d0550f58ae
# Objective Unblock #18162. #15396 added the `'s` lifetime to `QueryData::Item` to make it possible for query items to borrow from the state. The state isn't passed directly to `QueryData::fetch()`, so it also added the `'s` lifetime to `WorldQuery::Fetch` so that we can pass the borrows through there. Unfortunately, having `WorldQuery::Fetch` borrow from the state makes it impossible to have owned state, because we store the state and the `Fetch` in the same `struct` during iteration. ## Solution Undo the change to add the `'s` lifetime to `WorldQuery::Fetch`. Instead, add a `&'s Self::State` parameter to `QueryData::fetch()` and `QueryFilter::filter_fetch()` so that borrows from the state can be passed directly to query items. --------- Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com> Co-authored-by: Emerson Coskey <emerson@coskey.dev>
230 lines
11 KiB
Rust
230 lines
11 KiB
Rust
use crate::{
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archetype::Archetype,
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component::{ComponentId, Components, Tick},
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query::FilteredAccess,
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storage::Table,
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world::{unsafe_world_cell::UnsafeWorldCell, World},
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};
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use variadics_please::all_tuples;
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/// Types that can be used as parameters in a [`Query`].
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/// Types that implement this should also implement either [`QueryData`] or [`QueryFilter`]
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///
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/// # Safety
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///
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/// Implementor must ensure that
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/// [`update_component_access`], [`QueryData::provide_extra_access`], [`matches_component_set`], [`QueryData::fetch`], [`QueryFilter::filter_fetch`] and [`init_fetch`]
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/// obey the following:
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///
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/// - For each component mutably accessed by [`QueryData::fetch`], [`update_component_access`] or [`QueryData::provide_extra_access`] should add write access unless read or write access has already been added, in which case it should panic.
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/// - For each component readonly accessed by [`QueryData::fetch`] or [`QueryFilter::filter_fetch`], [`update_component_access`] or [`QueryData::provide_extra_access`] should add read access unless write access has already been added, in which case it should panic.
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/// - If `fetch` mutably accesses the same component twice, [`update_component_access`] should panic.
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/// - [`update_component_access`] may not add a `Without` filter for a component unless [`matches_component_set`] always returns `false` when the component set contains that component.
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/// - [`update_component_access`] may not add a `With` filter for a component unless [`matches_component_set`] always returns `false` when the component set doesn't contain that component.
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/// - In cases where the query represents a disjunction (such as an `Or` filter) where each element is a valid [`WorldQuery`], the following rules must be obeyed:
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/// - [`matches_component_set`] must be a disjunction of the element's implementations
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/// - [`update_component_access`] must replace the filters with a disjunction of filters
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/// - Each filter in that disjunction must be a conjunction of the corresponding element's filter with the previous `access`
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/// - For each resource readonly accessed by [`init_fetch`], [`update_component_access`] should add read access.
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/// - Mutable resource access is not allowed.
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/// - Any access added during [`QueryData::provide_extra_access`] must be a subset of `available_access`, and must not conflict with any access in `access`.
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///
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/// When implementing [`update_component_access`], note that `add_read` and `add_write` both also add a `With` filter, whereas `extend_access` does not change the filters.
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///
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/// [`QueryData::provide_extra_access`]: crate::query::QueryData::provide_extra_access
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/// [`QueryData::fetch`]: crate::query::QueryData::fetch
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/// [`QueryFilter::filter_fetch`]: crate::query::QueryFilter::filter_fetch
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/// [`init_fetch`]: Self::init_fetch
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/// [`matches_component_set`]: Self::matches_component_set
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/// [`Query`]: crate::system::Query
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/// [`update_component_access`]: Self::update_component_access
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/// [`QueryData`]: crate::query::QueryData
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/// [`QueryFilter`]: crate::query::QueryFilter
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pub unsafe trait WorldQuery {
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/// Per archetype/table state retrieved by this [`WorldQuery`] to compute [`Self::Item`](crate::query::QueryData::Item) for each entity.
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type Fetch<'w>: Clone;
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/// State used to construct a [`Self::Fetch`](WorldQuery::Fetch). This will be cached inside [`QueryState`](crate::query::QueryState),
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/// so it is best to move as much data / computation here as possible to reduce the cost of
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/// constructing [`Self::Fetch`](WorldQuery::Fetch).
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type State: Send + Sync + Sized;
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/// This function manually implements subtyping for the query fetches.
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fn shrink_fetch<'wlong: 'wshort, 'wshort>(fetch: Self::Fetch<'wlong>) -> Self::Fetch<'wshort>;
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/// Creates a new instance of [`Self::Fetch`](WorldQuery::Fetch),
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/// by combining data from the [`World`] with the cached [`Self::State`](WorldQuery::State).
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/// Readonly accesses resources registered in [`WorldQuery::update_component_access`].
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///
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/// # Safety
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///
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/// - `state` must have been initialized (via [`WorldQuery::init_state`]) using the same `world` passed
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/// in to this function.
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/// - `world` must have the **right** to access any access registered in `update_component_access`.
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/// - There must not be simultaneous resource access conflicting with readonly resource access registered in [`WorldQuery::update_component_access`].
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unsafe fn init_fetch<'w, 's>(
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world: UnsafeWorldCell<'w>,
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state: &'s Self::State,
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last_run: Tick,
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this_run: Tick,
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) -> Self::Fetch<'w>;
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/// Returns true if (and only if) every table of every archetype matched by this fetch contains
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/// all of the matched components.
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///
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/// This is used to select a more efficient "table iterator"
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/// for "dense" queries. If this returns true, [`WorldQuery::set_table`] must be used before
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/// [`QueryData::fetch`](crate::query::QueryData::fetch) can be called for iterators. If this returns false,
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/// [`WorldQuery::set_archetype`] must be used before [`QueryData::fetch`](crate::query::QueryData::fetch) can be called for
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/// iterators.
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const IS_DENSE: bool;
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/// Adjusts internal state to account for the next [`Archetype`]. This will always be called on
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/// archetypes that match this [`WorldQuery`].
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///
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/// # Safety
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///
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/// - `archetype` and `tables` must be from the same [`World`] that [`WorldQuery::init_state`] was called on.
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/// - `table` must correspond to `archetype`.
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/// - `state` must be the [`State`](Self::State) that `fetch` was initialized with.
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unsafe fn set_archetype<'w, 's>(
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fetch: &mut Self::Fetch<'w>,
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state: &'s Self::State,
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archetype: &'w Archetype,
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table: &'w Table,
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);
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/// Adjusts internal state to account for the next [`Table`]. This will always be called on tables
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/// that match this [`WorldQuery`].
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///
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/// # Safety
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///
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/// - `table` must be from the same [`World`] that [`WorldQuery::init_state`] was called on.
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/// - `state` must be the [`State`](Self::State) that `fetch` was initialized with.
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unsafe fn set_table<'w, 's>(
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fetch: &mut Self::Fetch<'w>,
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state: &'s Self::State,
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table: &'w Table,
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);
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/// Adds any component accesses used by this [`WorldQuery`] to `access`.
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///
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/// Used to check which queries are disjoint and can run in parallel
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// This does not have a default body of `{}` because 99% of cases need to add accesses
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// and forgetting to do so would be unsound.
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fn update_component_access(state: &Self::State, access: &mut FilteredAccess<ComponentId>);
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/// Creates and initializes a [`State`](WorldQuery::State) for this [`WorldQuery`] type.
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fn init_state(world: &mut World) -> Self::State;
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/// Attempts to initialize a [`State`](WorldQuery::State) for this [`WorldQuery`] type using read-only
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/// access to [`Components`].
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fn get_state(components: &Components) -> Option<Self::State>;
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/// Returns `true` if this query matches a set of components. Otherwise, returns `false`.
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///
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/// Used to check which [`Archetype`]s can be skipped by the query
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/// (if none of the [`Component`](crate::component::Component)s match).
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/// This is how archetypal query filters like `With` work.
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fn matches_component_set(
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state: &Self::State,
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set_contains_id: &impl Fn(ComponentId) -> bool,
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) -> bool;
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}
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macro_rules! impl_tuple_world_query {
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($(#[$meta:meta])* $(($name: ident, $state: ident)),*) => {
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#[expect(
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clippy::allow_attributes,
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reason = "This is a tuple-related macro; as such the lints below may not always apply."
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)]
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#[allow(
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non_snake_case,
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reason = "The names of some variables are provided by the macro's caller, not by us."
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)]
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#[allow(
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unused_variables,
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reason = "Zero-length tuples won't use any of the parameters."
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)]
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#[allow(
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clippy::unused_unit,
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reason = "Zero-length tuples will generate some function bodies equivalent to `()`; however, this macro is meant for all applicable tuples, and as such it makes no sense to rewrite it just for that case."
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)]
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$(#[$meta])*
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/// SAFETY:
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/// `fetch` accesses are the conjunction of the subqueries' accesses
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/// This is sound because `update_component_access` adds accesses according to the implementations of all the subqueries.
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/// `update_component_access` adds all `With` and `Without` filters from the subqueries.
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/// This is sound because `matches_component_set` always returns `false` if any the subqueries' implementations return `false`.
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unsafe impl<$($name: WorldQuery),*> WorldQuery for ($($name,)*) {
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type Fetch<'w> = ($($name::Fetch<'w>,)*);
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type State = ($($name::State,)*);
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fn shrink_fetch<'wlong: 'wshort, 'wshort>(fetch: Self::Fetch<'wlong>) -> Self::Fetch<'wshort> {
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let ($($name,)*) = fetch;
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($(
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$name::shrink_fetch($name),
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)*)
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}
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#[inline]
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unsafe fn init_fetch<'w, 's>(world: UnsafeWorldCell<'w>, state: &'s Self::State, last_run: Tick, this_run: Tick) -> Self::Fetch<'w> {
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let ($($name,)*) = state;
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// SAFETY: The invariants are upheld by the caller.
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($(unsafe { $name::init_fetch(world, $name, last_run, this_run) },)*)
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}
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const IS_DENSE: bool = true $(&& $name::IS_DENSE)*;
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#[inline]
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unsafe fn set_archetype<'w, 's>(
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fetch: &mut Self::Fetch<'w>,
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state: &'s Self::State,
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archetype: &'w Archetype,
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table: &'w Table
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) {
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let ($($name,)*) = fetch;
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let ($($state,)*) = state;
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// SAFETY: The invariants are upheld by the caller.
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$(unsafe { $name::set_archetype($name, $state, archetype, table); })*
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}
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#[inline]
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unsafe fn set_table<'w, 's>(fetch: &mut Self::Fetch<'w>, state: &'s Self::State, table: &'w Table) {
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let ($($name,)*) = fetch;
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let ($($state,)*) = state;
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// SAFETY: The invariants are upheld by the caller.
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$(unsafe { $name::set_table($name, $state, table); })*
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}
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fn update_component_access(state: &Self::State, access: &mut FilteredAccess<ComponentId>) {
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let ($($name,)*) = state;
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$($name::update_component_access($name, access);)*
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}
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fn init_state(world: &mut World) -> Self::State {
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($($name::init_state(world),)*)
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}
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fn get_state(components: &Components) -> Option<Self::State> {
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Some(($($name::get_state(components)?,)*))
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}
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fn matches_component_set(state: &Self::State, set_contains_id: &impl Fn(ComponentId) -> bool) -> bool {
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let ($($name,)*) = state;
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true $(&& $name::matches_component_set($name, set_contains_id))*
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}
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}
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};
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}
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all_tuples!(
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#[doc(fake_variadic)]
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impl_tuple_world_query,
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0,
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15,
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F,
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S
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);
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