util: create new abstraction for compression engines
Currently, util.py has "compressors" and "decompressors" dicts
mapping compression algorithms to callables returning objects that
perform well-defined operations. In addition, revlog.py has code
for calling into a compressor or decompressor explicitly. And, there
is code in the wire protocol for performing zlib compression.
The 3rd party lz4revlog extension has demonstrated the utility of
supporting alternative compression formats for revlog storage. But
it stops short of supporting lz4 for bundles and the wire protocol.
There are also plans to support zstd as a general compression
replacement.
So, there appears to be a market for a unified API for registering
compression engines. This commit starts the process of establishing
one.
This commit establishes a base class/interface for defining
compression engines and how they will be used. A collection class
to hold references to registered compression engines has also been
introduced.
The built-in zlib, bz2, truncated bz2, and no-op compression engines
are registered with a singleton instance of the collection class.
The compression engine API will change once consumers are ported
to the new API and some common patterns can be simplified at the
engine API level. So don't get too attached to the API...
[This file is here for historical purposes, all recent contributors
should appear in the changelog directly]
Andrea Arcangeli <andrea at suse.de>
Thomas Arendsen Hein <thomas at intevation.de>
Goffredo Baroncelli <kreijack at libero.it>
Muli Ben-Yehuda <mulix at mulix.org>
Mikael Berthe <mikael at lilotux.net>
Benoit Boissinot <bboissin at gmail.com>
Brendan Cully <brendan at kublai.com>
Vincent Danjean <vdanjean.ml at free.fr>
Jake Edge <jake at edge2.net>
Michael Fetterman <michael.fetterman at intel.com>
Edouard Gomez <ed.gomez at free.fr>
Eric Hopper <hopper at omnifarious.org>
Alecs King <alecsk at gmail.com>
Volker Kleinfeld <Volker.Kleinfeld at gmx.de>
Vadim Lebedev <vadim at mbdsys.com>
Christopher Li <hg at chrisli.org>
Chris Mason <mason at suse.com>
Colin McMillen <mcmillen at cs.cmu.edu>
Wojciech Milkowski <wmilkowski at interia.pl>
Chad Netzer <chad.netzer at gmail.com>
Bryan O'Sullivan <bos at serpentine.com>
Vicent Seguí Pascual <vseguip at gmail.com>
Sean Perry <shaleh at speakeasy.net>
Nguyen Anh Quynh <aquynh at gmail.com>
Ollivier Robert <roberto at keltia.freenix.fr>
Alexander Schremmer <alex at alexanderweb.de>
Arun Sharma <arun at sharma-home.net>
Josef "Jeff" Sipek <jeffpc at optonline.net>
Kevin Smith <yarcs at qualitycode.com>
TK Soh <teekaysoh at yahoo.com>
Radoslaw Szkodzinski <astralstorm at gorzow.mm.pl>
Samuel Tardieu <sam at rfc1149.net>
K Thananchayan <thananck at yahoo.com>
Andrew Thompson <andrewkt at aktzero.com>
Michael S. Tsirkin <mst at mellanox.co.il>
Rafael Villar Burke <pachi at mmn-arquitectos.com>
Tristan Wibberley <tristan at wibberley.org>
Mark Williamson <mark.williamson at cl.cam.ac.uk>