feat(core): add fast path api for copying registries

ecsact_rt_entt/runtime/ecsact_rt_entt_core.cc

@@ -40,6 +40,22 @@ auto ecsact_clone_registry( //
 	return cloned_reg_id;
 }
 
+void ecsact_copy_registry(
+	ecsact_registry_id src_id,
+	ecsact_registry_id dst_id
+) {
+	auto& src_reg = ecsact::entt::get_registry(src_id);
+	auto& dst_reg = ecsact::entt::get_registry(dst_id);
+	dst_reg = {};
+	ecsact::entt::ecsact_init_registry_storage(dst_reg);
+	for(auto&& [entity_id] : src_reg.template storage<entt::entity>().each()) {
+		[[maybe_unused]] auto cloned_entity_id = dst_reg.create(entity_id);
+		assert(cloned_entity_id == entity_id);
+	}
+	ecsact::entt::copy_components(src_reg, dst_reg);
+}
+
+
 auto ecsact_hash_registry(ecsact_registry_id reg_id) -> uint64_t {
 	auto& reg = ecsact::entt::get_registry(reg_id);
 	return ecsact::entt::hash_registry(reg);

ecsact_runtime/ecsact/runtime/core.h

@@ -52,10 +52,19 @@ ECSACT_CORE_API_FN(void, ecsact_destroy_registry)
  * If `ecsact_hash_registry` is defined then the cloned registry hash must
  * match the original registry.
  */
-ECSACT_CORE_API_FN(ecsact_registry_id, ecsact_clone_registry)
-( //
+ECSACT_CORE_API_FN(ecsact_registry_id, ecsact_clone_registry)(
 	ecsact_registry_id registry,
-	const char*        registry_name);
+	const char*        registry_name
+);
+
+/**
+ * Copies all entities and components from a source registry to a destination
+ * registry. The destination registry is cleared before copy.
+ */
+ECSACT_CORE_API_FN(void, ecsact_copy_registry)(
+	ecsact_registry_id src_registry,
+	ecsact_registry_id dest_registry
+);
 
 /**
  * Creates a hash of current state of the registry. The algorithm is
@@ -295,6 +304,7 @@ ECSACT_CORE_API_FN(ecsact_stream_error, ecsact_stream)
 		fn(ecsact_create_registry, __VA_ARGS__);             \
 		fn(ecsact_destroy_registry, __VA_ARGS__);            \
 		fn(ecsact_clone_registry, __VA_ARGS__);              \
+		fn(ecsact_copy_registry, __VA_ARGS__);               \
 		fn(ecsact_hash_registry, __VA_ARGS__);               \
 		fn(ecsact_clear_registry, __VA_ARGS__);              \
 		fn(ecsact_create_entity, __VA_ARGS__);               \

ecsact_runtime/ecsact/runtime/core.hh

@@ -648,6 +648,11 @@ public:
 		return cloned_registry;
 	}
 
+	ECSACT_ALWAYS_INLINE auto copy_to(const registry& dest) const -> void {
+		ecsact_copy_registry(_id, dest.id());
+	}
+
+
 	ECSACT_ALWAYS_INLINE auto hash() const -> uint64_t {
 		return ecsact_hash_registry(_id);
 	}