crcengine

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========== CrcEngine

A python library for CRC calculation providing table-based as well as bit-bashing implementations (for reference).

• Free software: GNU General Public License v3
• Documentation: https://crcengine.readthedocs.io.

Installing

CrcEngine can be installing using pip with

.. code-block:: python

pip install crcengine

Usage

Pre-defined algorithms such as CRC32 are available. Tailored algorithms can be created by calling CrcEngine.create() and other related methods.

A calculation engine for a specific named algorithm can be obtained using CrcEngine.new(). Algorithms which are not pre-defined can be created using CrcEngine.create()

A list of pre-defined algorithms can be obtained using crcengine.algorithms_available()

.. code-block:: python

list(crcengine.algorithms_available()) ['crc8', 'crc8-autosar', 'crc8-bluetooth', 'crc8-ccitt', 'crc8-gsm-b', 'crc8-sae-j1850', 'crc15-can', 'crc16-kermit', 'crc16-ccitt-true', 'crc16-xmodem', 'crc16-autosar', 'crc16-ccitt-false', 'crc16-cdma2000', 'crc16-ibm', 'crc16-modbus', 'crc16-profibus', 'crc24-flexray16-a', 'crc24-flexray16-b', 'crc32', 'crc32-bzip2', 'crc32-c', 'crc64-ecma']

Built-in algorithms

crc8, crc8-autosar, crc8-bluetooth, crc8-ccitt, crc8-gsm-b, crc8-sae-j1850, crc15-can, crc16-kermit, crc16-ccitt-true, crc16-xmodem, crc16-autosar, crc16-ccitt-false, crc16-cdma2000, crc16-ibm, crc16-modbus, crc16-profibus, crc24-flexray16-a, crc24-flexray16-b, crc32, crc32-bzip2, crc32-c, crc64-ecma

Examples
--------
Using a pre-defined algorithm

.. code-block:: python

  import crcengine
  crc_algorithm = crcengine.new('crc32-bzip2')
  result = crc_algorithm(b'123456789')
  print('CRC=0x{:08x}'.format(result))

Output:
> CRC=0xfc891918

Defining an algorithm

.. code-block:: python

  import crcengine
  params = crcengine.CrcParams(0x864cfb, 24, 0xb704ce, reflect_in=False, reflect_out=False, xor_out=0)
  crc_openpgp = crcengine.create_from_params(params)
  # this is equivalent to
  crc_openpgp = crcengine.create(params=params)
  # invocation
  result = crc_openpgp(b'123456789')
  print(f'CRC=0x{result:08x}')

When using create() `params` must be passed as a keyword parameter, since the function also accepts polynomial and seed
parameters for backwards compatibility.

Code Generation
---------------
The library can generate C code for a given table-algorithm. The code produced
is intended to be a reasonable compromise between size, complexity and speed
without requiring allocation of memory for table generation at runtime.

Faster implementations of specific algorithms can be achieved in software which
unroll loops and pipeline the operations different bytes to introduce
parallelism in the calculation see intel_soft_src_ for example. Some processors
also include instructions specifically for crc calculation.

.. _intel_soft_src: https://github.com/intel/soft-crc

Code Generation Example usage:

Generating code into a directory named "out" by passing CRC parameters

.. code-block:: python

params = crcengine.get_algorithm_params('crc32')
crcengine.generate_code(params, 'out/')

or referencing the algorithm by name

.. code-block:: python

crcengine.generate_code('crc16-xmodem', 'out/')

Downloading

• The source is available on github_
• Git clone crcengine.git_
• On pypi.org_

.. _github: https://github.com/GardenTools/crcengine .. _crcengine.git: https://github.com/GardenTools/crcengine.git .. _pypi.org: https://pypi.org/project/crcengine/

Running the tests

Tests can be performed directly by executing pytest in the "tests" directory

Running the Codegen tests

The codegen tests make use of ceedling_ which is expected to be installed as a ruby gem. The unit tests are configured to compile with gcc.

.. _ceedling: https://github.com/ThrowTheSwitch/Ceedling

---

With thanks to Greg Cook for providing such a thoroughly collated list of CRC definitions_

.. _CRC definitions: http://reveng.sourceforge.net/crc-catalogue/all.htm