set component in field and iter

Author: elebras1

examples/src/main/java/com/github/elebras1/flecs/examples/AdvancedSystemExample.java

@@ -72,10 +72,7 @@ public static void main(String[] args) {
 
                         float newX = pos.x() + vel.dx() * it.deltaTime();
                         float newY = pos.y() + vel.dy() * it.deltaTime();
-                        long entityId = it.entity(i);
-                        Entity entity = world.obtainEntity(entityId);
-                        entity.set(new Position(newX, newY));
-                        // Note: System.out.printf removed to avoid synchronization issues with multi-threading
+                        positions.set(i, new Position(newX, newY));
                     }
                 });
 

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

@@ -1,5 +1,6 @@
 package com.github.elebras1.flecs;
 
+import java.lang.foreign.Arena;
 import java.lang.foreign.MemorySegment;
 
 public class Field<T> {
@@ -34,4 +35,20 @@ public T get(int i) {
 
         return this.component.read(elementSegment);
     }
+
+    public void set(int i, T componentData) {
+        if (!this.isSet()) {
+            throw new IllegalStateException("Field is not set.");
+        }
+        if (i < 0 || i >= this.count) {
+            throw new IndexOutOfBoundsException("Index " + i + " out of bounds for count " + this.count);
+        }
+
+        try (Arena tempArena = Arena.ofConfined()) {
+            long elementOffset = i * this.component.size();
+            MemorySegment elementSegment = this.memorySegment.asSlice(elementOffset, this.component.size());
+
+            this.component.write(elementSegment, componentData, tempArena);
+        }
+    }
 }

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

@@ -147,6 +147,59 @@ public <T> boolean fieldBoolean(Class<T> componentClass, int index, String field
         return this.fieldPtr(componentClass, index, fieldName, i, offset).get(ValueLayout.JAVA_BOOLEAN, offset[0]);
     }
 
+    public <T> byte fieldByte(Class<T> componentClass, int index, String fieldName, int i) {
+        long[] offset = new long[1];
+        return this.fieldPtr(componentClass, index, fieldName, i, offset).get(ValueLayout.JAVA_BYTE, offset[0]);
+    }
+
+    public <T> String fieldString(Class<T> componentClass, int index, String fieldName, int i) {
+        long[] offset = new long[1];
+        MemorySegment stringPointer = this.fieldPtr(componentClass, index, fieldName, i, offset).get(ValueLayout.ADDRESS.withByteAlignment(1), offset[0]);
+        if (stringPointer.address() == 0) {
+            return null;
+        }
+        return stringPointer.reinterpret(Long.MAX_VALUE).getString(0);
+    }
+
+    public <T> void setFieldInt(Class<T> componentClass, int index, String fieldName, int i, int value) {
+        long[] offset = new long[1];
+        this.fieldPtr(componentClass, index, fieldName, i, offset).set(ValueLayout.JAVA_INT, offset[0], value);
+    }
+
+    public <T> void setFieldFloat(Class<T> componentClass, int index, String fieldName, int i, float value) {
+        long[] offset = new long[1];
+        this.fieldPtr(componentClass, index, fieldName, i, offset).set(ValueLayout.JAVA_FLOAT, offset[0], value);
+    }
+
+    public <T> void setFieldDouble(Class<T> componentClass, int index, String fieldName, int i, double value) {
+        long[] offset = new long[1];
+        this.fieldPtr(componentClass, index, fieldName, i, offset).set(ValueLayout.JAVA_DOUBLE, offset[0], value);
+    }
+
+    public <T> void setFieldLong(Class<T> componentClass, int index, String fieldName, int i, long value) {
+        long[] offset = new long[1];
+        this.fieldPtr(componentClass, index, fieldName, i, offset).set(ValueLayout.JAVA_LONG, offset[0], value);
+    }
+
+    public <T> void setFieldShort(Class<T> componentClass, int index, String fieldName, int i, short value) {
+        long[] offset = new long[1];
+        this.fieldPtr(componentClass, index, fieldName, i, offset).set(ValueLayout.JAVA_SHORT, offset[0], value);
+    }
+
+    public <T> void setFieldBoolean(Class<T> componentClass, int index, String fieldName, int i, boolean value) {
+        long[] offset = new long[1];
+        this.fieldPtr(componentClass, index, fieldName, i, offset).set(ValueLayout.JAVA_BOOLEAN, offset[0], value);
+    }
+
+    public <T> void setFieldByte(Class<T> componentClass, int index, String fieldName, int i, byte value) {
+        long[] offset = new long[1];
+        this.fieldPtr(componentClass, index, fieldName, i, offset).set(ValueLayout.JAVA_BYTE, offset[0], value);
+    }
+
+    public <T> void setFieldString(Class<T> componentClass, int index, String fieldName, int i, String value) {
+        // TODO
+    }
+
     public long event() {
         return ecs_iter_t.event(this.nativeIter);
     }