Yes.
This function was not carefully specified, we just have to acknowledge
that. it was a past mistake, but now it's here, and we need to support
it in a stable way.
About that function, the only thing to do is to properly document what
it actually does, and keep it that way. There is no reason to change the
behaviour.
At one point, this badly specified function could be deprecated, before
being removed in a later release.
It is easy to add deprecation warnings and recommendations not to use
with alternative api indications.
Here is a proposal for a timeline
-now:
* document that crc16 is deprecated and will be removed. do not change
its behaviour.
* add code and accurate documentation for any well specified crc16
function that is required, based on a common implementation or not, not
important. it's just optimization at this point.
-later:
* remove the legacy crc16
* do the same for any other crc function like crc32 if available.
What does the community think about that ?
Sebastien
On 09/04/2025 14:05, Nathan Hartman wrote:
I think the real problem here is that the function is called crc16()
with no details about which CRC polynomial is used. Maybe it's better
not to have this function at all and to have *only* functions with
names like crc16ibm() or crc16ccitt(). Then it is much more clear what
CRC is being called in other code and there will be no risk of
breaking compatibility in the future.
On Wed, Apr 9, 2025 at 5:44 AM chao an <magicd...@gmail.com> wrote:
Seriously, I have no interest in crc16 at all, and I don't think
your 15 years of experience in cryptography deserves my respect.
These are all old technologies. I just want to help people who
have problems in Nuttx.
I also hope that every time someone asks about the implementation
of crc16, you can reply to them as soon as possible instead of
hiding behind emails.
I won't reply to any messages from you anymore, I wish you all the
best, thanks.
BRs,
Sebastien Lorquet <sebast...@lorquet.fr> 于2025年4月9日周三
17:17写道：
Why are you so unwilling to change your opinion?
You are ready to break nuttx just for your comfort, in
whatever way it may take to advance your own agenda. That is
very political.
I dont like that.
We need a consensus, and a majority of this thread is against
the change you want to make. So it should be cancelled.
Rememeber this thread is a vote. My vote is No. Close the pull
request. Do another one that has chances to be consensually
accepted. Let's vote again.
I will paste the quote that Greg posted in the thread about
the modlib change:
Rules for voting are a little different for code changes.
The required Apache voting process is
here:https://www.apache.org/foundation/voting.html
For code changes, that document says: "Votes on code modifications follow consensus
approval<https://www.apache.org/foundation/glossary.html#ConsensusApproval>
<https://www.apache.org/foundation/glossary.html#ConsensusApproval>. In this scenario, a negative vote constitutes a
veto<https://www.apache.org/foundation/voting.html#Veto> <https://www.apache.org/foundation/voting.html#Veto>,
which the voting group (generally the PMC of a project) cannot override. Again, this model may be modified by a lazy
consensus<https://www.apache.org/foundation/voting.html#LazyConsensus>
<https://www.apache.org/foundation/voting.html#LazyConsensus> declaration when the request for a vote is raised, but
the full-stop nature of a negative vote does not change. Under normal (non-lazy consensus) conditions, the proposal requires
three +1 votes and no -1 votes in order to pass; if it fails to garner the requisite amount of support, it doesn't. Then the
proposer either withdraws the proposal or modifies the code and resubmits it, or the proposal simply languishes as an open
issue until someone gets around to removing it."
And "For code-modification votes, +1 votes are in favour of the proposal, but -1
votes are vetos<https://www.apache.org/foundation/voting.html#Veto>
<https://www.apache.org/foundation/voting.html#Veto> and kill the proposal dead until all
vetoers withdraw their -1 votes.
Unless the proposer declares that the vote is using lazy
consensus<https://www.apache.org/foundation/voting.html#LazyConsensus>
<https://www.apache.org/foundation/voting.html#LazyConsensus>, three +1 votes are required
for a code-modification proposal to pass."
Sebastien
On 09/04/2025 10:20, chao an wrote:
I like your second option, so could we remove the
implementation of both crc16/crc16part interfaces and rename
to crc16xmodem/crc16xmodempart?
BRs,
Sebastien Lorquet <sebast...@lorquet.fr> 于2025年4月9日周三
16:00写道：
Hello,
once again, the number of usage is unimportant and
irrelevant.
The ONLY thing that matters is that when I call function
POOP, it always does POOP. Not something else.
Because users you are unaware of expect this function to
do POOP and they may not be able to change their code.
If you want different crc functions, use something else.
A better example than the building: the zip format
zip uses adler32 which is not even a proper crc and is
largely suboptimal.
zip developers NEVER changed this in decades, even if
they know it's bad. Why? because otherwise, old zip files
would become completely unusable.
We have the same issue.
The default crc is bad? OK, deal with it. Add better
functions. Document everywhere that the default crc is
deprecated and should not be used because more accurate
functions are available.
But dont change the damn thing.
I am against changing the default implementation of the
legacy function silently.
I would be less mad if you REMOVED the old function
rather than silently changing its behaviour. (that would
still be bad, however)
Sebastien
On 09/04/2025 05:12, chao an wrote:
I can empathize. But we just don't want to fill this
regret again in the new building.
The lack of standards is currently the biggest issue
hindering the promotion of this proposal.
Another interesting thing, I'd like to share another
data from github:
if we search for the lookup table of crc16 on GitHub,
you'll find that CRC-16/IBM with a higher use rate:
CRC-16/IBM: 3.1k
https://github.com/search?q=%220x0000%2C+0xc0c1%2C+0xc181%2C+0x0140%2C+0xc301%2C+0x03c0%2C+0x0280%2C+0xc241%2C%22&type=code
<https://github.com/search?q=%220x0000%2C+0xc0c1%2C+0xc181%2C+0x0140%2C+0xc301%2C+0x03c0%2C+0x0280%2C+0xc241%2C%22&type=code>
image.png
CRC-16/XMODEM: 304
https://github.com/search?q=%220x0000%2C++0x1021%2C++0x2042%2C++0x3063%2C++0x4084%2C++0x50a5%2C++0x60c6%2C++0x70e7%2C%22&type=code
<https://github.com/search?q=%220x0000%2C++0x1021%2C++0x2042%2C++0x3063%2C++0x4084%2C++0x50a5%2C++0x60c6%2C++0x70e7%2C%22&type=code>
image.png
BRs,
Tomek CEDRO <to...@cedro.info> 于2025年4月9日周三
10:52写道：
On Wed, Apr 9, 2025 at 3:45 AM chao an
<magicd...@gmail.com> wrote:
> > > > On Tue, Apr 8, 2025 at 7:17 PM Lwazi Dube
<lwa...@gmail.com> wrote:
> > > > An open source project's ability to innovate
should not be
> > > > held up by your preferences.
> > >
> > > The last sentence is completely wrong. Its not
about "preference" but
> > > impacting self-compatibility and long term
maintenance. Messing the
> > > foundations and defaults is not innovation.
Try building a home when
> > > the project constantly changes during the
process, when you have 10
> > > floors ready and suddenly you need to change
pavements. Innovation is
> > > when you create new functionality and give
users a choice without
> > > breaking existing working stuff.
>
> So you think it's more important to maintain your
current 10 floors
> building, and it's none of your business if a 100
floors skyscraper appears
> in the future? so could you afford all the
developer time spent on this
> kind of problem?
Anchao, what I meant was to finish 10 floor building
as planned
(development), let people live inside that building
(maintenance), and
move development resources to 100 floor building as
planned, without
changing plans in the middle of construction, not
getting stuck on 10
floor building construction because plans change all
the time and
never getting to that 100 floor building. Its good
to have solid
immutable tools that you can depend on. Imagine
there are devices
already deployed out there that may not be possible
to update, yes
maintenance (in terms of keeping them
inter-operational) may be the
priority in that case, because replacing all devices
may wipe out the
company and leave owner with ubearable financial debt.
I know this CRC is an important and quite hard
problem, and I hope
there can be a win-win solution where users have
choice when they need
one, thank you for bringing this up to the
attention.. to be honest I
have no clue what is the best solution here if there
is no standard to
relay on :-)
--
CeDeROM, SQ7MHZ, http://www.tomek.cedro.info
