binascii.crc_hqx() can return negative integer

[serhiy-storchaka]

BPO	23728
Nosy	@gpshead, @serhiy-storchaka
Files	binascii_crc_hqx_empty_data.patch

^{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 = 'https://github.com/serhiy-storchaka'
closed_at = <Date 2015-04-20.08:25:22.999>
created_at = <Date 2015-03-20.21:52:50.158>
labels = ['extension-modules', 'easy', 'type-bug']
title = 'binascii.crc_hqx() can return negative integer'
updated_at = <Date 2015-04-20.08:25:22.999>
user = 'https://github.com/serhiy-storchaka'

bugs.python.org fields:

activity = <Date 2015-04-20.08:25:22.999>
actor = 'serhiy.storchaka'
assignee = 'serhiy.storchaka'
closed = True
closed_date = <Date 2015-04-20.08:25:22.999>
closer = 'serhiy.storchaka'
components = ['Extension Modules']
creation = <Date 2015-03-20.21:52:50.158>
creator = 'serhiy.storchaka'
dependencies = []
files = ['38834']
hgrepos = []
issue_num = 23728
keywords = ['patch', 'easy']
message_count = 3.0
messages = ['238726', '240087', '241616']
nosy_count = 3.0
nosy_names = ['gregory.p.smith', 'python-dev', 'serhiy.storchaka']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue23728'
versions = ['Python 3.4', 'Python 3.5']

[serhiy-storchaka]

zlib.adler32(), zlib.crc32(), and binascii.crc32() always return 32-bit unsigned integer in Python 3. binascii.crc_hqx() almost always returns 16-bit unsigned integer. But there is an exception. The result can negative only when arguments of binascii.crc_hqx() are empty bytes and negative integer. This looks as a bug and should be fixed. But may be no need to apply changes to maintained releases.

[serhiy-storchaka]

Nobody proposed a patch, so I do this.

[python-dev]

New changeset 0ead02929df2 by Serhiy Storchaka in branch '3.4':
Issue bpo-23728: binascii.crc_hqx() could return an integer outside of the range
https://hg.python.org/cpython/rev/0ead02929df2

New changeset abb86c6b11b2 by Serhiy Storchaka in branch 'default':
Issue bpo-23728: binascii.crc_hqx() could return an integer outside of the range
https://hg.python.org/cpython/rev/abb86c6b11b2

New changeset 17702fd8ac0d by Serhiy Storchaka in branch '2.7':
Issue bpo-23728: Added a test for binascii.crc_hqx().
https://hg.python.org/cpython/rev/17702fd8ac0d