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AB CIP @tags walker � CIP Symbol Object decoder + LibplctagTagEnumerator #130

Merged
dohertj2 merged 1 commits from abcip-tags-walker into v2 2026-04-19 21:15:18 -04:00
Conversation 0 Commits 1 Files Changed 6 +396 -4
6 changed files with 396 additions and 4 deletions
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10
src/ZB.MOM.WW.OtOpcUa.Driver.AbCip/AbCipDriver.cs
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@@ -44,7 +44,7 @@ public sealed class AbCipDriver : IDriver, IReadable, IWritable, ITagDiscovery,
_options = options;
_driverInstanceId = driverInstanceId;
_tagFactory = tagFactory ?? new LibplctagTagFactory();
_enumeratorFactory = enumeratorFactory ?? new EmptyAbCipTagEnumeratorFactory();
_enumeratorFactory = enumeratorFactory ?? new LibplctagTagEnumeratorFactory();
_poll = new PollGroupEngine(
reader: ReadAsync,
onChange: (handle, tagRef, snapshot) =>
@@ -559,9 +559,11 @@ public sealed class AbCipDriver : IDriver, IReadable, IWritable, ITagDiscovery,
deviceFolder.Variable(tag.Name, tag.Name, ToAttributeInfo(tag));
}
// Controller-discovered tags — optional. Default enumerator returns an empty sequence;
// tests + the follow-up real @tags walker plug in via the ctor parameter.
if (_devices.TryGetValue(device.HostAddress, out var state))
// Controller-discovered tags — opt-in via EnableControllerBrowse. The real @tags
// walker (LibplctagTagEnumerator) is the factory default since task #178 shipped,
// so leaving the flag off keeps the strict-config path for deployments where only
// declared tags should appear.
if (_options.EnableControllerBrowse && _devices.TryGetValue(device.HostAddress, out var state))
{
using var enumerator = _enumeratorFactory.Create();
var deviceParams = new AbCipTagCreateParams(

9
src/ZB.MOM.WW.OtOpcUa.Driver.AbCip/AbCipDriverOptions.cs
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@@ -29,6 +29,15 @@ public sealed class AbCipDriverOptions
/// not pass a more specific value. Matches the Modbus driver's 2-second default.
/// </summary>
public TimeSpan Timeout { get; init; } = TimeSpan.FromSeconds(2);
/// <summary>
/// When <c>true</c>, <c>DiscoverAsync</c> walks each device's Logix symbol table via
/// the <c>@tags</c> pseudo-tag + surfaces controller-resident globals under a
/// <c>Discovered/</c> sub-folder. Pre-declared tags always emit regardless. Default
/// <c>false</c> to keep the strict-config path for deployments where only declared tags
/// should appear in the address space.
/// </summary>
public bool EnableControllerBrowse { get; init; }
}
/// <summary>

128
src/ZB.MOM.WW.OtOpcUa.Driver.AbCip/CipSymbolObjectDecoder.cs Normal file
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@@ -0,0 +1,128 @@
using System.Buffers.Binary;
using System.Text;
namespace ZB.MOM.WW.OtOpcUa.Driver.AbCip;
/// <summary>
/// Decoder for the CIP Symbol Object (class 0x6B) response returned by Logix controllers
/// when a client reads the <c>@tags</c> pseudo-tag. Parses the concatenated tag-info
/// entries into a sequence of <see cref="AbCipDiscoveredTag"/>s that the driver can stream
/// into the address-space builder.
/// </summary>
/// <remarks>
/// <para>Entry layout (little-endian) per Rockwell CIP Vol 1 + Logix 5000 CIP Programming
/// Manual (1756-PM019 chapter "Symbol Object"), cross-checked against libplctag's
/// <c>ab/cip.c</c> <c>handle_listed_tags_reply</c>:</para>
/// <list type="table">
/// <item><term>u32</term><description>Symbol Instance ID — opaque identifier for the tag.</description></item>
/// <item><term>u16</term><description>Symbol Type — lower 12 bits = CIP type code (0xC1 BOOL,
/// 0xC2 SINT, …, 0xD0 STRING). Bit 12 = system-tag flag. Bit 13 = reserved.
/// Bit 15 = struct flag; when set, the lower 12 bits are the template instance id
/// (not a primitive type code).</description></item>
/// <item><term>u16</term><description>Element length — bytes per element (e.g. 4 for DINT).</description></item>
/// <item><term>u32 × 3</term><description>Array dimensions — zero for scalar tags.</description></item>
/// <item><term>u16</term><description>Symbol name length in bytes.</description></item>
/// <item><term>u8 × N</term><description>ASCII symbol name, padded to an even byte boundary.</description></item>
/// </list>
///
/// <para><c>Program:</c>-scope tags arrive with their scope prefix baked into the name
/// (<c>Program:MainProgram.StepIndex</c>); decoder strips the prefix + emits the scope
/// separately so the driver's IAddressSpaceBuilder can organise them.</para>
/// </remarks>
public static class CipSymbolObjectDecoder
{
// Fixed header size in bytes — instance-id(4) + symbol-type(2) + element-length(2)
// + array-dims(4×3) + name-length(2) = 22.
private const int FixedHeaderSize = 22;
private const ushort SymbolTypeSystemFlag = 0x1000;
private const ushort SymbolTypeStructFlag = 0x8000;
private const ushort SymbolTypeTypeCodeMask = 0x0FFF;
/// <summary>
/// Decode the raw <c>@tags</c> blob into an enumerable sequence. Malformed entries at
/// the tail cause decoding to stop gracefully — the caller gets whatever it could parse
/// cleanly before the corruption.
/// </summary>
public static IEnumerable<AbCipDiscoveredTag> Decode(byte[] buffer)
{
ArgumentNullException.ThrowIfNull(buffer);
return DecodeImpl(buffer);
}
private static IEnumerable<AbCipDiscoveredTag> DecodeImpl(byte[] buffer)
{
var pos = 0;
while (pos + FixedHeaderSize <= buffer.Length)
{
var instanceId = BinaryPrimitives.ReadUInt32LittleEndian(buffer.AsSpan(pos));
var symbolType = BinaryPrimitives.ReadUInt16LittleEndian(buffer.AsSpan(pos + 4));
// element_length at pos+6 (u16) — useful for array sizing but not surfaced here
// array_dims at pos+8, pos+12, pos+16 — same (scalar-tag case has all zeros)
var nameLength = BinaryPrimitives.ReadUInt16LittleEndian(buffer.AsSpan(pos + 20));
pos += FixedHeaderSize;
if (pos + nameLength > buffer.Length) break;
var name = Encoding.ASCII.GetString(buffer, pos, nameLength);
pos += nameLength;
if ((pos & 1) != 0) pos++; // even-align for the next entry
if (string.IsNullOrWhiteSpace(name)) continue;
var isSystem = (symbolType & SymbolTypeSystemFlag) != 0;
var isStruct = (symbolType & SymbolTypeStructFlag) != 0;
var typeCode = symbolType & SymbolTypeTypeCodeMask;
var (programScope, simpleName) = SplitProgramScope(name);
var dataType = isStruct ? AbCipDataType.Structure : MapTypeCode((byte)typeCode);
yield return new AbCipDiscoveredTag(
Name: simpleName,
ProgramScope: programScope,
DataType: dataType ?? AbCipDataType.Structure, // unknown type code → treat as opaque
ReadOnly: false, // Symbol Object doesn't carry write-protection bits; lift via AccessControl Object later
IsSystemTag: isSystem);
_ = instanceId; // retained in the wire format for diagnostics; not surfaced to the driver today
}
}
/// <summary>
/// Split a <c>Program:MainProgram.StepIndex</c>-style name into its scope + local
/// parts. Names without the <c>Program:</c> prefix pass through unchanged.
/// </summary>
internal static (string? programScope, string simpleName) SplitProgramScope(string fullName)
{
const string prefix = "Program:";
if (!fullName.StartsWith(prefix, StringComparison.Ordinal)) return (null, fullName);
var afterPrefix = fullName[prefix.Length..];
var dot = afterPrefix.IndexOf('.');
if (dot <= 0) return (null, fullName); // malformed scope — surface the raw name
return (afterPrefix[..dot], afterPrefix[(dot + 1)..]);
}
/// <summary>
/// Map a CIP atomic type code (lower 12 bits of the symbol-type field) to our
/// <see cref="AbCipDataType"/> surface. Returns <c>null</c> for unrecognised codes —
/// caller treats those as <see cref="AbCipDataType.Structure"/> so the symbol is still
/// surfaced + downstream config can add a concrete type override.
/// </summary>
internal static AbCipDataType? MapTypeCode(byte typeCode) => typeCode switch
{
0xC1 => AbCipDataType.Bool,
0xC2 => AbCipDataType.SInt,
0xC3 => AbCipDataType.Int,
0xC4 => AbCipDataType.DInt,
0xC5 => AbCipDataType.LInt,
0xC6 => AbCipDataType.USInt,
0xC7 => AbCipDataType.UInt,
0xC8 => AbCipDataType.UDInt,
0xC9 => AbCipDataType.ULInt,
0xCA => AbCipDataType.Real,
0xCB => AbCipDataType.LReal,
0xCD => AbCipDataType.Dt, // DATE
0xCF => AbCipDataType.Dt, // DATE_AND_TIME
0xD0 => AbCipDataType.String,
_ => null,
};
}

63
src/ZB.MOM.WW.OtOpcUa.Driver.AbCip/LibplctagTagEnumerator.cs Normal file
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@@ -0,0 +1,63 @@
using System.Runtime.CompilerServices;
using libplctag;
namespace ZB.MOM.WW.OtOpcUa.Driver.AbCip;
/// <summary>
/// Real <see cref="IAbCipTagEnumerator"/> that walks a Logix controller's symbol table by
/// reading the <c>@tags</c> pseudo-tag via libplctag + decoding the CIP Symbol Object
/// response with <see cref="CipSymbolObjectDecoder"/>.
/// </summary>
/// <remarks>
/// <para>libplctag's <c>Tag.GetBuffer()</c> returns the raw Symbol Object bytes when the
/// tag name is <c>@tags</c>. The decoder walks the concatenated entries + emits
/// <see cref="AbCipDiscoveredTag"/> records matching our driver surface.</para>
///
/// <para>Task #178 closed the stub gap from PR 5 — <see cref="EmptyAbCipTagEnumerator"/>
/// is still available for tests that don't want to touch the native library, but the
/// production factory default now wires this implementation in.</para>
/// </remarks>
internal sealed class LibplctagTagEnumerator : IAbCipTagEnumerator
{
private Tag? _tag;
public async IAsyncEnumerable<AbCipDiscoveredTag> EnumerateAsync(
AbCipTagCreateParams deviceParams,
[EnumeratorCancellation] CancellationToken cancellationToken)
{
// Build a tag specifically for the @tags pseudo — same gateway + path as the device,
// distinguished by the name alone.
_tag = new Tag
{
Gateway = deviceParams.Gateway,
Path = deviceParams.CipPath,
PlcType = MapPlcType(deviceParams.LibplctagPlcAttribute),
Protocol = Protocol.ab_eip,
Name = "@tags",
Timeout = deviceParams.Timeout,
};
await _tag.InitializeAsync(cancellationToken).ConfigureAwait(false);
await _tag.ReadAsync(cancellationToken).ConfigureAwait(false);
var buffer = _tag.GetBuffer();
foreach (var tag in CipSymbolObjectDecoder.Decode(buffer))
yield return tag;
}
public void Dispose() => _tag?.Dispose();
private static PlcType MapPlcType(string attribute) => attribute switch
{
"controllogix" => PlcType.ControlLogix,
"compactlogix" => PlcType.ControlLogix,
"micro800" => PlcType.Micro800,
_ => PlcType.ControlLogix,
};
}
/// <summary>Factory for <see cref="LibplctagTagEnumerator"/>.</summary>
internal sealed class LibplctagTagEnumeratorFactory : IAbCipTagEnumeratorFactory
{
public IAbCipTagEnumerator Create() => new LibplctagTagEnumerator();
}

4
tests/ZB.MOM.WW.OtOpcUa.Driver.AbCip.Tests/AbCipDriverDiscoveryTests.cs
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@@ -97,6 +97,7 @@ public sealed class AbCipDriverDiscoveryTests
var drv = new AbCipDriver(new AbCipDriverOptions
{
Devices = [new AbCipDeviceOptions("ab://10.0.0.5/1,0")],
EnableControllerBrowse = true,
}, "drv-1", enumeratorFactory: enumeratorFactory);
await drv.InitializeAsync("{}", CancellationToken.None);
@@ -119,6 +120,7 @@ public sealed class AbCipDriverDiscoveryTests
var drv = new AbCipDriver(new AbCipDriverOptions
{
Devices = [new AbCipDeviceOptions("ab://10.0.0.5/1,0")],
EnableControllerBrowse = true,
}, "drv-1", enumeratorFactory: factory);
await drv.InitializeAsync("{}", CancellationToken.None);
@@ -137,6 +139,7 @@ public sealed class AbCipDriverDiscoveryTests
var drv = new AbCipDriver(new AbCipDriverOptions
{
Devices = [new AbCipDeviceOptions("ab://10.0.0.5/1,0")],
EnableControllerBrowse = true,
}, "drv-1", enumeratorFactory: factory);
await drv.InitializeAsync("{}", CancellationToken.None);
@@ -153,6 +156,7 @@ public sealed class AbCipDriverDiscoveryTests
{
Devices = [new AbCipDeviceOptions("ab://10.0.0.5:44818/1,2,3", AbCipPlcFamily.ControlLogix)],
Timeout = TimeSpan.FromSeconds(7),
EnableControllerBrowse = true,
}, "drv-1", enumeratorFactory: factory);
await drv.InitializeAsync("{}", CancellationToken.None);

186
tests/ZB.MOM.WW.OtOpcUa.Driver.AbCip.Tests/CipSymbolObjectDecoderTests.cs Normal file
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@@ -0,0 +1,186 @@
using System.Buffers.Binary;
using System.Text;
using Shouldly;
using Xunit;
using ZB.MOM.WW.OtOpcUa.Driver.AbCip;
namespace ZB.MOM.WW.OtOpcUa.Driver.AbCip.Tests;
[Trait("Category", "Unit")]
public sealed class CipSymbolObjectDecoderTests
{
/// <summary>
/// Build one Symbol Object entry in the byte layout
/// <c>instance_id(u32) symbol_type(u16) element_length(u16) array_dims(u32×3) name_len(u16) name[len] pad</c>.
/// </summary>
private static byte[] BuildEntry(
uint instanceId,
ushort symbolType,
ushort elementLength,
(uint, uint, uint) arrayDims,
string name)
{
var nameBytes = Encoding.ASCII.GetBytes(name);
var nameLen = nameBytes.Length;
var totalLen = 22 + nameLen;
if ((totalLen & 1) != 0) totalLen++; // pad to even
var buf = new byte[totalLen];
BinaryPrimitives.WriteUInt32LittleEndian(buf.AsSpan(0), instanceId);
BinaryPrimitives.WriteUInt16LittleEndian(buf.AsSpan(4), symbolType);
BinaryPrimitives.WriteUInt16LittleEndian(buf.AsSpan(6), elementLength);
BinaryPrimitives.WriteUInt32LittleEndian(buf.AsSpan(8), arrayDims.Item1);
BinaryPrimitives.WriteUInt32LittleEndian(buf.AsSpan(12), arrayDims.Item2);
BinaryPrimitives.WriteUInt32LittleEndian(buf.AsSpan(16), arrayDims.Item3);
BinaryPrimitives.WriteUInt16LittleEndian(buf.AsSpan(20), (ushort)nameLen);
Buffer.BlockCopy(nameBytes, 0, buf, 22, nameLen);
return buf;
}
private static byte[] Concat(params byte[][] chunks)
{
var total = chunks.Sum(c => c.Length);
var result = new byte[total];
var pos = 0;
foreach (var c in chunks)
{
Buffer.BlockCopy(c, 0, result, pos, c.Length);
pos += c.Length;
}
return result;
}
[Fact]
public void Single_DInt_entry_decodes_to_scalar_DInt_tag()
{
var bytes = BuildEntry(
instanceId: 42,
symbolType: 0xC4,
elementLength: 4,
arrayDims: (0, 0, 0),
name: "Counter");
var tags = CipSymbolObjectDecoder.Decode(bytes).ToList();
tags.Count.ShouldBe(1);
tags[0].Name.ShouldBe("Counter");
tags[0].ProgramScope.ShouldBeNull();
tags[0].DataType.ShouldBe(AbCipDataType.DInt);
tags[0].IsSystemTag.ShouldBeFalse();
}
[Theory]
[InlineData((byte)0xC1, AbCipDataType.Bool)]
[InlineData((byte)0xC2, AbCipDataType.SInt)]
[InlineData((byte)0xC3, AbCipDataType.Int)]
[InlineData((byte)0xC4, AbCipDataType.DInt)]
[InlineData((byte)0xC5, AbCipDataType.LInt)]
[InlineData((byte)0xC6, AbCipDataType.USInt)]
[InlineData((byte)0xC7, AbCipDataType.UInt)]
[InlineData((byte)0xC8, AbCipDataType.UDInt)]
[InlineData((byte)0xC9, AbCipDataType.ULInt)]
[InlineData((byte)0xCA, AbCipDataType.Real)]
[InlineData((byte)0xCB, AbCipDataType.LReal)]
[InlineData((byte)0xD0, AbCipDataType.String)]
public void Every_known_atomic_type_code_maps_to_correct_AbCipDataType(byte typeCode, AbCipDataType expected)
{
CipSymbolObjectDecoder.MapTypeCode(typeCode).ShouldBe(expected);
}
[Fact]
public void Unknown_type_code_returns_null_so_caller_treats_as_opaque()
{
CipSymbolObjectDecoder.MapTypeCode(0xFF).ShouldBeNull();
}
[Fact]
public void Struct_flag_overrides_type_code_and_yields_Structure()
{
// 0x8000 (struct) + 0x1234 (template instance id in lower 12 bits; uses 0x234)
var bytes = BuildEntry(
instanceId: 5,
symbolType: 0x8000 | 0x0234,
elementLength: 16,
arrayDims: (0, 0, 0),
name: "Motor1");
var tag = CipSymbolObjectDecoder.Decode(bytes).Single();
tag.DataType.ShouldBe(AbCipDataType.Structure);
}
[Fact]
public void System_flag_surfaces_as_IsSystemTag_true()
{
var bytes = BuildEntry(
instanceId: 99,
symbolType: 0x1000 | 0xC4, // system flag + DINT
elementLength: 4,
arrayDims: (0, 0, 0),
name: "__Reserved_1");
var tag = CipSymbolObjectDecoder.Decode(bytes).Single();
tag.IsSystemTag.ShouldBeTrue();
tag.DataType.ShouldBe(AbCipDataType.DInt);
}
[Fact]
public void Program_scope_name_splits_prefix_into_ProgramScope()
{
var bytes = BuildEntry(
instanceId: 1,
symbolType: 0xC4,
elementLength: 4,
arrayDims: (0, 0, 0),
name: "Program:MainProgram.StepIndex");
var tag = CipSymbolObjectDecoder.Decode(bytes).Single();
tag.ProgramScope.ShouldBe("MainProgram");
tag.Name.ShouldBe("StepIndex");
}
[Fact]
public void Multiple_entries_decode_in_wire_order_with_even_padding()
{
// Name "Abc" is 3 bytes — triggers the even-pad branch between entries.
var bytes = Concat(
BuildEntry(1, 0xC4, 4, (0, 0, 0), "Abc"), // DINT named "Abc" (3-byte name, pads to 4)
BuildEntry(2, 0xCA, 4, (0, 0, 0), "Pi")); // REAL named "Pi"
var tags = CipSymbolObjectDecoder.Decode(bytes).ToList();
tags.Count.ShouldBe(2);
tags[0].Name.ShouldBe("Abc");
tags[0].DataType.ShouldBe(AbCipDataType.DInt);
tags[1].Name.ShouldBe("Pi");
tags[1].DataType.ShouldBe(AbCipDataType.Real);
}
[Fact]
public void Truncated_buffer_stops_decoding_gracefully()
{
var full = BuildEntry(7, 0xC4, 4, (0, 0, 0), "Counter");
// Deliberately chop off the last 5 bytes — decoder should bail cleanly, not throw.
var truncated = full.Take(full.Length - 5).ToArray();
CipSymbolObjectDecoder.Decode(truncated).ToList().Count.ShouldBeLessThan(1); // 0 — didn't parse the broken entry
}
[Fact]
public void Empty_buffer_yields_no_tags()
{
CipSymbolObjectDecoder.Decode([]).ShouldBeEmpty();
}
[Theory]
[InlineData("Counter", null, "Counter")]
[InlineData("Program:MainProgram.Step", "MainProgram", "Step")]
[InlineData("Program:MyProg.a.b.c", "MyProg", "a.b.c")]
[InlineData("Program:", null, "Program:")] // malformed — no dot
[InlineData("Program:OnlyProg", null, "Program:OnlyProg")]
[InlineData("Motor.Status.Running", null, "Motor.Status.Running")]
public void SplitProgramScope_handles_every_shape(string input, string? expectedScope, string expectedName)
{
var (scope, name) = CipSymbolObjectDecoder.SplitProgramScope(input);
scope.ShouldBe(expectedScope);
name.ShouldBe(expectedName);
}
}