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use crate::{self as bevy_asset};
use crate::{Asset, AssetEvent, AssetHandleProvider, AssetId, AssetServer, Handle, UntypedHandle};
use bevy_ecs::{
prelude::EventWriter,
system::{Res, ResMut, Resource},
};
use bevy_reflect::{Reflect, TypePath};
use bevy_utils::HashMap;
use crossbeam_channel::{Receiver, Sender};
use serde::{Deserialize, Serialize};
use std::{
any::TypeId,
iter::Enumerate,
marker::PhantomData,
sync::{atomic::AtomicU32, Arc},
};
use thiserror::Error;
use uuid::Uuid;
/// A generational runtime-only identifier for a specific [`Asset`] stored in [`Assets`]. This is optimized for efficient runtime
/// usage and is not suitable for identifying assets across app runs.
#[derive(
Debug, Copy, Clone, Eq, PartialEq, Hash, Ord, PartialOrd, Reflect, Serialize, Deserialize,
)]
pub struct AssetIndex {
pub(crate) generation: u32,
pub(crate) index: u32,
}
impl AssetIndex {
/// Convert the [`AssetIndex`] into an opaque blob of bits to transport it in circumstances where carrying a strongly typed index isn't possible.
///
/// The result of this function should not be relied upon for anything except putting it back into [`AssetIndex::from_bits`] to recover the index.
pub fn to_bits(self) -> u64 {
let Self { generation, index } = self;
((generation as u64) << 32) | index as u64
}
/// Convert an opaque `u64` acquired from [`AssetIndex::to_bits`] back into an [`AssetIndex`]. This should not be used with any inputs other than those
/// derived from [`AssetIndex::to_bits`], as there are no guarantees for what will happen with such inputs.
pub fn from_bits(bits: u64) -> Self {
let index = ((bits << 32) >> 32) as u32;
let generation = (bits >> 32) as u32;
Self { generation, index }
}
}
/// Allocates generational [`AssetIndex`] values and facilitates their reuse.
pub(crate) struct AssetIndexAllocator {
/// A monotonically increasing index.
next_index: AtomicU32,
recycled_queue_sender: Sender<AssetIndex>,
/// This receives every recycled [`AssetIndex`]. It serves as a buffer/queue to store indices ready for reuse.
recycled_queue_receiver: Receiver<AssetIndex>,
recycled_sender: Sender<AssetIndex>,
recycled_receiver: Receiver<AssetIndex>,
}
impl Default for AssetIndexAllocator {
fn default() -> Self {
let (recycled_queue_sender, recycled_queue_receiver) = crossbeam_channel::unbounded();
let (recycled_sender, recycled_receiver) = crossbeam_channel::unbounded();
Self {
recycled_queue_sender,
recycled_queue_receiver,
recycled_sender,
recycled_receiver,
next_index: Default::default(),
}
}
}
impl AssetIndexAllocator {
/// Reserves a new [`AssetIndex`], either by reusing a recycled index (with an incremented generation), or by creating a new index
/// by incrementing the index counter for a given asset type `A`.
pub fn reserve(&self) -> AssetIndex {
if let Ok(mut recycled) = self.recycled_queue_receiver.try_recv() {
recycled.generation += 1;
self.recycled_sender.send(recycled).unwrap();
recycled
} else {
AssetIndex {
index: self
.next_index
.fetch_add(1, std::sync::atomic::Ordering::Relaxed),
generation: 0,
}
}
}
/// Queues the given `index` for reuse. This should only be done if the `index` is no longer being used.
pub fn recycle(&self, index: AssetIndex) {
self.recycled_queue_sender.send(index).unwrap();
}
}
/// A "loaded asset" containing the untyped handle for an asset stored in a given [`AssetPath`].
///
/// [`AssetPath`]: crate::AssetPath
#[derive(Asset, TypePath)]
pub struct LoadedUntypedAsset {
#[dependency]
pub handle: UntypedHandle,
}
// PERF: do we actually need this to be an enum? Can we just use an "invalid" generation instead
#[derive(Default)]
enum Entry<A: Asset> {
/// None is an indicator that this entry does not have live handles.
#[default]
None,
/// Some is an indicator that there is a live handle active for the entry at this [`AssetIndex`]
Some { value: Option<A>, generation: u32 },
}
/// Stores [`Asset`] values in a Vec-like storage identified by [`AssetIndex`].
struct DenseAssetStorage<A: Asset> {
storage: Vec<Entry<A>>,
len: u32,
allocator: Arc<AssetIndexAllocator>,
}
impl<A: Asset> Default for DenseAssetStorage<A> {
fn default() -> Self {
Self {
len: 0,
storage: Default::default(),
allocator: Default::default(),
}
}
}
impl<A: Asset> DenseAssetStorage<A> {
// Returns the number of assets stored.
pub(crate) fn len(&self) -> usize {
self.len as usize
}
// Returns `true` if there are no assets stored.
pub(crate) fn is_empty(&self) -> bool {
self.len == 0
}
/// Insert the value at the given index. Returns true if a value already exists (and was replaced)
pub(crate) fn insert(
&mut self,
index: AssetIndex,
asset: A,
) -> Result<bool, InvalidGenerationError> {
self.flush();
let entry = &mut self.storage[index.index as usize];
if let Entry::Some { value, generation } = entry {
if *generation == index.generation {
let exists = value.is_some();
if !exists {
self.len += 1;
}
*value = Some(asset);
Ok(exists)
} else {
Err(InvalidGenerationError {
index,
current_generation: *generation,
})
}
} else {
unreachable!("entries should always be valid after a flush");
}
}
/// Removes the asset stored at the given `index` and returns it as [`Some`] (if the asset exists).
/// This will recycle the id and allow new entries to be inserted.
pub(crate) fn remove_dropped(&mut self, index: AssetIndex) -> Option<A> {
self.remove_internal(index, |dense_storage| {
dense_storage.storage[index.index as usize] = Entry::None;
dense_storage.allocator.recycle(index);
})
}
/// Removes the asset stored at the given `index` and returns it as [`Some`] (if the asset exists).
/// This will _not_ recycle the id. New values with the current ID can still be inserted. The ID will
/// not be reused until [`DenseAssetStorage::remove_dropped`] is called.
pub(crate) fn remove_still_alive(&mut self, index: AssetIndex) -> Option<A> {
self.remove_internal(index, |_| {})
}
fn remove_internal(
&mut self,
index: AssetIndex,
removed_action: impl FnOnce(&mut Self),
) -> Option<A> {
self.flush();
let value = match &mut self.storage[index.index as usize] {
Entry::None => return None,
Entry::Some { value, generation } => {
if *generation == index.generation {
value.take().map(|value| {
self.len -= 1;
value
})
} else {
return None;
}
}
};
removed_action(self);
value
}
pub(crate) fn get(&self, index: AssetIndex) -> Option<&A> {
let entry = self.storage.get(index.index as usize)?;
match entry {
Entry::None => None,
Entry::Some { value, generation } => {
if *generation == index.generation {
value.as_ref()
} else {
None
}
}
}
}
pub(crate) fn get_mut(&mut self, index: AssetIndex) -> Option<&mut A> {
let entry = self.storage.get_mut(index.index as usize)?;
match entry {
Entry::None => None,
Entry::Some { value, generation } => {
if *generation == index.generation {
value.as_mut()
} else {
None
}
}
}
}
pub(crate) fn flush(&mut self) {
// NOTE: this assumes the allocator index is monotonically increasing.
let new_len = self
.allocator
.next_index
.load(std::sync::atomic::Ordering::Relaxed);
self.storage.resize_with(new_len as usize, || Entry::Some {
value: None,
generation: 0,
});
while let Ok(recycled) = self.allocator.recycled_receiver.try_recv() {
let entry = &mut self.storage[recycled.index as usize];
*entry = Entry::Some {
value: None,
generation: recycled.generation,
};
}
}
pub(crate) fn get_index_allocator(&self) -> Arc<AssetIndexAllocator> {
self.allocator.clone()
}
pub(crate) fn ids(&self) -> impl Iterator<Item = AssetId<A>> + '_ {
self.storage
.iter()
.enumerate()
.filter_map(|(i, v)| match v {
Entry::None => None,
Entry::Some { value, generation } => {
if value.is_some() {
Some(AssetId::from(AssetIndex {
index: i as u32,
generation: *generation,
}))
} else {
None
}
}
})
}
}
/// Stores [`Asset`] values identified by their [`AssetId`].
///
/// Assets identified by [`AssetId::Index`] will be stored in a "dense" vec-like storage. This is more efficient, but it means that
/// the assets can only be identified at runtime. This is the default behavior.
///
/// Assets identified by [`AssetId::Uuid`] will be stored in a hashmap. This is less efficient, but it means that the assets can be referenced
/// at compile time.
///
/// This tracks (and queues) [`AssetEvent`] events whenever changes to the collection occur.
#[derive(Resource)]
pub struct Assets<A: Asset> {
dense_storage: DenseAssetStorage<A>,
hash_map: HashMap<Uuid, A>,
handle_provider: AssetHandleProvider,
queued_events: Vec<AssetEvent<A>>,
/// Assets managed by the `Assets` struct with live strong `Handle`s
/// originating from `get_strong_handle`.
duplicate_handles: HashMap<AssetId<A>, u16>,
}
impl<A: Asset> Default for Assets<A> {
fn default() -> Self {
let dense_storage = DenseAssetStorage::default();
let handle_provider =
AssetHandleProvider::new(TypeId::of::<A>(), dense_storage.get_index_allocator());
Self {
dense_storage,
handle_provider,
hash_map: Default::default(),
queued_events: Default::default(),
duplicate_handles: Default::default(),
}
}
}
impl<A: Asset> Assets<A> {
/// Retrieves an [`AssetHandleProvider`] capable of reserving new [`Handle`] values for assets that will be stored in this
/// collection.
pub fn get_handle_provider(&self) -> AssetHandleProvider {
self.handle_provider.clone()
}
/// Reserves a new [`Handle`] for an asset that will be stored in this collection.
pub fn reserve_handle(&self) -> Handle<A> {
self.handle_provider.reserve_handle().typed::<A>()
}
/// Inserts the given `asset`, identified by the given `id`. If an asset already exists for `id`, it will be replaced.
pub fn insert(&mut self, id: impl Into<AssetId<A>>, asset: A) {
match id.into() {
AssetId::Index { index, .. } => {
self.insert_with_index(index, asset).unwrap();
}
AssetId::Uuid { uuid } => {
self.insert_with_uuid(uuid, asset);
}
}
}
/// Retrieves an [`Asset`] stored for the given `id` if it exists. If it does not exist, it will be inserted using `insert_fn`.
// PERF: Optimize this or remove it
pub fn get_or_insert_with(
&mut self,
id: impl Into<AssetId<A>>,
insert_fn: impl FnOnce() -> A,
) -> &mut A {
let id: AssetId<A> = id.into();
if self.get(id).is_none() {
self.insert(id, insert_fn());
}
self.get_mut(id).unwrap()
}
/// Returns `true` if the `id` exists in this collection. Otherwise it returns `false`.
pub fn contains(&self, id: impl Into<AssetId<A>>) -> bool {
match id.into() {
AssetId::Index { index, .. } => self.dense_storage.get(index).is_some(),
AssetId::Uuid { uuid } => self.hash_map.contains_key(&uuid),
}
}
pub(crate) fn insert_with_uuid(&mut self, uuid: Uuid, asset: A) -> Option<A> {
let result = self.hash_map.insert(uuid, asset);
if result.is_some() {
self.queued_events
.push(AssetEvent::Modified { id: uuid.into() });
} else {
self.queued_events
.push(AssetEvent::Added { id: uuid.into() });
}
result
}
pub(crate) fn insert_with_index(
&mut self,
index: AssetIndex,
asset: A,
) -> Result<bool, InvalidGenerationError> {
let replaced = self.dense_storage.insert(index, asset)?;
if replaced {
self.queued_events
.push(AssetEvent::Modified { id: index.into() });
} else {
self.queued_events
.push(AssetEvent::Added { id: index.into() });
}
Ok(replaced)
}
/// Adds the given `asset` and allocates a new strong [`Handle`] for it.
#[inline]
pub fn add(&mut self, asset: impl Into<A>) -> Handle<A> {
let index = self.dense_storage.allocator.reserve();
self.insert_with_index(index, asset.into()).unwrap();
Handle::Strong(
self.handle_provider
.get_handle(index.into(), false, None, None),
)
}
/// Upgrade an `AssetId` into a strong `Handle` that will prevent asset drop.
///
/// Returns `None` if the provided `id` is not part of this `Assets` collection.
/// For example, it may have been dropped earlier.
#[inline]
pub fn get_strong_handle(&mut self, id: AssetId<A>) -> Option<Handle<A>> {
if !self.contains(id) {
return None;
}
*self.duplicate_handles.entry(id).or_insert(0) += 1;
let index = match id {
AssetId::Index { index, .. } => index.into(),
AssetId::Uuid { uuid } => uuid.into(),
};
Some(Handle::Strong(
self.handle_provider.get_handle(index, false, None, None),
))
}
/// Retrieves a reference to the [`Asset`] with the given `id`, if it exists.
/// Note that this supports anything that implements `Into<AssetId<A>>`, which includes [`Handle`] and [`AssetId`].
#[inline]
pub fn get(&self, id: impl Into<AssetId<A>>) -> Option<&A> {
match id.into() {
AssetId::Index { index, .. } => self.dense_storage.get(index),
AssetId::Uuid { uuid } => self.hash_map.get(&uuid),
}
}
/// Retrieves a mutable reference to the [`Asset`] with the given `id`, if it exists.
/// Note that this supports anything that implements `Into<AssetId<A>>`, which includes [`Handle`] and [`AssetId`].
#[inline]
pub fn get_mut(&mut self, id: impl Into<AssetId<A>>) -> Option<&mut A> {
let id: AssetId<A> = id.into();
let result = match id {
AssetId::Index { index, .. } => self.dense_storage.get_mut(index),
AssetId::Uuid { uuid } => self.hash_map.get_mut(&uuid),
};
if result.is_some() {
self.queued_events.push(AssetEvent::Modified { id });
}
result
}
/// Removes (and returns) the [`Asset`] with the given `id`, if it exists.
/// Note that this supports anything that implements `Into<AssetId<A>>`, which includes [`Handle`] and [`AssetId`].
pub fn remove(&mut self, id: impl Into<AssetId<A>>) -> Option<A> {
let id: AssetId<A> = id.into();
let result = self.remove_untracked(id);
if result.is_some() {
self.queued_events.push(AssetEvent::Removed { id });
}
result
}
/// Removes (and returns) the [`Asset`] with the given `id`, if it exists. This skips emitting [`AssetEvent::Removed`].
/// Note that this supports anything that implements `Into<AssetId<A>>`, which includes [`Handle`] and [`AssetId`].
pub fn remove_untracked(&mut self, id: impl Into<AssetId<A>>) -> Option<A> {
let id: AssetId<A> = id.into();
self.duplicate_handles.remove(&id);
match id {
AssetId::Index { index, .. } => self.dense_storage.remove_still_alive(index),
AssetId::Uuid { uuid } => self.hash_map.remove(&uuid),
}
}
/// Removes the [`Asset`] with the given `id`.
pub(crate) fn remove_dropped(&mut self, id: AssetId<A>) {
match self.duplicate_handles.get_mut(&id) {
None | Some(0) => {}
Some(value) => {
*value -= 1;
return;
}
}
let existed = match id {
AssetId::Index { index, .. } => self.dense_storage.remove_dropped(index).is_some(),
AssetId::Uuid { uuid } => self.hash_map.remove(&uuid).is_some(),
};
if existed {
self.queued_events.push(AssetEvent::Removed { id });
}
}
/// Returns `true` if there are no assets in this collection.
pub fn is_empty(&self) -> bool {
self.dense_storage.is_empty() && self.hash_map.is_empty()
}
/// Returns the number of assets currently stored in the collection.
pub fn len(&self) -> usize {
self.dense_storage.len() + self.hash_map.len()
}
/// Returns an iterator over the [`AssetId`] of every [`Asset`] stored in this collection.
pub fn ids(&self) -> impl Iterator<Item = AssetId<A>> + '_ {
self.dense_storage
.ids()
.chain(self.hash_map.keys().map(|uuid| AssetId::from(*uuid)))
}
/// Returns an iterator over the [`AssetId`] and [`Asset`] ref of every asset in this collection.
// PERF: this could be accelerated if we implement a skip list. Consider the cost/benefits
pub fn iter(&self) -> impl Iterator<Item = (AssetId<A>, &A)> {
self.dense_storage
.storage
.iter()
.enumerate()
.filter_map(|(i, v)| match v {
Entry::None => None,
Entry::Some { value, generation } => value.as_ref().map(|v| {
let id = AssetId::Index {
index: AssetIndex {
generation: *generation,
index: i as u32,
},
marker: PhantomData,
};
(id, v)
}),
})
.chain(
self.hash_map
.iter()
.map(|(i, v)| (AssetId::Uuid { uuid: *i }, v)),
)
}
/// Returns an iterator over the [`AssetId`] and mutable [`Asset`] ref of every asset in this collection.
// PERF: this could be accelerated if we implement a skip list. Consider the cost/benefits
pub fn iter_mut(&mut self) -> AssetsMutIterator<'_, A> {
AssetsMutIterator {
dense_storage: self.dense_storage.storage.iter_mut().enumerate(),
hash_map: self.hash_map.iter_mut(),
queued_events: &mut self.queued_events,
}
}
/// A system that synchronizes the state of assets in this collection with the [`AssetServer`]. This manages
/// [`Handle`] drop events.
pub fn track_assets(mut assets: ResMut<Self>, asset_server: Res<AssetServer>) {
let assets = &mut *assets;
// note that we must hold this lock for the entire duration of this function to ensure
// that `asset_server.load` calls that occur during it block, which ensures that
// re-loads are kicked off appropriately. This function must be "transactional" relative
// to other asset info operations
let mut infos = asset_server.data.infos.write();
while let Ok(drop_event) = assets.handle_provider.drop_receiver.try_recv() {
let id = drop_event.id.typed();
if drop_event.asset_server_managed {
let untyped_id = id.untyped();
// the process_handle_drop call checks whether new handles have been created since the drop event was fired, before removing the asset
if !infos.process_handle_drop(untyped_id) {
// a new handle has been created, or the asset doesn't exist
continue;
}
}
assets.queued_events.push(AssetEvent::Unused { id });
assets.remove_dropped(id);
}
}
/// A system that applies accumulated asset change events to the [`Events`] resource.
///
/// [`Events`]: bevy_ecs::event::Events
pub fn asset_events(mut assets: ResMut<Self>, mut events: EventWriter<AssetEvent<A>>) {
events.send_batch(assets.queued_events.drain(..));
}
/// A run condition for [`asset_events`]. The system will not run if there are no events to
/// flush.
///
/// [`asset_events`]: Self::asset_events
pub(crate) fn asset_events_condition(assets: Res<Self>) -> bool {
!assets.queued_events.is_empty()
}
}
/// A mutable iterator over [`Assets`].
pub struct AssetsMutIterator<'a, A: Asset> {
queued_events: &'a mut Vec<AssetEvent<A>>,
dense_storage: Enumerate<std::slice::IterMut<'a, Entry<A>>>,
hash_map: bevy_utils::hashbrown::hash_map::IterMut<'a, Uuid, A>,
}
impl<'a, A: Asset> Iterator for AssetsMutIterator<'a, A> {
type Item = (AssetId<A>, &'a mut A);
fn next(&mut self) -> Option<Self::Item> {
for (i, entry) in &mut self.dense_storage {
match entry {
Entry::None => {
continue;
}
Entry::Some { value, generation } => {
let id = AssetId::Index {
index: AssetIndex {
generation: *generation,
index: i as u32,
},
marker: PhantomData,
};
self.queued_events.push(AssetEvent::Modified { id });
if let Some(value) = value {
return Some((id, value));
}
}
}
}
if let Some((key, value)) = self.hash_map.next() {
let id = AssetId::Uuid { uuid: *key };
self.queued_events.push(AssetEvent::Modified { id });
Some((id, value))
} else {
None
}
}
}
#[derive(Error, Debug)]
#[error("AssetIndex {index:?} has an invalid generation. The current generation is: '{current_generation}'.")]
pub struct InvalidGenerationError {
index: AssetIndex,
current_generation: u32,
}
#[cfg(test)]
mod test {
use crate::AssetIndex;
#[test]
fn asset_index_round_trip() {
let asset_index = AssetIndex {
generation: 42,
index: 1337,
};
let roundtripped = AssetIndex::from_bits(asset_index.to_bits());
assert_eq!(asset_index, roundtripped);
}
}