Ok, thanks a lot for the answer! Thanks also to Bo! I summarized the results and added them as an answer to the original SO thread where hopefully a lot of people can find them without going through the pain I had:
http://stackoverflow.com/a/26886634/1421332 I also will have a look into the contribution guidelines. -- Kind Regards Bernhard Lindner > Von: interest-bounces+private=bernhard-lindner...@qt-project.org > [mailto:interest-bounces+private=bernhard-lindner...@qt-project.org] Im > Auftrag von Alejandro Exojo > Gesendet: Mittwoch, 12. November 2014 09:22 > An: interest@qt-project.org > Betreff: Re: [Interest] Strange behaviour of QByteArray reserve/reallocation > mechansim > > El Monday 10 November 2014, Bernhard escribió: > > So after all I am not supposed to use clear() or operator=() after > > calling reserve()? That should be documented. Without that knowledge > > it obviously is impossible to use reserve() in a sensible way. > > There was a similar question on the development mailing list about clearing > QVector while keeping the capacity. The solution seems to use erase(), and > that is not available on QByteArray, but see below. > > http://lists.qt-project.org/pipermail/development/2014- > November/019015.html > > > If you don't have an idea how that could be improved on the code side > > I would file a suggestion about extending the documentation a bit. > > I think that this will work for you (if I understood your use case): > > QByteArray buffer; > buffer.reserve(1000); > buffer.append("foo"); > qDebug() << "buffer" << buffer.capacity() << buffer; > > buffer.truncate(0); > buffer.append("bar"); > qDebug() << "buffer" << buffer.capacity() << buffer; > > This prints: > > buffer 1000 "foo" > buffer 1000 "bar" > > As Bo explained, operator= doesn't work because of the implicit sharing. It > can be tricky to document which member functions will hold the reserved > memory without adding lots of noise to each member description. Maybe > the Qt developers don't even want to commit to keeping the same > behaviour during all the Qt5 timespan. > > Sending a patch to improve the documentation is easy once you do the initial > procedure: > > http://qt-project.org/wiki/Qt-Contribution-Guidelines > > -- > Alex (a.k.a. suy) | GPG ID 0x0B8B0BC2 > http://barnacity.net/ | http://disperso.net > _______________________________________________ > Interest mailing list > Interest@qt-project.org > http://lists.qt-project.org/mailman/listinfo/interest _______________________________________________ Interest mailing list Interest@qt-project.org http://lists.qt-project.org/mailman/listinfo/interest
