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7451 :: Compiling some functions into a lib from nim itself

• mantielero (orginal) [2021-01-30T17:19:19+01:00] view original

  Long ago, I played a little bit with FMU which is like a black box used for simulations in the context of Simulink, Dymola and many others.

  An FMU is a zip file with:

  • an xml description
  • a library (.so, .dll, ...)
  • data

  In order to create the library, you create a three functions with a particular name. For example, something like:

  
  proc setStartValues(comp:ptr ModelInstance) {.exportc: "$1".} =
      comp.i[counter] = 1
  
  proc calculateValues(comp:ptr ModelInstance) {.exportc: "$1".}=
      if comp.state == modelInitializationMode:
          # set first time event
          comp.eventInfo.nextEventTimeDefined = fmi2True
          comp.eventInfo.nextEventTime        = 1 + comp.time
  
  proc eventUpdate(comp:ptr ModelInstance, eventInfo:ptr fmi2EventInfo, timeEvent:cint, isNewEventIteration:cint) {.exportc: "$1".} =
      if timeEvent != 0:
          comp.i[counter] += 1;
          if comp.i[counter] == 13:
              eventInfo.terminateSimulation  = fmi2True
              eventInfo.nextEventTimeDefined = fmi2False
          else:
              eventInfo.nextEventTimeDefined = fmi2True
              eventInfo.nextEventTime        = 1 + comp.time
  Run

  In order to create the .so, I used FFI with fmusdk which is in C. You create the .so by compiling the inc.nim code like:

  
  nim c --nimcache:.cache --app:lib -o:inc.so inc.nim
  Run

  For me, the easy way would be having a file with those three functions, and another program to create and package everything up. This approach is what it is done by PythonFMU.

  I was wondering if I could do a export_fmu function that operates like this:

  proc setStartValues(comp:ptr ModelInstance) {.exportc: "$1".} =
      ...
  
  proc calculateValues(comp:ptr ModelInstance) {.exportc: "$1".}=
      ...
  
  proc eventUpdate(comp:ptr ModelInstance, eventInfo:ptr fmi2EventInfo, timeEvent:cint, isNewEventIteration:cint) {.exportc: "$1".} =
      ...
  
  proc main =
     export_fmu(setStartValues, calculateValues, eventUpdate)
  Run

  Could this be feasible? How could I compile just those functions as library from nim?

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