MergeCorridorEndMoved alloc fix

src/DotRecast.Core/Buffers/RcRentedArray.cs

@@ -43,6 +43,11 @@ namespace DotRecast.Core.Buffers
             return _array;
         }
 
+        public Span<T> AsSpan()
+        {
+            return new Span<T>(_array, 0, Length);
+        }
+
 
         public void Dispose()
         {

src/DotRecast.Core/Collections/CollectionExtensions.cs

@@ -45,5 +45,11 @@ namespace DotRecast.Core.Collections
                 (list[k], list[n]) = (list[n], list[k]);
             }
         }
+
+        public static void AddRange<T>(this IList<T> list, Span<T> span)
+        {
+            foreach (var i in span) 
+                list.Add(i);
+        }
     }
 }

src/DotRecast.Detour.Crowd/DtPathCorridor.cs

@@ -33,7 +33,7 @@ namespace DotRecast.Detour.Crowd
         private RcVec3f m_pos;
         private RcVec3f m_target;
 
-        private List<long> m_path;
+        private List<long> m_path = new List<long>();
         private int m_npath;
         private int m_maxPath;
 
@@ -89,7 +89,8 @@ namespace DotRecast.Detour.Crowd
         /// @return True if the initialization succeeded.
         public bool Init(int maxPath)
         {
-            m_path = new List<long>(maxPath);
+            if (m_path.Capacity < maxPath)
+                m_path.Capacity = maxPath;
             m_npath = 0;
             m_maxPath = maxPath;
             return true;
@@ -218,7 +219,7 @@ namespace DotRecast.Detour.Crowd
             {
                 if (res.Count > 1 && t > 0.99f)
                 {
-                    m_npath = DtPathUtils.MergeCorridorStartShortcut(ref m_path, m_npath, m_maxPath, res, res.Count);
+                    m_npath = DtPathUtils.MergeCorridorStartShortcut(m_path, m_npath, m_maxPath, res, res.Count);
                 }
             }
         }
@@ -250,7 +251,7 @@ namespace DotRecast.Detour.Crowd
 
             if (status.Succeeded() && res.Count > 0)
             {
-                m_npath = DtPathUtils.MergeCorridorStartShortcut(ref m_path, m_npath, m_maxPath, res, res.Count);
+                m_npath = DtPathUtils.MergeCorridorStartShortcut(m_path, m_npath, m_maxPath, res, res.Count);
                 return true;
             }
 
@@ -276,7 +277,7 @@ namespace DotRecast.Detour.Crowd
             }
 
             // Prune path
-            m_path = m_path.GetRange(npos, m_npath - npos);
+            m_path.RemoveRange(0, npos);
             m_npath -= npos;
 
             refs[0] = prevRef;
@@ -322,7 +323,7 @@ namespace DotRecast.Detour.Crowd
             var status = navquery.MoveAlongSurface(m_path[0], m_pos, npos, filter, out var result, visited, out var nvisited, MAX_VISITED);
             if (status.Succeeded())
             {
-                m_npath = DtPathUtils.MergeCorridorStartMoved(ref m_path, m_npath, m_maxPath, visited, nvisited);
+                m_npath = DtPathUtils.MergeCorridorStartMoved(m_path, m_npath, m_maxPath, visited, nvisited);
 
                 // Adjust the position to stay on top of the navmesh.
                 m_pos = result;
@@ -366,7 +367,7 @@ namespace DotRecast.Detour.Crowd
             var status = navquery.MoveAlongSurface(m_path[^1], m_target, npos, filter, out var result, visited, out nvisited, MAX_VISITED);
             if (status.Succeeded())
             {
-                m_npath = DtPathUtils.MergeCorridorEndMoved(ref m_path, m_npath, m_maxPath, visited, nvisited);
+                m_npath = DtPathUtils.MergeCorridorEndMoved(m_path, m_npath, m_maxPath, visited, nvisited);
 
                 // TODO: should we do that?
                 // Adjust the position to stay on top of the navmesh.
@@ -394,7 +395,11 @@ namespace DotRecast.Detour.Crowd
         public void SetCorridor(RcVec3f target, List<long> path)
         {
             m_target = target;
-            m_path = new List<long>(path);
+            if(path != m_path)
+            {
+                m_path.Clear();
+                m_path.AddRange(path);
+            }
             m_npath = path.Count;
         }
 
@@ -444,7 +449,7 @@ namespace DotRecast.Detour.Crowd
             else if (n < m_npath)
             {
                 // The path is partially usable.
-                m_path = m_path.GetRange(0, n);
+                m_path.RemoveRange(n, m_path.Count - n);
                 m_npath = n;
             }
 

src/DotRecast.Detour/DtPathUtils.cs

@@ -20,7 +20,10 @@ freely, subject to the following restrictions:
 
 using System;
 using System.Collections.Generic;
+using DotRecast.Core.Buffers;
+using DotRecast.Core.Collections;
 using DotRecast.Core.Numerics;
+using CollectionExtensions = DotRecast.Core.Collections.CollectionExtensions;
 
 namespace DotRecast.Detour
 {
@@ -148,7 +151,7 @@ namespace DotRecast.Detour
             return npath;
         }
 
-        public static int MergeCorridorStartMoved(ref List<long> path, int npath, int maxPath, Span<long> visited, int nvisited)
+        public static int MergeCorridorStartMoved(List<long> path, int npath, int maxPath, Span<long> visited, int nvisited)
         {
             int furthestPath = -1;
             int furthestVisited = -1;
@@ -180,22 +183,23 @@ namespace DotRecast.Detour
             }
 
             // Concatenate paths.
-
+            var endIndex = nvisited - 1;
+            var length1 = endIndex - furthestVisited;
+            var length2 = npath - furthestPath;
+            using var result = RcRentedArray.Rent<long>(length1 + length2);
             // Adjust beginning of the buffer to include the visited.
-            List<long> result = new List<long>();
             // Store visited
-            for (int i = nvisited - 1; i > furthestVisited; --i)
-            {
-                result.Add(visited[i]);
+            for (int i = 0; i < length1; ++i) 
+                result[i] = visited[endIndex - i];
+            
+            path.CopyTo(furthestPath, result.AsArray(), length1, length2);
+
+            path.Clear();
+            CollectionExtensions.AddRange(path, result.AsSpan());
+            return result.Length;
         }
 
-            result.AddRange(path.GetRange(furthestPath, npath - furthestPath));
-
-            path = result;
-            return result.Count;
-        }
-
-        public static int MergeCorridorEndMoved(ref List<long> path, int npath, int maxPath, Span<long> visited, int nvisited)
+        public static int MergeCorridorEndMoved(List<long> path, int npath, int maxPath, Span<long> visited, int nvisited)
         {
             int furthestPath = -1;
             int furthestVisited = -1;
@@ -227,17 +231,18 @@ namespace DotRecast.Detour
             }
 
             // Concatenate paths.
-            List<long> result = path.GetRange(0, furthestPath);
-            foreach (var v in visited.Slice(furthestVisited, nvisited - furthestVisited))
-            {
-                result.Add(v);
+            var length1 = furthestPath;
+            var length2 = nvisited - furthestVisited;
+            using var result = RcRentedArray.Rent<long>(length1 + length2);
+            path.CopyTo(0, result.AsArray(), 0, length1);
+            visited.Slice(furthestVisited, nvisited - furthestVisited).CopyTo(result.AsSpan().Slice(length1, length2));
+
+            path.Clear();
+            CollectionExtensions.AddRange(path, result.AsSpan());
+            return path.Count;
         }
 
-            path = result;
-            return result.Count;
-        }
-
-        public static int MergeCorridorStartShortcut(ref List<long> path, int npath, int maxPath, List<long> visited, int nvisited)
+        public static int MergeCorridorStartShortcut(List<long> path, int npath, int maxPath, List<long> visited, int nvisited)
         {
             int furthestPath = -1;
             int furthestVisited = -1;
@@ -271,11 +276,15 @@ namespace DotRecast.Detour
             // Concatenate paths.
 
             // Adjust beginning of the buffer to include the visited.
-            List<long> result = visited.GetRange(0, furthestVisited);
-            result.AddRange(path.GetRange(furthestPath, npath - furthestPath));
+            var length1 = furthestVisited;
+            var length2 = npath - furthestPath;
+            using var result = RcRentedArray.Rent<long>(length1 + length2);
+            visited.CopyTo(0, result.AsArray(), 0, length1);
+            path.CopyTo(furthestPath, result.AsArray(), length1, length2);
 
-            path = result;
-            return result.Count;
+            path.Clear();
+            CollectionExtensions.AddRange(path, result.AsSpan());
+            return path.Count;
         }
     }
 }

src/DotRecast.Recast.Toolset/Tools/RcTestNavMeshTool.cs

@@ -98,7 +98,7 @@ namespace DotRecast.Recast.Toolset.Tools
 
                 iterPos = result;
 
-                pathIterPolyCount = DtPathUtils.MergeCorridorStartMoved(ref pathIterPolys, pathIterPolyCount, MAX_POLYS, visited, nvisited);
+                pathIterPolyCount = DtPathUtils.MergeCorridorStartMoved(pathIterPolys, pathIterPolyCount, MAX_POLYS, visited, nvisited);
                 pathIterPolyCount = DtPathUtils.FixupShortcuts(ref pathIterPolys, pathIterPolyCount, navQuery);
 
                 var status = navQuery.GetPolyHeight(pathIterPolys[0], result, out var h);