Ashin Walpola
b2b57fa39e
asn1/ Three tests assert exact bytes - CamEncodeGoldenTest, DenmAirReceiveTest and SpatemUperCodecTest - and their expected values came from asn1tools compiled against ETSI modules that existed only as an untracked working copy on one machine. A golden-byte fixture nobody else can regenerate is a fixture nobody can safely touch, so the modules are now in the repo. Only the seven .asn files those tests need are copied, 576 KB of a 4.2 MB checkout; the upstream Rust parser is not used by this project at all. Verified sufficient in isolation: copied into an empty directory, all three specs compile and reproduce the committed golden CAM bytes byte-identically. Source is consider it GmbH's C-ITS-Parser (github.com/consider-it/C-ITS-Parser) at f457426, MIT licensed - LICENSE is retained alongside as that requires. The schemas themselves are ETSI's standard definitions; upstream's contribution is assembling them into a compilable set. asn1/README.md records the provenance, which module pairs with which message, and the rule that matters: never regenerate a golden fixture from this project's own encoder, because sharing a mistake between encoder and decoder is exactly the failure these files exist to catch. Doc references in the codecs and tests now point at asn1/ instead of the untracked checkout, and C-ITS-Parser/ is gitignored so the working copy beside the project is never picked up. Untracked local state - .idea/deploymentTargetSelector.xml rewrites itself on every deploy, so it has been showing as modified in essentially every commit. Along with deviceManager.xml, appInsightsSettings.xml and studiobot.xml it is per-machine state, not project configuration. - obu-firmware/sdkconfig.old is ESP-IDF build output - it is the previous sdkconfig, rewritten on every build. sdkconfig.defaults remains tracked, since that is the configuration actually chosen. All five stay on disk; only the tracking is removed. Also ignores .claude/settings.local.json, which is per-machine, while leaving the skills beside it committable as project knowledge.
71 lines
3.2 KiB
Markdown
71 lines
3.2 KiB
Markdown
# ETSI ASN.1 modules
|
|
|
|
The ASN.1 schemas this project's UPER codecs are validated against. **Schemas only** — no parser
|
|
code. Nothing in the app or the firmware reads these files at build or run time; they exist so the
|
|
hand-written codecs in `app/src/main/java/.../domain/asn1/` can be checked against an independent
|
|
implementation.
|
|
|
|
## Why this is here rather than just documented
|
|
|
|
Three of this project's tests assert exact bytes:
|
|
|
|
- `CamEncodeGoldenTest` — the CAM this app transmits, byte for byte
|
|
- `DenmAirReceiveTest`, `SpatemUperCodecTest` — real captured frames with field values
|
|
|
|
Those expected values were produced by decoding with `asn1tools` compiled from these modules. Without
|
|
them the fixtures cannot be regenerated or re-verified, and a golden-byte test you cannot regenerate
|
|
is a test nobody can safely touch.
|
|
|
|
This matters because the project has shipped the same class of bug three times: a field encoded with
|
|
the wrong number of bits, which this codebase then read back with the *same* wrong number. Phone and
|
|
ESP32 agree perfectly with each other and with nothing else, so every internal round-trip test passes
|
|
while the frames on air are malformed (`CurvatureCalculationMode`, the GeoNetworking reserved bytes,
|
|
`yawRateConfidence`). Only a second, independent implementation catches that — which is what these
|
|
modules provide.
|
|
|
|
## Provenance
|
|
|
|
Taken from consider it GmbH's C-ITS-Parser:
|
|
|
|
- <https://github.com/consider-it/C-ITS-Parser>
|
|
- commit `f457426efc2486fac49a02fc9a1c8c7762d160e9`
|
|
- MIT licensed — see `LICENSE`, retained here as the licence requires
|
|
|
|
Only the seven `.asn` files below are copied, out of a 4.2 MB checkout. The upstream Rust parser is
|
|
not used by this project in any way. The schemas themselves are ETSI's standard definitions; the
|
|
upstream repo's contribution is assembling them into a compilable set.
|
|
|
|
| file | used for |
|
|
|---|---|
|
|
| `cam_1_4_1.asn` + `cdd_1_3_1_1.asn` | CAM encode/decode |
|
|
| `denm_1_3_1.asn` + `cdd_1_3_1_1.asn` | DENM decode |
|
|
| `spatem_2_2_1.asn`, `mapem_2_2_1.asn`, `dsrc_2_2_1.asn`, `cdd_2_2_1.asn` | SPATEM/MAPEM decode |
|
|
|
|
Note CAM/DENM use the release-1 common dictionary (`cdd_1_3_1_1`) while SPATEM/MAPEM use release 2
|
|
(`cdd_2_2_1`). Both are needed; they are not interchangeable.
|
|
|
|
These seven were verified sufficient on their own: copied into an empty directory, all three specs
|
|
compile and reproduce the committed golden bytes.
|
|
|
|
## Regenerating a fixture
|
|
|
|
Requires Python with `asn1tools` (verified with 0.167.0):
|
|
|
|
```python
|
|
import asn1tools
|
|
spec = asn1tools.compile_files(["asn1/cam_1_4_1.asn", "asn1/cdd_1_3_1_1.asn"], "uper")
|
|
spec.decode("CAM", raw_uper_bytes)
|
|
```
|
|
|
|
For SPATEM, compile `spatem_2_2_1.asn`, `mapem_2_2_1.asn`, `dsrc_2_2_1.asn`, `cdd_2_2_1.asn`
|
|
together and decode `"SPATEM"`.
|
|
|
|
**Never regenerate a golden fixture from this project's own encoder output** — that is precisely the
|
|
mistake these files exist to catch. Regenerate through `asn1tools`, or the test is worthless.
|
|
|
|
## Updating
|
|
|
|
Re-pin deliberately, not casually. If a newer ETSI release is adopted, copy the new modules, then
|
|
re-run the golden-byte tests and confirm any change in expected bytes is explained by the spec
|
|
change rather than by a decoder regression.
|