+extern void buffer_readonly_view(struct buffer_if *n, const void*, int32_t len);
+extern void buffer_readonly_clone(struct buffer_if *n, const struct buffer_if*);
+ /* Caller must only use unappend, unprepend et al. on n.
+ * New buffer state (in n) before this can be undefined. After use,
+ * it must NOT be freed. */
+