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Stored (uncompressed) ZipExtFile in zipfile can be seekable at lower cost #88339
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assignee = 'https://github.com/gpshead'
closed_at = None
created_at = <Date 2021-05-19.02:28:39.857>
labels = ['type-feature', 'library', '3.11']
title = 'Stored (uncompressed) ZipExtFile in zipfile can be seekable at lower cost'
updated_at = <Date 2021-08-18.17:30:30.110>
user = 'https://github.com/JuniorJPDJ'bugs.python.org fields:
activity = <Date 2021-08-18.17:30:30.110>
actor = 'gregory.p.smith'
assignee = 'gregory.p.smith'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2021-05-19.02:28:39.857>
creator = 'juniorjpdj'
dependencies = []
files = []
hgrepos = []
issue_num = 44173
keywords = ['patch']
message_count = 1.0
messages = ['393918']
nosy_count = 5.0
nosy_names = ['twouters', 'gregory.p.smith', 'alanmcintyre', 'serhiy.storchaka', 'juniorjpdj']
pr_nums = ['26227', '27737']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue44173'
versions = ['Python 3.11']Metadata
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JuniorJPDJ commentedon May 19, 2021
At the moment stored ZipExtFile is being read to the place of seek like all other compressed variants.
It's not needed as it's possible to freely seek uncompressed file inside zip without this penalty.
Lots of apps depend on ZipExtFile seeking ability and it would lower performance and IO penalty significantly.
I've POC patch created.
It disables CRC checking after first seek as it's impossible to check CRC if we are not reading whole file.
gh-88339: enable fast seeking of uncompressed unencrypted zipfile.Zip…
gpshead commentedon Aug 6, 2022
merged for 3.12. thanks for the contribution!
pythongh-88339: enable fast seeking of uncompressed unencrypted zipfi…