Add pycore_byteswap.h internal header file with _Py_bswap32() function

[vstinner]

BPO	40302
Nosy	@pitrou, @vstinner, @serhiy-storchaka, @sir-sigurd
PRs	bpo-40302: Add _Py_bswap32() function to pyport.h #19552 bpo-40302: Optimize UTF-32 encoder SWAB4() #19572 bpo-40302: Replace PY_INT64_T with int64_t #19573 Use standard integer types instead of Python aliases #15659

^{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 2020-04-17.17:15:00.250>
created_at = <Date 2020-04-16.14:22:55.752>
labels = ['interpreter-core', '3.9']
title = 'Add pycore_byteswap.h internal header file with _Py_bswap32() function'
updated_at = <Date 2020-05-10.19:30:18.130>
user = 'https://github.com/vstinner'

bugs.python.org fields:

activity = <Date 2020-05-10.19:30:18.130>
actor = 'sir-sigurd'
assignee = 'none'
closed = True
closed_date = <Date 2020-04-17.17:15:00.250>
closer = 'vstinner'
components = ['Interpreter Core']
creation = <Date 2020-04-16.14:22:55.752>
creator = 'vstinner'
dependencies = []
files = []
hgrepos = []
issue_num = 40302
keywords = ['patch']
message_count = 7.0
messages = ['366600', '366603', '366610', '366659', '366667', '366668', '366669']
nosy_count = 4.0
nosy_names = ['pitrou', 'vstinner', 'serhiy.storchaka', 'sir-sigurd']
pr_nums = ['19552', '19572', '19573', '15659']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue40302'
versions = ['Python 3.9']

[vstinner]

There are multiple files which have to swap bytes. I propose to add functions for that:

• _Py_bswap16(): uint16_t
• _Py_bswap32(): uint32_t
• _Py_bswap64(): uint64_t

[pitrou]

Isn't pyport.h a public header? IMHO you should put in a private header and make it an inline function there.

Here is for example what we do in Arrow:
https://github.com/apache/arrow/blob/master/cpp/src/arrow/util/bit_util.h#L48

[vstinner]

We have another function which may be grouped somehow in the same category: _Py_bit_length().

[vstinner]

New changeset 1ae035b by Victor Stinner in branch 'master':
bpo-40302: Add pycore_byteswap.h header file (GH-19552)
1ae035b

[vstinner]

New changeset 1a1bd2e by Victor Stinner in branch 'master':
bpo-40302: Replace PY_INT64_T with int64_t (GH-19573)
1a1bd2e

[vstinner]

New changeset d7c657d by Victor Stinner in branch 'master':
bpo-40302: UTF-32 encoder SWAB4() macro use a|b rather than a+b (GH-19572)
d7c657d

[vstinner]

FYI this issue was motivated by the implementation of random.Random().randbytes(): bpo-40286.