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// Copyright 2019 Google LLC // // Licensed under the Apache License, Version 2.0 (the "License"); // you may not use this file except in compliance with the License. // You may obtain a copy of the License at // // https://www.apache.org/licenses/LICENSE-2.0 // // Unless required by applicable law or agreed to in writing, software // distributed under the License is distributed on an "AS IS" BASIS, // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. // See the License for the specific language governing permissions and // limitations under the License. use crate::alloc::vec::Vec; use core::any::TypeId; use core::convert::TryFrom; use core::{fmt, mem, ptr}; #[cfg(feature = "std")] use std::error::Error; use hashbrown::{HashMap, HashSet}; use crate::archetype::Archetype; use crate::entities::{Entities, Location}; use crate::{ Bundle, DynamicBundle, Entity, EntityRef, MissingComponent, NoSuchEntity, Query, QueryBorrow, QueryOne, Ref, RefMut, }; /// An unordered collection of entities, each having any number of distinctly typed components /// /// Similar to `HashMap<Entity, Vec<Box<dyn Any>>>` where each `Vec` never contains two of the same /// type, but far more efficient to traverse. /// /// The components of entities who have the same set of component types are stored in contiguous /// runs, allowing for extremely fast, cache-friendly iteration. pub struct World { entities: Entities, index: HashMap<Vec<TypeId>, u32>, archetypes: Vec<Archetype>, archetype_generation: u64, } impl World { /// Create an empty world pub fn new() -> Self { // `flush` assumes archetype 0 always exists, representing entities with no components. let mut archetypes = Vec::new(); archetypes.push(Archetype::new(Vec::new())); let mut index = HashMap::default(); index.insert(Vec::new(), 0); Self { entities: Entities::default(), index, archetypes, archetype_generation: 0, } } /// Create an entity with certain components /// /// Returns the ID of the newly created entity. /// /// Arguments can be tuples, structs annotated with `#[derive(Bundle)]`, or the result of /// calling `build` on an `EntityBuilder`, which is useful if the set of components isn't /// statically known. To spawn an entity with only one component, use a one-element tuple like /// `(x,)`. /// /// Any type that satisfies `Send + Sync + 'static` can be used as a component. /// /// # Example /// ``` /// # use hecs::*; /// let mut world = World::new(); /// let a = world.spawn((123, "abc")); /// let b = world.spawn((456, true)); /// ``` pub fn spawn(&mut self, components: impl DynamicBundle) -> Entity { // Ensure all entity allocations are accounted for so `self.entities` can realloc if // necessary self.flush(); let entity = self.entities.alloc(); let archetype_id = components.with_ids(|ids| { self.index.get(ids).copied().unwrap_or_else(|| { let x = self.archetypes.len() as u32; self.archetypes.push(Archetype::new(components.type_info())); self.index.insert(ids.to_vec(), x); self.archetype_generation += 1; x }) }); let archetype = &mut self.archetypes[archetype_id as usize]; unsafe { let index = archetype.allocate(entity.id); components.put(|ptr, ty, size| { archetype.put_dynamic(ptr, ty, size, index); true }); self.entities.meta[entity.id as usize].location = Location { archetype: archetype_id, index, }; } entity } /// Efficiently spawn a large number of entities with the same components /// /// Faster than calling `spawn` repeatedly with the same components. /// /// # Example /// ``` /// # use hecs::*; /// let mut world = World::new(); /// let entities = world.spawn_batch((0..1_000).map(|i| (i, "abc"))).collect::<Vec<_>>(); /// for i in 0..1_000 { /// assert_eq!(*world.get::<i32>(entities[i]).unwrap(), i as i32); /// } /// ``` pub fn spawn_batch<I>(&mut self, iter: I) -> SpawnBatchIter<'_, I::IntoIter> where I: IntoIterator, I::Item: Bundle, { // Ensure all entity allocations are accounted for so `self.entities` can realloc if // necessary self.flush(); let iter = iter.into_iter(); let (lower, upper) = iter.size_hint(); let archetype_id = self.reserve_inner::<I::Item>( u32::try_from(upper.unwrap_or(lower)).expect("iterator too large"), ); SpawnBatchIter { inner: iter, entities: &mut self.entities, archetype_id, archetype: &mut self.archetypes[archetype_id as usize], } } /// Allocate an entity ID concurrently /// /// Unlike `spawn`, this can be called simultaneously to other operations on the `World` such as /// queries, but does not immediately create an entity. Reserved entities are not visible to /// queries or world iteration, but can be otherwise operated on freely. Operations that /// uniquely borrow the world, such as `insert` or `despawn`, will cause all outstanding /// reserved entities to become real entities before proceeding. This can also be done /// explicitly by calling `flush`. /// /// Useful for reserving an ID that will later have components attached to it with `insert`. pub fn reserve_entity(&self) -> Entity { self.entities.reserve_entity() } /// Destroy an entity and all its components pub fn despawn(&mut self, entity: Entity) -> Result<(), NoSuchEntity> { self.flush(); let loc = self.entities.free(entity)?; if let Some(moved) = unsafe { self.archetypes[loc.archetype as usize].remove(loc.index) } { self.entities.meta[moved as usize].location.index = loc.index; } Ok(()) } /// Ensure `additional` entities with exact components `T` can be spawned without reallocating pub fn reserve<T: Bundle>(&mut self, additional: u32) { self.reserve_inner::<T>(additional); } fn reserve_inner<T: Bundle>(&mut self, additional: u32) -> u32 { self.flush(); self.entities.reserve(additional); let archetype_id = T::with_static_ids(|ids| { self.index.get(ids).copied().unwrap_or_else(|| { let x = self.archetypes.len() as u32; self.archetypes.push(Archetype::new(T::static_type_info())); self.index.insert(ids.to_vec(), x); self.archetype_generation += 1; x }) }); self.archetypes[archetype_id as usize].reserve(additional); archetype_id } /// Despawn all entities /// /// Preserves allocated storage for reuse. pub fn clear(&mut self) { for x in &mut self.archetypes { x.clear(); } self.entities.clear(); } /// Whether `entity` still exists pub fn contains(&self, entity: Entity) -> bool { self.entities.contains(entity) } /// Efficiently iterate over all entities that have certain components /// /// Calling `iter` on the returned value yields `(Entity, Q)` tuples, where `Q` is some query /// type. A query type is `&T`, `&mut T`, a tuple of query types, or an `Option` wrapping a /// query type, where `T` is any component type. Components queried with `&mut` must only appear /// once. Entities which do not have a component type referenced outside of an `Option` will be /// skipped. /// /// Entities are yielded in arbitrary order. /// /// The returned `QueryBorrow` can be further transformed with combinator methods; see its /// documentation for details. /// /// Iterating a query will panic if it would violate an existing unique reference or construct /// an invalid unique reference. This occurs when two simultaneously-active queries could expose /// the same entity. Simultaneous queries can access the same component type if and only if the /// world contains no entities that have all components required by both queries, assuming no /// other component borrows are outstanding. /// /// Iterating a query yields references with lifetimes bound to the `QueryBorrow` returned /// here. To ensure those are invalidated, the return value of this method must be dropped for /// its dynamic borrows from the world to be released. Similarly, lifetime rules ensure that /// references obtained from a query cannot outlive the `QueryBorrow`. /// /// # Example /// ``` /// # use hecs::*; /// let mut world = World::new(); /// let a = world.spawn((123, true, "abc")); /// let b = world.spawn((456, false)); /// let c = world.spawn((42, "def")); /// let entities = world.query::<(&i32, &bool)>() /// .iter() /// .map(|(e, (&i, &b))| (e, i, b)) // Copy out of the world /// .collect::<Vec<_>>(); /// assert_eq!(entities.len(), 2); /// assert!(entities.contains(&(a, 123, true))); /// assert!(entities.contains(&(b, 456, false))); /// ``` pub fn query<Q: Query>(&self) -> QueryBorrow<'_, Q> { QueryBorrow::new(&self.entities.meta, &self.archetypes) } /// Prepare a query against a single entity /// /// Call `get` on the resulting `QueryOne` to actually execute the query. The `QueryOne` value /// is responsible for releasing the dynamically-checked borrow made by `get`, so it can't be /// dropped while references returned by `get` are live. /// /// Handy for accessing multiple components simultaneously. /// /// # Example /// ``` /// # use hecs::*; /// let mut world = World::new(); /// let a = world.spawn((123, true, "abc")); /// // The returned query must outlive the borrow made by `get` /// let mut query = world.query_one::<(&mut i32, &bool)>(a).unwrap(); /// let (number, flag) = query.get().unwrap(); /// if *flag { *number *= 2; } /// assert_eq!(*number, 246); /// ``` pub fn query_one<Q: Query>(&self, entity: Entity) -> Result<QueryOne<'_, Q>, NoSuchEntity> { let loc = self.entities.get(entity)?; Ok(unsafe { QueryOne::new(&self.archetypes[loc.archetype as usize], loc.index) }) } /// Borrow the `T` component of `entity` /// /// Panics if the component is already uniquely borrowed from another entity with the same /// components. pub fn get<T: Component>(&self, entity: Entity) -> Result<Ref<'_, T>, ComponentError> { let loc = self.entities.get(entity)?; if loc.archetype == 0 { return Err(MissingComponent::new::<T>().into()); } Ok(unsafe { Ref::new(&self.archetypes[loc.archetype as usize], loc.index)? }) } /// Uniquely borrow the `T` component of `entity` /// /// Panics if the component is already borrowed from another entity with the same components. pub fn get_mut<T: Component>(&self, entity: Entity) -> Result<RefMut<'_, T>, ComponentError> { let loc = self.entities.get(entity)?; if loc.archetype == 0 { return Err(MissingComponent::new::<T>().into()); } Ok(unsafe { RefMut::new(&self.archetypes[loc.archetype as usize], loc.index)? }) } /// Access an entity regardless of its component types /// /// Does not immediately borrow any component. pub fn entity(&self, entity: Entity) -> Result<EntityRef<'_>, NoSuchEntity> { Ok(match self.entities.get(entity)? { Location { archetype: 0, .. } => EntityRef::empty(), loc => unsafe { EntityRef::new(&self.archetypes[loc.archetype as usize], loc.index) }, }) } /// Iterate over all entities in the world /// /// Entities are yielded in arbitrary order. Prefer `World::query` for better performance when /// components will be accessed in predictable patterns. /// /// # Example /// ``` /// # use hecs::*; /// let mut world = World::new(); /// let a = world.spawn(()); /// let b = world.spawn(()); /// let ids = world.iter().map(|(id, _)| id).collect::<Vec<_>>(); /// assert_eq!(ids.len(), 2); /// assert!(ids.contains(&a)); /// assert!(ids.contains(&b)); /// ``` pub fn iter(&self) -> Iter<'_> { Iter::new(&self.archetypes, &self.entities) } /// Add `components` to `entity` /// /// Computational cost is proportional to the number of components `entity` has. If an entity /// already has a component of a certain type, it is dropped and replaced. /// /// When inserting a single component, see `insert_one` for convenience. /// /// # Example /// ``` /// # use hecs::*; /// let mut world = World::new(); /// let e = world.spawn((123, "abc")); /// world.insert(e, (456, true)); /// assert_eq!(*world.get::<i32>(e).unwrap(), 456); /// assert_eq!(*world.get::<bool>(e).unwrap(), true); /// ``` pub fn insert( &mut self, entity: Entity, components: impl DynamicBundle, ) -> Result<(), NoSuchEntity> { use hashbrown::hash_map::Entry; self.flush(); let loc = self.entities.get_mut(entity)?; unsafe { // Assemble Vec<TypeInfo> for the final entity let arch = &mut self.archetypes[loc.archetype as usize]; let mut info = arch.types().to_vec(); for ty in components.type_info() { if let Some(ptr) = arch.get_dynamic(ty.id(), ty.layout().size(), loc.index) { ty.drop(ptr.as_ptr()); } else { info.push(ty); } } info.sort(); // Find the archetype it'll live in let elements = info.iter().map(|x| x.id()).collect::<Vec<_>>(); let target = match self.index.entry(elements) { Entry::Occupied(x) => *x.get(), Entry::Vacant(x) => { let index = self.archetypes.len() as u32; self.archetypes.push(Archetype::new(info)); x.insert(index); self.archetype_generation += 1; index } }; if target == loc.archetype { // Update components in the current archetype let arch = &mut self.archetypes[loc.archetype as usize]; components.put(|ptr, ty, size| { arch.put_dynamic(ptr, ty, size, loc.index); true }); return Ok(()); } // Move into a new archetype let (source_arch, target_arch) = index2( &mut self.archetypes, loc.archetype as usize, target as usize, ); let target_index = target_arch.allocate(entity.id); loc.archetype = target; let old_index = mem::replace(&mut loc.index, target_index); if let Some(moved) = source_arch.move_to(old_index, |ptr, ty, size| { target_arch.put_dynamic(ptr, ty, size, target_index); }) { self.entities.meta[moved as usize].location.index = old_index; } components.put(|ptr, ty, size| { target_arch.put_dynamic(ptr, ty, size, target_index); true }); } Ok(()) } /// Add `component` to `entity` /// /// See `insert`. pub fn insert_one( &mut self, entity: Entity, component: impl Component, ) -> Result<(), NoSuchEntity> { self.insert(entity, (component,)) } /// Remove components from `entity` /// /// Computational cost is proportional to the number of components `entity` has. The entity /// itself is not removed, even if no components remain; use `despawn` for that. If any /// component in `T` is not present in `entity`, no components are removed and an error is /// returned. /// /// When removing a single component, see `remove_one` for convenience. /// /// # Example /// ``` /// # use hecs::*; /// let mut world = World::new(); /// let e = world.spawn((123, "abc", true)); /// assert_eq!(world.remove::<(i32, &str)>(e), Ok((123, "abc"))); /// assert!(world.get::<i32>(e).is_err()); /// assert!(world.get::<&str>(e).is_err()); /// assert_eq!(*world.get::<bool>(e).unwrap(), true); /// ``` pub fn remove<T: Bundle>(&mut self, entity: Entity) -> Result<T, ComponentError> { use hashbrown::hash_map::Entry; self.flush(); let loc = self.entities.get_mut(entity)?; unsafe { let removed = T::with_static_ids(|ids| ids.iter().copied().collect::<HashSet<_>>()); let info = self.archetypes[loc.archetype as usize] .types() .iter() .cloned() .filter(|x| !removed.contains(&x.id())) .collect::<Vec<_>>(); let elements = info.iter().map(|x| x.id()).collect::<Vec<_>>(); let target = match self.index.entry(elements) { Entry::Occupied(x) => *x.get(), Entry::Vacant(x) => { self.archetypes.push(Archetype::new(info)); let index = (self.archetypes.len() - 1) as u32; x.insert(index); self.archetype_generation += 1; index } }; let old_index = loc.index; let source_arch = &self.archetypes[loc.archetype as usize]; let bundle = T::get(|ty, size| source_arch.get_dynamic(ty, size, old_index))?; let (source_arch, target_arch) = index2( &mut self.archetypes, loc.archetype as usize, target as usize, ); let target_index = target_arch.allocate(entity.id); loc.archetype = target; loc.index = target_index; if let Some(moved) = source_arch.move_to(old_index, |src, ty, size| { // Only move the components present in the target archetype, i.e. the non-removed ones. if let Some(dst) = target_arch.get_dynamic(ty, size, target_index) { ptr::copy_nonoverlapping(src, dst.as_ptr(), size); } }) { self.entities.meta[moved as usize].location.index = old_index; } Ok(bundle) } } /// Remove the `T` component from `entity` /// /// See `remove`. pub fn remove_one<T: Component>(&mut self, entity: Entity) -> Result<T, ComponentError> { self.remove::<(T,)>(entity).map(|(x,)| x) } /// Borrow the `T` component of `entity` without safety checks /// /// Should only be used as a building block for safe abstractions. /// /// # Safety /// /// `entity` must have been previously obtained from this `World`, and no unique borrow of the /// same component of `entity` may be live simultaneous to the returned reference. pub unsafe fn get_unchecked<T: Component>(&self, entity: Entity) -> Result<&T, ComponentError> { let loc = self.entities.get(entity)?; if loc.archetype == 0 { return Err(MissingComponent::new::<T>().into()); } Ok(&*self.archetypes[loc.archetype as usize] .get::<T>() .ok_or_else(MissingComponent::new::<T>)? .as_ptr() .add(loc.index as usize)) } /// Uniquely borrow the `T` component of `entity` without safety checks /// /// Should only be used as a building block for safe abstractions. /// /// # Safety /// /// `entity` must have been previously obtained from this `World`, and no borrow of the same /// component of `entity` may be live simultaneous to the returned reference. pub unsafe fn get_unchecked_mut<T: Component>( &self, entity: Entity, ) -> Result<&mut T, ComponentError> { let loc = self.entities.get(entity)?; if loc.archetype == 0 { return Err(MissingComponent::new::<T>().into()); } Ok(&mut *self.archetypes[loc.archetype as usize] .get::<T>() .ok_or_else(MissingComponent::new::<T>)? .as_ptr() .add(loc.index as usize)) } /// Convert all reserved entities into empty entities that can be iterated and accessed /// /// Invoked implicitly by `spawn`, `despawn`, `insert`, and `remove`. pub fn flush(&mut self) { let arch = &mut self.archetypes[0]; for id in self.entities.flush() { self.entities.meta[id as usize].location.index = unsafe { arch.allocate(id) }; } for i in 0..self.entities.reserved_len() { let id = self.entities.reserved(i); self.entities.meta[id as usize].location.index = unsafe { arch.allocate(id) }; } self.entities.clear_reserved(); } /// Inspect the archetypes that entities are organized into /// /// Useful for dynamically scheduling concurrent queries by checking borrows in advance. Does /// not provide access to entities. pub fn archetypes(&self) -> impl ExactSizeIterator<Item = &'_ Archetype> + '_ { self.archetypes.iter() } /// Returns a distinct value after `archetypes` is changed /// /// Store the current value after deriving information from `archetypes`, then check whether the /// value returned by this function differs before attempting an operation that relies on its /// correctness. Useful for determining whether e.g. a concurrent query execution plan is still /// correct. /// /// The generation may be, but is not necessarily, changed as a result of adding or removing any /// entity or component. /// /// # Example /// ``` /// # use hecs::*; /// let mut world = World::new(); /// let initial_gen = world.archetypes_generation(); /// world.spawn((123, "abc")); /// assert_ne!(initial_gen, world.archetypes_generation()); /// ``` pub fn archetypes_generation(&self) -> ArchetypesGeneration { ArchetypesGeneration(self.archetype_generation) } } unsafe impl Send for World {} unsafe impl Sync for World {} impl Default for World { fn default() -> Self { Self::new() } } impl<'a> IntoIterator for &'a World { type IntoIter = Iter<'a>; type Item = (Entity, EntityRef<'a>); fn into_iter(self) -> Iter<'a> { self.iter() } } fn index2<T>(x: &mut [T], i: usize, j: usize) -> (&mut T, &mut T) { assert!(i != j); assert!(i < x.len()); assert!(j < x.len()); let ptr = x.as_mut_ptr(); unsafe { (&mut *ptr.add(i), &mut *ptr.add(j)) } } /// Errors that arise when accessing components #[derive(Debug, Clone, Eq, PartialEq, Hash)] pub enum ComponentError { /// The entity was already despawned NoSuchEntity, /// The entity did not have a requested component MissingComponent(MissingComponent), } #[cfg(feature = "std")] impl Error for ComponentError {} impl fmt::Display for ComponentError { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { use ComponentError::*; match *self { NoSuchEntity => f.write_str("no such entity"), MissingComponent(ref x) => x.fmt(f), } } } impl From<NoSuchEntity> for ComponentError { fn from(NoSuchEntity: NoSuchEntity) -> Self { ComponentError::NoSuchEntity } } impl From<MissingComponent> for ComponentError { fn from(x: MissingComponent) -> Self { ComponentError::MissingComponent(x) } } /// Types that can be components, implemented automatically for all `Send + Sync + 'static` types /// /// This is just a convenient shorthand for `Send + Sync + 'static`, and never needs to be /// implemented manually. pub trait Component: Send + Sync + 'static {} impl<T: Send + Sync + 'static> Component for T {} /// Iterator over all of a world's entities pub struct Iter<'a> { archetypes: core::slice::Iter<'a, Archetype>, entities: &'a Entities, current: Option<&'a Archetype>, index: u32, } impl<'a> Iter<'a> { fn new(archetypes: &'a [Archetype], entities: &'a Entities) -> Self { Self { archetypes: archetypes.iter(), entities, current: None, index: 0, } } } unsafe impl Send for Iter<'_> {} unsafe impl Sync for Iter<'_> {} impl<'a> Iterator for Iter<'a> { type Item = (Entity, EntityRef<'a>); fn next(&mut self) -> Option<Self::Item> { loop { match self.current { None => { self.current = Some(self.archetypes.next()?); self.index = 0; } Some(current) => { if self.index == current.len() as u32 { self.current = None; continue; } let index = self.index; self.index += 1; let id = current.entity_id(index); return Some(( Entity { id, generation: self.entities.meta[id as usize].generation, }, unsafe { EntityRef::new(current, index) }, )); } } } } fn size_hint(&self) -> (usize, Option<usize>) { (0, Some(self.entities.meta.len())) } } impl<A: DynamicBundle> Extend<A> for World { fn extend<T>(&mut self, iter: T) where T: IntoIterator<Item = A>, { for x in iter { self.spawn(x); } } } impl<A: DynamicBundle> core::iter::FromIterator<A> for World { fn from_iter<I: IntoIterator<Item = A>>(iter: I) -> Self { let mut world = World::new(); world.extend(iter); world } } /// Determines freshness of information derived from `World::archetypes` #[derive(Debug, Copy, Clone, Eq, PartialEq)] pub struct ArchetypesGeneration(u64); /// Entity IDs created by `World::spawn_batch` pub struct SpawnBatchIter<'a, I> where I: Iterator, I::Item: Bundle, { inner: I, entities: &'a mut Entities, archetype_id: u32, archetype: &'a mut Archetype, } impl<I> Drop for SpawnBatchIter<'_, I> where I: Iterator, I::Item: Bundle, { fn drop(&mut self) { for _ in self {} } } impl<I> Iterator for SpawnBatchIter<'_, I> where I: Iterator, I::Item: Bundle, { type Item = Entity; fn next(&mut self) -> Option<Entity> { let components = self.inner.next()?; let entity = self.entities.alloc(); unsafe { let index = self.archetype.allocate(entity.id); components.put(|ptr, ty, size| { self.archetype.put_dynamic(ptr, ty, size, index); true }); self.entities.meta[entity.id as usize].location = Location { archetype: self.archetype_id, index, }; } Some(entity) } fn size_hint(&self) -> (usize, Option<usize>) { self.inner.size_hint() } } impl<I, T> ExactSizeIterator for SpawnBatchIter<'_, I> where I: ExactSizeIterator<Item = T>, T: Bundle, { fn len(&self) -> usize { self.inner.len() } } #[cfg(test)] mod tests { use super::*; #[test] fn reuse_empty() { let mut world = World::new(); let a = world.spawn(()); world.despawn(a).unwrap(); let b = world.spawn(()); assert_eq!(a.id, b.id); assert_ne!(a.generation, b.generation); } #[test] fn reuse_populated() { let mut world = World::new(); let a = world.spawn((42,)); assert_eq!(*world.get::<i32>(a).unwrap(), 42); world.despawn(a).unwrap(); let b = world.spawn((true,)); assert_eq!(a.id, b.id); assert_ne!(a.generation, b.generation); assert!(world.get::<i32>(b).is_err()); assert!(*world.get::<bool>(b).unwrap()); } }