Re: CPP example NTTable builder

[Michael Davidsaver <mdavidsaver@gmail.com>]

On 06/19/2018 10:49 AM, Heinz Junkes wrote:
> HI,
> 
> try to create NTTable :
> 
>  NTTableBuilderPtr builder = NTTable::createBuilder();
>     
>     PVStructurePtr pvStructure = builder->
>             addColumn("ts", pvInt)->
>             addColumn("X", pvDouble)->
>             addColumn("Y", pvDouble)->
>             addColumn("Z", pvDouble)->
>             addDescriptor()->
>             addAlarm()->
>             addTimeStamp()->
>             createPVStructure();
> 
> Unfortunately, I always end up with "core-dump” on the RTEMS-system.

Are you able to test on another OS as well?

> I have not understood yet how to specify the length for the four arrays (pvInt, pvDouble [X,Y,Z] ) connected to the 4 columns.
> I thought I had to add an array structure to the 4 columns. But I found nothing in the nttable.h file how to do that.
> Every note is welcome as always.

As the reluctant maintainer of normativeTypesCPP I'm recommending not to use class NTTable.
I've not found it so helpful since, as you've found, it doesn't help with handling column data.

A more complete example, which should compile and not crash (it's late).

> #include <pv/pvData.h>
> #include <pv/standardField.h>
> namespace pvd = epics::pvData;
>
> static
> pvd::StructureConstPtr typedesc(pvd::getFieldCreate()->createFieldBuilder()
>                                 ->setId("epics:nt/NTTable:1.0")
>                                 ->addArray("labels", pvd::pvString)
>                                 ->addNestedStructure("value")
>                                     ->addArray("ts", pvd::pvInt)
>                                     ->addArray("X", pvd::pvDouble)
>                                     ->addArray("Y", pvd::pvDouble)
>                                     ->addArray("Z", pvd::pvDouble)
>                                 ->endNested()
>                                 //->add("timeStamp", pvd::getStandardField()->timeStamp()) // unused in this example
>                                 //->add("alarm", pvd::getStandardField()->alarm())
>                                 ->createStructure());
> 
> pvd::PVStructure::shared_pointer buildTable(){
>     pvd::shared_vector<std::string> labels;
>     labels.push_back("The TS");
>     labels.push_back("The X");
>     labels.push_back("The Y");
>     labels.push_back("The Z");
> 
>     pvd::shared_vector<pvd::int32> ts;
>     pvd::shared_vector<double> X, Y, Z;
> 
>     for(size_t i=0; i<10; i++) { // some fake data
>         ts.push_back(i*10);
>         X.push_back(i);
>         Y.push_back(i+1);
>         Z.push_back(i+2);
>     }
> 
>     pvd::PVStructure::shared_pointer value(pvd::getPVDataCreate()->createPVStructure(typedesc));
> 
>     value->getSubFieldT<pvd::PVScalarArray>("labels")->putFrom(freeze(labels));
>     value->getSubFieldT<pvd::PVScalarArray>("value.ts")->putFrom(freeze(ts));
>     value->getSubFieldT<pvd::PVScalarArray>("value.X")->putFrom(freeze(X));
>     value->getSubFieldT<pvd::PVScalarArray>("value.Y")->putFrom(freeze(Y));
>     value->getSubFieldT<pvd::PVScalarArray>("value.Z")->putFrom(freeze(Z));
> 
>     return value;
> }