wip 3

Author: ikpil

src/Box2D.NET/B2ContactPrepareSpan.cs

@@ -0,0 +1,18 @@
+// SPDX-FileCopyrightText: 2023 Erin Catto
+// SPDX-FileCopyrightText: 2025 Ikpil Choi(ikpil@naver.com)
+// SPDX-License-Identifier: MIT
+
+namespace Box2D.NET
+{
+    // Prepare/store run as a flat parallel-for over the whole wide-constraint
+    // range. Each span maps a slice of that range back to the owning color's
+    // contacts so workers can decode flat wide-slot indices without touching
+    // graph state. The spans array has one entry per active color plus a sentinel
+    // whose start == wideContactCount.
+    public struct B2ContactPrepareSpan
+    {
+        public int start;
+        public int count;
+        public B2ContactSim[] contacts;
+    }
+}