Re: Proper way to handle changes in the preferences

[Pascal Quantin <pascal () wireshark org>]

Hi Sake,

Le lun. 17 juin 2019 à 07:10, Sake Blok | SYN-bit <sake.blok () syn-bit nl> a
écrit :

> Hi,
>
> I'm working on a patch to add the possibility to show times in milli- or
> microsecond units. While working this out, I see a need to change the name
> of certain preferences and/or change the values of other preferences. This
> will however break compatibility with older versions of Wireshark in
> reading/writing the preferences (in my case, settings in the "recent" file).
>
> Is there a way to add backwards compatibility in preference items by
> converting old preference settings into new ones?
> And is there a way to add code to the current versions to do the reverse
> for forward compatibility, so at least future minor versions of old major
> versions will be able to handle this correctly?
>
> Things that I might want to change are:
>
> # Timestamp display precision.
> # One of: AUTO, SEC, DSEC, CSEC, MSEC, USEC, NSEC
> gui.time_precision: MSEC
>
> to:
>
> # Timestamp display precision.
> # One of: AUTO, 0DECIMALS, 1DECIMAL, 2DECIMALS, 3DECIMALS, 6DECIMALS,
> 9DECIMALS
> gui.time_precision: AUTO
>
> and
>
> # Seconds display format.
> # One of: SECONDS, HOUR_MIN_SEC
> gui.seconds_format: SECONDS
>
> to
>
> # Seconds display format.
> # One of: SECONDS, MILLISECONDS, MICROSECONDS, HOUR_MIN_SEC
> gui.time_units: SECONDS
>
> Are there some guidelines available in handling preferences between
> wireshark versions?

You can find some code handling preferences rename in epan/prefs.c file,
set_pref() function. This is probably the right place to put some
conversion code between the old and new format.

Cheers,
Pascal.

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