anycrc 0.9.0

The fastest Python CRC Library

This is a Cython module with bindings to the crcany library. It supports calculating CRC hashes of arbitary sizes as well as updating a CRC hash over time. Anycrc supports all of the CRCs listed in the RevEng CRC Catalogue.

Installation

pip install anycrc

Usage

Use an existing model:

>>> import anycrc
>>> crc32 = anycrc.Model('CRC32')
>>> crc32.calc(b'Hello World!')
472456355

Read the data in chunks:

>>> crc32.update(b'Hello ')
3928882368
>>> crc32.update(b'World!')
472456355

The update method changes the internally stored CRC value, while calc doesn't. You can use get to retrieve the CRC value stored within the object:

>>> crc32.get()
472456355

To specify the starting CRC value:

>>> crc32.set(3928882368)
>>> crc32.calc('World!')
472456355

To go back to the initial value, use:

>>> crc32.reset()

Create a CRC with specific parameters:

>>> crc32 = anycrc.CRC(width=32, poly=0x04c11db7, init=0xffffffff, refin=True, refout=True, xorout=0xffffffff)
>>> crc32.calc('Hello World!')
472456355

For non-reflected CRCs, the length of the data can be specified in bits:

>>> crc32 = anycrc.Model('CRC32-MPEG-2')
>>> data = b'Hello World!'
>>> crc32.update(data, length=48)
>>> crc32.update(data[6:], length=48)
2498069329

Or by using the bitarray module:

>>> from bitarray import bitarray
>>> bits = bitarray()
>>> bits.frombytes(b'Hello World!')
>>> crc32.update(bits[:50])
>>> crc32.update(bits[50:])
2498069329

For a list of pre-built models, check models.py. To get a list of the models at any time, use the following command:

python -m anycrc models

The maximum possible CRC width is 128 bits. CRCs with a width larger than 64 bits use the slower byte-by-byte algorithm.

Benchmark

Module	Time Elapsed (s)	Speed (GiB/s)	Relative
anycrc	0.36	2.56	1.00
zlib	0.48	1.95	1.31
fastcrc	1.50	0.62	4.13
crcmod-plus	1.50	0.62	4.13

Tested on a 10th generation Intel i7 processor.