sparse set

src/ecs.odin

@@ -7,6 +7,13 @@ STARTUP :: 0
 UPDATE :: 1
 DRAW :: 2
 
+@(private)
+sparse_entity_limit: int
+
+get_entity_limit :: proc() -> int {
+	return sparse_entity_limit
+}
+
 App :: struct {
 	systems:  map[int][dynamic]proc(),
 	plugins:  [dynamic]proc(app: ^App),
@@ -27,13 +34,14 @@ add_plugin :: proc(app: ^App, plugin: proc(app: ^App)) {
 }
 
 // run the app
-run :: proc(app: ^App) {
+run :: proc(app: ^App, entity_limit: int = 1000) {
+	sparse_entity_limit = entity_limit
 	for p in app.plugins {
 		p(app)
 	}
 	for i in app.systems[STARTUP] {i()}
 
-	_, window := single(&Window)
+	window, _ := single(&Window)
 	rl.InitWindow(window.width, window.height, strings.clone_to_cstring(window.title))
 	defer rl.CloseWindow()
 

src/entities.odin

@@ -5,7 +5,9 @@ import "core:fmt"
 Entity :: distinct u32
 
 Storage :: struct($T: typeid) {
-	data: map[Entity]T,
+	dense:    [dynamic]T,
+	entities: [dynamic]Entity,
+	sparse:   map[Entity]int,
 }
 
 // adds a new entity id to app and returns it
@@ -24,33 +26,37 @@ add_component :: proc {
 
 // initializes new component of type and add to Storage
 add_fresh_component :: proc(entity: Entity, storage: ^Storage($T)) {
-	storage.data[entity] = T{}
+	append(&storage.dense, T{})
+	append(&storage.entities, entity)
+	i := len(storage.dense) - 1
+	defer storage.sparse[entity] = i
 }
 
 // creates a copy of component type with data and add to Storage
 add_component_with_data :: proc(entity: Entity, storage: ^Storage($T), component: T) {
-	storage.data[entity] = component
+	append(&storage.dense, component)
+	append(&storage.entities, entity)
+	i := len(storage.dense) - 1
+	defer storage.sparse[entity] = i
 }
 
 // get components saved in Storage
 // returns storage.data
-slice :: proc(storage: ^Storage($T)) -> map[Entity]T {
-	return storage.data
+slice :: proc(storage: ^Storage($T)) -> [dynamic]T {
+	return storage.dense
+}
+
+slice_entity :: proc(storage: ^Storage($T)) -> [dynamic]Entity {
+	return storage.entities
 }
 
 // get component saved in Storage
 // returns Entity and component of type
-single :: proc(storage: ^Storage($T)) -> (Entity, ^T) {
-	for i, &v in slice(storage) {
-		return i, &v
-	}
-	return 0, nil
+single :: proc(storage: ^Storage($T)) -> (^T, Entity) {
+	return &storage.dense[0], storage.entities[0]
 }
 
 // get component of type from entity
 get_component :: proc(entity: Entity, storage: ^Storage($T)) -> ^T {
-	if _, exists := storage.data[entity]; exists {
-		return &storage.data[entity]
-	}
-	return new(T)
+	return &storage.dense[storage.sparse[entity]]
 }

src/systems.odin

@@ -17,8 +17,10 @@ DefaultPlugin :: proc(app: ^App) {
 
 @(private)
 draw_sprite :: proc() {
-	for i, &v in slice(&Sprite) {
-		sprite_transform := get_component(i, &Transform)
+	components := slice(&Sprite)
+	entities := slice_entity(&Sprite)
+	for &v, i in components {
+		sprite_transform := get_component(entities[i], &Transform)
 		rl.DrawTexture(
 			v.texture,
 			i32(sprite_transform.translation.x),