Struct enumerator for GetAllGrids (#2624)

Robust.Shared/Map/GridEnumerator.cs

@@ -0,0 +1,31 @@
+using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
+using Robust.Shared.GameObjects;
+
+namespace Robust.Shared.Map;
+
+public struct GridEnumerator
+{
+    private Dictionary<GridId, EntityUid>.Enumerator _enumerator;
+    private EntityQuery<MapGridComponent> _query;
+
+    internal GridEnumerator(Dictionary<GridId, EntityUid>.Enumerator enumerator, EntityQuery<MapGridComponent> query)
+    {
+        _enumerator = enumerator;
+        _query = query;
+    }
+
+    public bool MoveNext([NotNullWhen(true)] out IMapGrid? grid)
+    {
+        if (!_enumerator.MoveNext())
+        {
+            grid = null;
+            return false;
+        }
+
+        var (_, uid) = _enumerator.Current;
+
+        grid = _query.GetComponent(uid).Grid;
+        return true;
+    }
+}

Robust.Shared/Map/IMapManager.cs

@@ -12,6 +12,11 @@ namespace Robust.Shared.Map
     /// </summary>
     public interface IMapManager : IPauseManager
     {
+        /// <summary>
+        /// A faster version of <see cref="GetAllGrids"/>
+        /// </summary>
+        GridEnumerator GetAllGridsEnumerator();
+
         IEnumerable<IMapGrid> GetAllGrids();
 
         /// <summary>

Robust.Shared/Map/MapManager.GridCollection.cs

@@ -116,9 +116,20 @@ internal partial class MapManager
         OnGridCreated?.Invoke(mapGrid.ParentMapId, mapGrid.Index);
     }
 
+    public GridEnumerator GetAllGridsEnumerator()
+    {
+        var query = EntityManager.GetEntityQuery<MapGridComponent>();
+        return new GridEnumerator(_grids.GetEnumerator(), query);
+    }
+
     public IEnumerable<IMapGrid> GetAllGrids()
     {
-        return EntityManager.EntityQuery<IMapGridComponent>(true).Select(c => c.Grid);
+        var compQuery = EntityManager.GetEntityQuery<MapGridComponent>();
+
+        foreach (var (_, uid) in _grids)
+        {
+            yield return compQuery.GetComponent(uid).Grid;
+        }
     }
 
     public IMapGrid CreateGrid(MapId currentMapId, GridId? forcedGridId = null, ushort chunkSize = 16)

Robust.Shared/Map/NetworkedMapManager.cs

@@ -62,8 +62,12 @@ internal sealed class NetworkedMapManager : MapManager, INetworkedMapManager
     public GameStateMapData? GetStateData(GameTick fromTick)
     {
         var gridDatums = new Dictionary<GridId, GameStateMapData.GridDatum>();
-        foreach (MapGrid grid in GetAllGrids())
+        var enumerator = GetAllGridsEnumerator();
+
+        while (enumerator.MoveNext(out var iGrid))
         {
+            var grid = (MapGrid)iGrid;
+
             if (grid.LastTileModifiedTick < fromTick)
                 continue;