Best way to avoid deep copies when sending a large floating point sequence

kandel3

I have a slice that maps to an std::vector<float>. Although expected, I was hoping for there to be a way to avoid a deep copy when my program can only pass pointers. I need to use pointers because of exotic memory allocation requirements, aka page locked, etc.

At present I'm deep copying the pointed data into a vector, but I think something exists for strings (that maps to string_view). I can't figure out how to apply this to a sequence of floating point data.

sequence<float> InteropBuffer;
interface Interop
{
    void sendData(InteropBuffer input);
};

bernard

Hi Mikhail,

The simplest solution here is probably to use the cpp::array metadata, which will map your sequence<float> parameter to an array of floats (really a pair of pointers). See
https://doc.zeroc.com/pages/viewpage.action?pageId=16716050#C++MappingforSequences-ArrayMappingforSequenceParametersinC++ (Ice 3.6)

https://doc.zeroc.com/pages/viewpage.action?pageId=18255292#C++11MappingforSequences-ArrayMappingforSequenceParametersinC++ (Ice 3.7 with C++11)

You could also use a "view type", but this would require more coding:

• you'd map the sequence<float> sequence to your own C++ type with "view" semantics (meaning it does not own the float array memory): https://doc.zeroc.com/display/Ice36/The+cpp:type+and+cpp:view-type+Metadata+Directives#Thecpp:typeandcpp:view-typeMetadataDirectives-Avoidingcopieswithcpp:view-type (Ice 3.6). Let's call this custom type FloatArrayView.

• you'd tell Ice how to marshal and unmarshal this FloatArrayView through Stream Helpers: https://doc.zeroc.com/pages/viewpage.action?pageId=16716071 (Ice 3.6)

Best regards,
Bernard