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Auto: abcip-1.2 — STRINGnn variant decoding

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Closes #226

Adds nullable StringLength to AbCipTagDefinition + AbCipStructureMember
so STRING_20 / STRING_40 / STRING_80 UDT variants decode against the
right DATA-array capacity. The configured length threads through a new
StringMaxCapacity field on AbCipTagCreateParams and lands on the
libplctag Tag.StringMaxCapacity attribute (verified property on
libplctag 1.5.2). Null leaves libplctag's default 82-byte STRING in
place for back-compat. Driver gates on DataType == String so a stray
StringLength on a DINT tag doesn't reshape that buffer. UDT member
fan-out copies StringLength from the AbCipStructureMember onto the
synthesised member tag definition.

Tests: 4 new in AbCipDriverReadTests covering threaded StringMaxCapacity,
the null back-compat path, the non-String gate, and the UDT-member fan-out.
This commit is contained in:
Joseph Doherty
2026-04-25 12:53:20 -04:00
parent 1d9e40236b
commit d78a471e90
5 changed files with 102 additions and 5 deletions
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13
src/ZB.MOM.WW.OtOpcUa.Driver.AbCip/AbCipDriverOptions.cs
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@@ -92,6 +92,13 @@ public sealed record AbCipDeviceOptions(
/// GuardLogix controller; non-safety writes violate the safety-partition isolation and are
/// rejected by the PLC anyway. Surfaces the intent explicitly instead of relying on the
/// write attempt failing at runtime.</param>
/// <param name="StringLength">Capacity of the DATA character array on a Logix STRING / STRINGnn
/// UDT — 82 for the stock <c>STRING</c>, 20/40/80/etc for user-defined <c>STRING_20</c>,
/// <c>STRING_40</c>, <c>STRING_80</c> variants. Threads through libplctag's
/// <c>str_max_capacity</c> attribute so the wrapper allocates the correct backing buffer
/// and <c>GetString</c> / <c>SetString</c> truncate at the right boundary. <c>null</c>
/// keeps libplctag's default 82-byte STRING behaviour for back-compat. Ignored for
/// non-<see cref="AbCipDataType.String"/> types.</param>
public sealed record AbCipTagDefinition(
string Name,
string DeviceHostAddress,
@@ -100,7 +107,8 @@ public sealed record AbCipTagDefinition(
bool Writable = true,
bool WriteIdempotent = false,
IReadOnlyList<AbCipStructureMember>? Members = null,
bool SafetyTag = false);
bool SafetyTag = false,
int? StringLength = null);
/// <summary>
/// One declared member of a UDT tag. Name is the member identifier on the PLC (e.g. <c>Speed</c>,
@@ -112,7 +120,8 @@ public sealed record AbCipStructureMember(
string Name,
AbCipDataType DataType,
bool Writable = true,
bool WriteIdempotent = false);
bool WriteIdempotent = false,
int? StringLength = null);
/// <summary>Which AB PLC family the device is — selects the profile applied to connection params.</summary>
public enum AbCipPlcFamily