[Xen-devel] [PATCH 1/1] tools/ocaml: Re-introduce Xenctrl.with_intf wrapper

[Christian Lindig <christian.lindig@xxxxxxxxxx>]

Commit 81946a73dc975a7dafe9017a8e61d1e64fdbedbf removed
Xenctrl.with_intf based on its undesirable behaviour of opening and
closing a Xenctrl connection with every invocation. This commit
re-introduces with_intf but with an updated behaviour: it maintains a
global Xenctrl connection which is opened upon first usage and kept
open. This handle can be obtained by clients using new functions
get_handle() and close_handle().

The main motivation of re-introducing with_intf is that otherwise
clients will have to implement this functionality individually.

Signed-off-by: Christian Lindig <christian.lindig@xxxxxxxxxx>
---
 tools/ocaml/libs/xc/xenctrl.ml  | 22 ++++++++++++++++++++++
 tools/ocaml/libs/xc/xenctrl.mli | 10 ++++++++++
 2 files changed, 32 insertions(+)

diff --git a/tools/ocaml/libs/xc/xenctrl.ml b/tools/ocaml/libs/xc/xenctrl.ml
index 955dd92546..44857a2d1c 100644
--- a/tools/ocaml/libs/xc/xenctrl.ml
+++ b/tools/ocaml/libs/xc/xenctrl.ml
@@ -141,6 +141,28 @@ type handle
 external interface_open: unit -> handle = "stub_xc_interface_open"
 external interface_close: handle -> unit = "stub_xc_interface_close"
 
+let handle = ref None
+
+let get_handle () = !handle
+
+let close_handle () =
+       match !handle with
+       | Some h -> interface_close h
+       | None -> ()
+
+let with_intf f =
+       match !handle with
+       | Some h -> f h
+       | None ->
+               let h =
+                       try interface_open () with
+                       | e ->
+                               let msg = Printexc.to_string e in
+                               failwith ("failed to open xenctrl: "^msg)
+               in
+               handle := Some h;
+               f h
+
 external domain_create: handle -> domctl_create_config -> domid
        = "stub_xc_domain_create"
 
diff --git a/tools/ocaml/libs/xc/xenctrl.mli b/tools/ocaml/libs/xc/xenctrl.mli
index eeed24fa96..b31d7fefe5 100644
--- a/tools/ocaml/libs/xc/xenctrl.mli
+++ b/tools/ocaml/libs/xc/xenctrl.mli
@@ -109,6 +109,16 @@ type handle
 external interface_open : unit -> handle = "stub_xc_interface_open"
 external interface_close : handle -> unit = "stub_xc_interface_close"
 
+(** [with_intf f] runs [f] with a global handle that is opened on demand
+ * and kept open. A client should use either [interface_open]
+ * or [with_intf] but not mix both.
+ *)
+val with_intf : (handle -> 'a) -> 'a
+(** [get_handle] returns the global handle used by [with_intf] *)
+val get_handle: unit -> handle option
+(** [close handle] closes the handle maintained by [with_intf] *)
+val close_handle: unit -> unit
+
 external domain_create : handle -> domctl_create_config -> domid
   = "stub_xc_domain_create"
 external domain_sethandle : handle -> domid -> string -> unit = 
"stub_xc_domain_sethandle"
-- 
2.19.1


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