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access.rs
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access.rs
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use crate::storage::SparseSetIndex;
use bevy_utils::HashSet;
use fixedbitset::FixedBitSet;
use std::marker::PhantomData;
/// Tracks read and write access to specific elements in a collection.
///
/// Used internally to ensure soundness during system initialization and execution.
/// See the [`is_compatible`](Access::is_compatible) and [`get_conflicts`](Access::get_conflicts) functions.
#[derive(Debug, Clone, Eq, PartialEq)]
pub struct Access<T: SparseSetIndex> {
/// All accessed elements.
reads_and_writes: FixedBitSet,
/// The exclusively-accessed elements.
writes: FixedBitSet,
/// Is `true` if this has access to all elements in the collection?
/// This field is a performance optimization for `&World` (also harder to mess up for soundness).
reads_all: bool,
marker: PhantomData<T>,
}
impl<T: SparseSetIndex> Default for Access<T> {
fn default() -> Self {
Self {
reads_all: false,
reads_and_writes: Default::default(),
writes: Default::default(),
marker: PhantomData,
}
}
}
impl<T: SparseSetIndex> Access<T> {
/// Increases the set capacity to the specified amount.
///
/// Does nothing if `capacity` is less than or equal to the current value.
pub fn grow(&mut self, capacity: usize) {
self.reads_and_writes.grow(capacity);
self.writes.grow(capacity);
}
/// Adds access to the element given by `index`.
pub fn add_read(&mut self, index: T) {
self.reads_and_writes.grow(index.sparse_set_index() + 1);
self.reads_and_writes.insert(index.sparse_set_index());
}
/// Adds exclusive access to the element given by `index`.
pub fn add_write(&mut self, index: T) {
self.reads_and_writes.grow(index.sparse_set_index() + 1);
self.reads_and_writes.insert(index.sparse_set_index());
self.writes.grow(index.sparse_set_index() + 1);
self.writes.insert(index.sparse_set_index());
}
/// Returns `true` if this can access the element given by `index`.
pub fn has_read(&self, index: T) -> bool {
if self.reads_all {
true
} else {
self.reads_and_writes.contains(index.sparse_set_index())
}
}
/// Returns `true` if this can exclusively access the element given by `index`.
pub fn has_write(&self, index: T) -> bool {
self.writes.contains(index.sparse_set_index())
}
/// Sets this as having access to all indexed elements (i.e. `&World`).
pub fn read_all(&mut self) {
self.reads_all = true;
}
/// Returns `true` if this has access to all indexed elements (i.e. `&World`).
pub fn has_read_all(&self) -> bool {
self.reads_all
}
/// Removes all accesses.
pub fn clear(&mut self) {
self.reads_all = false;
self.reads_and_writes.clear();
self.writes.clear();
}
/// Adds all access from `other`.
pub fn extend(&mut self, other: &Access<T>) {
self.reads_all = self.reads_all || other.reads_all;
self.reads_and_writes.union_with(&other.reads_and_writes);
self.writes.union_with(&other.writes);
}
/// Returns `true` if the access and `other` can be active at the same time.
///
/// `Access` instances are incompatible if one can write
/// an element that the other can read or write.
pub fn is_compatible(&self, other: &Access<T>) -> bool {
// Only systems that do not write data are compatible with systems that operate on `&World`.
if self.reads_all {
return other.writes.count_ones(..) == 0;
}
if other.reads_all {
return self.writes.count_ones(..) == 0;
}
self.writes.is_disjoint(&other.reads_and_writes)
&& self.reads_and_writes.is_disjoint(&other.writes)
}
/// Returns a vector of elements that the access and `other` cannot access at the same time.
pub fn get_conflicts(&self, other: &Access<T>) -> Vec<T> {
let mut conflicts = FixedBitSet::default();
if self.reads_all {
conflicts.extend(other.writes.ones());
}
if other.reads_all {
conflicts.extend(self.writes.ones());
}
conflicts.extend(self.writes.intersection(&other.reads_and_writes));
conflicts.extend(self.reads_and_writes.intersection(&other.writes));
conflicts
.ones()
.map(SparseSetIndex::get_sparse_set_index)
.collect()
}
/// Returns the indices of the elements this has access to.
pub fn reads_and_writes(&self) -> impl Iterator<Item = T> + '_ {
self.reads_and_writes.ones().map(T::get_sparse_set_index)
}
/// Returns the indices of the elements this has non-exclusive access to.
pub fn reads(&self) -> impl Iterator<Item = T> + '_ {
self.reads_and_writes
.difference(&self.writes)
.map(T::get_sparse_set_index)
}
/// Returns the indices of the elements this has exclusive access to.
pub fn writes(&self) -> impl Iterator<Item = T> + '_ {
self.writes.ones().map(T::get_sparse_set_index)
}
}
/// An [`Access`] that has been filtered to include and exclude certain combinations of elements.
///
/// Used internally to statically check if queries are disjoint.
///
/// Subtle: a `read` or `write` in `access` should not be considered to imply a
/// `with` access.
///
/// For example consider `Query<Option<&T>>` this only has a `read` of `T` as doing
/// otherwise would allow for queries to be considered disjoint that actually aren't:
/// - `Query<(&mut T, Option<&U>)>` read/write `T`, read `U`, with `U`
/// - `Query<&mut T, Without<U>>` read/write `T`, without `U`
/// from this we could reasonably conclude that the queries are disjoint but they aren't.
///
/// In order to solve this the actual access that `Query<(&mut T, Option<&U>)>` has
/// is read/write `T`, read `U`. It must still have a read `U` access otherwise the following
/// queries would be incorrectly considered disjoint:
/// - `Query<&mut T>` read/write `T`
/// - `Query<Option<&T>` accesses nothing
///
/// See comments the `WorldQuery` impls of `AnyOf`/`Option`/`Or` for more information.
#[derive(Debug, Clone, Eq, PartialEq)]
pub struct FilteredAccess<T: SparseSetIndex> {
access: Access<T>,
with: FixedBitSet,
without: FixedBitSet,
}
impl<T: SparseSetIndex> Default for FilteredAccess<T> {
fn default() -> Self {
Self {
access: Access::default(),
with: Default::default(),
without: Default::default(),
}
}
}
impl<T: SparseSetIndex> From<FilteredAccess<T>> for FilteredAccessSet<T> {
fn from(filtered_access: FilteredAccess<T>) -> Self {
let mut base = FilteredAccessSet::<T>::default();
base.add(filtered_access);
base
}
}
impl<T: SparseSetIndex> FilteredAccess<T> {
/// Returns a reference to the underlying unfiltered access.
#[inline]
pub fn access(&self) -> &Access<T> {
&self.access
}
/// Returns a mutable reference to the underlying unfiltered access.
#[inline]
pub fn access_mut(&mut self) -> &mut Access<T> {
&mut self.access
}
/// Adds access to the element given by `index`.
pub fn add_read(&mut self, index: T) {
self.access.add_read(index.clone());
self.add_with(index);
}
/// Adds exclusive access to the element given by `index`.
pub fn add_write(&mut self, index: T) {
self.access.add_write(index.clone());
self.add_with(index);
}
/// Retains only combinations where the element given by `index` is also present.
pub fn add_with(&mut self, index: T) {
self.with.grow(index.sparse_set_index() + 1);
self.with.insert(index.sparse_set_index());
}
/// Retains only combinations where the element given by `index` is not present.
pub fn add_without(&mut self, index: T) {
self.without.grow(index.sparse_set_index() + 1);
self.without.insert(index.sparse_set_index());
}
pub fn extend_intersect_filter(&mut self, other: &FilteredAccess<T>) {
self.without.intersect_with(&other.without);
self.with.intersect_with(&other.with);
}
pub fn extend_access(&mut self, other: &FilteredAccess<T>) {
self.access.extend(&other.access);
}
/// Returns `true` if this and `other` can be active at the same time.
pub fn is_compatible(&self, other: &FilteredAccess<T>) -> bool {
if self.access.is_compatible(&other.access) {
true
} else {
self.with.intersection(&other.without).next().is_some()
|| self.without.intersection(&other.with).next().is_some()
}
}
/// Returns a vector of elements that this and `other` cannot access at the same time.
pub fn get_conflicts(&self, other: &FilteredAccess<T>) -> Vec<T> {
if !self.is_compatible(other) {
// filters are disjoint, so we can just look at the unfiltered intersection
return self.access.get_conflicts(&other.access);
}
Vec::new()
}
/// Adds all access and filters from `other`.
pub fn extend(&mut self, access: &FilteredAccess<T>) {
self.access.extend(&access.access);
self.with.union_with(&access.with);
self.without.union_with(&access.without);
}
/// Sets the underlying unfiltered access as having access to all indexed elements.
pub fn read_all(&mut self) {
self.access.read_all();
}
}
/// A collection of [`FilteredAccess`] instances.
///
/// Used internally to statically check if systems have conflicting access.
#[derive(Debug, Clone)]
pub struct FilteredAccessSet<T: SparseSetIndex> {
combined_access: Access<T>,
filtered_accesses: Vec<FilteredAccess<T>>,
}
impl<T: SparseSetIndex> FilteredAccessSet<T> {
/// Returns a reference to the unfiltered access of the entire set.
#[inline]
pub fn combined_access(&self) -> &Access<T> {
&self.combined_access
}
/// Returns a mutable reference to the unfiltered access of the entire set.
#[inline]
pub fn combined_access_mut(&mut self) -> &mut Access<T> {
&mut self.combined_access
}
/// Returns `true` if this and `other` can be active at the same time.
pub fn is_compatible(&self, other: &FilteredAccessSet<T>) -> bool {
if self.combined_access.is_compatible(other.combined_access()) {
return true;
}
for filtered in &self.filtered_accesses {
for other_filtered in &other.filtered_accesses {
if !filtered.is_compatible(other_filtered) {
return false;
}
}
}
true
}
/// Returns a vector of elements that this set and `other` cannot access at the same time.
pub fn get_conflicts(&self, other: &FilteredAccessSet<T>) -> Vec<T> {
// if the unfiltered access is incompatible, must check each pair
let mut conflicts = HashSet::new();
if !self.combined_access.is_compatible(other.combined_access()) {
for filtered in &self.filtered_accesses {
for other_filtered in &other.filtered_accesses {
conflicts.extend(filtered.get_conflicts(other_filtered).into_iter());
}
}
}
conflicts.into_iter().collect()
}
/// Returns a vector of elements that this set and `other` cannot access at the same time.
pub fn get_conflicts_single(&self, filtered_access: &FilteredAccess<T>) -> Vec<T> {
// if the unfiltered access is incompatible, must check each pair
let mut conflicts = HashSet::new();
if !self.combined_access.is_compatible(filtered_access.access()) {
for filtered in &self.filtered_accesses {
conflicts.extend(filtered.get_conflicts(filtered_access).into_iter());
}
}
conflicts.into_iter().collect()
}
/// Adds the filtered access to the set.
pub fn add(&mut self, filtered_access: FilteredAccess<T>) {
self.combined_access.extend(&filtered_access.access);
self.filtered_accesses.push(filtered_access);
}
pub fn extend(&mut self, filtered_access_set: FilteredAccessSet<T>) {
self.combined_access
.extend(&filtered_access_set.combined_access);
self.filtered_accesses
.extend(filtered_access_set.filtered_accesses);
}
pub fn clear(&mut self) {
self.combined_access.clear();
self.filtered_accesses.clear();
}
}
impl<T: SparseSetIndex> Default for FilteredAccessSet<T> {
fn default() -> Self {
Self {
combined_access: Default::default(),
filtered_accesses: Vec::new(),
}
}
}
#[cfg(test)]
mod tests {
use crate::query::{Access, FilteredAccess};
#[test]
fn access_get_conflicts() {
let mut access_a = Access::<usize>::default();
access_a.add_read(0);
access_a.add_read(1);
let mut access_b = Access::<usize>::default();
access_b.add_read(0);
access_b.add_write(1);
assert_eq!(access_a.get_conflicts(&access_b), vec![1]);
let mut access_c = Access::<usize>::default();
access_c.add_write(0);
access_c.add_write(1);
assert_eq!(access_a.get_conflicts(&access_c), vec![0, 1]);
assert_eq!(access_b.get_conflicts(&access_c), vec![0, 1]);
let mut access_d = Access::<usize>::default();
access_d.add_read(0);
assert_eq!(access_d.get_conflicts(&access_a), vec![]);
assert_eq!(access_d.get_conflicts(&access_b), vec![]);
assert_eq!(access_d.get_conflicts(&access_c), vec![0]);
}
#[test]
fn filtered_access_extend() {
let mut access_a = FilteredAccess::<usize>::default();
access_a.add_read(0);
access_a.add_read(1);
access_a.add_with(2);
let mut access_b = FilteredAccess::<usize>::default();
access_b.add_read(0);
access_b.add_write(3);
access_b.add_without(4);
access_a.extend(&access_b);
let mut expected = FilteredAccess::<usize>::default();
expected.add_read(0);
expected.add_read(1);
expected.add_with(2);
expected.add_write(3);
expected.add_without(4);
assert!(access_a.eq(&expected));
}
}