other features

src/main/java/carpet/mixins/SpawnHelperMixin.java

@@ -1,24 +1,82 @@
 package carpet.mixins;
 
 import carpet.CarpetSettings;
+import carpet.fakes.WorldInterface;
 import carpet.utils.SpawnReporter;
 import net.minecraft.entity.Entity;
+import net.minecraft.entity.EntityType;
 import net.minecraft.entity.mob.MobEntity;
+import net.minecraft.util.math.BlockPos;
+import net.minecraft.util.math.BoundingBox;
+import net.minecraft.util.shape.VoxelShapes;
 import net.minecraft.world.SpawnHelper;
 import net.minecraft.world.World;
 import org.spongepowered.asm.mixin.Mixin;
 import org.spongepowered.asm.mixin.injection.At;
 import org.spongepowered.asm.mixin.injection.Redirect;
 
+import java.util.Map;
+
 @Mixin(SpawnHelper.class)
-public abstract class SpawnHelperMixin
+public class SpawnHelperMixin
 {
+    // in World: private static Map<EntityType, Entity> precookedMobs= new HashMap<>();
+
+    @Redirect(method = "spawnEntitiesInChunk", at = @At(
+            value = "INVOKE",
+            target = "Lnet/minecraft/world/World;doesNotCollide(Lnet/minecraft/util/math/BoundingBox;)Z"
+    ))
+    private static boolean doesNotCollide(World world, BoundingBox bb)
+    {
+        //.doesNotCollide is VERY expensive. On the other side - most worlds are not made of trapdoors in
+        // various configurations, but solid and 'passable' blocks, like air, water grass, etc.
+        // checking if in the BB of the entity are only passable blocks is very cheap and covers most cases
+        // in case something more complex happens - we default to full block collision check
+        if (CarpetSettings.b_lagFreeSpawning)
+        {
+            BlockPos.Mutable blockpos = new BlockPos.Mutable();
+            for (int x = (int)bb.minX,  maxx = (int)Math.ceil(bb.maxX); x < maxx; x++)
+                for (int z = (int)bb.minZ, maxz = (int)Math.ceil(bb.maxZ); z < maxz; z++)
+                    for (int y = (int)bb.minY, maxy = (int)Math.ceil(bb.maxY); y < maxy; y++)
+                    {
+                        blockpos.set(x, y, z);
+                        if (world.getBlockState(blockpos).getCollisionShape(world, blockpos) != VoxelShapes.empty())
+                            return world.doesNotCollide(bb);
+                    }
+            return true;
+        }
+        return world.doesNotCollide(bb);
+    }
+
+    @Redirect(method = "spawnEntitiesInChunk", at = @At(
+            value = "INVOKE",
+            target = "Lnet/minecraft/entity/EntityType;create(Lnet/minecraft/world/World;)Lnet/minecraft/entity/Entity;"
+    ))
+    private static Entity create(EntityType<?> entityType, World world_1)
+    {
+        if (CarpetSettings.b_lagFreeSpawning)
+        {
+            Map<EntityType, Entity> precookedMobs = ((WorldInterface)world_1).getPrecookedMobs();
+            if (precookedMobs.containsKey(entityType))
+                //this mob has been <init>'s but not used yet
+                return precookedMobs.get(entityType);
+            Entity e = entityType.create(world_1);
+            precookedMobs.put(entityType, e);
+            return e;
+        }
+        return entityType.create(world_1);
+    }
+
     @Redirect(method = "spawnEntitiesInChunk", at = @At(
             value = "INVOKE",
             target = "Lnet/minecraft/world/World;spawnEntity(Lnet/minecraft/entity/Entity;)Z"
     ))
-    private static boolean catchEntitySpawn(World world, Entity entity_1)
+    private static boolean spawnEntity(World world, Entity entity_1)
     {
+        if (CarpetSettings.b_lagFreeSpawning)
+            // we used the mob - next time we will create a new one when needed
+            ((WorldInterface) world).getPrecookedMobs().remove(entity_1.getType());
+
         if (SpawnReporter.track_spawns > 0L && SpawnReporter.local_spawns != null)
         {
             SpawnReporter.registerSpawn(
@@ -31,6 +89,4 @@ public abstract class SpawnHelperMixin
             return world.spawnEntity(entity_1);
         return false;
     }
-
-
 }