9.3 Using the Foreign Parser

The interface is the function foreign-parser:process-foreign-file.

Suppose we wish to generate the FLI definitions which interface to the C example from 5.2.4 Modifying a string in a C function. The header file test.h needs to be slightly different depending on the platform.

Windows version:

__declspec(dllexport) void __cdecl modify(char *string)

Non-Windows version:

void modify(char *string)

1. Load the Foreign Parser:

   (require "foreign-parser")
   

2. Now generate prototype FLI definitions:

   (foreign-parser:process-foreign-file 
    "test.h"
    :case-sensitive nil)
   =>
   ;;;    Output dff file #P"test-dff.lisp"
   ;;;    Parsing source file "test.h"
    
   ;;; Process-foreign-file : Preprocessing file
    
   ;;; Process-foreign-file : Level 1 parsing
    
   ;;; Process-foreign-file : Selecting foreign forms
   NIL
   

3. You should now have a Lisp file test-dff.lisp containing a form like this:

   (fli:define-foreign-function 
       (modify "modify" :source)
       ((string (:pointer :char)))
     :result-type
     :void
     :language
     :c
     :calling-convention
     :cdecl)
   

4. This edited version passes a string using :ef-mb-string:

   (fli:define-foreign-function
       (modify "modify" :source)
       ((string (:reference (:ef-mb-string :limit 256))))
     :result-type
     :void
     :language
     :c
     :calling-convention
     :cdecl)
   =>
   MODIFY
   

5. Create a DLL containing the C function.
6. Load the foreign code by:

   (fli:register-module "test.dll")
   

   or:

   (fli:register-module "/tmp/test.so")
   

7. Call the C function from LISP:

   (modify "Hello, I am in LISP")
   =>
   NIL
   "'Hello, I am in LISP' modified in a C function"