Adding empty struct support

Author: ktakashi

README.md

@@ -20,6 +20,7 @@ PFFI is a portable foreign function interface for R6RS Scheme implementations.
 - `define-type-alias` is introduced, similar usage as `typedef` in C.
 - `boolean` support for Scheme boolean.
 - Supporting array foreign variable.
+- Empty struct, i.e. `(define-foreign-struct foo)`, is supported
 
 ## Example
 

src/pffi/compat.mzscheme.sls

@@ -204,10 +204,15 @@
 
 (define-syntax callback
   (syntax-rules ()
+    ((_ (conv ...) ret (args ...))
+     (_cprocedure
+      (->immutable-list (list (ffi-type-descriptor-alias args) ...))
+      (ffi-type-descriptor-alias ret)))
     ((_ ret (args ...))
      (_cprocedure
       (->immutable-list (list (ffi-type-descriptor-alias args) ...))
       (ffi-type-descriptor-alias ret)))))
+
 (define-ftype void           _void)
 
 (define (open-shared-object path)

src/pffi/helper.chezscheme.sls

@@ -45,10 +45,16 @@
   (lambda (x)
     (define (register-type-alias! name alias)
       (hashtable-set! *typedef-table* name alias))
-    (syntax-case x (*)
+    (syntax-case x (* callback)
       ((_ name (* alias))
        (register-type-alias! (syntax->datum #'name) 'void*)
        #'(define-ftype name void*))
+      ((_ name (callback (conv ...) ret (args ...)))
+       (register-type-alias! (syntax->datum #'name) (syntax->datum 'void*))
+       #'(define-ftype name void*))
+      ((_ name (callback ret (args ...)))
+       (register-type-alias! (syntax->datum #'name) 'void*)
+       #'(define-ftype name void*))
       ((_ name alias)
        (register-type-alias! (syntax->datum #'name) (syntax->datum #'alias))
        #'(define-ftype name alias)))))

src/pffi/misc.sls

@@ -34,10 +34,10 @@
     (import (only (rnrs) define-syntax syntax-rules define *)
 	    (only (srfi :13) string-map)
             (only (srfi :1) take drop drop-right split-at)
-	    (only (pffi compat) pointer))
+	    (only (pffi compat) pointer callback))
 
 (define-syntax define-type-alias
-  (syntax-rules (*)
+  (syntax-rules (* callback)
     ((_ name (* alias)) (define name pointer))
     ((_ name alias) (define name alias))))
 

src/pffi/struct.sls

@@ -193,10 +193,12 @@
       t))
 
 (define (struct-alignment lis)
-  (apply max (map (lambda (l)
-                    (if (foreign-struct-descriptor? l)
-                        (generic-foreign-struct-descriptor-alignment l)
-                        (type-descriptor-size l))) lis)))
+  (if (null? lis)
+      0
+      (apply max (map (lambda (l)
+			(if (foreign-struct-descriptor? l)
+                            (generic-foreign-struct-descriptor-alignment l)
+                            (type-descriptor-size l))) lis))))
 
 ;; ref
 ;;  http://en.wikipedia.org/wiki/Data_structure_alignment

src/pffi/struct/helper.sls

@@ -66,7 +66,7 @@
 				  x (car fields))))))
        (let loop ((clauses clauses) (fs #f) (par #f) (proto #f) (align #f))
 	 (syntax-case clauses (fields parent protocol alginment)
-	   (() (list fs par proto align))
+	   (() (list (or fs '()) par proto align))
 	   (((fields defs (... ...)) . rest)
 	    (or (not fs)
 		(syntax-violation who "only one fields clause allowed" x

tests/test.scm

@@ -382,4 +382,9 @@
     (test-equal "count p-st" 10 (st-parent-count st))))
 
 
+;; empty struct
+(let ()
+  (define-foreign-struct ok)
+  (test-equal "size of empty struct" 0 size-of-ok))
+
 (test-end)