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fix(ablegacy): gate array read on isArray:true; 1-element arrays + assumption comments (review C-2/I-3)

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This commit is contained in:
Joseph Doherty
2026-06-16 22:14:36 -04:00
parent 3bbe39c166
commit ce5d46be08
4 changed files with 162 additions and 38 deletions
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src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.AbLegacy/AbLegacyDriver.cs
+27 -16
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@@ -267,15 +267,15 @@ public sealed class AbLegacyDriver : IDriver, IReadable, IWritable, ITagDiscover
await runtime.ReadAsync(cancellationToken).ConfigureAwait(false);
status = runtime.GetStatus();
var parsed = AbLegacyAddress.TryParse(def.Address);
// Phase 4c #137 — when the tag addresses a multi-element span (ArrayLength > 1)
// decode the whole contiguous read into a typed CLR array; otherwise decode a
// single scalar value as before. The runtime was created with a matching
// ElementCount in EnsureTagRuntimeAsync so its buffer holds all the elements.
var arrayLen = EffectiveArrayLength(def);
// Phase 4c #137 — an ARRAY tag (non-null ArrayLength, ≥1) decodes the whole
// contiguous read into a typed CLR array of that count, INCLUDING a 1-element
// array (review I-3); a SCALAR tag (null ArrayLength) decodes a single value.
// The runtime was created with a matching ElementCount in EnsureTagRuntimeAsync
// so its buffer holds all the elements.
if (status != 0)
value = null;
else if (arrayLen > 1)
value = runtime.DecodeArray(def.DataType, arrayLen);
else if (IsArrayTag(def))
value = runtime.DecodeArray(def.DataType, EffectiveArrayLength(def));
else
value = runtime.DecodeValue(def.DataType, parsed?.BitIndex);
}
@@ -439,11 +439,14 @@ public sealed class AbLegacyDriver : IDriver, IReadable, IWritable, ITagDiscover
foreach (var tag in tagsForDevice)
{
// Phase 4c #137 — PCCC data files are inherently arrays of elements (a single N7
// file is up to 256 words). A tag whose ArrayLength addresses a multi-element span
// now materialises a 1-D array OPC UA node. ArrayDim is clamped to the PCCC file
// maximum (AbLegacyArray.MaxElements = 256) so the declared dimension can never
// exceed what a single data file holds; an ArrayLength of 1 (or null) stays scalar.
var isArray = tag.ArrayLength is int len && len > 1;
// file is up to 256 words). The canonical contract: a tag is an ARRAY ⟺ its
// ArrayLength is non-null (≥1, set by the parser only when isArray:true). A tag
// with a non-null ArrayLength materialises a 1-D array OPC UA node, INCLUDING a
// 1-element array (ArrayLength:1 → a [1] node — review I-3). ArrayDim is clamped
// to the PCCC file maximum (AbLegacyArray.MaxElements = 256) so the declared
// dimension can never exceed what a single data file holds; ArrayLength == null
// (scalar) stays scalar.
var isArray = tag.ArrayLength is int len && len >= 1;
var arrayDim = isArray
? (uint)Math.Min(tag.ArrayLength!.Value, AbLegacyArray.MaxElements)
: (uint?)null;
@@ -685,15 +688,23 @@ public sealed class AbLegacyDriver : IDriver, IReadable, IWritable, ITagDiscover
}
}
/// <summary>
/// Phase 4c #137 — whether a tag definition is an ARRAY. The canonical contract: a tag is
/// an array ⟺ its <see cref="AbLegacyTagDefinition.ArrayLength"/> is non-null (the parser
/// sets it ≥1 only when isArray:true), so a 1-element array (ArrayLength:1) IS an array
/// (review I-3). <c>null</c> ArrayLength ⇒ scalar.
/// </summary>
private static bool IsArrayTag(AbLegacyTagDefinition def) => def.ArrayLength is int len && len >= 1;
/// <summary>
/// Phase 4c #137 — the effective libplctag element count for a tag definition: the tag's
/// <see cref="AbLegacyTagDefinition.ArrayLength"/> clamped to the PCCC file maximum
/// (<see cref="AbLegacyArray.MaxElements"/> = 256), or <c>1</c> when the tag is scalar
/// (null or non-positive ArrayLength). Used both to size the runtime at create time and to
/// decide whether the read path decodes a scalar or an array.
/// (<see cref="AbLegacyArray.MaxElements"/> = 256) when it is an array (≥1, INCLUDING 1),
/// or <c>1</c> when the tag is scalar (null ArrayLength). Used both to size the runtime at
/// create time and as the element count the read path decodes into an array.
/// </summary>
private static int EffectiveArrayLength(AbLegacyTagDefinition def) =>
def.ArrayLength is int len && len > 1 ? Math.Min(len, AbLegacyArray.MaxElements) : 1;
def.ArrayLength is int len && len >= 1 ? Math.Min(len, AbLegacyArray.MaxElements) : 1;
private async Task<IAbLegacyTagRuntime> EnsureTagRuntimeAsync(
DeviceState device, AbLegacyTagDefinition def, CancellationToken ct)