[Interest] Interest Digest, Vol 79, Issue 19

Roland Hughes roland at logikalsolutions.com
Wed Apr 25 15:53:26 CEST 2018

On 04/25/2018 08:24 AM, Thiago Macieira wrote:
> Another issue is that QDataStream tries to store all integers in big endian,
> unless you tell it otherwise. Since most machines are little-endian, that's a
> waste of CPU cycles, as you're doing the endian conversion twice, for little
> gain, however fast it is.
Be gentle and tread lightly here. Don't just take an x86 view of the 
world when considering this change. Having gray in the hair and a long 
time in the field has me recalling a reason behind that. Many embedded 
Qt projects were creating devices which fed data via hook or crook back 
to IBM, Amdahl, Prime, PowerPC based, etc. While Amdahl and Prime have 
ceased production they are still in the field and still being fed.


Unisys was little-endian but the COBOL compiler had USAGE IS COMP 
clauses which would import/use big-endian format. One of the few which 
had that. Most everyone else had to use FORTRAN or role their own 
special COBOL libraries. Yes, most of the systems catching the output 
were COBOL. It still is the largest "production" language in the world 
by application size and base.

What I'm trying to tell you is there was and still is a legitimate 
reason to have a QDataStream which can write big-endian. Don't just rip 
it out. Make it some kind of settable boolean flag in the class. There 
is no way to know just how many of these things are still out there and 
are still being developed. Most were in the world of defense 

Roland Hughes, President
Logikal Solutions


-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.qt-project.org/pipermail/interest/attachments/20180425/52b66e74/attachment.html>

More information about the Interest mailing list