新增identifierPool用于实体id复用

source/src/ECS/Entity.ts

@@ -9,7 +9,6 @@ module es {
     }
 
     export class Entity implements IEqualityComparable {
-        public static _idGenerator: number = 0;
         public static entityComparer: IComparer<Entity> = new EntityComparer();
         /**
          * 当前实体所属的场景
@@ -37,12 +36,12 @@ module es {
         public updateInterval: number = 1;
         public componentBits: Bits;
 
-        constructor(name: string) {
+        constructor(name: string, id: number) {
             this.components = new ComponentList(this);
             this.transform = new Transform(this);
             this.componentBits = new Bits();
             this.name = name;
-            this.id = Entity._idGenerator++;
+            this.id = id;
         }
 
         public _isDestroyed: boolean;
@@ -319,6 +318,7 @@ module es {
          */
         public destroy() {
             this._isDestroyed = true;
+            this.scene.identifierPool.checkIn(this.id);
             this.scene.entities.remove(this);
             this.transform.parent = null;
 

source/src/ECS/Scene.ts

@@ -13,11 +13,13 @@ module es {
         public readonly entityProcessors: EntityProcessorList;
 
         public readonly _sceneComponents: SceneComponent[] = [];
+        public readonly identifierPool: IdentifierPool;
         private _didSceneBegin: boolean;
 
         constructor() {
             this.entities = new EntityList(this);
             this.entityProcessors = new EntityProcessorList();
+            this.identifierPool = new IdentifierPool();
 
             this.initialize();
         }
@@ -145,7 +147,7 @@ module es {
          * @param name
          */
         public createEntity(name: string) {
-            let entity = new Entity(name);
+            let entity = new Entity(name, this.identifierPool.checkOut());
             return this.addEntity(entity);
         }
 

source/src/ECS/Utils/IdentifierPool.ts

@@ -0,0 +1,22 @@
+module es {
+    export class IdentifierPool {
+        private ids: Bag<number>;
+        private nextAvailableId_ = 0;
+
+        constructor() {
+            this.ids = new Bag<number>();
+        }
+
+        public checkOut(): number {
+            if (this.ids.size() > 0) {
+                return this.ids.removeLast();
+            }
+
+            return this.nextAvailableId_++;
+        }
+
+        public checkIn(id: number): void {
+            this.ids.add(id);
+        }
+    }
+}