crc

CRC

Calculate CRC checksums, verify CRC checksum, predefined CRC configurations, custom CRC configurations

• Documentation: https://nicoretti.github.io/crc
• Source Code: https://github.com/Nicoretti/crc

Available CRC Configurations

For convenience various frequently used crc configurations ship with the library out of the box.

CRC8	CRC16	CRC32	CRC64
CCITT	XMODEM	CRC32	CRC64
AUTOSAR	GSM	AUTOSAR
SAEJ1850	PROFIBUS	BZIP2
SAEJ1850_ZERO	MODBUS	POSIX
BLUETOOTH	IBM-3740
MAXIM-DOW	KERMIT

If you find yourself in the position, where having a new configuration available out of the box would be desirable, feel free to create a PR or file an issue.

Custom Configurations

If you want to create a custom configuration, you should have the following information available:

🗒 Note:

This library currently only supports bit widths of full bytes 8, 16, 24, 32, ...

• width
• polynom
• init value
• final xor value
• reversed input
• reversed output

In case you only have a name of a specific crc configuration/algorithm and you are unsure what are the specific parameters of it, a look into this crc-catalogue might help.

Requirements

• >= Python 3.8

Installation

pip install crc

Examples

Create a Calculator

Pre defined configuration

from crc import Calculator, Crc8

calculator = Calculator(Crc8.CCITT)

Custom configuration

from crc import Calculator, Configuration

config = Configuration(
    width=8,
    polynomial=0x07,
    init_value=0x00,
    final_xor_value=0x00,
    reverse_input=False,
    reverse_output=False,
)

calculator = Calculator(config)

Calculate a checksum

Standard

from crc import Calculator, Crc8

expected = 0xBC
data = bytes([0, 1, 2, 3, 4, 5])
calculator = Calculator(Crc8.CCITT)

assert expected == calculator.checksum(data)

Optimized for speed

from crc import Calculator, Crc8

expected = 0xBC
data = bytes([0, 1, 2, 3, 4, 5])
calculator = Calculator(Crc8.CCITT, optimized=True)

assert expected == calculator.checksum(data)

Verify a checksum

Standard

from crc import Calculator, Crc8

expected = 0xBC
data = bytes([0, 1, 2, 3, 4, 5])
calculator = Calculator(Crc8.CCITT)

assert calculator.verify(data, expected)

Optimized for speed

from crc import Calculator, Crc8

expected = 0xBC
data = bytes([0, 1, 2, 3, 4, 5])
calculator = Calculator(Crc8.CCITT, optimized=True)

assert calculator.verify(data, expected)

Calculate a checksum with raw registers

Register

from crc import Crc8, Register

expected = 0xBC
data = bytes([0, 1, 2, 3, 4, 5])
register = Register(Crc8.CCITT)

register.init()
register.update(data)
assert expected == register.digest()

TableBasedRegister

from crc import Crc8, TableBasedRegister

expected = 0xBC
data = bytes([0, 1, 2, 3, 4, 5])
register = TableBasedRegister(Crc8.CCITT)

register.init()
register.update(data)
assert expected == register.digest()

References & Resources

• A Painless guide to crc error detection algorithms
• CRC-Catalogue