[Development] QDataStream: blackbox or document all versions?

Konstantin Tokarev annulen at yandex.ru
Sun Sep 25 23:42:12 CEST 2016

25.09.2016, 06:58, "Thiago Macieira" <thiago.macieira at intel.com>:
> A thread[1] on the interest mailing list started when someone asked for the
> docs for the current format of the QDataStream wire protocol, to which I
> replied that it doesn't exist as we don't maintain such docs.
> Long story short, we have two options:
> Option 1: claim QDataStream is a blackbox and tell people that the only thing
> that can read QDataStream is QDataStream. That means removing the
> documentation file src/corelib/doc/src/datastreamformat.qdoc, as we don't want
> people getting any ideas that they could write their own decoders or encoders.
> Option 2: the opposite, saying that reading QDataStream's output is fine from
> non-Qt code and it's fine to write data that QDataStream should read. This
> means extending the documentation to cover ALL 17 wire formats (including
> bugs) and keeping it up to date whenever someone modifies the format.

I think there is also

Option 3: restore documentation of version 12 and declare that it's the only 
format version that is meant for use with 3rd party encoders and decoders.

> I am in favour of Option 1 because I really don't think QDataStream is a good
> format for exchanging data with non-Qt code. It's designed first and foremost
> for Qt's own internal data formats (sometimes even depending on internal
> details), the marshalling of certain types in certain versions is buggy and
> lossy. Instead, people should find a better transport format for their data, of
> which we already have in Qt:
>         XML
>         JSON
>         D-Bus
>         QSettings (to an extent)
> And I can add CBOR support if we want to.
> [1] http://lists.qt-project.org/pipermail/interest/2016-September/024387.html
> --
> Thiago Macieira - thiago.macieira (AT) intel.com
>   Software Architect - Intel Open Source Technology Center
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