feat(abcip): thread nested-struct template id so nested UDT members are addressable (#6)

2026-06-18 11:33:41 -04:00
parent 56c136b0fd
commit 3d8ce4e85f
5 changed files with 122 additions and 13 deletions
@@ -86,6 +86,31 @@ public sealed class CipTemplateObjectDecoderTests
        shape.Members.Single().DataType.ShouldBe(AbCipDataType.Structure);
    }

+    /// <summary>
+    ///     A struct member's lower 12 bits carry the nested UDT's template instance id (same
+    ///     encoding as the Symbol Object); the decoder captures it as <c>NestedTemplateId</c> so the
+    ///     nested shape can be fetched. A scalar member carries no nested id. Uses the FULL 12-bit
+    ///     mask (0x123 here exceeds a byte) to prove the id is not byte-truncated.
+    /// </summary>
+    [Fact]
+    public void Struct_member_captures_nested_template_id_scalar_member_does_not()
+    {
+        var bytes = BuildTemplate("ContainerUdt", instanceSize: 8,
+            ("Inner", info: (ushort)(0x8000 | 0x123), arraySize: 0, offset: 0), // struct + nested id 0x123
+            ("Count", info: 0xC4, arraySize: 0, offset: 4));                    // scalar DINT, no nested id
+
+        var shape = CipTemplateObjectDecoder.Decode(bytes);
+
+        shape.ShouldNotBeNull();
+        shape.Members.Count.ShouldBe(2);
+        shape.Members[0].Name.ShouldBe("Inner");
+        shape.Members[0].DataType.ShouldBe(AbCipDataType.Structure);
+        shape.Members[0].NestedTemplateId.ShouldBe(0x123u); // full 12-bit id, not byte-truncated
+        shape.Members[1].Name.ShouldBe("Count");
+        shape.Members[1].DataType.ShouldBe(AbCipDataType.DInt);
+        shape.Members[1].NestedTemplateId.ShouldBeNull();
+    }
+
    /// <summary>Verifies that array members carry correct non-one array lengths.</summary>
    [Fact]
    public void Array_member_carries_non_one_ArrayLength()