[Libguestfs] [libnbd PATCH v4 03/25] generator: Support Extent64 arg in C code

[Eric Blake]

See the earlier commit "Add Extent64 arg type" for rationale in
supporting a new generator arg type.  This patch adds the C bindings
for use of Extent64: it exposes a new 'struct nbd_extent' in
<libnbd.h>, as well as the code to generate the C bindings for passing
an extent64_closure once a new API uses the type in an upcoming patch.

Note that 'struct nbd_block_descriptor_64' in lib/nbd-protocol.h is
exactly the same as what we want to use in C.  But it is easier to
stick a new public type in <libnbd.h> than to figure out how to expose
just part of a header we only want to use internally, and leaves us
free to alter nbd-protocol.h (which is shared with nbdkit) without
affecting public API.

Signed-off-by: Eric Blake <eblake at redhat.com>
---

v4: split out of larger patch [Laszlo]
---
 generator/API.mli |  2 +-
 generator/C.ml    | 12 ++++++++++++
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/generator/API.mli b/generator/API.mli
index 80633018..96626c9b 100644
--- a/generator/API.mli
+++ b/generator/API.mli
@@ -52,7 +52,7 @@ and
 | BytesPersistOut of string * string
 | Closure of closure       (** function pointer + void *opaque *)
 | Enum of string * enum    (** enum/union type, int in C *)
-| Extent64 of string       (** extent descriptor *)
+| Extent64 of string       (** extent descriptor, struct nbd_extent in C *)
 | Fd of string             (** file descriptor *)
 | Flags of string * flags  (** flags, uint32_t in C *)
 | Int of string            (** small int *)
diff --git a/generator/C.ml b/generator/C.ml
index 606ba1e0..e5a2879b 100644
--- a/generator/C.ml
+++ b/generator/C.ml
@@ -308,6 +308,11 @@ and
          pr "%s, " n;
          if types then pr "size_t ";
          pr "%s" len
+      | CBArrayAndLen (Extent64 n, len) ->
+         if types then pr "nbd_extent *";
+         pr "%s, " n;
+         if types then pr "size_t ";
+         pr "%s" len
       | CBArrayAndLen _ -> assert false
       | CBBytesIn (n, len) ->
          if types then pr "const void *";
@@ -488,6 +493,13 @@ let
   pr "extern int nbd_get_errno (void);\n";
   pr "#define LIBNBD_HAVE_NBD_GET_ERRNO 1\n";
   pr "\n";
+  pr "/* This is used in the callback for nbd_block_status_64.\n";
+  pr " */\n";
+  pr "typedef struct {\n";
+  pr "  uint64_t length;\n";
+  pr "  uint64_t flags;\n";
+  pr "} nbd_extent;\n";
+  pr "\n";
   print_closure_structs ();
   List.iter (
     fun (name, { args; optargs; ret }) ->
-- 
2.41.0