perf(abcip): cache the declaration-only UDT layout per member list

P11: AbCipUdtReadPlanner called AbCipUdtMemberLayout.TryBuild(parent.Members) for every member reference on every poll - O(members^2) per parent per tick, a dictionary allocation each time. GetOrBuild caches the layout (including a "not groupable" verdict) in a ConditionalWeakTable keyed by the member list's identity, which is immutable for the life of the tag table; a re-init's new lists replace the entries and the old ones are collected with them. Refs #737 Claude-Session: https://claude.ai/code/session_01Ub9hGmYLQvn9XETzw7CMsT
2026-10-22 14:31:32 -04:00
parent 7cc8415310
commit fc94b87634
3 changed files with 47 additions and 1 deletions
@@ -99,4 +99,26 @@ public sealed class AbCipUdtMemberLayoutTests
            new AbCipStructureMember("Setpoints", AbCipDataType.Real, ElementCount: 4),
        }).ShouldBeNull();
    }
+
+    /// <summary>Review 07 P11: the layout is computed once per member list, not once per member per poll.</summary>
+    [Fact]
+    public void GetOrBuild_computes_a_layout_once_per_member_list()
+    {
+        IReadOnlyList<AbCipStructureMember> members =
+        [
+            new AbCipStructureMember("A", AbCipDataType.DInt),
+            new AbCipStructureMember("B", AbCipDataType.Real),
+        ];
+        var first = AbCipUdtMemberLayout.GetOrBuild(members);
+        first.ShouldNotBeNull();
+        first["B"].ShouldBe(4);
+        AbCipUdtMemberLayout.GetOrBuild(members).ShouldBeSameAs(first);
+
+        // Positive control: a different (equal-content) list is its own entry, and a not-groupable verdict caches too.
+        IReadOnlyList<AbCipStructureMember> copy = [.. members];
+        AbCipUdtMemberLayout.GetOrBuild(copy).ShouldNotBeSameAs(first);
+        IReadOnlyList<AbCipStructureMember> withBool = [new AbCipStructureMember("F", AbCipDataType.Bool)];
+        AbCipUdtMemberLayout.GetOrBuild(withBool).ShouldBeNull();
+        AbCipUdtMemberLayout.GetOrBuild(withBool).ShouldBeNull();
+    }
 }