0x20e4
manu: 0x20e4
FFFF: 0x2ef4
'''