Nested map in QCborStreamWriter ?

atrSbt

So far, I managed to write large nested maps of strings, floats and ints using nested QJsonMap's in a QJsonDocument, but only after all the data is generated, the writing process is slow and the outfile is huge (>400MB).
So I turned my attention to CBOR and its stream writer, but it seems that QCborStreamWriter does not handle nested maps (QCborStreamWriter::append() does not take a QCborMap as argument).
Is there a way to do it anyway or an alternative to QCborStreamWriter that handles nested maps ?
Thanks

JKSH

@atrSbt said in Nested map in QCborStreamWriter ?:

@JKSH I submitted the feature request here, I hope I did it correctly.

Yep, you did it correctly.

And it looks like the Qt Core maintainer has provided a simpler solution:

QCborStreamWriter stream = ...
QCborMap map = ...

map.toCborValue().toCbor(stream);

// OR:
QCborValue(map).toCbor(stream);

Christian Ehrlicher

QCBorMap has a toCBorValue() function.

atrSbt

Thank you for your reply @Christian-Ehrlicher
I see, however this probably won't work since append() does not take a QCborValue as an argument either. I suppose I could then convert the QCborValue further to a QByteArray, but I'm not sure if it's the best way to do this...

QCborStreamWriter writer;
writer.startArray();
QCBorMap map;
writer.append(map.toCBorValue().toByteArray());
writer.endArray();

Christian Ehrlicher

Ok I see.

Then a nested call to https://doc.qt.io/qt-6/qcborstreamwriter.html#startMap-1 / end map should work. Strange that there are no convenience functions for this.

atrSbt

Indeed this works:

QCborStreamWriter writer;
writer.startMap();
writer.append("A");
writer.append(1);
writer.append("B");
writer.append(2);
writer.append("C");
writer.startMap(); // start nested map
writer.append("C1");
writer.append(3.1);
writer.append("C2");
writer.append(3.2);
writer.append("C3");
writer.append(3.3);
writer.endMap(); // end nested map
writer.endMap();

and produces the following tree:

{
"A": 1,
"B": 2,
"C": {
  "C1": 3.1,
  "C2": 3.2,
  "C3": 3.3
},
"D": 4
}

But I agree, a convenience function would really help, especially with many nested levels and elements.
Thanks for your help !

JKSH

@atrSbt said in Nested map in QCborStreamWriter ?:

Indeed this works:

Great!

a convenience function would really help, especially with many nested levels and elements.

Would you be willing to submit a feature request to https://bugreports.qt.io/ ?

atrSbt

@JKSH I submitted the feature request here, I hope I did it correctly.

JKSH

@atrSbt said in Nested map in QCborStreamWriter ?:

@JKSH I submitted the feature request here, I hope I did it correctly.

Yep, you did it correctly.

And it looks like the Qt Core maintainer has provided a simpler solution:

QCborStreamWriter stream = ...
QCborMap map = ...

map.toCborValue().toCbor(stream);

// OR:
QCborValue(map).toCbor(stream);

atrSbt

Indeed. Is there a way one could set your post as the solution instead of Christian's ?

SGaist

Hi,

@atrSbt mark the thread as unsolved and then the newly elected answer as the correct one.

Feedback Wanted: Qt Hub

Nested map in QCborStreamWriter ?