Files
mxaccess/design
Joseph Doherty 0441a2e693 [M5] mxaccess-asb: F25 step 9 — Write operation
Closes the highest-value remaining IASBIDataV2 op. With Write landed,
the read+write+subscribe path is functionally complete in-memory.

API additions:
* `MinimalWriteValue { value: AsbVariant }` — carries just the Value
  payload. Optional ArrayElementIndex / Comment / HasQT / Status /
  Timestamp fields are deferred to a later iteration once a live
  capture confirms the WCF DataContract XML form.
* `build_write_request_body(items, values, write_handle)` per
  `AsbContracts.cs:181-194`:
  ```xml
  <WriteBasicRequest xmlns="urn:msg.data.asb.iom:2">
    <Items><ASBIData>{ItemIdentity[] binary}</ASBIData></Items>
    <Values>
      <WriteValue><Value><ASBIData>{Variant binary}</ASBIData></Value></WriteValue>
      ...
    </Values>
    <WriteHandle>{i32}</WriteHandle>
  </WriteBasicRequest>
  ```
  Items array uses the IAsbCustomSerializableType binary fast-path;
  each Value's inner Variant also uses the fast-path. WriteHandle is
  an Int32 (opaque correlation echoed in PublishWriteComplete).
* `decode_write_response` — per-item Status array (mirrors the
  unregister/register pattern).
* `AsbClient::write(items, values, write_handle)` — thin wrapper.

4 new tests:
* `write_request_body_carries_items_values_and_write_handle` — body
  shape sanity (WriteHandle = 7 Int32, WriteValue element present).
* `write_request_body_pairs_items_and_values_arrays` — 2 items + 2
  values produces 2 WriteValue elements.
* `write_response_round_trips_status_array` — Status decode.
* `write_response_missing_status_fails` — graceful MissingField
  error.

Workspace: 695 tests pass (was 691, +4).

Stubbed for next F25 iterations:
* `PublishWriteComplete` — empty request, `ItemWriteComplete[]`
  response.
* `DeleteMonitoredItems` — mirrors AddMonitoredItems pattern.
* Optional WriteValue fields (Comment / Timestamp / etc.) once a
  live capture confirms the wire-byte layout.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
2026-05-05 13:04:11 -04:00
..

design/ — Rust port architectural plan

This folder is the design contract for the Rust replacement of AVEVA/Wonderware MXAccess. It is the gap between the .NET reference in src/ and the Rust crates that will be written under a sibling rust/ workspace (per CLAUDE.md).

The folder is structured as a small set of focused documents. Read in order; each builds on the previous.

File Purpose
00-overview.md Mission, two-layer goal, architectural principles, non-goals
10-raw-layer.md Byte-accurate raw MXAccess layer (codec + transport + session)
20-async-layer.md Idiomatic Tokio async layer on top of the raw layer
30-crate-topology.md Cargo workspace, crates, dependencies, build/test commands
40-protocol-invariants.md Bill of materials: IIDs, opnums, envelope/handle bytes
50-error-model.md MxStatus, error types, panic/cancellation policy
60-roadmap.md Milestones M0..M6, validation strategy
70-risks-and-open-questions.md Parity gaps, unproven flows, cross-platform constraints
dependencies.md Cross- and within-milestone parallelism map; agent budget per phase
review.md Adversarial review log (BLOCKER/MAJOR/MINOR/NIT findings, all resolved)
prompt.md /loop driver prompt for autonomous M2M6 execution
followups.md Open / resolved deferred work items; auto-triaged by prompt.md Step 0 (created on first /loop run if missing)

The design is grounded in the .NET reference at src/ and the protocol artifacts in docs/, analysis/, and captures/. Do not introduce protocol behavior in these documents that is not already proven in the reference. When adding a new claim about wire format, cite either:

  • a .cs file path in src/MxNativeCodec/, src/MxNativeClient/, or src/MxAsbClient/, or
  • a docs/*.md spec file, or
  • a captures/0NN-frida-* directory or analysis/frida/*.tsv row.

This folder is documentation, not code. When the Rust workspace is created, the design here is the contract it must satisfy. When evidence in captures/ invalidates a design decision here, update the design first, then the code.

Reading order

  • New contributor: 00 → 30 → 10 → 40 → 20 → 50 → 60 → 70.
  • Protocol question: 40 first, then the relevant section of 10.
  • API question: 20 first, then 50.
  • Planning a milestone: 60 first, cross-reference 70 for blockers.
  • Scheduling concurrent work: dependencies.md for the per-phase parallelism map.
  • Driving M2M6 autonomously via /loop: prompt.md (and the followups.md triage log it maintains).