use dyn.load or library.dynam to call a C++ function in an R package

Question

I am very new to R. I would like to build an R package which will call a C++ function using .Call(). I have a NAMESPACE file, with

useDynLib(mypkg)

where mypkg is also the function name of my c++ code.

It works if I use this line at the begining of the mypkg.R file:

dyn.load("src/mypkg.so")

but I want to use library.dynam instead, so in the zzz.R file, I put

.onLoad<-function(libname, pkgname)
 {
 library.dynam("mypkg", pkgname, libname)
 }

It gives the error when checking the package:

...
Error in .Call("mypkg", PACKAGE = "mypkg") : 
C symbol name "mypkg" not in DLL for package "mypkg".
Error : unable to load R code in package 'mypkg'
...

It looks like the *.so file is generated in the wrong place? Why there is not /libs folder generated?

I would like to build the package to be os independent, is there a way to do it with dyn.load?

And this may be a very silly question, where did pkgname and libname get their input from?

Thank you very much for your help.

Answer 1

You could look at one of the many existing packages (with compiled source code) on CRAN .

Smaller and simpler is easier to grok, so you could eg look at digest which uses a NAMESPACE to load the one shared library built from the handful of C source files, and uses .Call() to access the main entry point.

And then there is of course the manual...