Joseph Doherty d89be2a011 fix(driver-ablegacy): resolve High code-review findings (Driver.AbLegacy-001, Driver.AbLegacy-006) ...

Driver.AbLegacy-001 — PCCC bit-index range. AbLegacyAddress.TryParse
accepted a bit index of 0..31 for every file type, but a 16-bit
N/B/I/O/S/A word only has bits 0..15. TryParse now range-checks the
bit index against the file's word width (0..15 for 16-bit element
files, 0..31 for the 32-bit L file, no bits on float files), so
addresses like N7:0/20 are rejected at parse time instead of silently
truncating in the (short) cast. WriteBitInWordAsync reads and writes
an L-file parent word as 32-bit Long and masks the RMW arithmetic to
the native width, so a sign-extended 16-bit decode can no longer
corrupt the high bits.

Driver.AbLegacy-006 — shared-runtime concurrency. A per-tag libplctag
Tag handle is cached and reused by both the server read path and the
poll loop, with no synchronisation around Read/GetStatus/DecodeValue.
Added a per-runtime SemaphoreSlim (DeviceState.GetRuntimeLock, keyed
by tag name); ReadAsync and WriteAsync now hold it across the whole
Read -> GetStatus -> Decode / Encode -> Write -> GetStatus sequence so
no two threads touch the same Tag handle concurrently.

Added xUnit + Shouldly regression coverage: AbLegacyBitIndexRangeTests
(per-file bit-range validation + L-file 32-bit RMW + sign-extension
safety) and AbLegacyRuntimeConcurrencyTests (overlap-detecting fake
proving concurrent read/read and read/write are serialised).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

2026-05-22 06:41:26 -04:00

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