copy with-c-layout to mem namespace

src/clj/coffi/mem.clj

@@ -1546,6 +1546,33 @@
   :args (s/cat :new-type qualified-keyword?
                :aliased-type any?))
 
+(defn- with-c-layout
+  "Forces a struct specification to C layout rules.
+
+  This will add padding fields between fields to match C alignment
+  requirements."
+  [struct-spec]
+  (let [aligned-fields
+        (loop [offset 0
+               aligned-fields []
+               fields (nth struct-spec 1)]
+          (if (seq fields)
+            (let [[[_ type :as field] & fields] fields
+                  size (mem/size-of type)
+                  align (mem/align-of type)
+                  r (rem offset align)]
+              (recur (cond-> (+ offset size)
+                       (pos? r) (+ (- align r)))
+                     (cond-> aligned-fields
+                       (pos? r) (conj [::padding [::mem/padding (- align r)]])
+                       :always (conj field))
+                     fields))
+            (let [strongest-alignment (reduce max (map (comp mem/align-of second) (nth struct-spec 1)))
+                  r (rem offset strongest-alignment)]
+              (cond-> aligned-fields
+                (pos? r) (conj [::padding [::mem/padding (- strongest-alignment r)]])))))]
+    (assoc struct-spec 1 aligned-fields)))
+
 (defn- typename->coffi-typename [_type]
   (get
    {'byte    ::byte