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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`].
///
/// [`Hasher`]: std::hash::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_utils::define_boxed_label;
/// define_boxed_label!(MyNewLabelTrait);
/// ```
#[macro_export]
macro_rules! define_boxed_label {
($label_trait_name:ident) => {
/// A strongly-typed label.
pub trait $label_trait_name: 'static + Send + Sync + ::std::fmt::Debug {
/// Return's the [TypeId] of this label, or the the ID of the
/// wrappped label type for `Box<dyn
#[doc = stringify!($label_trait_name)]
/// >`
///
/// [TypeId]: std::any::TypeId
fn inner_type_id(&self) -> ::std::any::TypeId {
std::any::TypeId::of::<Self>()
}
/// Clones this `
#[doc = stringify!($label_trait_name)]
/// `
fn dyn_clone(&self) -> 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 ::bevy_utils::label::DynEq;
/// Feeds this value into the given [`Hasher`].
///
/// [`Hasher`]: std::hash::Hasher
fn dyn_hash(&self, state: &mut dyn ::std::hash::Hasher);
}
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 ::std::convert::AsRef<dyn $label_trait_name> for dyn $label_trait_name {
#[inline]
fn as_ref(&self) -> &Self {
self
}
}
impl Clone for Box<dyn $label_trait_name> {
fn clone(&self) -> Self {
self.dyn_clone()
}
}
impl $label_trait_name for Box<dyn $label_trait_name> {
fn inner_type_id(&self) -> ::std::any::TypeId {
(**self).inner_type_id()
}
fn dyn_clone(&self) -> Box<dyn $label_trait_name> {
// Be explicit that we want to use the inner value
// to avoid infinite recursion.
(**self).dyn_clone()
}
fn as_dyn_eq(&self) -> &dyn ::bevy_utils::label::DynEq {
(**self).as_dyn_eq()
}
fn dyn_hash(&self, state: &mut dyn ::std::hash::Hasher) {
(**self).dyn_hash(state);
}
}
};
}
/// Macro to define a new label trait
///
/// # Example
///
/// ```
/// # use bevy_utils::define_label;
/// define_label!(
/// /// A class of labels.
/// MyNewLabelTrait,
/// /// Identifies a value that implements `MyNewLabelTrait`.
/// MyNewLabelId,
/// );
/// ```
#[macro_export]
macro_rules! define_label {
(
$(#[$label_attr:meta])*
$label_name:ident,
$(#[$id_attr:meta])*
$id_name:ident $(,)?
) => {
$(#[$id_attr])*
#[derive(Clone, Copy, PartialEq, Eq, Hash)]
pub struct $id_name(::core::any::TypeId, &'static str);
impl ::core::fmt::Debug for $id_name {
fn fmt(&self, f: &mut ::core::fmt::Formatter) -> ::core::fmt::Result {
write!(f, "{}", self.1)
}
}
$(#[$label_attr])*
pub trait $label_name: 'static {
/// Converts this type into an opaque, strongly-typed label.
fn as_label(&self) -> $id_name {
let id = self.type_id();
let label = self.as_str();
$id_name(id, label)
}
/// Returns the [`TypeId`] used to differentiate labels.
fn type_id(&self) -> ::core::any::TypeId {
::core::any::TypeId::of::<Self>()
}
/// Returns the representation of this label as a string literal.
///
/// In cases where you absolutely need a label to be determined at runtime,
/// you can use [`Box::leak`] to get a `'static` reference.
fn as_str(&self) -> &'static str;
}
impl $label_name for $id_name {
fn as_label(&self) -> Self {
*self
}
fn type_id(&self) -> ::core::any::TypeId {
self.0
}
fn as_str(&self) -> &'static str {
self.1
}
}
impl $label_name for &'static str {
fn as_str(&self) -> Self {
self
}
}
};
}