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/* This Source Code Form is subject to the terms of the Mozilla Public * License, v. 2.0. If a copy of the MPL was not distributed with this * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ //! # Tiny ECS //! //! The intention of this crate is that a basic ECS is provided, where //! you will be required to exercise a little additional control. //! //! Where most other ECS crates provide a mechanism for inserting "systems" //! in to the ECS to run against entities, this one leaves it out - you can //! think of it as a "system for entity/components". You will need to create //! external systems; these can be a function, a loop, or anything else. //! //! Internally this ECS is the use of `bitmasks`. Each entity ID is in //! practice an internal index number in to an array which contains bitmasks. //! The bitmasks themselves keep track of what components the entity has. //! //! **Note:** borrows of `Persist` are checked at runtime, but there are also //! some *unchecked* borrows provided. //! //! # Examples //! //! ## Demonstrating use //! //! ``` //! use tiny_ecs::Entities; //! use tiny_ecs::ECSError; //! //! // These are the "components" we will use //! struct Vector1 { //! x: i32, //! } //! struct Vector2 { //! x: i32, //! y: i32, //! } //! struct Vector3 { //! x: i32, //! y: i32, //! z: i32, //! } //! # fn main() -> Result<(), ECSError> { //! // Initialize the Entity collection //! let mut entities = Entities::new(Some(3), Some(3)); //! //! // Creating an entity uses the builder pattern. //! // Be sure to return the ID if you need to track it //! let entity_1 = entities.new_entity() //! .with(Vector1 { x: 42 })? //! .with(Vector3 { x: 3, y: 10, z: -12 })? //! .finalise()?; //! // The entity ID will increment up from 0 //! assert_eq!(entity_1, 0); //! //! // Do note however, that you can keep adding parts to this entity //! // via the builder pattern until you choose to create another entity //! //! // To add another entity you need to create one //! entities.new_entity() //! .with(Vector2 { x: 66, y: 6 })? //! .with(Vector1 { x: 6 })? //! .finalise()?; //! # Ok(()) //! # } //!``` //! //! ## Access an entities part of type `<T>` //! ``` //! # use tiny_ecs::Entities; //! # use tiny_ecs::ECSError; //! # fn main() -> Result<(), ECSError> { //! struct Vector3 {x: i32, y: i32, z: i32 } //! # let mut entities = Entities::new(Some(3), Some(3)); //! # let entity_1 = entities.new_entity() //! # .with(Vector3 { x: 3, y: 10, z: -12 })? //! # .finalise()?; //! // To get access to a part belonging to an entity you need //! // first to get the component map created for the part type //! // You need to 'anchor' this with a let or the ref is //! // dropped before you can use it //! let mut components = entities //! .borrow_mut::<Vector3>()?; //! // You can then use the part by getting a reference //! let mut part = components.get_mut(entity_1).unwrap(); //! assert_eq!(part.z, -12); //! # Ok(()) //! # } //! ``` //! //! ## Check if `Entity` contains a part type + remove part //! ``` //! # use tiny_ecs::Entities; //! # use tiny_ecs::ECSError; //! # fn main() -> Result<(), ECSError> { //! struct Vector1 {x: i32 } //! # let mut entities = Entities::new(Some(3), Some(3)); //! let entity_1 = entities.new_entity() //! .with(Vector1 { x: 3 })? //! .finalise()?; //! // You can check if an entity contains a part with the type signature //! if entities.entity_contains::<Vector1>(entity_1) { //! assert!(entities.rm_component_from::<Vector1>(entity_1).is_ok()); //! } //! assert_eq!(entities.entity_contains::<Vector1>(entity_1), false); //! # Ok(()) //! # } //! ``` //! //! ## A system that uses an `get_mut()` //! ``` //! # use tiny_ecs::{Entities, Persist}; //! # use tiny_ecs::ECSError; //! # fn main() -> Result<(), ECSError> { //! struct Vector1 {x: i32 } //! # let mut entities = Entities::new(Some(3), Some(3)); //! # entities.new_entity().with(Vector1 { x: 3 })?.finalise()?; //! //! // Make a system of some form that takes a `Persist<T>` arg //! fn some_system(mut components: &mut Persist<Vector1>) { //! // You can then iterate over the components directly //! for (k, v) in components.iter_mut().enumerate() { //! v.x += 1; //! assert!(v.x > k as i32); //! } //! } //! # let mut components = entities.borrow_mut::<Vector1>()?; //! some_system(&mut components); //! # Ok(()) //! # } //! ``` //! //! ## Get components for an entity ID list //! ``` //! # use tiny_ecs::{Entities, Persist}; //! # use tiny_ecs::ECSError; //! # fn main() -> Result<(), ECSError> { //! struct Vector1 {x: i32 } //! # let mut entities = Entities::new(Some(3), Some(3)); //! # entities.new_entity().with(Vector1 { x: 3 })?.finalise()?; //! //! // A system that fetches the components for only the entities you are require //! fn second_system(active: &[usize], mut v1_map: &mut Persist<Vector1>) { //! for id in active { //! if let Some(part) = v1_map.get_mut(*id) { //! part.x = 42; //! } //! } //! } //! # let mut components = entities.borrow_mut::<Vector1>()?; //! second_system(&[0, 1, 2], &mut components); //! # Ok(()) //! # } //! ``` //! //! ## A more complex system using Persists directly //! ``` //! # use tiny_ecs::Entities; //! # use tiny_ecs::ECSError; //! # fn main() -> Result<(), ECSError> { //! # struct Vector1 {x: i32 } //! # struct Vector2 {x: i32, y: i32 } //! # let mut entities = Entities::new(Some(3), Some(3)); //! # entities.new_entity() //! # .with(Vector1 { x: 3 })? //! # .with(Vector2 { x: 3, y: 3 })? //! # .finalise()?; //! //! // Or a system handles the `Entities` container directly //! fn other_system(active_ents: &[usize], entities: &mut Entities) -> Result<(), ECSError> { //! // You can mutably borrow multiple component maps at once //! let mut v1_components = entities //! .borrow_mut::<Vector1>()?; //! //! let mut v2_components = entities //! .borrow_mut::<Vector2>()?; //! //! // But not have a mutable borrow and immutable borrow to the same map //! // Fails at runtime! //! // let v2_components = entities.borrow::<Vector2>().unwrap(); //! for id in active_ents { //! if entities.entity_contains::<Vector1>(*id) && //! entities.entity_contains::<Vector2>(*id) { //! let v1_part = v1_components.get_mut(*id).unwrap(); //! let v2_part = v2_components.get_mut(*id).unwrap(); //! v1_part.x = 42; //! assert_ne!(v1_part.x, 43); //! assert_eq!(v1_part.x, 42); //! } //! } //! Ok(()) //! } //! other_system(&[0, 1, 2], &mut entities); //! # Ok(()) //! # } //! ``` mod errors; pub use crate::errors::*; use hashbrown::HashMap; pub use persist_o_vec::Persist; use std::any::{Any, TypeId}; use std::cell::{Ref, RefCell, RefMut}; use std::ops::{Deref, DerefMut}; #[cfg(feature = "component_max_31")] type BitMaskType = u32; #[cfg(feature = "component_max_63")] type BitMaskType = u64; #[cfg(feature = "component_max_127")] type BitMaskType = u128; #[cfg(feature = "component_max_31")] const BIT_MASK_MAX: BitMaskType = 31; #[cfg(feature = "component_max_63")] const BIT_MASK_MAX: BitMaskType = 63; #[cfg(feature = "component_max_127")] const BIT_MASK_MAX: BitMaskType = 127; // Bitmask used to fill the initial mask list, and replace deleted entities const EMPTY: BitMaskType = 0; /// Immutable reference container for `Persist` returned by `Entities::borrow()` /// /// This struct is required to contain a hidden borrow to the requested `Persist`. /// The reason for this is so we can borrow multiple `Persist`, but not break the /// borrow checker rules for borrows on a single `Persist`. pub struct MapRef<'a, T> { _borrow: Ref<'a, dyn Any>, value: &'a Persist<T>, } impl<'a, T: 'static> MapRef<'a, T> { fn new(value: &'a RefCell<Box<dyn Any>>) -> Result<MapRef<'a, T>, ECSError> { let borrow = value.try_borrow().or(Err(ECSError::Borrow))?; // This is required to sidestep the borrow issue in root Entities struct let v = (unsafe { value.as_ptr().as_ref() }) .ok_or(ECSError::PtrRef)? .downcast_ref::<Persist<T>>() .ok_or(ECSError::Downcast)?; // And make it safe by keeping the lifetime of the borrow with the downcast Ok(MapRef { value: v, _borrow: borrow, }) } } impl<'a, T> Deref for MapRef<'a, T> { type Target = Persist<T>; #[inline] fn deref(&self) -> &Persist<T> { self.value } } /// Mutable reference container for `Persist` returned by `Entities::borrow_mut()` /// /// This struct is required to contain a hidden borrow to the requested `Persist`. /// The reason for this is so we can borrow multiple `Persist`, but not break the /// borrow checker rules for borrows on a single `Persist`. pub struct MapRefMut<'a, T> { _borrow: RefMut<'a, dyn Any>, value: &'a mut Persist<T>, } impl<'a, T: 'static> MapRefMut<'a, T> { #[inline] fn new(value: &'a RefCell<Box<dyn Any>>) -> Result<MapRefMut<'a, T>, ECSError> { let borrow = value.try_borrow_mut().or(Err(ECSError::BorrowMut))?; let v = (unsafe { value.as_ptr().as_mut() }) .ok_or(ECSError::PtrMut)? .downcast_mut::<Persist<T>>() .ok_or(ECSError::DowncastMut)?; Ok(MapRefMut { value: v, _borrow: borrow, }) } } impl<'a, T> Deref for MapRefMut<'a, T> { type Target = Persist<T>; #[inline] fn deref(&self) -> &Persist<T> { self.value } } impl<'a, T> DerefMut for MapRefMut<'a, T> { #[inline] fn deref_mut(&mut self) -> &mut Persist<T> { self.value } } /// This is the root of the ECS implementation #[derive(Debug)] pub struct Entities { // the index in to this Vec is the ID of the entity entity_masks: Vec<BitMaskType>, components: Vec<RefCell<Box<dyn Any>>>, next_free_entity: usize, current_entity: Option<usize>, vacated_slots: Vec<usize>, // BitMaskType is the mask assigned to the TypeId and is used to // quickly determine if an entity has a component type type_masks: HashMap<TypeId, (BitMaskType, usize)>, next_typemask: BitMaskType, } impl Default for Entities { /// Create a new `Entities` struct with no pre-allocated memory for maps fn default() -> Self { Entities::new(None, None) } } impl Entities { /// Create a new root entity container. /// /// - `entity_count` will initialize the entity map to this size. Good to /// do if you know the max count of entities you will handle /// - `component_count` is as above, for total unique component types/kinds /// /// For `component_count` there is a maximum of either 32, 64, or 128 individual /// parts you can add of which the index starts at 0 to n-1, depending on /// which is enabled by the crate features pub fn new(entity_count: Option<usize>, component_count: Option<usize>) -> Entities { if let Some(count) = component_count { if count as BitMaskType > BIT_MASK_MAX { // Must panic if the component count is larger than the mask size // as we can only insert this many anyway panic!( "Initial part count too large. Maximum of {} allowed", BIT_MASK_MAX ); } } Entities { entity_masks: vec![EMPTY; entity_count.unwrap_or(0)], components: Vec::with_capacity(component_count.unwrap_or(0)), next_free_entity: 0, current_entity: None, vacated_slots: Vec::new(), type_masks: HashMap::with_capacity(component_count.unwrap_or(0)), next_typemask: 1, } } /// Start the creation of a new entity /// /// If no parts are added to this call with `with()` then the entity will /// not be created. #[inline] pub fn new_entity(&mut self) -> &mut Self { if let Some(slot) = self.vacated_slots.pop() { self.current_entity = Some(slot); } else { self.current_entity = Some(self.next_free_entity); self.next_free_entity += 1; } self } /// Chained with `new_entity()` to add components /// /// `with()` can be chained multiple times to add many components. /// /// # Example /// /// ``` /// # use tiny_ecs::Entities; /// # use tiny_ecs::ECSError; /// # fn main() -> Result<(), ECSError> { /// struct Component1 {} /// struct Component2 {} /// /// # let mut entities = Entities::new(Some(3), Some(3)); /// let entity_1 = entities /// .new_entity() /// .with(Component1 {})? /// .with(Component2 {})? /// .finalise()?; /// assert_eq!(entity_1, 0); /// # Ok(()) /// # } /// ``` #[inline] pub fn with<T: 'static>(&mut self, part: T) -> Result<&mut Self, ECSError> { // Can't use .with() after entity is finalised if self.current_entity.is_none() { return Err(ECSError::WithAfterFinalise); } let type_id = TypeId::of::<T>(); // if the component doesn't already have a type_mask entry let (type_mask, type_index) = { if !self.type_masks.contains_key(&type_id) { if (self.type_masks.len() as BitMaskType) >= BIT_MASK_MAX { return Err(ECSError::BitMasksExhausted); } self.components .push(RefCell::new(Box::new(Persist::<T>::with_capacity( self.entity_masks.len() + self.vacated_slots.len(), )))); self.type_masks .insert(type_id, (self.next_typemask, self.components.len() - 1)); self.next_typemask <<= 1; } self.type_masks[&type_id] }; // TODO: overwrite? Crate user will need to be made aware when it happens if so // this shouldn't ever fail let entity_mask = self.entity_masks[self.current_entity.unwrap()]; if entity_mask & type_mask == type_mask { return Err(ECSError::AddDupeComponent); } // This really shouldn't ever fail let id = self.current_entity.unwrap(); if let Some(col) = self.components.get_mut(type_index) { col.borrow_mut() .downcast_mut::<Persist<T>>() .ok_or(ECSError::DowncastMut)? .insert(id, part); // update the entity mask let old = self.entity_masks[id]; self.entity_masks[id] = old | type_mask; } Ok(self) } /// Optional final call in creating an entity - returns ID. You can begin /// using the entity without calling this, but it is recommended that you do /// to prevent workplace accidents. /// /// If you don't finalise an entity you can keep adding /// components to it later. This isn't recommended though /// as it's easy to lose track of which entity you are working /// on. The `add_component()` method allows you to add extra /// components to an existing entity if you know the ID. #[inline] pub fn finalise(&mut self) -> Result<usize, ECSError> { if let Some(entity) = self.current_entity { self.current_entity = None; return Ok(entity); } Err(ECSError::FinaliseNonEntity) } /// Check if an entity ID is valid (alive and has components) /// /// If `false` then there are no components attached to this ID and /// the entity is `None`. #[inline] pub fn entity_exists(&self, id: usize) -> bool { if let Some(ent) = self.entity_masks.get(id) { return *ent > 0; } false } #[inline] pub fn entity_contains<T: 'static>(&self, id: usize) -> bool { if let Some(entity_mask) = self.entity_masks.get(id) { if let Some((type_mask, _)) = self.type_masks.get(&TypeId::of::<T>()) { if entity_mask & type_mask == *type_mask { return true; } } } false } #[deprecated] pub fn rm_component<T: 'static>(&mut self, id: usize) -> Result<(), ECSError> { self.rm_component_from::<T>(id) } /// Remove an entities part. If no components are left after part removal then /// the entity is considered deleted /// /// Removal requires the ID of the entity and the components type signature. /// /// # Example /// /// ``` /// # use tiny_ecs::Entities; /// # use tiny_ecs::ECSError; /// # fn main() -> Result<(), ECSError> { /// #[derive(Debug, PartialEq)] /// struct Test1 {} /// /// # let mut entities = Entities::new(Some(3), Some(3)); /// # let entity_1 = entities.new_entity() /// # .with(Test1 {})?.finalise()?; /// assert!(entities.rm_component_from::<Test1>(entity_1).is_ok()); /// assert!(!entities.entity_contains::<Test1>(entity_1)); /// # Ok(()) /// # } /// ``` #[inline] pub fn rm_component_from<T: 'static>(&mut self, id: usize) -> Result<(), ECSError> { let type_id = TypeId::of::<T>(); if let Some((type_mask, type_index)) = self.type_masks.get(&type_id) { if let Some(map) = self.components.get_mut(*type_index) { map.borrow_mut() .downcast_mut::<Persist<T>>() .ok_or(ECSError::DowncastMut)? .remove(id); self.entity_masks[id] ^= *type_mask; if self.entity_masks[id] == EMPTY { self.vacated_slots.push(id) } return Ok(()); } } Err(ECSError::NoComponentMap) } #[deprecated] pub fn add_component<T: 'static>(&mut self, id: usize, component: T) -> Result<(), ECSError> { self.add_component_to(id, component) } /// Add a component to the existing Entity ID /// /// # Example /// /// ``` /// # use tiny_ecs::Entities; /// # use tiny_ecs::ECSError; /// # fn main() -> Result<(), ECSError> { /// struct Test1 {} /// struct Test2 {} /// struct Test3 {} /// /// let mut entities = Entities::new(Some(3), Some(3)); /// let entity_1 = entities /// .new_entity() /// .with(Test1 {})? /// .with(Test2 {})? /// .finalise()?; /// entities.add_component_to(entity_1, Test3 {}); /// assert!(entities.entity_contains::<Test1>(entity_1)); /// # Ok(()) /// # } /// ``` #[inline] pub fn add_component_to<T: 'static>( &mut self, id: usize, component: T, ) -> Result<(), ECSError> { if let Some(ent) = self.entity_masks.get(id) { if *ent == 0 { return Err(ECSError::WithAfterFinalise); } } self.current_entity = Some(id); self.with(component)?.finalise()?; Ok(()) } /// Get a plain reference to the selected entity part map. Borrow rules are checked at runtime. /// /// You may have multiple immutable references to the requested `Persist` /// **type** but no mutable references if the same **typed** `Persist` /// is currently referenced. /// /// - `Option` is whether or not there is a part of `<T>` for that entity. /// - Borrowing (`Ref`) is checked at runtime. /// /// # Example /// ``` /// # use tiny_ecs::Entities; /// # use tiny_ecs::ECSError; /// # fn main() -> Result<(), ECSError> { /// # struct Test1 { x: u32 } /// # let mut entities = Entities::new(Some(3), Some(3)); /// # let entity_1 = entities.new_entity() /// # .with(Test1 { x: 666 })?.finalise()?; /// let components = entities /// .borrow::<Test1>() /// .unwrap(); /// let part = components.get(entity_1).unwrap(); /// # Ok(()) /// # } /// ``` #[inline(always)] pub fn borrow<T: 'static>(&self) -> Result<MapRef<T>, ECSError> { let type_id = TypeId::of::<T>(); if let Some((_, type_index)) = self.type_masks.get(&type_id) { if let Some(components) = self.components.get(*type_index) { return Ok(MapRef::new(components)?); } } Err(ECSError::NoComponentMap) } /// Allows you to borrow without runtime check overhead or to borrow when the standard /// borrow rules prevent you from doing so and you enforce safety /// /// # Safety /// Borrows are not checked at compile-time or runtime. An unchecked borrow /// on a mutably borrowed `Persist` is UB. #[inline(always)] pub unsafe fn borrow_unchecked<T: 'static>(&self) -> Result<&Persist<T>, ECSError> { let type_id = TypeId::of::<T>(); if let Some((_, type_index)) = self.type_masks.get(&type_id) { if let Some(components) = self.components.get(*type_index) { let components = (&*components.as_ptr()) .downcast_ref::<Persist<T>>() .ok_or(ECSError::Downcast)?; return Ok(components); } } Err(ECSError::NoComponentMap) } /// Get a mutable reference to the selected entity part map. Borrow rules are checked at runtime. /// /// You may have only one mutable reference to the requested `Persist` /// **type** and no immutable references. You can however, have multiple /// mutable references to different **types** of `Persist` /// /// - `Result` covers if the map was able to be borrowed mutably or not. /// - Borrowing is checked at runtime. /// /// # Example /// ``` /// # use tiny_ecs::Entities; /// # use tiny_ecs::ECSError; /// # fn main() -> Result<(), ECSError> { /// # #[derive(Debug, PartialEq)] /// # struct Test1 { x: u32 } /// # let mut entities = Entities::new(Some(3), Some(3)); /// # let entity_1 = entities.new_entity() /// # .with(Test1 { x: 0 })?.finalise()?; /// // Because we later need a ref to the same `Type` of map, the mut ref /// // will need to be scoped. If the later ref was of a different type, /// // eg: Vector2, then it wouldn't need scoping. /// { /// let mut components = entities /// .borrow_mut::<Test1>()?; /// for id in 0..5 { /// if let Some(part) = components.get_mut(id) { /// part.x = 42; /// } /// } /// } /// /// // Now get a ref to the modified part /// let components = entities.borrow::<Test1>()?; /// let part = components.get(entity_1).unwrap(); /// assert_eq!(part.x, 42); /// # Ok(()) /// # } /// ``` #[inline(always)] pub fn borrow_mut<T: 'static>(&self) -> Result<MapRefMut<T>, ECSError> { let type_id = TypeId::of::<T>(); if let Some((_, type_index)) = self.type_masks.get(&type_id) { if let Some(components) = self.components.get(*type_index) { return Ok(MapRefMut::new(components)?); } } Err(ECSError::NoComponentMap) } /// Allows you to borrow mutably without runtime check overhead or to borrow when the standard /// borrow rules prevent you from doing so and you enforce safety /// /// # Safety /// Borrows are not checked at compile-time or runtime. An unchecked mutable /// on an immutably borrowed `Persist` is UB. #[inline(always)] pub unsafe fn borrow_mut_unchecked<T: 'static>(&self) -> Result<&mut Persist<T>, ECSError> { let type_id = TypeId::of::<T>(); if let Some((_, type_index)) = self.type_masks.get(&type_id) { if let Some(components) = self.components.get(*type_index) { let components = (&mut *components.as_ptr()) .downcast_mut::<Persist<T>>() .ok_or(ECSError::Downcast)?; return Ok(components); } } Err(ECSError::NoComponentMap) } }