[Interest] reading from and writing to a file with QDataStream

[Thiago Macieira]

On terça-feira, 8 de março de 2016 21:27:52 PST Nikita Krupenko wrote:
> 2016-03-08 19:30 GMT+02:00 Thiago Macieira <thiago.macieira at intel.com>:
> > Indeed, but look at how you've combined two or more examples. You have a
> > byte array, you create a QDataStream on it, write some data, then you
> > used QDataStream to write that byte array to another byte array. You
> > probably didn't want that.
> 
> It could be useful, if I want to write checksum of the data to the
> file. To do this, I can write
> some data to the QByteArray wrapped in QDataStream, then calculate
> checksum using
> qChecksum() (or QCriptographicHash) and then write byte array and
> checksum to the file.

You could do that, but this is not what I was talking about.

The problem was that Sina caused redundancy in the data:

<32-bit value N+4> <32-bit value N/2> <string of length N/2>

Do you see the redundancy?

In your case, just make sure you don't use QDataStream to write the bytearray 
that was check-summed, or you'll do the same as the above.

-- 
Thiago Macieira - thiago.macieira (AT) intel.com
  Software Architect - Intel Open Source Technology Center