Add PyFloat_(Pack|Unpack)(2|4|8) to the public C API
Closed this issue · 12 comments
| BPO | 46906 |
|---|---|
| Nosy | @malemburg, @rhettinger, @mdickinson, @vstinner, @methane |
| PRs |
Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.
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GitHub fields:
assignee = None
closed_at = <Date 2022-03-14.15:58:36.669>
created_at = <Date 2022-03-03.03:09:32.087>
labels = ['expert-C-API', '3.11']
title = 'Add PyFloat_(Pack|Unpack)(2|4|8) to the public C API'
updated_at = <Date 2022-03-14.15:58:36.668>
user = 'https://github.com/methane'bugs.python.org fields:
activity = <Date 2022-03-14.15:58:36.668>
actor = 'vstinner'
assignee = 'none'
closed = True
closed_date = <Date 2022-03-14.15:58:36.669>
closer = 'vstinner'
components = ['C API']
creation = <Date 2022-03-03.03:09:32.087>
creator = 'methane'
dependencies = []
files = []
hgrepos = []
issue_num = 46906
keywords = ['patch']
message_count = 12.0
messages = ['414401', '414410', '414411', '414416', '414419', '414427', '414944', '414952', '414953', '414954', '415151', '415152']
nosy_count = 6.0
nosy_names = ['lemburg', 'rhettinger', 'mark.dickinson', 'vstinner', 'stutzbach', 'methane']
pr_nums = ['31649', '31657', '31832', '31866']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue46906'
versions = ['Python 3.11']Original issue. msgpack/msgpack-python#497
_PyFloat_(Pack|Unpack)(4|8) is very nice API for serializers like msgpack.
Converting double and float into char[] is not trivial and these APIs do it in very efficient way.
And these APIs don't reveal CPython internal strucutre. It just convert double and float into char[].
So please keep these APIs public for libraries like msgpack.
I disagree. A function should be either fully public: tested, documented. Or fully internal.
In the past, many functions were in both, in the gray area.
If these functions are useful, please make them *public* and document them. I'm +1 to make these functions public.
OK. By quick grepping, I found only msgpack and bitstruct use these API.
It is not enough number to make them public.
I reopen the issue, I would like to make these functions public :-) I searched for the 6 functions moved to the internal C API and I found 6 projets using it in the top 5000 PyPI projects (at 2022-01-26):
- msgpack
- ddtrace
- bitstruct
- pickle5
- line_profiler
- zodbpickle
The 6 functions are used:
- _PyFloat_Pack2()
- _PyFloat_Pack4()
- _PyFloat_Pack8()
- _PyFloat_Unpack2()
- _PyFloat_Unpack4()
- _PyFloat_Unpack8()
The pack/unpack functions have been moved to the internal C API by this change:
commit 0a883a7
Author: Victor Stinner <vstinner@python.org>
Date: Thu Oct 14 23:41:06 2021 +0200
bpo-35134: Add [Include/cpython/floatobject.h](https://github.com/python/cpython/blob/main/Include/cpython/floatobject.h) (GH-28957)
Split [Include/floatobject.h](https://github.com/python/cpython/blob/main/Include/floatobject.h) into sub-files: add
[Include/cpython/floatobject.h](https://github.com/python/cpython/blob/main/Include/cpython/floatobject.h) and
[Include/internal/pycore_floatobject.h](https://github.com/python/cpython/blob/main/Include/internal/pycore_floatobject.h).
I prepared a pythoncapi_compat PR to provide these functions to Python 3.10 and older:
python/pythoncapi-compat#26
Note: bpo-11734 (commit 7c4e409) added _PyFloat_Pack2() and _PyFloat_Unpack2() to Python 3.6.0b1.
PR for msgpack: msgpack/msgpack-python#499
PR for bitstruct: eerimoq/bitstruct#26
zodbpickle issue: zopefoundation/zodbpickle#67
msgpack and bitstruct use the newly added functions: my two PRs got merged. msgpack was my main motivation to add these functions :-)
Thanks to great reviews, the functions got a new better documentation!
I close the issue. Thanks again for reviews!