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#![cfg_attr(docsrs, feature(doc_auto_cfg))]
#![allow(unsafe_code)]
#![doc(
html_logo_url = "https://bevyengine.org/assets/icon.png",
html_favicon_url = "https://bevyengine.org/assets/icon.png"
)]
//! General utilities for first-party [Bevy] engine crates.
//!
//! [Bevy]: https://bevyengine.org/
//!
#[allow(missing_docs)]
pub mod prelude {
pub use crate::default;
}
pub mod futures;
mod short_names;
pub use short_names::get_short_name;
pub mod synccell;
pub mod syncunsafecell;
mod cow_arc;
mod default;
mod once;
mod parallel_queue;
pub use ahash::{AHasher, RandomState};
pub use bevy_utils_proc_macros::*;
pub use cow_arc::*;
pub use default::default;
pub use hashbrown;
pub use parallel_queue::*;
pub use tracing;
pub use web_time::{Duration, Instant, SystemTime, SystemTimeError, TryFromFloatSecsError};
use hashbrown::hash_map::RawEntryMut;
use std::{
any::TypeId,
fmt::Debug,
hash::{BuildHasher, BuildHasherDefault, Hash, Hasher},
marker::PhantomData,
mem::ManuallyDrop,
ops::Deref,
};
#[cfg(not(target_arch = "wasm32"))]
mod conditional_send {
/// Use [`ConditionalSend`] to mark an optional Send trait bound. Useful as on certain platforms (eg. WASM),
/// futures aren't Send.
pub trait ConditionalSend: Send {}
impl<T: Send> ConditionalSend for T {}
}
#[cfg(target_arch = "wasm32")]
#[allow(missing_docs)]
mod conditional_send {
pub trait ConditionalSend {}
impl<T> ConditionalSend for T {}
}
pub use conditional_send::*;
/// Use [`ConditionalSendFuture`] for a future with an optional Send trait bound, as on certain platforms (eg. WASM),
/// futures aren't Send.
pub trait ConditionalSendFuture: std::future::Future + ConditionalSend {}
impl<T: std::future::Future + ConditionalSend> ConditionalSendFuture for T {}
/// An owned and dynamically typed Future used when you can't statically type your result or need to add some indirection.
pub type BoxedFuture<'a, T> = std::pin::Pin<Box<dyn ConditionalSendFuture<Output = T> + 'a>>;
/// A shortcut alias for [`hashbrown::hash_map::Entry`].
pub type Entry<'a, K, V, S = BuildHasherDefault<AHasher>> = hashbrown::hash_map::Entry<'a, K, V, S>;
/// A hasher builder that will create a fixed hasher.
#[derive(Debug, Clone, Default)]
pub struct FixedState;
impl BuildHasher for FixedState {
type Hasher = AHasher;
#[inline]
fn build_hasher(&self) -> AHasher {
RandomState::with_seeds(
0b10010101111011100000010011000100,
0b00000011001001101011001001111000,
0b11001111011010110111100010110101,
0b00000100001111100011010011010101,
)
.build_hasher()
}
}
/// A [`HashMap`][hashbrown::HashMap] implementing aHash, a high
/// speed keyed hashing algorithm intended for use in in-memory hashmaps.
///
/// aHash is designed for performance and is NOT cryptographically secure.
///
/// Within the same execution of the program iteration order of different
/// `HashMap`s only depends on the order of insertions and deletions,
/// but it will not be stable between multiple executions of the program.
pub type HashMap<K, V> = hashbrown::HashMap<K, V, BuildHasherDefault<AHasher>>;
/// A stable hash map implementing aHash, a high speed keyed hashing algorithm
/// intended for use in in-memory hashmaps.
///
/// Unlike [`HashMap`] the iteration order stability extends between executions
/// using the same Bevy version on the same device.
///
/// aHash is designed for performance and is NOT cryptographically secure.
#[deprecated(
note = "Will be required to use the hash library of your choice. Alias for: hashbrown::HashMap<K, V, FixedState>"
)]
pub type StableHashMap<K, V> = hashbrown::HashMap<K, V, FixedState>;
/// A [`HashSet`][hashbrown::HashSet] implementing aHash, a high
/// speed keyed hashing algorithm intended for use in in-memory hashmaps.
///
/// aHash is designed for performance and is NOT cryptographically secure.
///
/// Within the same execution of the program iteration order of different
/// `HashSet`s only depends on the order of insertions and deletions,
/// but it will not be stable between multiple executions of the program.
pub type HashSet<K> = hashbrown::HashSet<K, BuildHasherDefault<AHasher>>;
/// A stable hash set implementing aHash, a high speed keyed hashing algorithm
/// intended for use in in-memory hashmaps.
///
/// Unlike [`HashMap`] the iteration order stability extends between executions
/// using the same Bevy version on the same device.
///
/// aHash is designed for performance and is NOT cryptographically secure.
#[deprecated(
note = "Will be required to use the hash library of your choice. Alias for: hashbrown::HashSet<K, FixedState>"
)]
pub type StableHashSet<K> = hashbrown::HashSet<K, FixedState>;
/// A pre-hashed value of a specific type. Pre-hashing enables memoization of hashes that are expensive to compute.
/// It also enables faster [`PartialEq`] comparisons by short circuiting on hash equality.
/// See [`PassHash`] and [`PassHasher`] for a "pass through" [`BuildHasher`] and [`Hasher`] implementation
/// designed to work with [`Hashed`]
/// See [`PreHashMap`] for a hashmap pre-configured to use [`Hashed`] keys.
pub struct Hashed<V, H = FixedState> {
hash: u64,
value: V,
marker: PhantomData<H>,
}
impl<V: Hash, H: BuildHasher + Default> Hashed<V, H> {
/// Pre-hashes the given value using the [`BuildHasher`] configured in the [`Hashed`] type.
pub fn new(value: V) -> Self {
Self {
hash: H::default().hash_one(&value),
value,
marker: PhantomData,
}
}
/// The pre-computed hash.
#[inline]
pub fn hash(&self) -> u64 {
self.hash
}
}
impl<V, H> Hash for Hashed<V, H> {
#[inline]
fn hash<R: Hasher>(&self, state: &mut R) {
state.write_u64(self.hash);
}
}
impl<V, H> Deref for Hashed<V, H> {
type Target = V;
#[inline]
fn deref(&self) -> &Self::Target {
&self.value
}
}
impl<V: PartialEq, H> PartialEq for Hashed<V, H> {
/// A fast impl of [`PartialEq`] that first checks that `other`'s pre-computed hash
/// matches this value's pre-computed hash.
#[inline]
fn eq(&self, other: &Self) -> bool {
self.hash == other.hash && self.value.eq(&other.value)
}
}
impl<V: Debug, H> Debug for Hashed<V, H> {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
f.debug_struct("Hashed")
.field("hash", &self.hash)
.field("value", &self.value)
.finish()
}
}
impl<V: Clone, H> Clone for Hashed<V, H> {
#[inline]
fn clone(&self) -> Self {
Self {
hash: self.hash,
value: self.value.clone(),
marker: PhantomData,
}
}
}
impl<V: Eq, H> Eq for Hashed<V, H> {}
/// A [`BuildHasher`] that results in a [`PassHasher`].
#[derive(Default, Clone)]
pub struct PassHash;
impl BuildHasher for PassHash {
type Hasher = PassHasher;
fn build_hasher(&self) -> Self::Hasher {
PassHasher::default()
}
}
/// A no-op hash that only works on `u64`s. Will panic if attempting to
/// hash a type containing non-u64 fields.
#[derive(Debug, Default)]
pub struct PassHasher {
hash: u64,
}
impl Hasher for PassHasher {
#[inline]
fn finish(&self) -> u64 {
self.hash
}
fn write(&mut self, _bytes: &[u8]) {
panic!("can only hash u64 using PassHasher");
}
#[inline]
fn write_u64(&mut self, i: u64) {
self.hash = i;
}
}
/// A [`HashMap`] pre-configured to use [`Hashed`] keys and [`PassHash`] passthrough hashing.
/// Iteration order only depends on the order of insertions and deletions.
pub type PreHashMap<K, V> = hashbrown::HashMap<Hashed<K>, V, PassHash>;
/// Extension methods intended to add functionality to [`PreHashMap`].
pub trait PreHashMapExt<K, V> {
/// Tries to get or insert the value for the given `key` using the pre-computed hash first.
/// If the [`PreHashMap`] does not already contain the `key`, it will clone it and insert
/// the value returned by `func`.
fn get_or_insert_with<F: FnOnce() -> V>(&mut self, key: &Hashed<K>, func: F) -> &mut V;
}
impl<K: Hash + Eq + PartialEq + Clone, V> PreHashMapExt<K, V> for PreHashMap<K, V> {
#[inline]
fn get_or_insert_with<F: FnOnce() -> V>(&mut self, key: &Hashed<K>, func: F) -> &mut V {
let entry = self
.raw_entry_mut()
.from_key_hashed_nocheck(key.hash(), key);
match entry {
RawEntryMut::Occupied(entry) => entry.into_mut(),
RawEntryMut::Vacant(entry) => {
let (_, value) = entry.insert_hashed_nocheck(key.hash(), key.clone(), func());
value
}
}
}
}
/// A [`BuildHasher`] that results in a [`EntityHasher`].
#[derive(Default, Clone)]
pub struct EntityHash;
impl BuildHasher for EntityHash {
type Hasher = EntityHasher;
fn build_hasher(&self) -> Self::Hasher {
EntityHasher::default()
}
}
/// A very fast hash that is only designed to work on generational indices
/// like `Entity`. It will panic if attempting to hash a type containing
/// non-u64 fields.
///
/// This is heavily optimized for typical cases, where you have mostly live
/// entities, and works particularly well for contiguous indices.
///
/// If you have an unusual case -- say all your indices are multiples of 256
/// or most of the entities are dead generations -- then you might want also to
/// try [`AHasher`] for a slower hash computation but fewer lookup conflicts.
#[derive(Debug, Default)]
pub struct EntityHasher {
hash: u64,
}
impl Hasher for EntityHasher {
#[inline]
fn finish(&self) -> u64 {
self.hash
}
fn write(&mut self, _bytes: &[u8]) {
panic!("can only hash u64 using EntityHasher");
}
#[inline]
fn write_u64(&mut self, bits: u64) {
// SwissTable (and thus `hashbrown`) cares about two things from the hash:
// - H1: low bits (masked by `2ⁿ-1`) to pick the slot in which to store the item
// - H2: high 7 bits are used to SIMD optimize hash collision probing
// For more see <https://abseil.io/about/design/swisstables#metadata-layout>
// This hash function assumes that the entity ids are still well-distributed,
// so for H1 leaves the entity id alone in the low bits so that id locality
// will also give memory locality for things spawned together.
// For H2, take advantage of the fact that while multiplication doesn't
// spread entropy to the low bits, it's incredibly good at spreading it
// upward, which is exactly where we need it the most.
// While this does include the generation in the output, it doesn't do so
// *usefully*. H1 won't care until you have over 3 billion entities in
// the table, and H2 won't care until something hits generation 33 million.
// Thus the comment suggesting that this is best for live entities,
// where there won't be generation conflicts where it would matter.
// The high 32 bits of this are ⅟φ for Fibonacci hashing. That works
// particularly well for hashing for the same reason as described in
// <https://extremelearning.com.au/unreasonable-effectiveness-of-quasirandom-sequences/>
// It loses no information because it has a modular inverse.
// (Specifically, `0x144c_bc89_u32 * 0x9e37_79b9_u32 == 1`.)
//
// The low 32 bits make that part of the just product a pass-through.
const UPPER_PHI: u64 = 0x9e37_79b9_0000_0001;
// This is `(MAGIC * index + generation) << 32 + index`, in a single instruction.
self.hash = bits.wrapping_mul(UPPER_PHI);
}
}
/// A [`HashMap`] pre-configured to use [`EntityHash`] hashing.
/// Iteration order only depends on the order of insertions and deletions.
pub type EntityHashMap<K, V> = hashbrown::HashMap<K, V, EntityHash>;
/// A [`HashSet`] pre-configured to use [`EntityHash`] hashing.
/// Iteration order only depends on the order of insertions and deletions.
pub type EntityHashSet<T> = hashbrown::HashSet<T, EntityHash>;
/// A specialized hashmap type with Key of [`TypeId`]
/// Iteration order only depends on the order of insertions and deletions.
pub type TypeIdMap<V> = hashbrown::HashMap<TypeId, V, NoOpHash>;
/// [`BuildHasher`] for types that already contain a high-quality hash.
#[derive(Clone, Default)]
pub struct NoOpHash;
impl BuildHasher for NoOpHash {
type Hasher = NoOpHasher;
fn build_hasher(&self) -> Self::Hasher {
NoOpHasher(0)
}
}
#[doc(hidden)]
pub struct NoOpHasher(u64);
// This is for types that already contain a high-quality hash and want to skip
// re-hashing that hash.
impl std::hash::Hasher for NoOpHasher {
fn finish(&self) -> u64 {
self.0
}
fn write(&mut self, bytes: &[u8]) {
// This should never be called by consumers. Prefer to call `write_u64` instead.
// Don't break applications (slower fallback, just check in test):
self.0 = bytes.iter().fold(self.0, |hash, b| {
hash.rotate_left(8).wrapping_add(*b as u64)
});
}
#[inline]
fn write_u64(&mut self, i: u64) {
self.0 = i;
}
}
/// A type which calls a function when dropped.
/// This can be used to ensure that cleanup code is run even in case of a panic.
///
/// Note that this only works for panics that [unwind](https://doc.rust-lang.org/nomicon/unwinding.html)
/// -- any code within `OnDrop` will be skipped if a panic does not unwind.
/// In most cases, this will just work.
///
/// # Examples
///
/// ```
/// # use bevy_utils::OnDrop;
/// # fn test_panic(do_panic: bool, log: impl FnOnce(&str)) {
/// // This will print a message when the variable `_catch` gets dropped,
/// // even if a panic occurs before we reach the end of this scope.
/// // This is similar to a `try ... catch` block in languages such as C++.
/// let _catch = OnDrop::new(|| log("Oops, a panic occurred and this function didn't complete!"));
///
/// // Some code that may panic...
/// // ...
/// # if do_panic { panic!() }
///
/// // Make sure the message only gets printed if a panic occurs.
/// // If we remove this line, then the message will be printed regardless of whether a panic occurs
/// // -- similar to a `try ... finally` block.
/// std::mem::forget(_catch);
/// # }
/// #
/// # test_panic(false, |_| unreachable!());
/// # let mut did_log = false;
/// # std::panic::catch_unwind(std::panic::AssertUnwindSafe(|| {
/// # test_panic(true, |_| did_log = true);
/// # }));
/// # assert!(did_log);
/// ```
pub struct OnDrop<F: FnOnce()> {
callback: ManuallyDrop<F>,
}
impl<F: FnOnce()> OnDrop<F> {
/// Returns an object that will invoke the specified callback when dropped.
pub fn new(callback: F) -> Self {
Self {
callback: ManuallyDrop::new(callback),
}
}
}
impl<F: FnOnce()> Drop for OnDrop<F> {
fn drop(&mut self) {
// SAFETY: We may move out of `self`, since this instance can never be observed after it's dropped.
let callback = unsafe { ManuallyDrop::take(&mut self.callback) };
callback();
}
}
/// Calls the [`tracing::info!`] macro on a value.
pub fn info<T: Debug>(data: T) {
tracing::info!("{:?}", data);
}
/// Calls the [`tracing::debug!`] macro on a value.
pub fn dbg<T: Debug>(data: T) {
tracing::debug!("{:?}", data);
}
/// Processes a [`Result`] by calling the [`tracing::warn!`] macro in case of an [`Err`] value.
pub fn warn<E: Debug>(result: Result<(), E>) {
if let Err(warn) = result {
tracing::warn!("{:?}", warn);
}
}
/// Processes a [`Result`] by calling the [`tracing::error!`] macro in case of an [`Err`] value.
pub fn error<E: Debug>(result: Result<(), E>) {
if let Err(error) = result {
tracing::error!("{:?}", error);
}
}
/// Like [`tracing::trace`], but conditional on cargo feature `detailed_trace`.
#[macro_export]
macro_rules! detailed_trace {
($($tts:tt)*) => {
if cfg!(detailed_trace) {
bevy_utils::tracing::trace!($($tts)*);
}
}
}
#[cfg(test)]
mod tests {
use super::*;
use static_assertions::assert_impl_all;
// Check that the HashMaps are Clone if the key/values are Clone
assert_impl_all!(PreHashMap::<u64, usize>: Clone);
#[test]
fn fast_typeid_hash() {
struct Hasher;
impl std::hash::Hasher for Hasher {
fn finish(&self) -> u64 {
0
}
fn write(&mut self, _: &[u8]) {
panic!("Hashing of std::any::TypeId changed");
}
fn write_u64(&mut self, _: u64) {}
}
std::hash::Hash::hash(&TypeId::of::<()>(), &mut Hasher);
}
#[test]
fn stable_hash_within_same_program_execution() {
let mut map_1 = HashMap::new();
let mut map_2 = HashMap::new();
for i in 1..10 {
map_1.insert(i, i);
map_2.insert(i, i);
}
assert_eq!(
map_1.iter().collect::<Vec<_>>(),
map_2.iter().collect::<Vec<_>>()
);
}
}