[Development] QDataStream: blackbox or document all versions?

Konstantin Tokarev annulen at yandex.ru
Sun Sep 25 23:37:25 CEST 2016

26.09.2016, 00:12, "Konstantin Tokarev" <annulen at yandex.ru>:
> 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 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.
> In case you are going to implement CBOR from scratch, please support string
> reference extension [1] which is needed to encode repeating strings (most
> importantly, data keys) efficiently.
> [1] http://cbor.schmorp.de/stringref

BTW, newly emerged SuperPack format goes further and introduces repeated keyset


>>  [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
>>  _______________________________________________
>>  Development mailing list
>>  Development at qt-project.org
>>  http://lists.qt-project.org/mailman/listinfo/development
> --
> Regards,
> Konstantin
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