[s7] S7 — Optimized DB / S7Plus (decision PR) #408

dohertj2 · 2026-04-26T11:25:33-04:00

dohertj2 commented

2026-04-26 11:25:33 -04:00

Summary

Multi-variable PDU packing for S7 — replaces per-tag Plc.ReadAsync loop with Plc.ReadMultipleVarsAsync batching.

S7ReadPacker.cs (new) static helper:
- Classifies tags as packable / fallback / unknown.
- Builds S7.Net.Types.DataItem with VarType, Count, DB, StartByteAdr, BitAdr.
- Computes PDU item budget: (pduSize - 18) / 12, capped at 19 items per call.
- Bin-packs preserving caller order.
S7Driver.ReadAsync — classifies inputs into unknown / packable / fallback. Packable batches dispatch via Plc.ReadMultipleVarsAsync; decodes each DataItem.Value back to per-tag snapshots. Falls back to per-tag ReadOneAsync on batch-level failure so one bad tag doesn't poison the rest of the batch.
Arrays, strings, dates, 64-bit ints, UDT-shaped types remain on the existing per-tag path (variable-width or special encoding).

Test plan

dotnet build src/ZB.MOM.WW.OtOpcUa.Driver.S7 — clean (0 / 0)
dotnet test tests/ZB.MOM.WW.OtOpcUa.Driver.S7.Tests — 163 / 163 passed (14 new in S7ReadPackerTests: item-budget math, bin-packing 100 items into ≤6 batches, packability classification across all S7DataType values, DataItem field mapping (DB / area / VarType / BitAdr), value reinterpret (signed Int16/Int32 from unsigned wire))
Integration tests — Snap7-server fixture supports it; not exercised in this PR

🤖 Auto-generated by the Mode-B execution loop. Closes #292.

Closes #304

## Summary Multi-variable PDU packing for S7 — replaces per-tag `Plc.ReadAsync` loop with `Plc.ReadMultipleVarsAsync` batching. - **`S7ReadPacker.cs`** (new) static helper: - Classifies tags as packable / fallback / unknown. - Builds `S7.Net.Types.DataItem` with `VarType`, `Count`, `DB`, `StartByteAdr`, `BitAdr`. - Computes PDU item budget: `(pduSize - 18) / 12`, capped at **19 items** per call. - Bin-packs preserving caller order. - **`S7Driver.ReadAsync`** — classifies inputs into unknown / packable / fallback. Packable batches dispatch via `Plc.ReadMultipleVarsAsync`; decodes each `DataItem.Value` back to per-tag snapshots. Falls back to per-tag `ReadOneAsync` on **batch-level** failure so one bad tag doesn't poison the rest of the batch. - Arrays, strings, dates, 64-bit ints, UDT-shaped types remain on the existing per-tag path (variable-width or special encoding). ## Test plan - [x] `dotnet build src/ZB.MOM.WW.OtOpcUa.Driver.S7` — clean (0 / 0) - [x] `dotnet test tests/ZB.MOM.WW.OtOpcUa.Driver.S7.Tests` — **163 / 163 passed** (14 new in `S7ReadPackerTests`: item-budget math, bin-packing 100 items into ≤6 batches, packability classification across all `S7DataType` values, `DataItem` field mapping (DB / area / VarType / BitAdr), value reinterpret (signed Int16/Int32 from unsigned wire)) - [ ] Integration tests — Snap7-server fixture supports it; not exercised in this PR 🤖 Auto-generated by the Mode-B execution loop. Closes #292. Closes #304

dohertj2 added 1 commit 2026-04-26 11:25:35 -04:00

Auto: s7-f — Optimized DB / S7Plus decision (Track 1+3 docs-only) b217ca61ce