CPP interop, passing argument by reference (char*& and int&)

[Charles]

Hello again,

I'm trying to wrap a c++ library, the function I want to call has the following 
prototype:

`void UnpackGWDat( unsigned char *input, int insize, unsigned char *&output, 
int &outsize )`

I tried the following wrapper:
    
    
    proc unpackWrapper(input: cstring, inputSize: cint, output {.byref.}: 
cstring, outputSize {.byref.}: cint)  {.importcpp: "UnpackGWDat(@)".}
    
    import sequtils
    
    proc uncompress*(compressed: openArray[byte], compressedSize: int): cstring 
=
      
      var input: string
      input.setLen(compressedSize)
      for i in 0..<compressedSize:
        input[i] = cast[char](compressed[i])
      
      var
        uncompressedFile: cstring
        uncompressedSize: cint
      
      unpackWrapper(input, cast[cint](compressedSize), uncompressedFile, 
uncompressedSize)
      
      return uncompressedFile
    
    
    
    Run

I get the following error:

`.cache/nim/dat_d/@mhuffman.nim.cpp:967:75: error: cannot bind rvalue 
‘(unsigned char*)uncompressedFile’ to ‘unsigned char*&’ 967 | 
UnpackGWDat(nimToCStringConv(input), ((int) (compressedSize_p1)), 
uncompressedFile, uncompressedSize);`

What would be the correct way to do this?