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//! Helpers for working with Bevy reflection.
use crate::TypeInfo;
use bevy_utils::{FixedState, NoOpHash, TypeIdMap};
use std::{
any::{Any, TypeId},
hash::BuildHasher,
sync::{OnceLock, PoisonError, RwLock},
};
/// A type that can be stored in a ([`Non`])[`GenericTypeCell`].
///
/// [`Non`]: NonGenericTypeCell
pub trait TypedProperty: sealed::Sealed {
type Stored: 'static;
}
/// Used to store a [`String`] in a [`GenericTypePathCell`] as part of a [`TypePath`] implementation.
///
/// [`TypePath`]: crate::TypePath
pub struct TypePathComponent;
mod sealed {
use super::{TypeInfo, TypePathComponent, TypedProperty};
pub trait Sealed {}
impl Sealed for TypeInfo {}
impl Sealed for TypePathComponent {}
impl TypedProperty for TypeInfo {
type Stored = Self;
}
impl TypedProperty for TypePathComponent {
type Stored = String;
}
}
/// A container for [`TypeInfo`] over non-generic types, allowing instances to be stored statically.
///
/// This is specifically meant for use with _non_-generic types. If your type _is_ generic,
/// then use [`GenericTypeCell`] instead. Otherwise, it will not take into account all
/// monomorphizations of your type.
///
/// Non-generic [`TypePath`]s should be trivially generated with string literals and [`concat!`].
///
/// ## Example
///
/// ```
/// # use std::any::Any;
/// # use bevy_reflect::{DynamicTypePath, NamedField, Reflect, ReflectMut, ReflectOwned, ReflectRef, StructInfo, Typed, TypeInfo, TypePath, ApplyError};
/// use bevy_reflect::utility::NonGenericTypeInfoCell;
///
/// struct Foo {
/// bar: i32
/// }
///
/// impl Typed for Foo {
/// fn type_info() -> &'static TypeInfo {
/// static CELL: NonGenericTypeInfoCell = NonGenericTypeInfoCell::new();
/// CELL.get_or_set(|| {
/// let fields = [NamedField::new::<i32>("bar")];
/// let info = StructInfo::new::<Self>(&fields);
/// TypeInfo::Struct(info)
/// })
/// }
/// }
/// # impl TypePath for Foo {
/// # fn type_path() -> &'static str { todo!() }
/// # fn short_type_path() -> &'static str { todo!() }
/// # }
/// # impl Reflect for Foo {
/// # fn get_represented_type_info(&self) -> Option<&'static TypeInfo> { todo!() }
/// # fn into_any(self: Box<Self>) -> Box<dyn Any> { todo!() }
/// # fn as_any(&self) -> &dyn Any { todo!() }
/// # fn as_any_mut(&mut self) -> &mut dyn Any { todo!() }
/// # fn into_reflect(self: Box<Self>) -> Box<dyn Reflect> { todo!() }
/// # fn as_reflect(&self) -> &dyn Reflect { todo!() }
/// # fn as_reflect_mut(&mut self) -> &mut dyn Reflect { todo!() }
/// # fn try_apply(&mut self, value: &dyn Reflect) -> Result<(), ApplyError> { todo!() }
/// # fn set(&mut self, value: Box<dyn Reflect>) -> Result<(), Box<dyn Reflect>> { todo!() }
/// # fn reflect_ref(&self) -> ReflectRef { todo!() }
/// # fn reflect_mut(&mut self) -> ReflectMut { todo!() }
/// # fn reflect_owned(self: Box<Self>) -> ReflectOwned { todo!() }
/// # fn clone_value(&self) -> Box<dyn Reflect> { todo!() }
/// # }
/// ```
///
/// [`TypePath`]: crate::TypePath
pub struct NonGenericTypeCell<T: TypedProperty>(OnceLock<T::Stored>);
/// See [`NonGenericTypeCell`].
pub type NonGenericTypeInfoCell = NonGenericTypeCell<TypeInfo>;
impl<T: TypedProperty> NonGenericTypeCell<T> {
/// Initialize a [`NonGenericTypeCell`] for non-generic types.
pub const fn new() -> Self {
Self(OnceLock::new())
}
/// Returns a reference to the [`TypedProperty`] stored in the cell.
///
/// If there is no entry found, a new one will be generated from the given function.
pub fn get_or_set<F>(&self, f: F) -> &T::Stored
where
F: FnOnce() -> T::Stored,
{
self.0.get_or_init(f)
}
}
impl<T: TypedProperty> Default for NonGenericTypeCell<T> {
fn default() -> Self {
Self::new()
}
}
/// A container for [`TypedProperty`] over generic types, allowing instances to be stored statically.
///
/// This is specifically meant for use with generic types. If your type isn't generic,
/// then use [`NonGenericTypeCell`] instead as it should be much more performant.
///
/// `#[derive(TypePath)]` and [`impl_type_path`] should always be used over [`GenericTypePathCell`]
/// where possible.
///
/// ## Examples
///
/// Implementing [`TypeInfo`] with generics.
///
/// ```
/// # use std::any::Any;
/// # use bevy_reflect::{DynamicTypePath, Reflect, ReflectMut, ReflectOwned, ReflectRef, TupleStructInfo, Typed, TypeInfo, TypePath, UnnamedField, ApplyError};
/// use bevy_reflect::utility::GenericTypeInfoCell;
///
/// struct Foo<T>(T);
///
/// impl<T: Reflect + TypePath> Typed for Foo<T> {
/// fn type_info() -> &'static TypeInfo {
/// static CELL: GenericTypeInfoCell = GenericTypeInfoCell::new();
/// CELL.get_or_insert::<Self, _>(|| {
/// let fields = [UnnamedField::new::<T>(0)];
/// let info = TupleStructInfo::new::<Self>(&fields);
/// TypeInfo::TupleStruct(info)
/// })
/// }
/// }
/// # impl<T: TypePath> TypePath for Foo<T> {
/// # fn type_path() -> &'static str { todo!() }
/// # fn short_type_path() -> &'static str { todo!() }
/// # }
/// # impl<T: Reflect + TypePath> Reflect for Foo<T> {
/// # fn get_represented_type_info(&self) -> Option<&'static TypeInfo> { todo!() }
/// # fn into_any(self: Box<Self>) -> Box<dyn Any> { todo!() }
/// # fn as_any(&self) -> &dyn Any { todo!() }
/// # fn as_any_mut(&mut self) -> &mut dyn Any { todo!() }
/// # fn into_reflect(self: Box<Self>) -> Box<dyn Reflect> { todo!() }
/// # fn as_reflect(&self) -> &dyn Reflect { todo!() }
/// # fn as_reflect_mut(&mut self) -> &mut dyn Reflect { todo!() }
/// # fn try_apply(&mut self, value: &dyn Reflect) -> Result<(), ApplyError> { todo!() }
/// # fn set(&mut self, value: Box<dyn Reflect>) -> Result<(), Box<dyn Reflect>> { todo!() }
/// # fn reflect_ref(&self) -> ReflectRef { todo!() }
/// # fn reflect_mut(&mut self) -> ReflectMut { todo!() }
/// # fn reflect_owned(self: Box<Self>) -> ReflectOwned { todo!() }
/// # fn clone_value(&self) -> Box<dyn Reflect> { todo!() }
/// # }
/// ```
///
/// Implementing [`TypePath`] with generics.
///
/// ```
/// # use std::any::Any;
/// # use bevy_reflect::TypePath;
/// use bevy_reflect::utility::GenericTypePathCell;
///
/// struct Foo<T>(T);
///
/// impl<T: TypePath> TypePath for Foo<T> {
/// fn type_path() -> &'static str {
/// static CELL: GenericTypePathCell = GenericTypePathCell::new();
/// CELL.get_or_insert::<Self, _>(|| format!("my_crate::foo::Foo<{}>", T::type_path()))
/// }
///
/// fn short_type_path() -> &'static str {
/// static CELL: GenericTypePathCell = GenericTypePathCell::new();
/// CELL.get_or_insert::<Self, _>(|| format!("Foo<{}>", T::short_type_path()))
/// }
///
/// fn type_ident() -> Option<&'static str> {
/// Some("Foo")
/// }
///
/// fn module_path() -> Option<&'static str> {
/// Some("my_crate::foo")
/// }
///
/// fn crate_name() -> Option<&'static str> {
/// Some("my_crate")
/// }
/// }
/// ```
/// [`impl_type_path`]: crate::impl_type_path
/// [`TypePath`]: crate::TypePath
pub struct GenericTypeCell<T: TypedProperty>(RwLock<TypeIdMap<&'static T::Stored>>);
/// See [`GenericTypeCell`].
pub type GenericTypeInfoCell = GenericTypeCell<TypeInfo>;
/// See [`GenericTypeCell`].
pub type GenericTypePathCell = GenericTypeCell<TypePathComponent>;
impl<T: TypedProperty> GenericTypeCell<T> {
/// Initialize a [`GenericTypeCell`] for generic types.
pub const fn new() -> Self {
Self(RwLock::new(TypeIdMap::with_hasher(NoOpHash)))
}
/// Returns a reference to the [`TypedProperty`] stored in the cell.
///
/// This method will then return the correct [`TypedProperty`] reference for the given type `T`.
/// If there is no entry found, a new one will be generated from the given function.
pub fn get_or_insert<G, F>(&self, f: F) -> &T::Stored
where
G: Any + ?Sized,
F: FnOnce() -> T::Stored,
{
let type_id = TypeId::of::<G>();
// Put in a separate scope, so `mapping` is dropped before `f`,
// since `f` might want to call `get_or_insert` recursively
// and we don't want a deadlock!
{
let mapping = self.0.read().unwrap_or_else(PoisonError::into_inner);
if let Some(info) = mapping.get(&type_id) {
return info;
}
}
let value = f();
let mut mapping = self.0.write().unwrap_or_else(PoisonError::into_inner);
mapping
.entry(type_id)
.insert({
// We leak here in order to obtain a `&'static` reference.
// Otherwise, we won't be able to return a reference due to the `RwLock`.
// This should be okay, though, since we expect it to remain statically
// available over the course of the application.
Box::leak(Box::new(value))
})
.get()
}
}
impl<T: TypedProperty> Default for GenericTypeCell<T> {
fn default() -> Self {
Self::new()
}
}
/// Deterministic fixed state hasher to be used by implementors of [`Reflect::reflect_hash`].
///
/// Hashes should be deterministic across processes so hashes can be used as
/// checksums for saved scenes, rollback snapshots etc. This function returns
/// such a hasher.
///
/// [`Reflect::reflect_hash`]: crate::Reflect
#[inline]
pub fn reflect_hasher() -> bevy_utils::AHasher {
FixedState.build_hasher()
}