+(* Not implemented:
+ (* Opaque buffer which can contain arbitrary 8 bit data.
+ * In the C API, this is expressed as <char *, int> pair.
+ * Most other languages have a string type which can contain
+ * ASCII NUL. We use whatever type is appropriate for each
+ * language.
+ * Buffers are limited by the total message size. To transfer
+ * large blocks of data, use FileIn/FileOut parameters instead.
+ * To return an arbitrary buffer, use RBufferOut.
+ *)
+ | BufferIn of string
+*)