crcmod for calculating CRCs

The software in this repository is a modernised version of the crcmod Python package, originally written by Ray Buvel. I took the original source code of crcmod 1.7, dropped support for Python 2, reformatted the source files with black, ran it through ruff, and added a modern build pipeline around it based on setuptools, pytest, tox and cibuildwheel so I can create pre-compiled wheels for the package using Github Actions.

Version 2.0.0 of this package is a drop-in replacement for crcmod 1.7 if you are running Python 3.7 or later.

The contents of the original README file follows from here, with minor alterations to the building and testing instructions to describe how it is done now with the new setup.

---

The software in this package is a Python module for generating objects that compute the Cyclic Redundancy Check (CRC). There is no attempt in this package to explain how the CRC works. There are a number of resources on the web that give a good explanation of the algorithms. Just do a Google search for "crc calculation" and browse till you find what you need. Another resource can be found in chapter 20 of the book "Numerical Recipes in C" by Press et. al.

This package allows the use of any 8, 16, 24, 32, or 64 bit CRC. You can generate a Python function for the selected polynomial or an instance of the Crc class which provides the same interface as the md5 and sha modules from the Python standard library. A Crc class instance can also generate C/C++ source code that can be used in another application.

Guidelines

Documentation is available from the doc strings. It is up to you to decide what polynomials to use in your application. If someone has not specified the polynomials to use, you will need to do some research to find one suitable for your application. Examples are available in the unit tests in the tests folder. You may also use the predefined module to select one of the standard polynomials.

If you need to generate code for another language, I suggest you subclass the Crc class and replace the method generateCode. Use generateCode as a model for the new version.

Dependencies

Python version

This package supports Python 3.7 and newer.

Building C extension

To build the C extension, the appropriate compiler tools for your platform must be installed. Refer to the Python documentation for building C extensions for details. If you have a C compiler and all the usual Python development tools, including the build frontend, then running python -m build should build the package.

Installation

The crcmod-plus package is installed from PyPI using pip. Run the following command:

$ pip install crcmod-plus

Unit testing

crcmod-plus uses pytest as the testing environment. You can run the unit tests with:

$ pytest tests

Code generation

The crcmod package is capable of generating C functions that can be compiled with a C or C++ compiler. In the tests directory, there is an examples.py script that demonstrates how to use the code generator. The result of this is written out to the file examples.c. The generated code was checked to make sure it compiles with the GCC compiler.

License

The crcmod-plus package is released under the MIT license. See the LICENSE file for details.

Authors

• Ray Buvel (the original crcmod package)

Contributors

• Craig McQueen (contributor of the original crcmod package)
• Tamas Nepusz (modernisation into crcmod-plus)