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6833 :: Dynamic loading of C++ library

• fortea (orginal) [2020-09-18T01:16:37+02:00] view original

  Hello all, I'm completely new to Nim, but after having ridden a lot of tutorials, I completely fall in love with him.

  For really being able to use it, I need a couple of libraries. Hopefully, all of them are available from C++ or already partially implemented.

  I'm trying to use a large state-of-art library for Music Information Processing (Essentia). For now, I want to just load it dynamically, then I will try to understand how to create a good API.

  I'm trying to use nimline for loading it dynamically. Below is my code, that should compute the spectrum of a random array. Here is an example from C++ to understand how the library works. Here, instead, the official documentation.

  import nimline
  import random
  
  cppincludes("./essentia/src/")
  cpplibpaths("./essentia/build/src/libessentia.so")
  
  defineCppType(OutputBase, "essentia::standard::OutputBase", "essentia/algorithmfactory.h")
  defineCppType(InputBase, "essentia::standard::InputBase", "essentia/algorithmfactory.h")
  defineCppType(Algorithm, "essentia::standard::Algorithm", "essentia/algorithmfactory.h")
  defineCppType(AlgorithmFactory, "essentia::standard::AlgorithmFactory", "essentia/algorithmfactory.h")
  
  proc main() =
      var FactoryType: AlgorithmFactory
      let factory: CppRef[AlgorithmFactory] = FactoryType.instance().to(CppRef[AlgorithmFactory])
      let spectrometer = factory.create("Spectrum").to(CppRef[Algorithm])
      
      var spectrum: seq[float32]
      var randArray: array[0..100, float32]
      for i in 0..<randArray.len:
          randArray[i] = rand(0.0..100.0)
      
      spectrometer.output("spectrum").to(CppRef[InputBase]).set(spectrum).to(void)
      spectrometer.input("spectrum").to(CppRef[InputBase]).set(randArray).to(void)
      spectrometer.compute().to(void)
      
      echo spectrum
  
  main()
  
  
  Run

  I get the following error at C++/C compile time:

  
  /home/sapo/.cache/nim/nimline_test_d/@mnimline_test.nim.cpp: In function ‘void main__B027HVeEntcgpQ9b3jKwZeQ()’:
  /home/sapo/.cache/nim/nimline_test_d/@mnimline_test.nim.cpp:230:40: error: ‘essentia::EssentiaFactory<BaseAlgorithm>::EssentiaFactory() [with BaseAlgorithm = essentia::standard::Algorithm]’ is protected within this context
    230 |   essentia::standard::AlgorithmFactory FactoryType;
        |                                        ^~~~~~~~~~~
  In file included from /home/sapo/.cache/nim/nimline_test_d/@mnimline_test.nim.cpp:12:
  ./essentia/src/essentia/algorithmfactory.h:149:3: note: declared protected here
    149 |   EssentiaFactory() {}
        |   ^~~~~~~~~~~~~~~
  /home/sapo/.cache/nim/nimline_test_d/@mnimline_test.nim.cpp:235:78: error: no matching function for call to ‘tyObject_CppRef__uzjF6kB2mFZZbGG9cViAamA::tyObject_CppRef__uzjF6kB2mFZZbGG9cViAamA(essentia::EssentiaFactory<essentia::standard::Algorithm>&)’
    235 | y = (tyObject_CppRef__uzjF6kB2mFZZbGG9cViAamA)(FactoryType.instance());
        |                                                                      ^
  
  /home/sapo/.cache/nim/nimline_test_d/@mnimline_test.nim.cpp:50:8: note: candidate: ‘tyObject_CppRef__uzjF6kB2mFZZbGG9cViAamA::tyObject_CppRef__uzjF6kB2mFZZbGG9cViAamA()’
     50 | struct tyObject_CppRef__uzjF6kB2mFZZbGG9cViAamA {
        |        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  /home/sapo/.cache/nim/nimline_test_d/@mnimline_test.nim.cpp:50:8: note:   candidate expects 0 arguments, 1 provided
  /home/sapo/.cache/nim/nimline_test_d/@mnimline_test.nim.cpp:50:8: note: candidate: ‘constexpr tyObject_CppRef__uzjF6kB2mFZZbGG9cViAamA::tyObject_CppRef__uzjF6kB2mFZZbGG9cViAamA(const tyObject_CppRef__uzjF6kB2mFZZbGG9cViAamA&)’
  /home/sapo/.cache/nim/nimline_test_d/@mnimline_test.nim.cpp:50:8: note:   no known conversion for argument 1 from ‘essentia::EssentiaFactory<essentia::standard::Algorithm>’ to ‘const tyObject_CppRef__uzjF6kB2mFZZbGG9cViAamA&’
  /home/sapo/.cache/nim/nimline_test_d/@mnimline_test.nim.cpp:50:8: note: candidate: ‘constexpr tyObject_CppRef__uzjF6kB2mFZZbGG9cViAamA::tyObject_CppRef__uzjF6kB2mFZZbGG9cViAamA(tyObject_CppRef__uzjF6kB2mFZZbGG9cViAamA&&)’
  /home/sapo/.cache/nim/nimline_test_d/@mnimline_test.nim.cpp:50:8: note:   no known conversion for argument 1 from ‘essentia::EssentiaFactory<essentia::standard::Algorithm>’ to ‘tyObject_CppRef__uzjF6kB2mFZZbGG9cViAamA&&’
  /home/sapo/.cache/nim/nimline_test_d/@mnimline_test.nim.cpp:237:95: error: no matching function for call to ‘tyObject_CppRef__3L9aJJuGBh50W6K9cBuua6HA::tyObject_CppRef__3L9aJJuGBh50W6K9cBuua6HA(essentia::standard::Algorithm*)’
    237 | t_CppRef__3L9aJJuGBh50W6K9cBuua6HA)((*factory.p).create(("Spectrum")));
        |                                                                      ^
  
  /home/sapo/.cache/nim/nimline_test_d/@mnimline_test.nim.cpp:53:8: note: candidate: ‘tyObject_CppRef__3L9aJJuGBh50W6K9cBuua6HA::tyObject_CppRef__3L9aJJuGBh50W6K9cBuua6HA()’
     53 | struct tyObject_CppRef__3L9aJJuGBh50W6K9cBuua6HA {
        |        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  /home/sapo/.cache/nim/nimline_test_d/@mnimline_test.nim.cpp:53:8: note:   candidate expects 0 arguments, 1 provided
  /home/sapo/.cache/nim/nimline_test_d/@mnimline_test.nim.cpp:53:8: note: candidate: ‘constexpr tyObject_CppRef__3L9aJJuGBh50W6K9cBuua6HA::tyObject_CppRef__3L9aJJuGBh50W6K9cBuua6HA(const tyObject_CppRef__3L9aJJuGBh50W6K9cBuua6HA&)’
  /home/sapo/.cache/nim/nimline_test_d/@mnimline_test.nim.cpp:53:8: note:   no known conversion for argument 1 from ‘essentia::standard::Algorithm*’ to ‘const tyObject_CppRef__3L9aJJuGBh50W6K9cBuua6HA&’
  /home/sapo/.cache/nim/nimline_test_d/@mnimline_test.nim.cpp:53:8: note: candidate: ‘constexpr tyObject_CppRef__3L9aJJuGBh50W6K9cBuua6HA::tyObject_CppRef__3L9aJJuGBh50W6K9cBuua6HA(tyObject_CppRef__3L9aJJuGBh50W6K9cBuua6HA&&)’
  /home/sapo/.cache/nim/nimline_test_d/@mnimline_test.nim.cpp:53:8: note:   no known conversion for argument 1 from ‘essentia::standard::Algorithm*’ to ‘tyObject_CppRef__3L9aJJuGBh50W6K9cBuua6HA&&’
  /home/sapo/.cache/nim/nimline_test_d/@mnimline_test.nim.cpp:263:128: error: no matching function for call to ‘tyObject_CppRef__SdQetZheNEfwTjB9cyvL0KQ::tyObject_CppRef__SdQetZheNEfwTjB9cyvL0KQ(essentia::standard::OutputBase&)’
    263 | Ref__SdQetZheNEfwTjB9cyvL0KQ)((*spectrometer.p).output(("spectrum"))));
        |                                                                     ^
  
  /home/sapo/.cache/nim/nimline_test_d/@mnimline_test.nim.cpp:56:8: note: candidate: ‘tyObject_CppRef__SdQetZheNEfwTjB9cyvL0KQ::tyObject_CppRef__SdQetZheNEfwTjB9cyvL0KQ()’
     56 | struct tyObject_CppRef__SdQetZheNEfwTjB9cyvL0KQ {
        |        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  /home/sapo/.cache/nim/nimline_test_d/@mnimline_test.nim.cpp:56:8: note:   candidate expects 0 arguments, 1 provided
  /home/sapo/.cache/nim/nimline_test_d/@mnimline_test.nim.cpp:56:8: note: candidate: ‘constexpr tyObject_CppRef__SdQetZheNEfwTjB9cyvL0KQ::tyObject_CppRef__SdQetZheNEfwTjB9cyvL0KQ(const tyObject_CppRef__SdQetZheNEfwTjB9cyvL0KQ&)’
  /home/sapo/.cache/nim/nimline_test_d/@mnimline_test.nim.cpp:56:8: note:   no known conversion for argument 1 from ‘essentia::standard::OutputBase’ to ‘const tyObject_CppRef__SdQetZheNEfwTjB9cyvL0KQ&’
  /home/sapo/.cache/nim/nimline_test_d/@mnimline_test.nim.cpp:56:8: note: candidate: ‘constexpr tyObject_CppRef__SdQetZheNEfwTjB9cyvL0KQ::tyObject_CppRef__SdQetZheNEfwTjB9cyvL0KQ(tyObject_CppRef__SdQetZheNEfwTjB9cyvL0KQ&&)’
  /home/sapo/.cache/nim/nimline_test_d/@mnimline_test.nim.cpp:56:8: note:   no known conversion for argument 1 from ‘essentia::standard::OutputBase’ to ‘tyObject_CppRef__SdQetZheNEfwTjB9cyvL0KQ&&’
  /home/sapo/.cache/nim/nimline_test_d/@mnimline_test.nim.cpp:269:129: error: no matching function for call to ‘tyObject_CppRef__SdQetZheNEfwTjB9cyvL0KQ::tyObject_CppRef__SdQetZheNEfwTjB9cyvL0KQ(essentia::standard::InputBase&)’
    269 | pRef__SdQetZheNEfwTjB9cyvL0KQ)((*spectrometer.p).input(("spectrum"))));
        |                                                                     ^
  
  /home/sapo/.cache/nim/nimline_test_d/@mnimline_test.nim.cpp:56:8: note: candidate: ‘tyObject_CppRef__SdQetZheNEfwTjB9cyvL0KQ::tyObject_CppRef__SdQetZheNEfwTjB9cyvL0KQ()’
     56 | struct tyObject_CppRef__SdQetZheNEfwTjB9cyvL0KQ {
        |        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  /home/sapo/.cache/nim/nimline_test_d/@mnimline_test.nim.cpp:56:8: note:   candidate expects 0 arguments, 1 provided
  /home/sapo/.cache/nim/nimline_test_d/@mnimline_test.nim.cpp:56:8: note: candidate: ‘constexpr tyObject_CppRef__SdQetZheNEfwTjB9cyvL0KQ::tyObject_CppRef__SdQetZheNEfwTjB9cyvL0KQ(const tyObject_CppRef__SdQetZheNEfwTjB9cyvL0KQ&)’
  /home/sapo/.cache/nim/nimline_test_d/@mnimline_test.nim.cpp:56:8: note:   no known conversion for argument 1 from ‘essentia::standard::InputBase’ to ‘const tyObject_CppRef__SdQetZheNEfwTjB9cyvL0KQ&’
  /home/sapo/.cache/nim/nimline_test_d/@mnimline_test.nim.cpp:56:8: note: candidate: ‘constexpr tyObject_CppRef__SdQetZheNEfwTjB9cyvL0KQ::tyObject_CppRef__SdQetZheNEfwTjB9cyvL0KQ(tyObject_CppRef__SdQetZheNEfwTjB9cyvL0KQ&&)’
  /home/sapo/.cache/nim/nimline_test_d/@mnimline_test.nim.cpp:56:8: note:   no known conversion for argument 1 from ‘essentia::standard::InputBase’ to ‘tyObject_CppRef__SdQetZheNEfwTjB9cyvL0KQ&&’
  Error: execution of an external compiler program 'gcc -c  -w -march=x86-64 -mtune=generic -O2 -pipe -fno-plt -D_FORTIFY_SOURCE=2 -I./essentia/src/   -I/usr/lib/nim -I/home/sapo/Develop/nim -o /home/sapo/.cache/nim/nimline_test_d/@mnimline_test.nim.cpp.o /home/sapo/.cache/nim/nimline_test_d/@mnimline_test.nim.cpp' failed with exit code: 1
  Run

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• Araq (orginal) [2020-09-18T12:19:18+02:00] view original

  I am unfamiliar with "nimline", please ask also on nimline's issue tracker.

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• fortea (orginal) [2020-09-18T17:47:51+02:00] view original

  I was in contact with the nimline developer by email and he suggested to use nim ptr in place of the CppRef and to use the nimline invokeFunction utility to call a global static methods.

  The problem I have now is that I have a let my_algorithm: ptr Algorithm and I need to call its method input which accepts a string as argument (docs here.

  If I do my_algorithm.input("spectrum") nim tries to execute input(my_algorithm, "spectrum") which obviously is not found in the library. How can I deal with this?

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• shirleyquirk (orginal) [2020-09-18T18:22:50+02:00] view original

  In general, the importcpp pragma but I don't know how that interacts with nimline

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• mratsim (orginal) [2020-09-18T18:24:35+02:00] view original

  I'm not sure if Essentia objects are complex enough to warrant nimline but here is an compilable example of a C++ wrapper:

  • https://github.com/numforge/agent-smith/blob/a2d9251/third_party/ale_wrap.nim#L191-L197

  And an example for C++ vectors, it's pretty straightforward

  • https://github.com/numforge/agent-smith/blob/a2d9251/third_party/std_cpp.nim#L19-L31

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• fortea (orginal) [2020-09-20T22:17:05+02:00] view original

  It looks like you can call methods of Algorithm, so my_algorithm[].input("spectrum") would be my guess

  Thanks! this solved many problems. I'm still trying to understand why I needed it. Is it something like C's (*my_algorithm).input("spectrum")?

  Now the code is compilable and runnable, but it espects a n``std::vector<float>`` whre I can use nim's arrays or seqs. Any idea for a proper casting?

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• mratsim (orginal) [2020-09-21T08:11:24+02:00] view original

  But it seems strange not being able to convert seq to vector

  They have slightly different representation, and one is GC-ed the other is not (unless you compile with --gc:arc). Use copyMem if you want to transfer data from Nim seqs<->std::vector.

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