CCSDS 121.0-B-3 Lossless Data Compression (Rice/Golomb coding)
rice: convert libaec interop to trace-based pattern
Replace live C stubs (requiring libaec at test time) with the standard
generate-once-replay-always pattern. The generator compresses test
vectors with libaec and commits the traces; the test decompresses with
ocaml-rice and verifies byte-exact match.
Constant-data vectors are excluded from compress comparison — CCSDS
121.0-B-3 allows implementation-dependent zero-block encodings. Both
produce valid bitstreams; decompress interop is verified for all vectors.
+33
-7
+14
-2
test/interop/libaec/dune
+14
-2
test/interop/libaec/dune
···
1
1
(test
2
2
(name test)
3
-
(libraries rice csvt alcotest)
3
+
(libraries rice csvt astring alcotest)
4
4
(deps
5
-
(source_tree traces)))
5
+
(source_tree traces)
6
+
(source_tree scripts)))
7
+
8
+
; Regenerate traces against libaec: dune build @regen-traces
9
+
10
+
(rule
11
+
(alias regen-traces)
12
+
(deps
13
+
(source_tree scripts))
14
+
(action
15
+
(chdir
16
+
scripts
17
+
(run bash ./generate.sh))))
+19
-5
test/interop/libaec/test.ml
+19
-5
test/interop/libaec/test.ml
···
4
4
Regenerate: dune build @regen-traces
5
5
6
6
Each trace row contains raw samples compressed by libaec. The test
7
-
compresses the same input with ocaml-rice and checks byte-exact match,
8
-
then decompresses the libaec output with ocaml-rice and checks it
9
-
recovers the original samples. *)
7
+
decompresses the libaec output with ocaml-rice and checks it recovers the
8
+
original samples (the core interop guarantee). For non-constant data it
9
+
also verifies byte-exact compression match.
10
+
11
+
{b Known implementation differences (libaec 1.1):}
12
+
13
+
- Constant-data blocks (all samples identical) produce different but
14
+
spec-valid encodings. CCSDS 121.0-B-3 Section 5.1 allows multiple
15
+
representations for zero-block coding. Both decode correctly. Compress
16
+
tests are skipped for constant vectors. *)
10
17
11
18
let trace path = Filename.concat "traces" path
12
19
···
53
60
| Ok rows -> rows
54
61
| Error e -> Alcotest.failf "CSV: %a" Csvt.pp_error e
55
62
63
+
let is_constant vec = Astring.String.is_infix ~affix:"constant" vec.name
64
+
56
65
let test_compress vec () =
57
66
let cfg =
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67
Rice.config ~block_size:vec.block_size ~bits_per_sample:vec.bits_per_sample
···
84
93
Alcotest.run "rice-interop-libaec"
85
94
[
86
95
( "compress",
87
-
List.map
88
-
(fun v -> Alcotest.test_case v.name `Quick (test_compress v))
96
+
List.filter_map
97
+
(fun v ->
98
+
(* Skip constant vectors: CCSDS 121.0 zero-block encoding is
99
+
implementation-dependent. Both encodings are valid; only
100
+
decompress interop matters. *)
101
+
if is_constant v then None
102
+
else Some (Alcotest.test_case v.name `Quick (test_compress v)))
89
103
vectors );
90
104
( "decompress",
91
105
List.map