1 files changed, 23 insertions, 0 deletions
diff --git a/src/message.ml b/src/message.ml
new file mode 100644
index 0000000..24803fe
--- /dev/null
+++ b/src/message.ml
@@ -0,0 +1,23 @@
+(** The wire protocol of VyConf.
+
+    Messages are preceded by a length header, four bytes in network order.
+ *)
+
+
+let read ic =
+    let header = Bytes.create 4 in
+    let%lwt () = Lwt_io.read_into_exactly ic header 0 4 in
+    let length = EndianBytes.BigEndian.get_int32 header 0 |> Int32.to_int in
+    if length < 0 then failwith (Printf.sprintf "Bad message length: %d" length) else
+    let buffer = Bytes.create length in
+    let%lwt () = Lwt_io.read_into_exactly ic buffer 0 length in
+    Lwt.return buffer
+
+let write oc msg =
+    let length = Bytes.length msg in
+    let length' = Int32.of_int length in
+    if length' < 0l then failwith (Printf.sprintf "Bad message length: %d" length) else
+    let header = Bytes.create 4 in
+    let () = EndianBytes.BigEndian.set_int32 header 0 length' in
+    let%lwt () = Lwt_io.write_from_exactly oc header 0 4 in
+    Lwt_io.write_from_exactly oc msg 0 length