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//! Traits used by label implementations
use std::{
any::Any,
hash::{Hash, Hasher},
};
/// An object safe version of [`Eq`]. This trait is automatically implemented
/// for any `'static` type that implements `Eq`.
pub trait DynEq: Any {
/// Casts the type to `dyn Any`.
fn as_any(&self) -> &dyn Any;
/// This method tests for `self` and `other` values to be equal.
///
/// Implementers should avoid returning `true` when the underlying types are
/// not the same.
fn dyn_eq(&self, other: &dyn DynEq) -> bool;
}
impl<T> DynEq for T
where
T: Any + Eq,
{
fn as_any(&self) -> &dyn Any {
self
}
fn dyn_eq(&self, other: &dyn DynEq) -> bool {
if let Some(other) = other.as_any().downcast_ref::<T>() {
return self == other;
}
false
}
}
/// An object safe version of [`Hash`]. This trait is automatically implemented
/// for any `'static` type that implements `Hash`.
pub trait DynHash: DynEq {
/// Casts the type to `dyn Any`.
fn as_dyn_eq(&self) -> &dyn DynEq;
/// Feeds this value into the given [`Hasher`].
fn dyn_hash(&self, state: &mut dyn Hasher);
}
impl<T> DynHash for T
where
T: DynEq + Hash,
{
fn as_dyn_eq(&self) -> &dyn DynEq {
self
}
fn dyn_hash(&self, mut state: &mut dyn Hasher) {
T::hash(self, &mut state);
self.type_id().hash(&mut state);
}
}
/// Macro to define a new label trait
///
/// # Example
///
/// ```
/// # use bevy_ecs::define_label;
/// define_label!(
/// /// Documentation of label trait
/// MyNewLabelTrait,
/// MY_NEW_LABEL_TRAIT_INTERNER
/// );
///
/// define_label!(
/// /// Documentation of another label trait
/// MyNewExtendedLabelTrait,
/// MY_NEW_EXTENDED_LABEL_TRAIT_INTERNER,
/// extra_methods: {
/// // Extra methods for the trait can be defined here
/// fn additional_method(&self) -> i32;
/// },
/// extra_methods_impl: {
/// // Implementation of the extra methods for Interned<dyn MyNewExtendedLabelTrait>
/// fn additional_method(&self) -> i32 {
/// 0
/// }
/// }
/// );
/// ```
#[macro_export]
macro_rules! define_label {
(
$(#[$label_attr:meta])*
$label_trait_name:ident,
$interner_name:ident
) => {
$crate::define_label!(
$(#[$label_attr])*
$label_trait_name,
$interner_name,
extra_methods: {},
extra_methods_impl: {}
);
};
(
$(#[$label_attr:meta])*
$label_trait_name:ident,
$interner_name:ident,
extra_methods: { $($trait_extra_methods:tt)* },
extra_methods_impl: { $($interned_extra_methods_impl:tt)* }
) => {
$(#[$label_attr])*
pub trait $label_trait_name: 'static + Send + Sync + ::std::fmt::Debug {
$($trait_extra_methods)*
/// Clones this `
#[doc = stringify!($label_trait_name)]
///`.
fn dyn_clone(&self) -> ::std::boxed::Box<dyn $label_trait_name>;
/// Casts this value to a form where it can be compared with other type-erased values.
fn as_dyn_eq(&self) -> &dyn $crate::label::DynEq;
/// Feeds this value into the given [`Hasher`].
fn dyn_hash(&self, state: &mut dyn ::std::hash::Hasher);
/// Returns an [`Interned`] value corresponding to `self`.
fn intern(&self) -> $crate::intern::Interned<dyn $label_trait_name>
where Self: Sized {
$interner_name.intern(self)
}
}
impl $label_trait_name for $crate::intern::Interned<dyn $label_trait_name> {
$($interned_extra_methods_impl)*
fn dyn_clone(&self) -> ::std::boxed::Box<dyn $label_trait_name> {
(**self).dyn_clone()
}
/// Casts this value to a form where it can be compared with other type-erased values.
fn as_dyn_eq(&self) -> &dyn $crate::label::DynEq {
(**self).as_dyn_eq()
}
fn dyn_hash(&self, state: &mut dyn ::std::hash::Hasher) {
(**self).dyn_hash(state);
}
fn intern(&self) -> Self {
*self
}
}
impl PartialEq for dyn $label_trait_name {
fn eq(&self, other: &Self) -> bool {
self.as_dyn_eq().dyn_eq(other.as_dyn_eq())
}
}
impl Eq for dyn $label_trait_name {}
impl ::std::hash::Hash for dyn $label_trait_name {
fn hash<H: ::std::hash::Hasher>(&self, state: &mut H) {
self.dyn_hash(state);
}
}
impl $crate::intern::Internable for dyn $label_trait_name {
fn leak(&self) -> &'static Self {
Box::leak(self.dyn_clone())
}
fn ref_eq(&self, other: &Self) -> bool {
use ::std::ptr;
// Test that both the type id and pointer address are equivalent.
self.as_dyn_eq().type_id() == other.as_dyn_eq().type_id()
&& ptr::addr_eq(ptr::from_ref::<Self>(self), ptr::from_ref::<Self>(other))
}
fn ref_hash<H: ::std::hash::Hasher>(&self, state: &mut H) {
use ::std::{hash::Hash, ptr};
// Hash the type id...
self.as_dyn_eq().type_id().hash(state);
// ...and the pointer address.
// Cast to a unit `()` first to discard any pointer metadata.
ptr::from_ref::<Self>(self).cast::<()>().hash(state);
}
}
static $interner_name: $crate::intern::Interner<dyn $label_trait_name> =
$crate::intern::Interner::new();
};
}