Iter 18. Consolidates the embedding-vs-risk-factor hashing-input
selection behind a single typed API. Replaces the two ad-hoc paths
that lived in emitter.rs through iter 17:
* inline `emb.as_slice().iter().flat_map(|f| f.to_le_bytes())`
* private `canonical_risk_bytes(&inputs) -> [u8; 16]`
Added (gated on `feature = "std"`):
- src/identity_features.rs:
* IdentityFeatures<'a> enum: Embedding(&'a IdentityEmbedding) |
RiskFactors { sep, stab, consist, conf }
* from_embedding / from_risk_factors const constructors
* canonical_byte_len() const fn — no allocation, predicts wire length
* write_canonical_bytes(&mut Vec<u8>) — reusable-buffer path
* canonical_bytes() -> Vec<u8> — allocating convenience
* compute_hash(&SignatureHasher, day_epoch) -> [u8; 32]
* RISK_FACTOR_BYTES const (= 16)
- pub use IdentityFeatures, RISK_FACTOR_BYTES from lib.rs
Refactor:
- src/emitter.rs: derived_hash now uses
let features = match &embedding {
Some(emb) => IdentityFeatures::from_embedding(emb),
None => IdentityFeatures::from_risk_factors(sep, stab, consist, conf),
};
features.compute_hash(h, day_epoch)
Local canonical_risk_bytes helper removed (superseded).
tests/identity_features_encoder.rs (9 named tests, all green):
embedding_canonical_length_is_dim_times_four
risk_factor_canonical_length_is_sixteen_bytes
embedding_canonical_bytes_match_manual_flatten
risk_factor_canonical_bytes_match_explicit_le_layout
write_canonical_bytes_appends_to_existing_buffer
compute_hash_matches_direct_hasher_invocation
embedding_and_risk_factors_produce_different_hashes
iter_16_wire_compat_embedding_path *** backward-compat regression ***
iter_16_wire_compat_risk_factor_path *** backward-compat regression ***
These two tests assert that the refactored encoder produces
bit-identical hashes to iter 16's inline path. Existing deployed
nodes upgrading to iter 18 see no rf_signature_hash flip.
ACs progressed:
- ADR-120 §2.3 — features canonical-bytes representation now has a
single source of truth in the codebase; future feature additions
pass through one named encoder rather than scattered byte-fiddling.
- ADR-118 invariant I2 — IdentityFeatures borrows &IdentityEmbedding,
it doesn't take ownership. The embedding's Drop / no-Serialize
guarantees continue to hold across the canonical-bytes path.
Test config:
- cargo test --no-default-features → 72 passed (identity_features cfg-out)
- cargo test → 137 passed (128 + 9)
Out of scope (next iter target):
- Wire IdentityFeatures into a public emitter input path so callers
can supply pre-constructed IdentityFeatures rather than the bare
embedding + risk factors. (Soft refactor; current API is sufficient.)
- BfldPipeline facade — single struct combining BfldEmitter +
BfldFrame producer + MQTT publisher (ADR-118 §2.1 lib.rs entry point).
Co-Authored-By: claude-flow <ruv@ruv.net>
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