zlib.compress should have a wbits argument

[rhpvorderman]

BPO	43612
Nosy	@ambv, @rhpvorderman
PRs	bpo-43612: Add wbits parameter to zlib.compress #25011 bpo-43613: Faster implementation of gzip.compress and gzip.decompress #27941

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

Show more details

GitHub fields:

assignee = None
closed_at = <Date 2021-09-02.15:03:42.859>
created_at = <Date 2021-03-24.06:04:20.507>
labels = ['extension-modules', 'type-feature', '3.11']
title = 'zlib.compress should have a wbits argument'
updated_at = <Date 2021-09-03.07:28:10.530>
user = 'https://github.com/rhpvorderman'

bugs.python.org fields:

activity = <Date 2021-09-03.07:28:10.530>
actor = 'rhpvorderman'
assignee = 'none'
closed = True
closed_date = <Date 2021-09-02.15:03:42.859>
closer = 'lukasz.langa'
components = ['Extension Modules']
creation = <Date 2021-03-24.06:04:20.507>
creator = 'rhpvorderman'
dependencies = []
files = []
hgrepos = []
issue_num = 43612
keywords = ['patch']
message_count = 4.0
messages = ['389437', '391881', '400922', '400982']
nosy_count = 2.0
nosy_names = ['lukasz.langa', 'rhpvorderman']
pr_nums = ['25011', '27941']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue43612'
versions = ['Python 3.11']

[rhpvorderman]

zlib.compress can now only be used to output zlib blocks.
Arguably zlib.compress(my_data, level, wbits=-15) is even more useful as it gives you a raw deflate block. That is quite interesting if you are writing your own file format and want to use compression, but like to use a different hash.

Also gzip.compress(data, level, mtime) is extremely slow due to it instantiating a GzipFile object which then streams a bytes object. Explicitly not taking advantage of the fact that the bytes object is entirely in memory already (I will create another bug for this). zlib.compress(my_data, level, wbits=31) should be faster in all possible circumstances, but that option is not available now.

[rhpvorderman]

A patch was created, but has not been reviewed yet.

[ambv]

Thanks for your contribution, Ruben! ✨ 🍰 ✨

[rhpvorderman]

Thanks for the review, Lukasz! It was fun to create the PR and optimize the performance for gzip.py as well.