crcmanip

A command line interface tool that lets you reverse and freely change CRC checksums through smart file patching.

It's a successor to my previous C++ variant of this project. Even though this version is written in Python, the performance is comparable to the old C++ version.

Features

Patching and calculating CRC checksums for:

• CRC32
• CRC32POSIX (cksum from GNU coreutils)
• CRC16CCITT
• CRC16IBM
• CRC16XMODEM

How it works

It appends a few bytes at the end of the file so that the file checksum computes to a given hexadecimal hash.

Example

$ echo -n hello > test.txt
$ crc32 test.txt
3610a686
$ crcmanip calc test.txt
3610A686
$ crcmanip patch test.txt deadbeef
$ crcmanip calc test.txt
DEADBEEF
$ crc32 test.txt
deadbeef
$ cat test.txt
helloE~40

Installing

To install the newest version from GitHub:

$ git clone https://github.com/rr-/pycrcmanip.git
$ cd pycrcmanip
$ pip install --user .
$ crcmanip --help

Testing

$ pytest

Contributing

To set up the project:

pip install --user poetry poethepoet

git clone https://github.com/rr-/pycrcmanip.git
cd pycrcmanip

poetry install
poetry run pre-commit install

To run tests:

poe test

To run the profiler:

poe profile

To clean build artifacts:

poe clean