+=item B<BIO_write(b, in, inl, written)>
+
+ callback_ex(b, BIO_CB_WRITE, in, inl, 0, 0L, 1L, written)
+
+or
+
+ callback(b, BIO_CB_WRITE, in, inl, 0L, 1L)
+
+is called before the write and
+
+ callback_ex(b, BIO_CB_WRITE | BIO_CB_RETURN, in, inl, 0, 0L, retvalue, written)
+
+or
+
+ callback(b, BIO_CB_WRITE|BIO_CB_RETURN, in, inl, 0L, retvalue)