CCSDS Synchronization and Channel Coding (131.0-B, 231.0-B)
Remove self-test interop tests (COP-1, SCC, TCF)
These used pure Python generators (struct.pack, manual bitfield
encoding) that reimplemented the spec — not independent oracles.
Per interop-testing skill: "The generator MUST call the upstream
tool's public API. Never reimplement, transcribe, or inline."
A Python script that packs the same bits our OCaml code does
validates nothing about cross-implementation compatibility.
Proper replacements:
- COP-1: dariol83/ccsds has COP-1 support (Java)
- SCC: dariol83/ccsds has CLTU/randomizer (Java)
- TCF: spacepackets has CDS/CUC time code support (Python)
-272
-1
test/interop/python/.gitignore
-1
test/interop/python/.gitignore
···
1
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scripts/.venv/
-19
test/interop/python/dune
-19
test/interop/python/dune
···
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(test
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(name test)
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(libraries scc alcotest)
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(deps
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(source_tree traces)
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(source_tree scripts)))
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; Regenerate traces: REGEN_TRACES=1 dune build @regen-traces
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(rule
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(alias regen-traces)
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(enabled_if
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(= %{env:REGEN_TRACES=0} 1))
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(deps
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(source_tree scripts))
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(action
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(chdir
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scripts
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(run ./generate.py))))
-125
test/interop/python/scripts/generate.py
-125
test/interop/python/scripts/generate.py
···
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#!/usr/bin/env python3
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"""Generate SCC interop traces for ocaml-scc.
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Oracle: Python (no deps needed for ASM pattern + randomizer LFSR + CLTU BCH)
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Install: no dependencies
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Tests:
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- ASM marker: 0x1ACFFC1D
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- Randomizer: CCSDS LFSR pseudo-random sequence (first 255 bytes)
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- CLTU BCH: BCH(63,56) parity for known inputs
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Traces are committed to git. Only re-run when changing inputs
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or upgrading the oracle.
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"""
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import os, sys, struct
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TRACE_DIR = os.path.join(os.path.dirname(__file__), "..", "traces")
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# --- ASM marker ---
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ASM_MARKER = bytes([0x1A, 0xCF, 0xFC, 0x1D])
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# --- CCSDS Randomizer (LFSR) ---
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# Polynomial: h(x) = x^8 + x^7 + x^5 + x^3 + 1
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# Initial state: 0xFF
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# LFSR shifts right; output from bit 0; feedback enters at bit 7
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# Feedback is XOR of bits 0, 3, 5, 7
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# Output bits are packed MSB-first into bytes
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def ccsds_randomizer_sequence(n_bytes):
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state = 0xFF
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result = []
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for _ in range(n_bytes):
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byte = 0
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for _ in range(8):
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out = state & 1
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xor_all = (state ^ (state >> 3) ^ (state >> 5) ^ (state >> 7)) & 1
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state = (state >> 1) | (xor_all << 7)
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byte = (byte << 1) | out
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result.append(byte)
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return bytes(result)
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# --- CLTU BCH(63,56) ---
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# Generator polynomial: g(x) = x^7 + x^6 + x^2 + 1 = 0x45
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# Processes 56 data bits (7 bytes) MSB-first through LFSR
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# Parity bits are complemented, placed in MSB 7 bits with filler bit (0) in LSB
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BCH_POLY = 0x45
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def bch_parity(data_7bytes):
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"""Compute BCH(63,56) parity for 7 data bytes.
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Returns the parity byte (complemented, MSB-aligned with filler bit)."""
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sr = 0
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for byte_val in data_7bytes:
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for j in range(7, -1, -1):
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din = (byte_val >> j) & 1
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fb = ((sr >> 6) ^ din) & 1
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sr = ((sr << 1) ^ (BCH_POLY if fb else 0)) & 0x7F
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# Complement parity bits, shift to MSB 7 bits, filler bit (0) in LSB
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return ((~sr & 0x7F) << 1) & 0xFF
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def cltu_encode(frame):
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"""Encode a TC frame as CLTU with BCH codeblocks."""
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start_seq = b'\xEB\x90'
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tail_seq = b'\xC5\xC5\xC5\xC5\xC5\xC5\xC5\x79'
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fill_byte = 0x55
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codeblock_data = 7
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# Split frame into 7-byte chunks
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codeblocks = []
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for i in range(0, len(frame), codeblock_data):
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chunk = frame[i:i + codeblock_data]
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# Pad with fill bytes if needed
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if len(chunk) < codeblock_data:
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chunk = chunk + bytes([fill_byte] * (codeblock_data - len(chunk)))
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parity = bch_parity(chunk)
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codeblocks.append(chunk + bytes([parity]))
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return start_seq + b''.join(codeblocks) + tail_seq
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# --- Generate traces ---
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os.makedirs(TRACE_DIR, exist_ok=True)
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with open(os.path.join(TRACE_DIR, "vectors.csv"), "w") as f:
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f.write("# SCC interop test vectors\n")
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f.write("# Oracle: Python (CCSDS spec reference implementation)\n")
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f.write("# Format: type,name,params...\n")
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f.write("#\n")
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f.write("# asm,name,marker_hex\n")
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f.write("# randomizer,name,length,sequence_hex\n")
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f.write("# bch,name,data_hex,parity_hex\n")
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f.write("# cltu,name,frame_hex,cltu_hex\n")
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# ASM marker
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f.write(f"asm,marker,{ASM_MARKER.hex()}\n")
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# Randomizer sequence
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for n in [20, 255]:
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seq = ccsds_randomizer_sequence(n)
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f.write(f"randomizer,pn_{n},{n},{seq.hex()}\n")
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# BCH parity for known inputs
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bch_inputs = [
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("zeros", bytes(7)),
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("ones", bytes([0x01] * 7)),
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("ascending", bytes(range(7))),
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("all_ff", bytes([0xFF] * 7)),
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("hello", b"Hello, " ),
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]
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for name, data in bch_inputs:
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parity = bch_parity(data)
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f.write(f"bch,{name},{data.hex()},{parity:02x}\n")
114
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# CLTU encode for known frames
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cltu_frames = [
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("short_frame", bytes(range(7))),
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("two_codeblocks", bytes(range(10))),
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("hello_frame", b"Hello, CCSDS!"),
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]
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for name, frame in cltu_frames:
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cltu = cltu_encode(frame)
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f.write(f"cltu,{name},{frame.hex()},{cltu.hex()}\n")
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print(f"Wrote {TRACE_DIR}/vectors.csv")
-108
test/interop/python/test.ml
-108
test/interop/python/test.ml
···
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(** Python interop tests for ocaml-scc.
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Traces generated by: Python (CCSDS spec reference implementation)
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Regenerate: REGEN_TRACES=1 dune build @regen-traces *)
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let trace path = Filename.concat "traces" path
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(* Parse CSV trace: skip comments (#), split on comma *)
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let parse_csv path =
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let ic = open_in (trace path) in
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let lines = ref [] in
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(try
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while true do
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let line = input_line ic in
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if String.length line > 0 && line.[0] <> '#' then
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lines := String.split_on_char ',' line :: !lines
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done
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with End_of_file -> ());
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close_in ic;
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List.rev !lines
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let bytes_of_hex hex =
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let len = String.length hex / 2 in
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Bytes.init len (fun i ->
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Char.chr (int_of_string ("0x" ^ String.sub hex (i * 2) 2)))
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let hex_of_bytes b =
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let buf = Buffer.create (Bytes.length b * 2) in
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Bytes.iter
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(fun c -> Buffer.add_string buf (Printf.sprintf "%02x" (Char.code c)))
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b;
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Buffer.contents buf
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(* --- ASM tests --- *)
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let test_asm_marker expected_hex () =
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let expected = bytes_of_hex expected_hex in
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let marker = Scc.Sync.Asm.marker in
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if marker <> expected then
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Alcotest.failf "ASM marker mismatch\n expected: %s\n got: %s"
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expected_hex (hex_of_bytes marker)
42
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(* --- Randomizer tests --- *)
44
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let test_randomizer_sequence expected_len expected_hex () =
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let expected = bytes_of_hex expected_hex in
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let got = Scc.Coding.Randomizer.sequence expected_len in
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if got <> expected then
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Alcotest.failf
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"randomizer sequence (%d bytes) mismatch\n expected: %s\n got: %s"
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expected_len expected_hex (hex_of_bytes got)
52
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53
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(* --- BCH parity tests --- *)
54
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let test_bch_parity data_hex expected_parity_hex () =
56
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let data = bytes_of_hex data_hex in
57
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let expected = int_of_string ("0x" ^ expected_parity_hex) in
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let got = Char.code (Scc.Sync.Cltu.bch_parity data 0) in
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if got <> expected then
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Alcotest.failf
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"BCH parity mismatch for %s\n expected: %02x\n got: %02x" data_hex
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expected got
63
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64
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(* --- CLTU encode tests --- *)
65
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66
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let test_cltu_encode frame_hex expected_hex () =
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let frame = bytes_of_hex frame_hex in
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let expected = bytes_of_hex expected_hex in
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let got = Scc.Sync.Cltu.encode frame in
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if got <> expected then
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Alcotest.failf "CLTU encode mismatch\n expected: %s\n got: %s"
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expected_hex (hex_of_bytes got)
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let () =
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let rows = parse_csv "vectors.csv" in
76
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let asm_tests = ref [] in
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let randomizer_tests = ref [] in
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let bch_tests = ref [] in
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let cltu_tests = ref [] in
80
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List.iter
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(fun row ->
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match row with
83
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| [ "asm"; name; marker_hex ] ->
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asm_tests :=
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Alcotest.test_case name `Quick (test_asm_marker marker_hex)
86
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:: !asm_tests
87
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| [ "randomizer"; name; len_s; seq_hex ] ->
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randomizer_tests :=
89
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Alcotest.test_case name `Quick
90
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(test_randomizer_sequence (int_of_string len_s) seq_hex)
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:: !randomizer_tests
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| [ "bch"; name; data_hex; parity_hex ] ->
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bch_tests :=
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Alcotest.test_case name `Quick (test_bch_parity data_hex parity_hex)
95
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:: !bch_tests
96
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| [ "cltu"; name; frame_hex; cltu_hex ] ->
97
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cltu_tests :=
98
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Alcotest.test_case name `Quick (test_cltu_encode frame_hex cltu_hex)
99
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:: !cltu_tests
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| _ -> Alcotest.failf "bad CSV row: %s" (String.concat "," row))
101
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rows;
102
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Alcotest.run "scc-interop"
103
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[
104
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("asm", List.rev !asm_tests);
105
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("randomizer", List.rev !randomizer_tests);
106
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("bch", List.rev !bch_tests);
107
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("cltu", List.rev !cltu_tests);
108
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]
-19
test/interop/python/traces/vectors.csv
-19
test/interop/python/traces/vectors.csv
···
1
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# SCC interop test vectors
2
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# Oracle: Python (CCSDS spec reference implementation)
3
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# Format: type,name,params...
4
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#
5
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# asm,name,marker_hex
6
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# randomizer,name,length,sequence_hex
7
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# bch,name,data_hex,parity_hex
8
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# cltu,name,frame_hex,cltu_hex
9
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asm,marker,1acffc1d
10
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randomizer,pn_20,20,ff480ec09a0d70bc8e2c93ada7b746ce5a977dcc
11
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randomizer,pn_255,255,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
12
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bch,zeros,00000000000000,fe
13
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bch,ones,01010101010101,42
14
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bch,ascending,00010203040506,c6
15
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bch,all_ff,ffffffffffffff,86
16
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bch,hello,48656c6c6f2c20,8a
17
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cltu,short_frame,00010203040506,eb9000010203040506c6c5c5c5c5c5c5c579
18
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cltu,two_codeblocks,00010203040506070809,eb9000010203040506c607080955555555f2c5c5c5c5c5c5c579
19
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cltu,hello_frame,48656c6c6f2c20434353445321,eb9048656c6c6f2c208a43435344532155b6c5c5c5c5c5c5c579