From 55f50ddaf31fe1cb4cda4d15e387280e8f7a8242 Mon Sep 17 00:00:00 2001
From: Philipp Gesang <phg@phi-gamma.net>
Date: Sat, 3 Nov 2018 19:58:42 +0100
Subject: sid: add channel handlers for binary representation

---
 sid.ml  | 26 ++++++++++++++++++++++++++
 sid.mli | 12 ++++++++++++
 2 files changed, 38 insertions(+)

diff --git a/sid.ml b/sid.ml
index 12d708a..0d5c89b 100644
--- a/sid.ml
+++ b/sid.ml
@@ -221,6 +221,32 @@ module PacketRep = struct (* [MS-DTYP] 2.4.22 *)
        ; sid_sub_auths  = sas
        }
 
+  let from_channel ?(endian=Little) ic =
+    try
+      let v = input_byte ic in
+      if v <> 0x01 then
+        Error (Printf.sprintf
+                 "input malformed: expected SID version=0x01, got 0x%0.2x" v) else
+      let nsa = input_byte ic in
+      if max_subauth_count < nsa then
+        Error (Printf.sprintf
+                 "input malformed: up to %d subAuthority elements permitted, \
+                  %d specified"
+                 max_subauth_count nsa) else
+      let n = sizeof_ident_auth + nsa * sizeof_sub_auth in
+      let b = Bytes.make (2 + n) '\x00' in
+      Bytes.set b 0 '\x01';
+      Bytes.set b 1 (char_of_int nsa);
+      really_input ic b 2 n;
+      decode ~endian b
+    with End_of_file ->
+      Error (Printf.sprintf
+               "input malformed: unexpected end of file at offset %d \
+                parsing SID" (pos_in ic))
+
+  let to_channel ?(endian=Little) oc s =
+    encode ~endian s |> output_bytes oc
+
 end (* [module PacketRep] *)
 
 module WellKnown = struct
diff --git a/sid.mli b/sid.mli
index e9b5c78..0a9fbd8 100644
--- a/sid.mli
+++ b/sid.mli
@@ -40,12 +40,24 @@ module StringFmt :
 module PacketRep :
   sig
     type endian = Big | Little
+    (** Specify the endianness when internalizing integers. Only relevant for
+        subauthorities as the identifier authority is specified as big endian.
+        The default is always [Little]. *)
+
     val decode : ?endian:endian -> bytes -> (t, string) result
     (** [decode endian b] decode the byte buffer [b] as a SID. *)
 
     val encode : ?endian:endian -> t -> bytes
     (** [encode endian s] convert SID [s] to the packet representation
         encoding subauthorities in endianness [endian]. *)
+
+    val from_channel : ?endian:endian -> in_channel -> (t, string) result
+    (** [from_channel endian ic] read binary SID from [ic] with endianness
+        [endian]. *)
+
+    val to_channel : ?endian:endian -> out_channel -> t -> unit
+    (** [to_channel endian oc s] write SID [s] in packet representation
+        to channel [oc] with endianness [endian]. *)
   end
 
 (** Pre-defined SID constansts and constructors with fixed identifier
-- 
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