.so files on Linux, .dylib files on macOS and .dll on Windows. Luna is able to work with object files coming from two sources: 1. System-wide available dynamic libraries. If a library is installed on your machine, Luna will be able to use it. Unfortunately, this requires all the users of your library to have the dynamic library installed in their systems. For most libraries this is not a good solution, it will, however, work fine for bindings to the most popular libraries and for quick prototyping. 2. Object files inside the project tree. You can drop any shared object file into the native_libs/PLATFORM directory inside your project (PLATFORM is macos, linux or windows) and use it from Luna. This is a great solution for making sure users are able to use your library without any external dependencies. It's also the only way to include your own C extension or wrapper.lookupSymbol function from Std.Foreign module. It takes a shared object file name and a name of the symbol to lookup, and returns a FunPtr object. The library resolution takes into account the most common naming conventions, so that it is possible to use the same call with a file named awesome.dylib as well as libawesome.4.so. So, in our example, you can just write:call method of FunPtr does. It takes two arguments – a representation for the output type and a list of objects of type CArg, representing the function arguments. Note that not every type can be represented as a C argument. The types that can (numeric types, pointers and a few more) are converted using their toCArg method. So, back to our example. The awesomeFunction expects and int and returns an int. Note that Luna's Ints are different from C's, so the latter are represented by the class CInt. This is what our function call looks like:CInt. Most Luna programs, however, use standard Ints and these cannot easily be represented in C. This can be fixed with the help of CInt.fromInt function, which converts an ordinary Int object into a CInt. It also returns a CInt, which again is not very handy. This can be fixed with the help of toInt method of CInt. The final version of our wrapper, which operates on Ints and from the outside is nearly indistinguishable from pure Luna code looks like this:Std.Foreign.C.Value module. This section is a short overview of all of them.fromInt and toInt methods, support comparison and basic arithmetic operators. The following table shows the C types and their Luna counterparts.CDouble and CFloat classes as counterparts of C's double and float, respectively. Both classes define fromReal and toReal methods for conversion between them and Luna's Real. They also support basic arithmetic and comparison operators.Pointer. It takes a single argument denoting the type of its content. So, for example, Pointer CInt corresponds to int* in C, while Pointer (Pointer None) is void**.X use the malloc method on pointer class:X object must define a byteSize method, returning the size in bytes of the structure. You can also use mallocElems to create arrays like so:free method – if you're done with your ptr just call ptr.free.read method. It works on a Ptr X and returns a value of type X. Keep in mind that in order for this to work, the X type must define a readPtr method that takes a bare pointer and plucks the fields one by one.ptr of type Pointer X, call ptr.write x. Again, this requires the type X to define writePtr method.ptr.moveBytes i method – it returns a new pointer, resulting from adding i bytes to ptr. There is also a moveElems method, that will move the pointer by the specified number of elements (i.e. by number of elements * element.byteSize bytes).X type call, like for pointer, malloc method just on the managed pointer class:mallocElems works just like for regular poinetrs. To create array with managed pointer use:ptr. For this finalizer function fin is required. Finalizer will be run when the pointer will be garbage collected:read, write, moveElems works the same way for managed pointers like for regular pointers.SHA1 function from openssl. It takes an input buffer of type unsigned char*, a size_t denoting the length of input and an output buffer of type unsigned char* and length 20. Suppose you have a list of Luna Ints and want to compute the SHA1 digest of this list, as another list of Ints. This is how this can be done with Luna's FFI: