Hi,
I have multiple C functions that I need to interface. I need
to support numeric scalars, strings and booleans and 1-4 dimensional
arrays of these. The programming problem I try to avoid is that I have
multiple different functions in my DLLs that all take as an input or
return all these datatypes. Now I can create a polymorphic interface
for all these functions, but I end-up having about 100 interface VIs
for each of my C function. This was still somehow acceptable in LabVIEW
8.0 but in LabVIEW 8.2 all these polymorphic VIs in my LVOOP project
gets read into memory at project open. So I have close to 1000 VIs read into memory when ever I open my project. It takes now about ten minutes to
open the project and some 150 MB of memory is consumed instantly. I
still need to expand my C interface library and LabVIEW doesn't simply
scale up to meet the needs of my project anymore.
I now
reserve my LabVIEW datatypes using DSNewHandle and DSNewPtr functions.
I then initialize the allocated memory blocks correctly and return the
handles to LabVIEW. LabVIEW complier interprets Call Library Function
Node terminals of my memory block as a specific data type.
So
what I thought was following. I don't want LabVIEW compiler to
interpret the data type at compile time. What I want to do is to return
a handle to the memory structure together with some metadata describing
the data type. Then all of my many functions would return this kind of
handle. Let's call this a data handle. Then I can later convert this
handle into a real datatype either by typecasting it somehow or by
passing it back to C code and expecting a certain type as a return.
This way I can reduce the number of needed interface VIs close to 100
which is still acceptable (i.e. LabVIEW 8.2 doesn't freeze).
So
I practically need a similar functionality as variant has. I cannot use
variants, since I need to avoid making memory copies and when I convert
to and from variant, my memory consumption increases to three fold. I
handle arrays that consume almos all available memory and I cannot
accept that memory is consumed ineffectively.
The question is,
can I use DSNewPtr and DSNewHandle functions to reserve a memory block
but not to return a LabVIEW structure of that size. Does LabVIEW
carbage collection automatically decide to dispose my block if I don't
correctly return it from my C immediately but only later at next call
to C code. Can I typecast a 1D U8 array to array of any dimensionality and any numeric data type without memory copy (i.e. does typecast work the way it works in C)?
If I cannot find a solution with this LabVIEW 8.20 scalability issue, I have to really consider transferring our project from LabVIEW to some other development environent like C++ or some of the .NET languages.
Regards,
Tomi
--
Tomi Maila
