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fix(s7): UInt64 box cast + Timer/Counter transient-write returns BadNotWritable (final review)

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M1: add missing (object) cast to UInt64 arm of DecodeScalarBlock switch expression,
matching the Int64 arm style and the comment that each arm is boxed explicitly.
M2: short-circuit Timer/Counter writes in WriteAsync to BadNotWritable before
WriteOneAsync, so transient equipment-tag refs (Writable=true from parser) return
the same status code as authored tags rejected at init — documented in the docs.
Adds 6 pure unit tests pinning the area-detection precondition the guard relies on.
EncodeScalarBlock Timer/Counter throws remain as the defensive backstop.
This commit is contained in:
Joseph Doherty
2026-06-17 06:31:41 -04:00
parent b7dfb5aff2
commit 988a7a938f
2 changed files with 48 additions and 2 deletions
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src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.S7/S7Driver.cs
+17 -1
View File
@@ -670,7 +670,7 @@ public sealed class S7Driver
return tag.DataType switch
{
S7DataType.Int64 => (object)System.Buffers.Binary.BinaryPrimitives.ReadInt64BigEndian(block),
S7DataType.UInt64 => System.Buffers.Binary.BinaryPrimitives.ReadUInt64BigEndian(block),
S7DataType.UInt64 => (object)System.Buffers.Binary.BinaryPrimitives.ReadUInt64BigEndian(block),
S7DataType.Float64 => System.Buffers.Binary.BinaryPrimitives.ReadDoubleBigEndian(block),
// S7 classic STRING: [maxLen byte][curLen byte][chars…]. S7.Net's S7String.FromByteArray
@@ -949,6 +949,22 @@ public sealed class S7Driver
results[i] = new WriteResult(StatusBadNotWritable);
continue;
}
// Timer/Counter transient-write guard: a transient equipment-tag ref is always
// resolved with Writable=true (S7EquipmentTagParser hardcodes it, and node-level
// auth governs writes), so Timer/Counter addresses bypass the !Writable gate above
// and would otherwise reach EncodeScalarBlock, which throws NotSupportedException →
// BadNotSupported. The docs say Timer/Counter writes return BadNotWritable. Detect
// the area here before the call so BOTH authored (caught by guard-d at init) and
// transient Timer/Counter writes consistently return BadNotWritable.
// TryParse (not Parse) so a malformed address falls through to the existing
// error path rather than throwing here.
if (_parsedByName.TryGetValue(tag.Name, out var tcParsed)
? tcParsed.Area is S7Area.Timer or S7Area.Counter
: (S7AddressParser.TryParse(tag.Address, out tcParsed) && tcParsed.Area is S7Area.Timer or S7Area.Counter))
{
results[i] = new WriteResult(StatusBadNotWritable);
continue;
}
try
{
await WriteOneAsync(plc, tag, w.Value, cancellationToken).ConfigureAwait(false);