CCSDS AOS (Advanced Orbiting Systems) Transfer Frame for satellite downlinks
Add CCSDS space protocol libraries: aos, clcw, uslp
New libraries for CCSDS (Consultative Committee for Space Data Systems)
protocols:
- ocaml-aos: AOS (Advanced Orbiting Systems) Transfer Frame (CCSDS 732.0-B-4)
- ocaml-clcw: CLCW (Communications Link Control Word) for COP-1
- ocaml-uslp: USLP (Unified Space Link Protocol) Transfer Frame
All use ocamlformat 0.28.1.
+825
+1
.ocamlformat
+1
.ocamlformat
···
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version = 0.28.1
+21
LICENSE.md
+21
LICENSE.md
···
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+
MIT License
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Copyright (c) 2025 Thomas Gazagnaire
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Permission is hereby granted, free of charge, to any person obtaining a copy
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of this software and associated documentation files (the "Software"), to deal
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in the Software without restriction, including without limitation the rights
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+
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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copies of the Software, and to permit persons to whom the Software is
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furnished to do so, subject to the following conditions:
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The above copyright notice and this permission notice shall be included in all
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copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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SOFTWARE.
+63
README.md
+63
README.md
···
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# ocaml-aos
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CCSDS AOS (Advanced Orbiting Systems) Transfer Frame parser and encoder.
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AOS frames are defined in [CCSDS 732.0-B-4](https://public.ccsds.org/Pubs/732x0b4.pdf)
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and used for high-rate downlinks from satellites.
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## Installation
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```
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opam install aos
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```
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## Usage
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```ocaml
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(* Decode an AOS frame *)
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let () =
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let buf = (* ... frame bytes ... *) in
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match Aos.decode buf with
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| Error e -> Printf.printf "Error: %a\n" Aos.pp_error e
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| Ok frame ->
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Printf.printf "SCID: %d, VCID: %d, Data: %d bytes\n"
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(Aos.scid_to_int frame.header.scid)
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(Aos.vcid_to_int frame.header.vcid)
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(String.length frame.data)
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+
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(* Create and encode an AOS frame *)
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let () =
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let scid = Aos.scid_exn 42 in
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let vcid = Aos.vcid_exn 5 in
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let frame = Aos.v ~scid ~vcid ~vcfc:12345 "payload data" in
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let encoded = Aos.encode frame in
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Printf.printf "Encoded: %d bytes\n" (String.length encoded)
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(* Create a frame with CLCW *)
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let () =
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let scid = Aos.scid_exn 42 in
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let vcid = Aos.vcid_exn 5 in
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let clcw_vcid = Clcw.vcid_exn 5 in
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let clcw = Clcw.v ~vcid:clcw_vcid ~report_value:100 () in
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let frame = Aos.with_clcw ~scid ~vcid ~vcfc:1 ~clcw "data" in
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let encoded = Aos.encode frame in
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Printf.printf "Frame with CLCW: %d bytes\n" (String.length encoded)
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```
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## Frame Format
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```
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Primary header (6 bytes):
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Byte 0-1: TFVN(2b) | SCID(8b) | VCID(6b)
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Byte 2-4: VC Frame Count (24b)
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Byte 5: RF(1b) | SF(1b) | spare(2b) | VFCC(4b)
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Optional insert zone (variable)
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Data field (variable)
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Optional OCF (4 bytes) - Contains CLCW
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Optional FECF (2 bytes) - CRC-16-CCITT
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```
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## License
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MIT
+31
aos.opam
+31
aos.opam
···
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# This file is generated by dune, edit dune-project instead
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opam-version: "2.0"
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synopsis: "CCSDS AOS Transfer Frames (CCSDS 732.0-B-4)"
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description:
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"Parser and encoder for CCSDS Advanced Orbiting Systems (AOS) Transfer Frames. Supports 6-byte primary header, insert zone, data field, Operational Control Field (OCF) with CLCW, and Frame Error Control Field (FECF) with CRC-16-CCITT."
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maintainer: ["Thomas Gazagnaire <thomas@gazagnaire.org>"]
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authors: ["Thomas Gazagnaire <thomas@gazagnaire.org>"]
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license: "MIT"
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depends: [
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"dune" {>= "3.0"}
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"ocaml" {>= "4.14"}
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"clcw" {>= "0.1"}
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"alcotest" {with-test}
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"crowbar" {with-test}
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"odoc" {with-doc}
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]
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build: [
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["dune" "subst"] {dev}
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[
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"dune"
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"build"
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"-p"
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name
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"-j"
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jobs
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"@install"
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"@runtest" {with-test}
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"@doc" {with-doc}
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]
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]
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dev-repo: "https://tangled.org/gazagnaire.org/ocaml-aos"
+26
dune-project
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dune-project
···
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(lang dune 3.0)
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(name aos)
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(generate_opam_files true)
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(license MIT)
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(authors "Thomas Gazagnaire <thomas@gazagnaire.org>")
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(maintainers "Thomas Gazagnaire <thomas@gazagnaire.org>")
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(source
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(uri https://tangled.org/gazagnaire.org/ocaml-aos))
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(package
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(name aos)
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(synopsis "CCSDS AOS Transfer Frames (CCSDS 732.0-B-4)")
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(description
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"Parser and encoder for CCSDS Advanced Orbiting Systems (AOS) Transfer \
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Frames. Supports 6-byte primary header, insert zone, data field, \
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Operational Control Field (OCF) with CLCW, and Frame Error Control Field \
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(FECF) with CRC-16-CCITT.")
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(depends
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(ocaml (>= 4.14))
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(clcw (>= 0.1))
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(alcotest :with-test)
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(crowbar :with-test)))
+24
fuzz/fuzz_aos.ml
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fuzz/fuzz_aos.ml
···
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(*---------------------------------------------------------------------------
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Copyright (c) 2025 Thomas Gazagnaire. All rights reserved.
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SPDX-License-Identifier: MIT
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---------------------------------------------------------------------------*)
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open Crowbar
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let () =
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add_test ~name:"aos roundtrip"
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[ range 256; range 64; range 0x1000000; bytes ]
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(fun scid_val vcid_val vcfc data ->
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match (Aos.scid scid_val, Aos.vcid vcid_val) with
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| Some scid, Some vcid -> (
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let frame = Aos.v ~scid ~vcid ~vcfc data in
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let encoded = Aos.encode frame in
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match Aos.decode encoded with
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| Error e -> fail (Fmt.str "decode failed: %a" Aos.pp_error e)
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| Ok frame' -> check_eq ~pp:Aos.pp ~eq:Aos.equal frame frame')
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| _ -> ())
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let () =
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add_test ~name:"aos decode random bytes" [ bytes ] (fun buf ->
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(* Just check decode doesn't crash on random input *)
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ignore (Aos.decode buf))
+379
lib/aos.ml
+379
lib/aos.ml
···
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(*---------------------------------------------------------------------------
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Copyright (c) 2025 Thomas Gazagnaire. All rights reserved.
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SPDX-License-Identifier: MIT
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---------------------------------------------------------------------------*)
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(** CCSDS AOS (Advanced Orbiting Systems) Transfer Frame (CCSDS 732.0-B-4).
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{b Primary header (6 bytes)}
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{v
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Byte 0-1: TFVN(2b) | SCID(8b) | VCID(6b)
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Byte 2-4: VC Frame Count (24b)
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Byte 5: RF(1b) | SF(1b) | spare(2b) | VFCC(4b)
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v}
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{b Invariants}
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- TFVN must be 0 or 1
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- SCID is 8 bits (0-255)
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- VCID is 6 bits (0-63), with 63 reserved for idle frames
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- VCFC is 24 bits (0-16,777,215) *)
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(* {1 Security limits} *)
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let max_frame_len = 2048
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(* {1 Spacecraft ID: 8 bits for AOS, 0-255} *)
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type scid = int
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let scid n = if n >= 0 && n <= 255 then Some n else None
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let scid_exn n =
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if n >= 0 && n <= 255 then n
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else invalid_arg (Printf.sprintf "scid: %d out of range 0-255" n)
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let scid_to_int s = s
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(* {1 Virtual Channel ID: 6 bits for AOS, 0-63} *)
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type vcid = int
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let vcid n = if n >= 0 && n <= 63 then Some n else None
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let vcid_exn n =
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if n >= 0 && n <= 63 then n
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else invalid_arg (Printf.sprintf "vcid: %d out of range 0-63" n)
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let vcid_to_int v = v
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(* {1 Constants} *)
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let header_len = 6
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let ocf_len = 4
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let fecf_len = 2
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let idle_vcid = 63
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(* {1 Types} *)
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type header = {
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version : int;
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scid : scid;
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vcid : vcid;
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vcfc : int;
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replay_flag : bool;
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vc_count_flag : bool;
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spare : int;
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vc_count_cycle : int;
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}
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type t = {
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header : header;
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insert_zone : string option;
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data : string;
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ocf : int option;
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fecf : int option;
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}
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type error =
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| Truncated of { need : int; have : int }
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| Invalid_version of int
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| Invalid_scid of int
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| Invalid_vcid of int
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| Fecf_mismatch of { expected : int; actual : int }
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let pp_error ppf = function
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| Truncated { need; have } ->
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Format.fprintf ppf "Truncated: need %d bytes, have %d" need have
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| Invalid_version v ->
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Format.fprintf ppf "Invalid version: %d (expected 0 or 1)" v
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| Invalid_scid s -> Format.fprintf ppf "Invalid SCID: %d" s
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| Invalid_vcid v -> Format.fprintf ppf "Invalid VCID: %d" v
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| Fecf_mismatch { expected; actual } ->
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Format.fprintf ppf "FECF mismatch: expected 0x%04X, got 0x%04X" expected
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actual
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(* {1 Binary helpers} *)
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let get_u8 s i = Char.code (String.get s i)
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let get_u16_be s i =
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let b0 = get_u8 s i in
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let b1 = get_u8 s (i + 1) in
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(b0 lsl 8) lor b1
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+
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let get_u24_be s i =
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let b0 = get_u8 s i in
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let b1 = get_u8 s (i + 1) in
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let b2 = get_u8 s (i + 2) in
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(b0 lsl 16) lor (b1 lsl 8) lor b2
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+
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let get_u32_be s i =
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let b0 = get_u8 s i in
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let b1 = get_u8 s (i + 1) in
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let b2 = get_u8 s (i + 2) in
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let b3 = get_u8 s (i + 3) in
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(b0 lsl 24) lor (b1 lsl 16) lor (b2 lsl 8) lor b3
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+
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let set_u8 b i v = Bytes.set b i (Char.chr (v land 0xFF))
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+
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let set_u16_be b i v =
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set_u8 b i (v lsr 8);
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set_u8 b (i + 1) v
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+
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let set_u24_be b i v =
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set_u8 b i (v lsr 16);
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set_u8 b (i + 1) (v lsr 8);
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set_u8 b (i + 2) v
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+
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let set_u32_be b i v =
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set_u8 b i (v lsr 24);
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set_u8 b (i + 1) (v lsr 16);
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set_u8 b (i + 2) (v lsr 8);
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set_u8 b (i + 3) v
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+
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(* {1 CRC-16-CCITT} *)
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+
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let crc16_ccitt_table =
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let table = Array.make 256 0 in
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for i = 0 to 255 do
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let crc = ref (i lsl 8) in
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for _ = 0 to 7 do
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if !crc land 0x8000 <> 0 then crc := (!crc lsl 1) lxor 0x1021
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else crc := !crc lsl 1
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done;
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table.(i) <- !crc land 0xFFFF
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done;
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table
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+
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let compute_fecf data =
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+
let crc = ref 0xFFFF in
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+
for i = 0 to String.length data - 1 do
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+
let byte = Char.code data.[i] in
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+
let idx = (!crc lsr 8) lxor byte land 0xFF in
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+
crc := (!crc lsl 8) lxor crc16_ccitt_table.(idx) land 0xFFFF
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done;
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!crc
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+
157
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(* {1 Header decoding} *)
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+
159
+
let decode_header buf =
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+
let len = String.length buf in
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+
if len < header_len then Error (Truncated { need = header_len; have = len })
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+
else
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+
let w0 = get_u16_be buf 0 in
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+
let version = (w0 lsr 14) land 0x3 in
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+
if version > 1 then Error (Invalid_version version)
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+
else
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+
let scid_val = (w0 lsr 6) land 0xFF in
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+
let vcid_val = w0 land 0x3F in
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+
let vcfc = get_u24_be buf 2 in
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+
let b5 = get_u8 buf 5 in
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+
let replay_flag = (b5 lsr 7) land 1 = 1 in
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+
let vc_count_flag = (b5 lsr 6) land 1 = 1 in
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+
let spare = (b5 lsr 4) land 0x3 in
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+
let vc_count_cycle = b5 land 0xF in
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Ok
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{
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version;
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scid = scid_val;
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vcid = vcid_val;
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vcfc;
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replay_flag;
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+
vc_count_flag;
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spare;
184
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vc_count_cycle;
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+
}
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+
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(* {1 Frame decoding} *)
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+
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+
let decode ?(frame_len = 0) ?(insert_zone_len = 0) ?(expect_ocf = true)
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+
?(expect_fecf = true) ?(check_fecf = true) buf =
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+
let buf_len = String.length buf in
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+
match decode_header buf with
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| Error e -> Error e
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+
| Ok header ->
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+
let ocf_size = if expect_ocf then ocf_len else 0 in
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+
let fecf_size = if expect_fecf then fecf_len else 0 in
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+
let frame_len = if frame_len > 0 then frame_len else buf_len in
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+
if buf_len < frame_len then
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Error (Truncated { need = frame_len; have = buf_len })
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+
else
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+
let data_len =
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+
frame_len - header_len - insert_zone_len - ocf_size - fecf_size
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in
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+
if data_len < 0 then
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Error
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+
(Truncated
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{
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+
need = header_len + insert_zone_len + ocf_size + fecf_size;
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+
have = frame_len;
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+
})
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+
else
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+
let insert_zone =
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+
if insert_zone_len > 0 then
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Some (String.sub buf header_len insert_zone_len)
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else None
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+
in
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+
let data_off = header_len + insert_zone_len in
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+
let data = String.sub buf data_off data_len in
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+
let ocf_off = data_off + data_len in
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+
let ocf =
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+
if ocf_size > 0 then Some (get_u32_be buf ocf_off) else None
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+
in
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+
let fecf_off = ocf_off + ocf_size in
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+
if fecf_size > 0 then
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+
let fecf_val = get_u16_be buf fecf_off in
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+
if check_fecf then
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let expected = compute_fecf (String.sub buf 0 fecf_off) in
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+
if expected <> fecf_val then
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Error (Fecf_mismatch { expected; actual = fecf_val })
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+
else Ok { header; insert_zone; data; ocf; fecf = Some fecf_val }
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+
else Ok { header; insert_zone; data; ocf; fecf = Some fecf_val }
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else Ok { header; insert_zone; data; ocf; fecf = None }
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+
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(* {1 Frame encoding} *)
235
+
236
+
let encode_header buf off hdr =
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(* Byte 0-1: version(2b) | scid(8b) | vcid(6b) *)
238
+
let w0 =
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((hdr.version land 0x3) lsl 14)
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lor ((scid_to_int hdr.scid land 0xFF) lsl 6)
241
+
lor (vcid_to_int hdr.vcid land 0x3F)
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+
in
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+
set_u16_be buf off w0;
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+
(* Byte 2-4: vcfc (24b) *)
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+
set_u24_be buf (off + 2) (hdr.vcfc land 0xFFFFFF);
246
+
(* Byte 5: rf(1b) | sf(1b) | spare(2b) | vfcc(4b) *)
247
+
let b5 =
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+
((if hdr.replay_flag then 1 else 0) lsl 7)
249
+
lor ((if hdr.vc_count_flag then 1 else 0) lsl 6)
250
+
lor ((hdr.spare land 0x3) lsl 4)
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+
lor (hdr.vc_count_cycle land 0xF)
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+
in
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+
set_u8 buf (off + 5) b5
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+
255
+
let encode ?(insert_zone_len = 0) ?(with_ocf = true) ?(with_fecf = true) frame =
256
+
let ocf_size = if with_ocf then ocf_len else 0 in
257
+
let fecf_size = if with_fecf then fecf_len else 0 in
258
+
let iz_len = insert_zone_len in
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+
let data_len = String.length frame.data in
260
+
let total_len = header_len + iz_len + data_len + ocf_size + fecf_size in
261
+
let buf = Bytes.make total_len '\000' in
262
+
(* Header *)
263
+
encode_header buf 0 frame.header;
264
+
(* Insert Zone *)
265
+
(match frame.insert_zone with
266
+
| Some iz when iz_len > 0 ->
267
+
let copy_len = min (String.length iz) iz_len in
268
+
Bytes.blit_string iz 0 buf header_len copy_len
269
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| _ -> ());
270
+
(* Data *)
271
+
Bytes.blit_string frame.data 0 buf (header_len + iz_len) data_len;
272
+
(* OCF *)
273
+
(if with_ocf then
274
+
let ocf_off = header_len + iz_len + data_len in
275
+
match frame.ocf with Some ocf -> set_u32_be buf ocf_off ocf | None -> ());
276
+
(* FECF *)
277
+
if with_fecf then begin
278
+
let fecf_off = header_len + iz_len + data_len + ocf_size in
279
+
let crc = compute_fecf (Bytes.sub_string buf 0 fecf_off) in
280
+
set_u16_be buf fecf_off crc
281
+
end;
282
+
Bytes.to_string buf
283
+
284
+
let encoded_len ?(insert_zone_len = 0) ?(with_ocf = true) ?(with_fecf = true)
285
+
frame =
286
+
let ocf_size = if with_ocf then ocf_len else 0 in
287
+
let fecf_size = if with_fecf then fecf_len else 0 in
288
+
header_len + insert_zone_len + String.length frame.data + ocf_size + fecf_size
289
+
290
+
(* {1 Predicates} *)
291
+
292
+
let is_idle frame = vcid_to_int frame.header.vcid = idle_vcid
293
+
294
+
(* {1 Pretty-printing} *)
295
+
296
+
let pp_header ppf hdr =
297
+
Format.fprintf ppf
298
+
"@[<hv 2>{ version=%d;@ scid=%d;@ vcid=%d;@ vcfc=%d;@ rf=%b;@ sf=%b }@]"
299
+
hdr.version hdr.scid hdr.vcid hdr.vcfc hdr.replay_flag hdr.vc_count_flag
300
+
301
+
let pp ppf frame =
302
+
Format.fprintf ppf "@[<v 2>AOS_frame %a@ data[%d bytes]%a%a%a@]" pp_header
303
+
frame.header (String.length frame.data)
304
+
(fun ppf -> function
305
+
| Some iz ->
306
+
Format.fprintf ppf "@ insert_zone[%d bytes]" (String.length iz)
307
+
| None -> ())
308
+
frame.insert_zone
309
+
(fun ppf -> function
310
+
| Some ocf -> Format.fprintf ppf "@ ocf=0x%08X" ocf | None -> ())
311
+
frame.ocf
312
+
(fun ppf -> function
313
+
| Some f -> Format.fprintf ppf "@ fecf=0x%04X" f | None -> ())
314
+
frame.fecf
315
+
316
+
let equal_header a b =
317
+
a.version = b.version && a.scid = b.scid && a.vcid = b.vcid && a.vcfc = b.vcfc
318
+
&& a.replay_flag = b.replay_flag
319
+
&& a.vc_count_flag = b.vc_count_flag
320
+
&& a.spare = b.spare
321
+
&& a.vc_count_cycle = b.vc_count_cycle
322
+
323
+
let equal a b =
324
+
let ocf_equal o1 o2 =
325
+
match (o1, o2) with
326
+
| None, None -> true
327
+
| Some x, Some y -> x = y
328
+
| None, Some 0 | Some 0, None -> true
329
+
| _ -> false
330
+
in
331
+
equal_header a.header b.header
332
+
&& a.insert_zone = b.insert_zone
333
+
&& a.data = b.data && ocf_equal a.ocf b.ocf
334
+
335
+
(* {1 Constructors} *)
336
+
337
+
let v ?(version = 1) ?(replay_flag = false) ?(vc_count_flag = false)
338
+
?(vc_count_cycle = 0) ?(insert_zone = None) ?(ocf = None) ?(fecf = None)
339
+
~scid ~vcid ~vcfc data =
340
+
let header =
341
+
{
342
+
version;
343
+
scid;
344
+
vcid;
345
+
vcfc = vcfc land 0xFFFFFF;
346
+
replay_flag;
347
+
vc_count_flag;
348
+
spare = 0;
349
+
vc_count_cycle = vc_count_cycle land 0xF;
350
+
}
351
+
in
352
+
{ header; insert_zone; data; ocf; fecf }
353
+
354
+
(* {1 CLCW Integration} *)
355
+
356
+
let get_clcw frame =
357
+
match frame.ocf with None -> None | Some word -> Some (Clcw.decode word)
358
+
359
+
let set_clcw frame clcw =
360
+
let ocf = Some (Clcw.encode clcw) in
361
+
{ frame with ocf }
362
+
363
+
let with_clcw ?(version = 1) ?(replay_flag = false) ?(vc_count_flag = false)
364
+
?(vc_count_cycle = 0) ?(insert_zone = None) ?(fecf = None) ~scid ~vcid ~vcfc
365
+
~clcw data =
366
+
let ocf = Some (Clcw.encode clcw) in
367
+
let header =
368
+
{
369
+
version;
370
+
scid;
371
+
vcid;
372
+
vcfc = vcfc land 0xFFFFFF;
373
+
replay_flag;
374
+
vc_count_flag;
375
+
spare = 0;
376
+
vc_count_cycle = vc_count_cycle land 0xF;
377
+
}
378
+
in
379
+
{ header; insert_zone; data; ocf; fecf }
+164
lib/aos.mli
+164
lib/aos.mli
···
1
+
(*---------------------------------------------------------------------------
2
+
Copyright (c) 2025 Thomas Gazagnaire. All rights reserved.
3
+
SPDX-License-Identifier: MIT
4
+
---------------------------------------------------------------------------*)
5
+
6
+
(** CCSDS AOS (Advanced Orbiting Systems) Transfer Frame (CCSDS 732.0-B-4).
7
+
8
+
AOS frames are used for high-rate downlinks from satellites. They feature a
9
+
6-byte primary header, optional insert zone, variable-length data field,
10
+
optional OCF (Operational Control Field with CLCW), and optional FECF (Frame
11
+
Error Control Field with CRC-16-CCITT). *)
12
+
13
+
(** {1 Constants} *)
14
+
15
+
val header_len : int
16
+
(** Primary header length (6 bytes). *)
17
+
18
+
val ocf_len : int
19
+
(** OCF length (4 bytes). *)
20
+
21
+
val fecf_len : int
22
+
(** FECF length (2 bytes). *)
23
+
24
+
val idle_vcid : int
25
+
(** Reserved VCID for idle frames (63). *)
26
+
27
+
val max_frame_len : int
28
+
(** Maximum frame length for security limits. *)
29
+
30
+
(** {1 Spacecraft ID} *)
31
+
32
+
type scid = private int
33
+
(** Spacecraft Identifier (8 bits, 0-255). *)
34
+
35
+
val scid : int -> scid option
36
+
val scid_exn : int -> scid
37
+
val scid_to_int : scid -> int
38
+
39
+
(** {1 Virtual Channel ID} *)
40
+
41
+
type vcid = private int
42
+
(** Virtual Channel Identifier (6 bits, 0-63). *)
43
+
44
+
val vcid : int -> vcid option
45
+
val vcid_exn : int -> vcid
46
+
val vcid_to_int : vcid -> int
47
+
48
+
(** {1 Types} *)
49
+
50
+
type header = {
51
+
version : int;
52
+
scid : scid;
53
+
vcid : vcid;
54
+
vcfc : int; (** Virtual Channel Frame Count (24 bits). *)
55
+
replay_flag : bool; (** Replay flag. *)
56
+
vc_count_flag : bool; (** VC count usage flag. *)
57
+
spare : int; (** Spare bits. *)
58
+
vc_count_cycle : int; (** VC count cycle (4 bits). *)
59
+
}
60
+
(** AOS frame primary header. *)
61
+
62
+
type t = {
63
+
header : header;
64
+
insert_zone : string option; (** Optional insert zone data. *)
65
+
data : string; (** Frame data field. *)
66
+
ocf : int option; (** Operational Control Field (32 bits). *)
67
+
fecf : int option; (** Frame Error Control Field (16 bits). *)
68
+
}
69
+
(** AOS Transfer Frame. *)
70
+
71
+
val equal_header : header -> header -> bool
72
+
val equal : t -> t -> bool
73
+
val pp_header : Format.formatter -> header -> unit
74
+
val pp : Format.formatter -> t -> unit
75
+
76
+
(** {1 Errors} *)
77
+
78
+
type error =
79
+
| Truncated of { need : int; have : int }
80
+
| Invalid_version of int
81
+
| Invalid_scid of int
82
+
| Invalid_vcid of int
83
+
| Fecf_mismatch of { expected : int; actual : int }
84
+
85
+
val pp_error : Format.formatter -> error -> unit
86
+
87
+
(** {1 Encoding/Decoding} *)
88
+
89
+
val decode :
90
+
?frame_len:int ->
91
+
?insert_zone_len:int ->
92
+
?expect_ocf:bool ->
93
+
?expect_fecf:bool ->
94
+
?check_fecf:bool ->
95
+
string ->
96
+
(t, error) result
97
+
(** [decode buf] decodes an AOS frame from [buf].
98
+
@param frame_len Expected frame length (default: buffer length)
99
+
@param insert_zone_len Insert zone length (default: 0)
100
+
@param expect_ocf Whether OCF is present (default: true)
101
+
@param expect_fecf Whether FECF is present (default: true)
102
+
@param check_fecf Whether to verify FECF (default: true) *)
103
+
104
+
val encode :
105
+
?insert_zone_len:int -> ?with_ocf:bool -> ?with_fecf:bool -> t -> string
106
+
(** [encode frame] encodes an AOS frame to a string.
107
+
@param insert_zone_len Insert zone length to reserve (default: 0)
108
+
@param with_ocf Whether to include OCF (default: true)
109
+
@param with_fecf Whether to include FECF (default: true) *)
110
+
111
+
val encoded_len :
112
+
?insert_zone_len:int -> ?with_ocf:bool -> ?with_fecf:bool -> t -> int
113
+
(** [encoded_len frame] returns the encoded length of [frame]. *)
114
+
115
+
(** {1 Predicates} *)
116
+
117
+
val is_idle : t -> bool
118
+
(** [is_idle frame] returns true if frame uses the idle VCID (63). *)
119
+
120
+
(** {1 Constructors} *)
121
+
122
+
val v :
123
+
?version:int ->
124
+
?replay_flag:bool ->
125
+
?vc_count_flag:bool ->
126
+
?vc_count_cycle:int ->
127
+
?insert_zone:string option ->
128
+
?ocf:int option ->
129
+
?fecf:int option ->
130
+
scid:scid ->
131
+
vcid:vcid ->
132
+
vcfc:int ->
133
+
string ->
134
+
t
135
+
(** [v ~scid ~vcid ~vcfc data] constructs an AOS frame. *)
136
+
137
+
(** {1 CLCW Integration} *)
138
+
139
+
val get_clcw : t -> (Clcw.t, Clcw.error) result option
140
+
(** [get_clcw frame] extracts and decodes the CLCW from the OCF if present. *)
141
+
142
+
val set_clcw : t -> Clcw.t -> t
143
+
(** [set_clcw frame clcw] sets the OCF to the encoded CLCW. *)
144
+
145
+
val with_clcw :
146
+
?version:int ->
147
+
?replay_flag:bool ->
148
+
?vc_count_flag:bool ->
149
+
?vc_count_cycle:int ->
150
+
?insert_zone:string option ->
151
+
?fecf:int option ->
152
+
scid:scid ->
153
+
vcid:vcid ->
154
+
vcfc:int ->
155
+
clcw:Clcw.t ->
156
+
string ->
157
+
t
158
+
(** [with_clcw ~scid ~vcid ~vcfc ~clcw data] constructs an AOS frame with CLCW.
159
+
*)
160
+
161
+
(** {1 CRC} *)
162
+
163
+
val compute_fecf : string -> int
164
+
(** [compute_fecf data] computes CRC-16-CCITT over [data]. *)
+101
test/test_aos.ml
+101
test/test_aos.ml
···
1
+
(*---------------------------------------------------------------------------
2
+
Copyright (c) 2025 Thomas Gazagnaire. All rights reserved.
3
+
SPDX-License-Identifier: MIT
4
+
---------------------------------------------------------------------------*)
5
+
6
+
let aos = Alcotest.testable Aos.pp Aos.equal
7
+
8
+
let test_roundtrip () =
9
+
let scid = Aos.scid_exn 42 in
10
+
let vcid = Aos.vcid_exn 5 in
11
+
let data = "Hello, AOS!" in
12
+
let frame = Aos.v ~scid ~vcid ~vcfc:12345 data in
13
+
let encoded = Aos.encode frame in
14
+
match Aos.decode encoded with
15
+
| Error e -> Alcotest.failf "decode failed: %a" Aos.pp_error e
16
+
| Ok frame' -> Alcotest.(check aos) "roundtrip" frame frame'
17
+
18
+
let test_roundtrip_no_ocf () =
19
+
let scid = Aos.scid_exn 10 in
20
+
let vcid = Aos.vcid_exn 0 in
21
+
let data = "No OCF" in
22
+
let frame = Aos.v ~scid ~vcid ~vcfc:0 ~ocf:None data in
23
+
let encoded = Aos.encode ~with_ocf:false frame in
24
+
match Aos.decode ~expect_ocf:false encoded with
25
+
| Error e -> Alcotest.failf "decode failed: %a" Aos.pp_error e
26
+
| Ok frame' -> Alcotest.(check aos) "roundtrip no ocf" frame frame'
27
+
28
+
let test_roundtrip_no_fecf () =
29
+
let scid = Aos.scid_exn 100 in
30
+
let vcid = Aos.vcid_exn 10 in
31
+
let data = "No FECF" in
32
+
let frame = Aos.v ~scid ~vcid ~vcfc:999 data in
33
+
let encoded = Aos.encode ~with_fecf:false frame in
34
+
match Aos.decode ~expect_fecf:false encoded with
35
+
| Error e -> Alcotest.failf "decode failed: %a" Aos.pp_error e
36
+
| Ok frame' -> Alcotest.(check aos) "roundtrip no fecf" frame frame'
37
+
38
+
let test_clcw_integration () =
39
+
let scid = Aos.scid_exn 50 in
40
+
let vcid = Aos.vcid_exn 1 in
41
+
let clcw_vcid = Clcw.vcid_exn 1 in
42
+
let clcw = Clcw.v ~vcid:clcw_vcid ~report_value:42 () in
43
+
let frame = Aos.with_clcw ~scid ~vcid ~vcfc:100 ~clcw "CLCW test" in
44
+
let encoded = Aos.encode frame in
45
+
match Aos.decode encoded with
46
+
| Error e -> Alcotest.failf "decode failed: %a" Aos.pp_error e
47
+
| Ok frame' -> (
48
+
match Aos.get_clcw frame' with
49
+
| None -> Alcotest.fail "no CLCW"
50
+
| Some (Error e) ->
51
+
Alcotest.failf "CLCW decode failed: %a" Clcw.pp_error e
52
+
| Some (Ok clcw') ->
53
+
Alcotest.(check int) "report_value" 42 clcw'.report_value)
54
+
55
+
let test_idle_frame () =
56
+
let scid = Aos.scid_exn 0 in
57
+
let vcid = Aos.vcid_exn 63 in
58
+
let frame = Aos.v ~scid ~vcid ~vcfc:0 "" in
59
+
Alcotest.(check bool) "is_idle" true (Aos.is_idle frame)
60
+
61
+
let test_fecf_check () =
62
+
let scid = Aos.scid_exn 1 in
63
+
let vcid = Aos.vcid_exn 1 in
64
+
let frame = Aos.v ~scid ~vcid ~vcfc:1 "data" in
65
+
let encoded = Aos.encode frame in
66
+
(* Corrupt the FECF *)
67
+
let corrupted = Bytes.of_string encoded in
68
+
let len = Bytes.length corrupted in
69
+
Bytes.set corrupted (len - 1) '\xFF';
70
+
match Aos.decode (Bytes.to_string corrupted) with
71
+
| Error (Aos.Fecf_mismatch _) -> ()
72
+
| Error e -> Alcotest.failf "expected Fecf_mismatch, got: %a" Aos.pp_error e
73
+
| Ok _ -> Alcotest.fail "expected error"
74
+
75
+
let test_vcid_bounds () =
76
+
Alcotest.(check bool) "vcid 0 valid" true (Option.is_some (Aos.vcid 0));
77
+
Alcotest.(check bool) "vcid 63 valid" true (Option.is_some (Aos.vcid 63));
78
+
Alcotest.(check bool) "vcid -1 invalid" true (Option.is_none (Aos.vcid (-1)));
79
+
Alcotest.(check bool) "vcid 64 invalid" true (Option.is_none (Aos.vcid 64))
80
+
81
+
let test_scid_bounds () =
82
+
Alcotest.(check bool) "scid 0 valid" true (Option.is_some (Aos.scid 0));
83
+
Alcotest.(check bool) "scid 255 valid" true (Option.is_some (Aos.scid 255));
84
+
Alcotest.(check bool) "scid -1 invalid" true (Option.is_none (Aos.scid (-1)));
85
+
Alcotest.(check bool) "scid 256 invalid" true (Option.is_none (Aos.scid 256))
86
+
87
+
let () =
88
+
Alcotest.run "aos"
89
+
[
90
+
( "aos",
91
+
[
92
+
Alcotest.test_case "roundtrip" `Quick test_roundtrip;
93
+
Alcotest.test_case "roundtrip_no_ocf" `Quick test_roundtrip_no_ocf;
94
+
Alcotest.test_case "roundtrip_no_fecf" `Quick test_roundtrip_no_fecf;
95
+
Alcotest.test_case "clcw_integration" `Quick test_clcw_integration;
96
+
Alcotest.test_case "idle_frame" `Quick test_idle_frame;
97
+
Alcotest.test_case "fecf_check" `Quick test_fecf_check;
98
+
Alcotest.test_case "vcid_bounds" `Quick test_vcid_bounds;
99
+
Alcotest.test_case "scid_bounds" `Quick test_scid_bounds;
100
+
] );
101
+
]