anycrc 1.2.1

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.

Installation

pip install anycrc

Usage

Use an existing model:

>>> import anycrc
>>> crc32 = anycrc.Model('CRC32-MPEG-2')
>>> crc32.calc(b'Hello World!')
2498069329

Read the data in chunks:

>>> crc32.update(b'Hello ')
>>> crc32.update(b'World!')
2498069329

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()
2498069329

To specify the starting CRC value:

>>> crc32.set(3788805874)
>>> crc32.calc('World!')
2498069329

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=False, refout=False, xorout=0x00000000)
>>> crc32.calc('Hello World!')
2498069329

The length of the data can be specified in bits by calling calc_bits or update_bits and passing a bitarray object:

>>> from bitarray import bitarray
>>> crc32 = anycrc.Model('CRC32-MPEG-2')
>>> bits = bitarray()
>>> bits.frombytes(b'Hello World!')
>>> crc32.update_bits(bits[:50])
>>> crc32.update_bits(bits[50:])
2498069329

To use bit lengths with reflected CRCs, create a little endian bitarray object: bitarray(endian='little')

To combine two CRCs, provide the second CRC value along with the length of the CRC's message in bytes:

>>> crc32 = anycrc.Model('CRC32-MPEG-2')
>>> value = crc32.calc(b'World!')
>>> crc32.update(b'Hello ')
>>> crc32.combine(value, len(b'World!'))
2498069329

There is also a combine_bits method where the length argument is expected to be in bits.

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 supported CRC width is 64 bits.

Benchmark

Module	Time Elapsed (s)	Speed (GiB/s)	Relative
anycrc	0.39	2.36	1.00
zlib	0.48	1.93	1.22
fastcrc	1.50	0.62	3.81
crcmod-plus	1.52	0.61	3.85

Tested on a 10th generation Intel i7 processor.