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Implementation of crc16 (CRC-16-CCITT) in python
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def crc16(data: bytes, poly=0x8408): | |
''' | |
CRC-16-CCITT Algorithm | |
''' | |
data = bytearray(data) | |
crc = 0xFFFF | |
for b in data: | |
cur_byte = 0xFF & b | |
for _ in range(0, 8): | |
if (crc & 0x0001) ^ (cur_byte & 0x0001): | |
crc = (crc >> 1) ^ poly | |
else: | |
crc >>= 1 | |
cur_byte >>= 1 | |
crc = (~crc & 0xFFFF) | |
crc = (crc << 8) | ((crc >> 8) & 0xFF) | |
return crc & 0xFFFF |
kjm1102
commented
Apr 27, 2023
via email
def crc16(data):
'''
CRC-16 (CCITT) implemented with a precomputed lookup table
'''
table = [
0x0000, 0x1021, 0x2042, 0x3063, 0x4084, 0x50A5, 0x60C6, 0x70E7,
0x8108, 0x9129, 0xA14A, 0xB16B, 0xC18C, 0xD1AD, 0xE1CE, 0xF1EF,
0x1231, 0x0210, 0x3273, 0x2252, 0x52B5, 0x4294, 0x72F7, 0x62D6,
0x9339, 0x8318, 0xB37B, 0xA35A, 0xD3BD, 0xC39C, 0xF3FF, 0xE3DE,
0x2462, 0x3443, 0x0420, 0x1401, 0x64E6, 0x74C7, 0x44A4, 0x5485,
0xA56A, 0xB54B, 0x8528, 0x9509, 0xE5EE, 0xF5CF, 0xC5AC, 0xD58D,
0x3653, 0x2672, 0x1611, 0x0630, 0x76D7, 0x66F6, 0x5695, 0x46B4,
0xB75B, 0xA77A, 0x9719, 0x8738, 0xF7DF, 0xE7FE, 0xD79D, 0xC7BC,
0x48C4, 0x58E5, 0x6886, 0x78A7, 0x0840, 0x1861, 0x2802, 0x3823,
0xC9CC, 0xD9ED, 0xE98E, 0xF9AF, 0x8948, 0x9969, 0xA90A, 0xB92B,
0x5AF5, 0x4AD4, 0x7AB7, 0x6A96, 0x1A71, 0x0A50, 0x3A33, 0x2A12,
0xDBFD, 0xCBDC, 0xFBBF, 0xEB9E, 0x9B79, 0x8B58, 0xBB3B, 0xAB1A,
0x6CA6, 0x7C87, 0x4CE4, 0x5CC5, 0x2C22, 0x3C03, 0x0C60, 0x1C41,
0xEDAE, 0xFD8F, 0xCDEC, 0xDDCD, 0xAD2A, 0xBD0B, 0x8D68, 0x9D49,
0x7E97, 0x6EB6, 0x5ED5, 0x4EF4, 0x3E13, 0x2E32, 0x1E51, 0x0E70,
0xFF9F, 0xEFBE, 0xDFDD, 0xCFFC, 0xBF1B, 0xAF3A, 0x9F59, 0x8F78,
0x9188, 0x81A9, 0xB1CA, 0xA1EB, 0xD10C, 0xC12D, 0xF14E, 0xE16F,
0x1080, 0x00A1, 0x30C2, 0x20E3, 0x5004, 0x4025, 0x7046, 0x6067,
0x83B9, 0x9398, 0xA3FB, 0xB3DA, 0xC33D, 0xD31C, 0xE37F, 0xF35E,
0x02B1, 0x1290, 0x22F3, 0x32D2, 0x4235, 0x5214, 0x6277, 0x7256,
0xB5EA, 0xA5CB, 0x95A8, 0x8589, 0xF56E, 0xE54F, 0xD52C, 0xC50D,
0x34E2, 0x24C3, 0x14A0, 0x0481, 0x7466, 0x6447, 0x5424, 0x4405,
0xA7DB, 0xB7FA, 0x8799, 0x97B8, 0xE75F, 0xF77E, 0xC71D, 0xD73C,
0x26D3, 0x36F2, 0x0691, 0x16B0, 0x6657, 0x7676, 0x4615, 0x5634,
0xD94C, 0xC96D, 0xF90E, 0xE92F, 0x99C8, 0x89E9, 0xB98A, 0xA9AB,
0x5844, 0x4865, 0x7806, 0x6827, 0x18C0, 0x08E1, 0x3882, 0x28A3,
0xCB7D, 0xDB5C, 0xEB3F, 0xFB1E, 0x8BF9, 0x9BD8, 0xABBB, 0xBB9A,
0x4A75, 0x5A54, 0x6A37, 0x7A16, 0x0AF1, 0x1AD0, 0x2AB3, 0x3A92,
0xFD2E, 0xED0F, 0xDD6C, 0xCD4D, 0xBDAA, 0xAD8B, 0x9DE8, 0x8DC9,
0x7C26, 0x6C07, 0x5C64, 0x4C45, 0x3CA2, 0x2C83, 0x1CE0, 0x0CC1,
0xEF1F, 0xFF3E, 0xCF5D, 0xDF7C, 0xAF9B, 0xBFBA, 0x8FD9, 0x9FF8,
0x6E17, 0x7E36, 0x4E55, 0x5E74, 0x2E93, 0x3EB2, 0x0ED1, 0x1EF0
]
crc = 0xFFFF
for byte in data:
crc = (crc << 8) ^ table[(crc >> 8) ^ byte]
crc &= 0xFFFF # important, crc
must stay 16bits all the way through
print(crc, '{:04X}'.format(crc))
return('{:04X}'.format(crc))
crc16(b'\x92')
…On Thu, 27 Apr 2023 at 17:44, TrajcheKrstev ***@***.***> wrote:
***@***.**** commented on this gist.
------------------------------
420B is returned by this particular variant of crc16 if you feed it with
b'45377 So if you can figure out the connection between that & your list
you're good to go. Unfortunately nothing obvious comes to mind.
… <#m_-2639103623622540039_>
Well converting it from binary to hexadecimal it’s 0x92 and according to
https://crccalc.com/ that should return 420B for CRC-16-CCITT-FALSE. If
that is a different one than the above code, how can i change the code for
this variant that i need?
—
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This also works
def crc_16(data):
crc=0xFFFF; POLYNOMIAL=0x1021
for c in data:
crc=crc^(c<<8)
for j in range(8): crc=(crc<<1)^POLYNOMIAL if crc & 0x8000 else crc<<1
crc = crc & 0xFFFF; crc='%.04X'%crc
print('msg', data, ' crc', crc); return crc
crc_16(b'\x92')
On Thu, 27 Apr 2023 at 18:35, Kris Mclean ***@***.***>
wrote:
…
def crc16(data):
'''
CRC-16 (CCITT) implemented with a precomputed lookup table
'''
table = [
0x0000, 0x1021, 0x2042, 0x3063, 0x4084, 0x50A5, 0x60C6, 0x70E7,
0x8108, 0x9129, 0xA14A, 0xB16B, 0xC18C, 0xD1AD, 0xE1CE, 0xF1EF,
0x1231, 0x0210, 0x3273, 0x2252, 0x52B5, 0x4294, 0x72F7, 0x62D6,
0x9339, 0x8318, 0xB37B, 0xA35A, 0xD3BD, 0xC39C, 0xF3FF, 0xE3DE,
0x2462, 0x3443, 0x0420, 0x1401, 0x64E6, 0x74C7, 0x44A4, 0x5485,
0xA56A, 0xB54B, 0x8528, 0x9509, 0xE5EE, 0xF5CF, 0xC5AC, 0xD58D,
0x3653, 0x2672, 0x1611, 0x0630, 0x76D7, 0x66F6, 0x5695, 0x46B4,
0xB75B, 0xA77A, 0x9719, 0x8738, 0xF7DF, 0xE7FE, 0xD79D, 0xC7BC,
0x48C4, 0x58E5, 0x6886, 0x78A7, 0x0840, 0x1861, 0x2802, 0x3823,
0xC9CC, 0xD9ED, 0xE98E, 0xF9AF, 0x8948, 0x9969, 0xA90A, 0xB92B,
0x5AF5, 0x4AD4, 0x7AB7, 0x6A96, 0x1A71, 0x0A50, 0x3A33, 0x2A12,
0xDBFD, 0xCBDC, 0xFBBF, 0xEB9E, 0x9B79, 0x8B58, 0xBB3B, 0xAB1A,
0x6CA6, 0x7C87, 0x4CE4, 0x5CC5, 0x2C22, 0x3C03, 0x0C60, 0x1C41,
0xEDAE, 0xFD8F, 0xCDEC, 0xDDCD, 0xAD2A, 0xBD0B, 0x8D68, 0x9D49,
0x7E97, 0x6EB6, 0x5ED5, 0x4EF4, 0x3E13, 0x2E32, 0x1E51, 0x0E70,
0xFF9F, 0xEFBE, 0xDFDD, 0xCFFC, 0xBF1B, 0xAF3A, 0x9F59, 0x8F78,
0x9188, 0x81A9, 0xB1CA, 0xA1EB, 0xD10C, 0xC12D, 0xF14E, 0xE16F,
0x1080, 0x00A1, 0x30C2, 0x20E3, 0x5004, 0x4025, 0x7046, 0x6067,
0x83B9, 0x9398, 0xA3FB, 0xB3DA, 0xC33D, 0xD31C, 0xE37F, 0xF35E,
0x02B1, 0x1290, 0x22F3, 0x32D2, 0x4235, 0x5214, 0x6277, 0x7256,
0xB5EA, 0xA5CB, 0x95A8, 0x8589, 0xF56E, 0xE54F, 0xD52C, 0xC50D,
0x34E2, 0x24C3, 0x14A0, 0x0481, 0x7466, 0x6447, 0x5424, 0x4405,
0xA7DB, 0xB7FA, 0x8799, 0x97B8, 0xE75F, 0xF77E, 0xC71D, 0xD73C,
0x26D3, 0x36F2, 0x0691, 0x16B0, 0x6657, 0x7676, 0x4615, 0x5634,
0xD94C, 0xC96D, 0xF90E, 0xE92F, 0x99C8, 0x89E9, 0xB98A, 0xA9AB,
0x5844, 0x4865, 0x7806, 0x6827, 0x18C0, 0x08E1, 0x3882, 0x28A3,
0xCB7D, 0xDB5C, 0xEB3F, 0xFB1E, 0x8BF9, 0x9BD8, 0xABBB, 0xBB9A,
0x4A75, 0x5A54, 0x6A37, 0x7A16, 0x0AF1, 0x1AD0, 0x2AB3, 0x3A92,
0xFD2E, 0xED0F, 0xDD6C, 0xCD4D, 0xBDAA, 0xAD8B, 0x9DE8, 0x8DC9,
0x7C26, 0x6C07, 0x5C64, 0x4C45, 0x3CA2, 0x2C83, 0x1CE0, 0x0CC1,
0xEF1F, 0xFF3E, 0xCF5D, 0xDF7C, 0xAF9B, 0xBFBA, 0x8FD9, 0x9FF8,
0x6E17, 0x7E36, 0x4E55, 0x5E74, 0x2E93, 0x3EB2, 0x0ED1, 0x1EF0
]
crc = 0xFFFF
for byte in data:
crc = (crc << 8) ^ table[(crc >> 8) ^ byte]
crc &= 0xFFFF # important, crc
must stay 16bits all the way through
print(crc, '{:04X}'.format(crc))
return('{:04X}'.format(crc))
crc16(b'\x92')
On Thu, 27 Apr 2023 at 17:44, TrajcheKrstev ***@***.***>
wrote:
> ***@***.**** commented on this gist.
> ------------------------------
>
> 420B is returned by this particular variant of crc16 if you feed it with
> b'45377 So if you can figure out the connection between that & your list
> you're good to go. Unfortunately nothing obvious comes to mind.
> … <#m_6125718102667563380_m_-2639103623622540039_>
>
> Well converting it from binary to hexadecimal it’s 0x92 and according to
> https://crccalc.com/ that should return 420B for CRC-16-CCITT-FALSE. If
> that is a different one than the above code, how can i change the code for
> this variant that i need?
>
> —
> Reply to this email directly, view it on GitHub
> <https://gist.github.com/oysstu/68072c44c02879a2abf94ef350d1c7c6#gistcomment-4550183>
> or unsubscribe
> <https://github.com/notifications/unsubscribe-auth/AV562M27VG3QMPOCZ3JCZHDXDIPURBFKMF2HI4TJMJ2XIZLTSKBKK5TBNR2WLJDHNFZXJJDOMFWWLK3UNBZGKYLEL52HS4DFQKSXMYLMOVS2I5DSOVS2I3TBNVS3W5DIOJSWCZC7OBQXE5DJMNUXAYLOORPWCY3UNF3GS5DZVRZXKYTKMVRXIX3UPFYGLK2HNFZXIQ3PNVWWK3TUUZ2G64DJMNZZDAVEOR4XAZNEM5UXG5FFOZQWY5LFVAZTOMRWGU4DSOFHORZGSZ3HMVZKMY3SMVQXIZI>
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> You are receiving this email because you commented on the thread.
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>
return('{:04X}'.format(crc))
Thanks, it works. Is there a better way to convert the list to be in a suitable format than this ChatGPT suggestion? (i'm very new to python)
bits_string = ''.join(str(bit) for bit in input_list)
int_value = int(bits_string, 2)
hex_value = hex(int_value)
hex_string = hex_value.replace('0x', '0x0') if len(hex_value) % 2 == 1 else hex_value
hex_value = bytes.fromhex(hex_string[2:])
crc=crc16(hex_value)
fromhex won't work if you're using upython? You could try
import binascii
bits_string = ''.join(str(bit) for bit in input_list)
int_value = int(bits_string, 2)
hex = hex(int_value)[2:]
hex_value = binascii.unhexlify(hex)
…On Thu, 27 Apr 2023 at 19:03, TrajcheKrstev ***@***.***> wrote:
***@***.**** commented on this gist.
------------------------------
return('{:04X}'.format(crc))
Thanks, it works. Is there a better way to convert the list to be in a
suitable format than this ChatGPT suggestion?
bits_string = ''.join(str(bit) for bit in input_list)
int_value = int(bits_string, 2)
hex_value = hex(int_value)
hex_string = hex_value.replace('0x', '0x0') if len(hex_value) % 2 == 1
else hex_value
hex_value = bytes.fromhex(hex_string[2:])
crc=crc16(hex_value)
—
Reply to this email directly, view it on GitHub
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@pragma31 if I have a payload like this : " 623e0200000000000000000000000000" where 623e is crc given by a software i want to verify it , so what should i pass to get this value to the function that you have written here crc16 , thanks
same if i want to use https://crccalc.com/
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