Refactor QVersionNumber so it stores values in-class

The common case of QVersionNumber is that there are few segments and
each segment is a small integers. So instead of allocating a
QVector<int>, just store those numbers in the class itself if
possible. Think of this as a "Small String Optimization" for
QVersionNumber.

QVector<int> costs 16 + 4*N bytes, plus malloc overhead. After this
change, QVersionNumber(5,4,0) will have an overhead of zero.

The memory layout is explained in the header. I've coded it so big
endian also works, but I have not tested it at all.

Aside from the special functions for QVersionNumber and operator>>, all
the rest of the algorithm could have been left unchanged. I only updated
segments(), normalized(), compare(), commonPrefix() and fromString() to
take advantage of the smaller implementation in a more efficient way.

Note: QVersionNumber's constructors often leave half of the object or
more uninitialized. That's not a problem.

Change-Id: I4a2a0ce09fce2580f02d678e2f80b1dba74bac9d
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>

0 files changed, 0 insertions, 0 deletions