+
+/* The following macros and typedefs allow an ASN1_ITEM
+ * to be embedded in a structure and referenced. Since
+ * the ASN1_ITEM pointers need to be globally accessible
+ * (possibly from shared libraries) they may exist in
+ * different forms. On platforms that support it the
+ * ASN1_ITEM structure itself will be globally exported.
+ * Other platforms will export a function that returns
+ * an ASN1_ITEM pointer.
+ *
+ * To handle both cases transparently the macros below
+ * should be used instead of hard coding an ASN1_ITEM
+ * pointer in a structure.
+ *
+ * The structure will look like this:
+ *
+ * typedef struct SOMETHING_st {
+ * ...
+ * ASN1_ITEM_EXP *iptr;
+ * ...
+ * } SOMETHING;
+ *
+ * It would be initialised as e.g.:
+ *
+ * SOMETHING somevar = {...,ASN1_ITEM_ref(X509),...};
+ *
+ * and the actual pointer extracted with:
+ *
+ * const ASN1_ITEM *it = ASN1_ITEM_ptr(somevar.iptr);
+ *
+ * Finally an ASN1_ITEM pointer can be extracted from an
+ * appropriate reference with: ASN1_ITEM_rptr(X509). This
+ * would be used when a function takes an ASN1_ITEM * argument.
+ *
+ */
+
+#ifndef ASN1_ITEM_FUNCTIONS
+
+/* ASN1_ITEM pointer exported type */
+typedef const ASN1_ITEM ASN1_ITEM_EXP;
+
+/* Macro to obtain ASN1_ITEM pointer from exported type */
+#define ASN1_ITEM_ptr(iptr) (iptr)
+
+/* Macro to include ASN1_ITEM pointer from base type */
+#define ASN1_ITEM_ref(iptr) (&(iptr##_it))
+
+#define ASN1_ITEM_rptr(ref) (&(ref##_it))
+