tools/ocaml/libs/xb: hide type of Xb.t

Hiding the type will make it easier to change the implementation
in the future without breaking code that relies on it.

No functional change.

Signed-off-by: Edwin Török <edvin.torok@citrix.com>
Acked-by: Christian Lindig <christian.lindig@citrix.com>
(cherry picked from commit 7ade30a145)

tools/ocaml/libs/xb/xb.ml

@@ -196,6 +196,9 @@ let peek_output con = Queue.peek con.pkt_out
 let input_len con = Queue.length con.pkt_in
 let has_in_packet con = Queue.length con.pkt_in > 0
 let get_in_packet con = Queue.pop con.pkt_in
+let has_partial_input con = match con.partial_in with
+	| HaveHdr _ -> true
+	| NoHdr (n, _) -> n < Partial.header_size ()
 let has_more_input con =
 	match con.backend with
 	| Fd _         -> false

tools/ocaml/libs/xb/xb.mli

@@ -66,13 +66,7 @@ type backend_mmap = {
 type backend_fd = { fd : Unix.file_descr; }
 type backend = Fd of backend_fd | Xenmmap of backend_mmap
 type partial_buf = HaveHdr of Partial.pkt | NoHdr of int * bytes
-type t = {
-  backend : backend;
-  pkt_in : Packet.t Queue.t;
-  pkt_out : Packet.t Queue.t;
-  mutable partial_in : partial_buf;
-  mutable partial_out : string;
-}
+type t
 val init_partial_in : unit -> partial_buf
 val reconnect : t -> unit
 val queue : t -> Packet.t -> unit
@@ -97,6 +91,7 @@ val has_output : t -> bool
 val peek_output : t -> Packet.t
 val input_len : t -> int
 val has_in_packet : t -> bool
+val has_partial_input : t -> bool
 val get_in_packet : t -> Packet.t
 val has_more_input : t -> bool
 val is_selectable : t -> bool

tools/ocaml/xenstored/connection.ml

@@ -125,9 +125,7 @@ let get_perm con =
 let set_target con target_domid =
 	con.perm <- Perms.Connection.set_target (get_perm con) ~perms:[Perms.READ; Perms.WRITE] target_domid
 
-let is_backend_mmap con = match con.xb.Xenbus.Xb.backend with
-	| Xenbus.Xb.Xenmmap _ -> true
-	| _ -> false
+let is_backend_mmap con = Xenbus.Xb.is_mmap con.xb
 
 let send_reply con tid rid ty data =
 	if (String.length data) > xenstore_payload_max && (is_backend_mmap con) then
@@ -280,9 +278,7 @@ let get_transaction con tid =
 
 let do_input con = Xenbus.Xb.input con.xb
 let has_input con = Xenbus.Xb.has_in_packet con.xb
-let has_partial_input con = match con.xb.Xenbus.Xb.partial_in with
-	| HaveHdr _ -> true
-	| NoHdr (n, _) -> n < Xenbus.Partial.header_size ()
+let has_partial_input con = Xenbus.Xb.has_partial_input con.xb
 let pop_in con = Xenbus.Xb.get_in_packet con.xb
 let has_more_input con = Xenbus.Xb.has_more_input con.xb