anycrc 0.5.0

Python CRC Computation 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. It takes advantage of crcany's ability to efficiently combine multiple CRCs to parallelize the CRC's calculation.

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. To go back to the initial value, use:

>>> crc32.reset()

Specify the starting CRC value:

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

Specify your own CRC parameters:

>>> # width, poly, init, refin, refout, xorout
>>> my_crc = anycrc.CRC(10, 0b0101010101, 0x3ff, True, False, 0)
>>> my_crc.calc('Hello World!')
35

The CRC will be computed in parallel when the input is large enough. If you want to disable parallelism, use:

>>> anycrc.set_parallel(False)

The CRC's width cannot exceed your system's maximum integer width.

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

Benchmarks

Calculating the CRC32 for lorem ipsum 1 million times:

Module	Time Elapsed (s)	Speed (GiB/s)	Relative
anycrc	0.22	1.91	1.00
zlib	0.28	1.47	1.28
fastcrc	0.80	0.52	3.66
crcmod-plus	0.91	0.46	4.13

Calculating the CRC32 for the text of lorem ipsum repeated 1 million times in a single pass:

Module	Time Elapsed (s)	Speed (GiB/s)	Relative
anycrc (parallel)	0.02	23.16	1.00
anycrc (serial)	0.20	2.08	11.15
zlib	0.22	1.92	12.05
fastcrc	0.68	0.61	37.89
crcmod-plus	0.67	0.62	37.40

Tested on a 12th generation Intel i7 processor. Parallel performance will depend on your system.

Notes

- Parallelism is disabled when the length of the input data is under 20k, as the serial method is faster in that case.

- The macOS build only supports the serial version.