Improvement on Field, Iter, observerBuilder and SystemBuilder

Field : resolve the map seach of component in the constructor
Iter : cached count
builders : reuse of iter

Author: elebras1

src/main/java/com/github/elebras1/flecs/Field.java

@@ -5,14 +5,12 @@
 public class Field<T> {
     private final MemorySegment memorySegment;
     private final int count;
-    private final Flecs world;
-    private final Class<T> componentClass;
+    private final Component<T> component;
 
     Field(MemorySegment memorySegment, int count, Flecs world, Class<T> componentClass) {
         this.memorySegment = memorySegment;
         this.count = count;
-        this.world = world;
-        this.componentClass = componentClass;
+        this.component = world.componentRegistry().getComponent(componentClass);
     }
 
     public boolean isSet() {
@@ -31,11 +29,9 @@ public T get(int i) {
             throw new IndexOutOfBoundsException("Index " + i + " out of bounds for count " + this.count);
         }
 
-        Component<T> component = this.world.componentRegistry().getComponent(this.componentClass);
+        long elementOffset = i * this.component.size();
+        MemorySegment elementSegment = this.memorySegment.asSlice(elementOffset, this.component.size());
 
-        long elementOffset = i * component.size();
-        MemorySegment elementSegment = this.memorySegment.asSlice(elementOffset, component.size());
-
-        return component.read(elementSegment);
+        return this.component.read(elementSegment);
     }
 }

src/main/java/com/github/elebras1/flecs/Iter.java

@@ -4,20 +4,31 @@
 
 public class Iter {
 
-    private final MemorySegment nativeIter;
+    private MemorySegment nativeIter;
     private final Flecs world;
+    private int count;
 
     Iter(MemorySegment nativeIter, Flecs world) {
         this.nativeIter = nativeIter;
         this.world = world;
+        this.count = -1;
+    }
+
+    void setNativeIter(MemorySegment nativeIter) {
+        this.nativeIter = nativeIter;
+        this.count = -1;
     }
 
     public boolean next() {
+        this.count = -1;
         return flecs_h.ecs_iter_next(this.nativeIter);
     }
 
     public int count() {
-        return ecs_iter_t.count(this.nativeIter);
+        if (this.count < 0) {
+            this.count = ecs_iter_t.count(this.nativeIter);
+        }
+        return this.count;
     }
 
     public long entityId(int index) {

src/main/java/com/github/elebras1/flecs/ObserverBuilder.java

@@ -159,9 +159,14 @@ public ObserverBuilder observerFlags(int flags) {
     public FlecsObserver iter(Query.IterCallback callback) {
         this.iterCallback = callback;
 
+        final Iter[] iterHolder = new Iter[1];
         MemorySegment callbackStub = ecs_iter_action_t.allocate(it -> {
-            Iter iter = new Iter(it, this.world);
-            callback.accept(iter);
+            if (iterHolder[0] == null) {
+                iterHolder[0] = new Iter(it, this.world);
+            } else {
+                iterHolder[0].setNativeIter(it);
+            }
+            callback.accept(iterHolder[0]);
         }, this.world.arena());
 
         ecs_observer_desc_t.callback(this.desc, callbackStub);
@@ -172,9 +177,14 @@ public FlecsObserver iter(Query.IterCallback callback) {
     public FlecsObserver run(Query.RunCallback callback) {
         this.runCallback = callback;
 
+        final Iter[] iterHolder = new Iter[1];
         MemorySegment callbackStub = ecs_run_action_t.allocate(it -> {
-            Iter iter = new Iter(it, this.world);
-            callback.accept(iter);
+            if (iterHolder[0] == null) {
+                iterHolder[0] = new Iter(it, this.world);
+            } else {
+                iterHolder[0].setNativeIter(it);
+            }
+            callback.accept(iterHolder[0]);
         }, this.world.arena());
 
         ecs_observer_desc_t.run(this.desc, callbackStub);

src/main/java/com/github/elebras1/flecs/SystemBuilder.java

@@ -187,9 +187,14 @@ public <T> SystemBuilder read(Class<T> componentClass) {
     public FlecsSystem iter(Query.IterCallback callback) {
         this.iterCallback = callback;
 
+        final Iter[] iterHolder = new Iter[1];
         MemorySegment callbackStub = ecs_iter_action_t.allocate(it -> {
-            Iter iter = new Iter(it, this.world);
-            callback.accept(iter);
+            if (iterHolder[0] == null) {
+                iterHolder[0] = new Iter(it, this.world);
+            } else {
+                iterHolder[0].setNativeIter(it);
+            }
+            callback.accept(iterHolder[0]);
         }, this.world.arena());
 
         ecs_system_desc_t.callback(this.desc, callbackStub);
@@ -200,9 +205,14 @@ public FlecsSystem iter(Query.IterCallback callback) {
     public FlecsSystem run(Query.RunCallback callback) {
         this.runCallback = callback;
 
+        final Iter[] iterHolder = new Iter[1];
         MemorySegment callbackStub = ecs_run_action_t.allocate(it -> {
-            Iter iter = new Iter(it, this.world);
-            callback.accept(iter);
+            if (iterHolder[0] == null) {
+                iterHolder[0] = new Iter(it, this.world);
+            } else {
+                iterHolder[0].setNativeIter(it);
+            }
+            callback.accept(iterHolder[0]);
         }, this.world.arena());
 
         ecs_system_desc_t.run(this.desc, callbackStub);