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feat(ablegacy): resolve indirect addresses at read/write time (#646)

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Claude-Session: https://claude.ai/code/session_01Ef2ozxS7QPanGT8uoATbTe
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Joseph Doherty
2026-10-08 16:53:56 -04:00
parent a8b07ae12d
commit b0b0ce9c77
9 changed files with 364 additions and 51 deletions
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docs/drivers/AbLegacy.md
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@@ -69,7 +69,7 @@ pieces for driver-side routing (e.g. deciding a bit needs read-modify-write):
| `I:0/0` / `O:1/2` / `S:1` | Input / output / status system files (no file number) |
| `I:017/07` | **PLC-5 only:** `I:`/`O:` word and bit indices are **octal** (#244); a digit 8/9 is a parse error |
| `RTC:0.HR` / `HSC:0.ACC` | **MicroLogix only:** function files RTC, HSC, DLS, MMI, PTO, PWM, STI, EII, IOS, BHI (#245) |
| `N7:[N7:0]` / `N[N7:0]:5` | Indirect (index word read from the PLC) — parsed, **not supported at runtime** (#247) |
| `N7:[N7:0]` / `N[N7:0]:5` | Indirect (index word read from the PLC) — resolved at read/write time (#646) |
`AbLegacyDataType` covers the corresponding PCCC types: `Bit`, `Int` (N), `Long`
(L), `Float` (F), `AnalogInt` (A), `String` (ST), and the `TimerElement` /
@@ -118,11 +118,18 @@ physical inputs and may reject the write.
members default to Int32). ⚠️ **Wire-unverified on both transports:** there is no capture and no simulator
coverage; the libplctag path passes the name through and the native transport has no file-type code for them, so
it refuses the tag as `Unsupported` (`BadNotSupported` to the client; see Wire evidence).
- **Indirect addressing (#247).** `N7:[N7:0]` (word from another address) and `N[N7:0]:5` (file from another
address) parse, one level deep (the inner address must be direct, and carries the family's octal rule).
**Runtime resolution is not implemented** (it needs a pre-read of the index word and per-resolved-address
runtimes): reads and writes of an indirect tag answer `BadNotSupported` before any runtime is created, on both
transports.
- **Indirect addressing (#247 parse, #646 runtime).** `N7:[N7:0]` (word from another address) and `N[N7:0]:5` (file
from another address) parse, one level deep (the inner address must be direct, and carries the family's octal rule).
At runtime the driver reads the inner address first (same runtime factory, so libplctag and Native alike), requires
an integer in range (word/element `0..255`, file `0..999`), composes the concrete address and runs the normal
read/write path against it. **The index is re-read on every read/write - never cached** - and the previous
resolution's handle is released when the index moves. A bad index (negative, too large, float/string source) is
`BadOutOfRange` for that tag only (no health impact); an inner-read failure propagates its own status (a wire
failure also degrades health like any read). **Writes** resolve then write and are **not atomic**: the index can
change between the two PLC accesses. Bit RMW writes (`B3:[N7:0]/4`) resolve first, then RMW the concrete word.
The Native transport never sees the bracket form (it receives the composed name), so N-file indirect stays inside
the wire-proven envelope; other file types are as (un)verified as their direct forms. Live-gated on `ab_server`
by `AbLegacyIndirectAddressingTests` (`N7:0=5`, `N7:5=42`, `N7:[N7:0]` reads 42).
## Configuration
@@ -211,7 +218,8 @@ Everything below is against the `ab_server` simulator; no real PCCC controller h
| N-file write (`N7:5`) | capture `slc500-write-n7` + native `AbLegacyReadSmokeTests` write/read round trip (SLC 500) |
| F-file read (`F8`) | one capture, `slc500-read-f8` (codec parity only; no native F write on a wire) |
| S (incl. the default probe `S:0`), B, T, C, R, L, ST, A, O, I | **none** — encoded from the PCCC file-type table |
| MicroLogix function files (RTC/HSC/...), PLC-5 octal I/O, indirect addressing | **none** — parsed only; native refuses function files and indirect names as Unsupported |
| MicroLogix function files (RTC/HSC/...), PLC-5 octal I/O | **none** — parsed only; native refuses function files as Unsupported |
| Indirect addressing (`N7:[N7:0]`) | `ab_server` N-file, both transports (#646) - resolved by the driver, the transport sees the composed address |
| T/C/R sub-elements (`.PRE`/`.ACC`/`.LEN`/`.POS`), 6-byte T/C/R element layout | **none** |
### Native known gaps