Faster zlib and gzip compatible compression and decompression by providing Python bindings for the ISA-L library.

This package provides Python bindings for the ISA-L library. The Intel(R) Intelligent Storage Acceleration Library (ISA-L) implements several key algorithms in assembly language. This includes a variety of functions to provide zlib/gzip-compatible compression.

python-isal provides the bindings by offering an isal_zlib and igzip module which are usable as drop-in replacements for the zlib and gzip modules from the stdlib (with some minor exceptions, see below).

Python-isal has faster versions of the stdlib's zlib and gzip module these are called isal_zlib and igzip respectively.

They can be imported as follows

from isal import isal_zlib
from isal import igzip

isal_zlib and igzip are meant to be used as drop in replacements so their api and functions are the same as the stdlib's modules. Except where ISA-L does not support the same calls as zlib (See differences below).

A full API documentation can be found on our readthedocs page.

python -m isal.igzip implements a simple gzip-like command line application (just like python -m gzip).

• with pip: pip install isal
• with conda: conda install python-isal

Installation is supported on Linux, Windows and MacOS. For more advanced installation options check the documentation.

• Compression level 0 in zlib and gzip means no compression, while in isal_zlib and igzip this is the lowest compression level. This is a design choice that was inherited from the ISA-L library.
• Compression levels range from 0 to 3, not 1 to 9. isal_zlib.Z_DEFAULT_COMPRESSION has been aliased to isal_zlib.ISAL_DEFAULT_COMPRESSION (2).
• isal_zlib only supports NO_FLUSH, SYNC_FLUSH, FULL_FLUSH and FINISH_FLUSH. Other flush modes are not supported and will raise errors.
• zlib.Z_DEFAULT_STRATEGY, zlib.Z_RLE etc. are exposed as isal_zlib.Z_DEFAULT_STRATEGY, isal_zlib.Z_RLE etc. for compatibility reasons. However, isal_zlib only supports a default strategy and will give warnings when other strategies are used.
• zlib supports different memory levels from 1 to 9 (with 8 default). isal_zlib supports memory levels smallest, small, medium, large and largest. These have been mapped to levels 1, 2-3, 4-6, 7-8 and 9. So isal_zlib can be used with zlib compatible memory levels.
• isal_zlib methods have a data argument which is positional only. In isal_zlib this is not enforced and it can also called as keyword argument. This is due to implementing isal_zlib in cython and maintaining backwards compatibility with python 3.6.
• igzip.open returns a class IGzipFile instead of GzipFile. Since the compression levels are not compatible, a difference in naming was chosen to reflect this. igzip.GzipFile does exist as an alias of igzip.IGzipFile for compatibility reasons.

Please make a PR or issue if you feel anything can be improved. Bug reports are also very welcome. Please report them on the github issue tracker.