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use crate::archetype::ArchetypeComponentId;
use crate::change_detection::{MutUntyped, TicksMut};
use crate::component::{ComponentId, ComponentTicks, Components, Tick, TickCells};
use crate::storage::{blob_vec::BlobVec, SparseSet};
use bevy_ptr::{OwningPtr, Ptr, UnsafeCellDeref};
use std::{cell::UnsafeCell, mem::ManuallyDrop, thread::ThreadId};
/// The type-erased backing storage and metadata for a single resource within a [`World`].
///
/// If `SEND` is false, values of this type will panic if dropped from a different thread.
///
/// [`World`]: crate::world::World
pub struct ResourceData<const SEND: bool> {
data: ManuallyDrop<BlobVec>,
added_ticks: UnsafeCell<Tick>,
changed_ticks: UnsafeCell<Tick>,
type_name: String,
id: ArchetypeComponentId,
origin_thread_id: Option<ThreadId>,
}
impl<const SEND: bool> Drop for ResourceData<SEND> {
fn drop(&mut self) {
if self.is_present() {
// If this thread is already panicking, panicking again will cause
// the entire process to abort. In this case we choose to avoid
// dropping or checking this altogether and just leak the column.
if std::thread::panicking() {
return;
}
self.validate_access();
}
// SAFETY: Drop is only called once upon dropping the ResourceData
// and is inaccessible after this as the parent ResourceData has
// been dropped. The validate_access call above will check that the
// data is dropped on the thread it was inserted from.
unsafe {
ManuallyDrop::drop(&mut self.data);
}
}
}
impl<const SEND: bool> ResourceData<SEND> {
/// The only row in the underlying `BlobVec`.
const ROW: usize = 0;
/// Validates the access to `!Send` resources is only done on the thread they were created from.
///
/// # Panics
/// If `SEND` is false, this will panic if called from a different thread than the one it was inserted from.
#[inline]
fn validate_access(&self) {
if SEND {
return;
}
if self.origin_thread_id != Some(std::thread::current().id()) {
// Panic in tests, as testing for aborting is nearly impossible
panic!(
"Attempted to access or drop non-send resource {} from thread {:?} on a thread {:?}. This is not allowed. Aborting.",
self.type_name,
self.origin_thread_id,
std::thread::current().id()
);
}
}
/// Returns true if the resource is populated.
#[inline]
pub fn is_present(&self) -> bool {
!self.data.is_empty()
}
/// Gets the [`ArchetypeComponentId`] for the resource.
#[inline]
pub fn id(&self) -> ArchetypeComponentId {
self.id
}
/// Returns a reference to the resource, if it exists.
///
/// # Panics
/// If `SEND` is false, this will panic if a value is present and is not accessed from the
/// original thread it was inserted from.
#[inline]
pub fn get_data(&self) -> Option<Ptr<'_>> {
self.is_present().then(|| {
self.validate_access();
// SAFETY: We've already checked if a value is present, and there should only be one.
unsafe { self.data.get_unchecked(Self::ROW) }
})
}
/// Returns a reference to the resource's change ticks, if it exists.
#[inline]
pub fn get_ticks(&self) -> Option<ComponentTicks> {
// SAFETY: This is being fetched through a read-only reference to Self, so no other mutable references
// to the ticks can exist.
unsafe {
self.is_present().then(|| ComponentTicks {
added: self.added_ticks.read(),
changed: self.changed_ticks.read(),
})
}
}
/// Returns references to the resource and its change ticks, if it exists.
///
/// # Panics
/// If `SEND` is false, this will panic if a value is present and is not accessed from the
/// original thread it was inserted in.
#[inline]
pub(crate) fn get_with_ticks(&self) -> Option<(Ptr<'_>, TickCells<'_>)> {
self.is_present().then(|| {
self.validate_access();
(
// SAFETY: We've already checked if a value is present, and there should only be one.
unsafe { self.data.get_unchecked(Self::ROW) },
TickCells {
added: &self.added_ticks,
changed: &self.changed_ticks,
},
)
})
}
/// Returns a mutable reference to the resource, if it exists.
///
/// # Panics
/// If `SEND` is false, this will panic if a value is present and is not accessed from the
/// original thread it was inserted in.
pub(crate) fn get_mut(&mut self, last_run: Tick, this_run: Tick) -> Option<MutUntyped<'_>> {
let (ptr, ticks) = self.get_with_ticks()?;
Some(MutUntyped {
// SAFETY: We have exclusive access to the underlying storage.
value: unsafe { ptr.assert_unique() },
// SAFETY: We have exclusive access to the underlying storage.
ticks: unsafe { TicksMut::from_tick_cells(ticks, last_run, this_run) },
})
}
/// Inserts a value into the resource. If a value is already present
/// it will be replaced.
///
/// # Panics
/// If `SEND` is false, this will panic if a value is present and is not replaced from
/// the original thread it was inserted in.
///
/// # Safety
/// - `value` must be valid for the underlying type for the resource.
#[inline]
pub(crate) unsafe fn insert(&mut self, value: OwningPtr<'_>, change_tick: Tick) {
if self.is_present() {
self.validate_access();
// SAFETY: The caller ensures that the provided value is valid for the underlying type and
// is properly initialized. We've ensured that a value is already present and previously
// initialized.
unsafe {
self.data.replace_unchecked(Self::ROW, value);
}
} else {
if !SEND {
self.origin_thread_id = Some(std::thread::current().id());
}
self.data.push(value);
*self.added_ticks.deref_mut() = change_tick;
}
*self.changed_ticks.deref_mut() = change_tick;
}
/// Inserts a value into the resource with a pre-existing change tick. If a
/// value is already present it will be replaced.
///
/// # Panics
/// If `SEND` is false, this will panic if a value is present and is not replaced from
/// the original thread it was inserted in.
///
/// # Safety
/// - `value` must be valid for the underlying type for the resource.
#[inline]
pub(crate) unsafe fn insert_with_ticks(
&mut self,
value: OwningPtr<'_>,
change_ticks: ComponentTicks,
) {
if self.is_present() {
self.validate_access();
// SAFETY: The caller ensures that the provided value is valid for the underlying type and
// is properly initialized. We've ensured that a value is already present and previously
// initialized.
unsafe {
self.data.replace_unchecked(Self::ROW, value);
}
} else {
if !SEND {
self.origin_thread_id = Some(std::thread::current().id());
}
self.data.push(value);
}
*self.added_ticks.deref_mut() = change_ticks.added;
*self.changed_ticks.deref_mut() = change_ticks.changed;
}
/// Removes a value from the resource, if present.
///
/// # Panics
/// If `SEND` is false, this will panic if a value is present and is not removed from the
/// original thread it was inserted from.
#[inline]
#[must_use = "The returned pointer to the removed component should be used or dropped"]
pub(crate) fn remove(&mut self) -> Option<(OwningPtr<'_>, ComponentTicks)> {
if !self.is_present() {
return None;
}
if !SEND {
self.validate_access();
}
// SAFETY: We've already validated that the row is present.
let res = unsafe { self.data.swap_remove_and_forget_unchecked(Self::ROW) };
// SAFETY: This function is being called through an exclusive mutable reference to Self, which
// makes it sound to read these ticks.
unsafe {
Some((
res,
ComponentTicks {
added: self.added_ticks.read(),
changed: self.changed_ticks.read(),
},
))
}
}
/// Removes a value from the resource, if present, and drops it.
///
/// # Panics
/// If `SEND` is false, this will panic if a value is present and is not
/// accessed from the original thread it was inserted in.
#[inline]
pub(crate) fn remove_and_drop(&mut self) {
if self.is_present() {
self.validate_access();
self.data.clear();
}
}
pub(crate) fn check_change_ticks(&mut self, change_tick: Tick) {
self.added_ticks.get_mut().check_tick(change_tick);
self.changed_ticks.get_mut().check_tick(change_tick);
}
}
/// The backing store for all [`Resource`]s stored in the [`World`].
///
/// [`Resource`]: crate::system::Resource
/// [`World`]: crate::world::World
#[derive(Default)]
pub struct Resources<const SEND: bool> {
resources: SparseSet<ComponentId, ResourceData<SEND>>,
}
impl<const SEND: bool> Resources<SEND> {
/// The total number of resources stored in the [`World`]
///
/// [`World`]: crate::world::World
#[inline]
pub fn len(&self) -> usize {
self.resources.len()
}
/// Iterate over all resources that have been initialized, i.e. given a [`ComponentId`]
pub fn iter(&self) -> impl Iterator<Item = (ComponentId, &ResourceData<SEND>)> {
self.resources.iter().map(|(id, data)| (*id, data))
}
/// Returns true if there are no resources stored in the [`World`],
/// false otherwise.
///
/// [`World`]: crate::world::World
#[inline]
pub fn is_empty(&self) -> bool {
self.resources.is_empty()
}
/// Gets read-only access to a resource, if it exists.
#[inline]
pub fn get(&self, component_id: ComponentId) -> Option<&ResourceData<SEND>> {
self.resources.get(component_id)
}
/// Clears all resources.
#[inline]
pub fn clear(&mut self) {
self.resources.clear();
}
/// Gets mutable access to a resource, if it exists.
#[inline]
pub(crate) fn get_mut(&mut self, component_id: ComponentId) -> Option<&mut ResourceData<SEND>> {
self.resources.get_mut(component_id)
}
/// Fetches or initializes a new resource and returns back its underlying column.
///
/// # Panics
/// Will panic if `component_id` is not valid for the provided `components`
/// If `SEND` is true, this will panic if `component_id`'s `ComponentInfo` is not registered as being `Send` + `Sync`.
pub(crate) fn initialize_with(
&mut self,
component_id: ComponentId,
components: &Components,
f: impl FnOnce() -> ArchetypeComponentId,
) -> &mut ResourceData<SEND> {
self.resources.get_or_insert_with(component_id, || {
let component_info = components.get_info(component_id).unwrap();
if SEND {
assert!(
component_info.is_send_and_sync(),
"Send + Sync resource {} initialized as non_send. It may have been inserted via World::insert_non_send_resource by accident. Try using World::insert_resource instead.",
component_info.name(),
);
}
// SAFETY: component_info.drop() is valid for the types that will be inserted.
let data = unsafe {
BlobVec::new(
component_info.layout(),
component_info.drop(),
1
)
};
ResourceData {
data: ManuallyDrop::new(data),
added_ticks: UnsafeCell::new(Tick::new(0)),
changed_ticks: UnsafeCell::new(Tick::new(0)),
type_name: String::from(component_info.name()),
id: f(),
origin_thread_id: None,
}
})
}
pub(crate) fn check_change_ticks(&mut self, change_tick: Tick) {
for info in self.resources.values_mut() {
info.check_change_ticks(change_tick);
}
}
}