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CRC

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

Checks Master Coverage License Downloads Supported Python Versions PyPi Package

Available CRC Configurations

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

CRC8 CRC16 CRC32 CRC64
CCITT CCITT CRC32 CRC64
AUTOSAR GSM AUTOSAR
SAJ1850 PROFIBUS BZIP2
BLUETOOTH MODBUS POSIX
MAXIM-DOW

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

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