1.7.1.1 In parameters

In parameters are passed as positional arguments in the order they are specified and do not affect the return values.

• A parameter with the string attribute can be passed either as a foreign pointer or as a Lisp string (converted to a foreign string with dynamic extent for the duration of the call).
• A parameter whose type is either an array type or a pointer type with a size_is attribute can be passed either as a foreign pointer or, if the element type is not a foreign aggregate type, as a Lisp array of the appropriate rank (converted to a foreign array with dynamic extent for the duration of the call).
• Otherwise, the Lisp value is converted using the FLI according to the mapping of types defined above.

For example, given the IDL

import "unknwn.idl";

[ object,

  uuid(E37A70A0-EFC9-11D5-BF02-000347024BE1)

]

interface IArgumentExamples : IUnknown

{

  typedef [string] char *argString;

  HRESULT inMethod([in] int inInt,

                   [in] argString inString,

                   [in] int inArraySize,

                   [in, size_is(inArraySize)] int *inArray);

}

the method in-method can be called with Lisp objects like this:

(let ((array #(7 6)))

  (call-com-interface (arg-example i-argument-examples

                                   in-method)

                      42

                      "the answer"

                      (length array)

                      array))

or with foreign pointers like this:

(fli:with-dynamic-foreign-objects ()

  (let* ((farray-size 2)

         (farray (fli:allocate-dynamic-foreign-object

                  :type :int

                  :nelems farray-size

                  :initial-contents '(7 6))))

    (fli:with-foreign-string (fstring elt-count byte-count)

        "the answer"

      (declare (ignore elt-count byte-count))

      (call-com-interface (arg-example i-argument-examples

                                       in-method)

                          42

                          fstring

                          farray-size

                          farray))))

Note that the int arguments are always passed as Lisp integer because int is a primitive type.