+
+ Example for using the new callback interface:
+
+ int (*my_callback)(int a, int b, BN_GENCB *cb) = ...;
+ void *my_arg = ...;
+ BN_GENCB my_cb;
+
+ BN_GENCB_set(&my_cb, my_callback, my_arg);
+
+ return BN_is_prime_ex(some_bignum, BN_prime_checks, NULL, &cb);
+ /* For the meaning of a, b in calls to my_callback(), see the
+ * documentation of the function that calls the callback.
+ * cb will point to my_cb; my_arg can be retrieved as cb->arg.
+ * my_callback should return 1 if it wants BN_is_prime_ex()
+ * to continue, or 0 to stop.
+ */
+