1 files changed, 137 insertions, 0 deletions
diff --git a/src/libs/intertrait/mod.rs b/src/libs/intertrait/mod.rs
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+/**
+ * Originally from Intertrait by CodeChain
+ *
+ * <https://github.com/CodeChain-io/intertrait>
+ * <https://crates.io/crates/intertrait/0.2.2>
+ *
+ * Licensed under either of
+ *
+ * Apache License, Version 2.0 (LICENSE-APACHE or <http://www.apache.org/licenses/LICENSE-2.0>)
+ * MIT license (LICENSE-MIT or <http://opensource.org/licenses/MIT>)
+
+ * at your option.
+*/
+use std::any::{Any, TypeId};
+use std::collections::HashMap;
+use std::rc::Rc;
+use std::sync::Arc;
+
+use linkme::distributed_slice;
+use once_cell::sync::Lazy;
+
+mod hasher;
+
+use hasher::BuildFastHasher;
+
+pub mod cast_box;
+pub mod cast_rc;
+
+pub type BoxedCaster = Box<dyn Any + Send + Sync>;
+
+#[distributed_slice]
+pub static CASTERS: [fn() -> (TypeId, BoxedCaster)] = [..];
+
+static CASTER_MAP: Lazy<HashMap<(TypeId, TypeId), BoxedCaster, BuildFastHasher>> =
+    Lazy::new(|| {
+        CASTERS
+            .iter()
+            .map(|f| {
+                let (type_id, caster) = f();
+                ((type_id, (*caster).type_id()), caster)
+            })
+            .collect()
+    });
+
+pub struct Caster<T: ?Sized + 'static>
+{
+    /// Casts a `Box` holding a trait object for `Any` to another `Box` holding a trait object
+    /// for trait `T`.
+    pub cast_box: fn(from: Box<dyn Any>) -> Box<T>,
+
+    /// Casts an `Rc` holding a trait object for `Any` to another `Rc` holding a trait object
+    /// for trait `T`.
+    pub cast_rc: fn(from: Rc<dyn Any>) -> Rc<T>,
+}
+
+impl<T: ?Sized + 'static> Caster<T>
+{
+    pub fn new(
+        cast_box: fn(from: Box<dyn Any>) -> Box<T>,
+        cast_rc: fn(from: Rc<dyn Any>) -> Rc<T>,
+    ) -> Caster<T>
+    {
+        Caster::<T> { cast_box, cast_rc }
+    }
+}
+
+/// Returns a `Caster<S, T>` from a concrete type `S` to a trait `T` implemented by it.
+fn caster<T: ?Sized + 'static>(type_id: TypeId) -> Option<&'static Caster<T>>
+{
+    CASTER_MAP
+        .get(&(type_id, TypeId::of::<Caster<T>>()))
+        .and_then(|caster| caster.downcast_ref::<Caster<T>>())
+}
+
+/// `CastFrom` must be extended by a trait that wants to allow for casting into another trait.
+///
+/// It is used for obtaining a trait object for [`Any`] from a trait object for its sub-trait,
+/// and blanket implemented for all `Sized + Any + 'static` types.
+///
+/// # Examples
+/// ```ignore
+/// trait Source: CastFrom {
+///     ...
+/// }
+/// ```
+pub trait CastFrom: Any + 'static
+{
+    /// Returns a `Box` of `Any`, which is backed by the type implementing this trait.
+    fn box_any(self: Box<Self>) -> Box<dyn Any>;
+
+    /// Returns an `Rc` of `Any`, which is backed by the type implementing this trait.
+    fn rc_any(self: Rc<Self>) -> Rc<dyn Any>;
+}
+
+pub trait CastFromSync: CastFrom + Sync + Send + 'static
+{
+    fn arc_any(self: Arc<Self>) -> Arc<dyn Any + Sync + Send + 'static>;
+}
+
+impl<T: Sized + Any + 'static> CastFrom for T
+{
+    fn box_any(self: Box<Self>) -> Box<dyn Any>
+    {
+        self
+    }
+
+    fn rc_any(self: Rc<Self>) -> Rc<dyn Any>
+    {
+        self
+    }
+}
+
+impl CastFrom for dyn Any + 'static
+{
+    fn box_any(self: Box<Self>) -> Box<dyn Any>
+    {
+        self
+    }
+
+    fn rc_any(self: Rc<Self>) -> Rc<dyn Any>
+    {
+        self
+    }
+}
+
+impl CastFrom for dyn Any + Sync + Send + 'static
+{
+    fn box_any(self: Box<Self>) -> Box<dyn Any>
+    {
+        self
+    }
+
+    fn rc_any(self: Rc<Self>) -> Rc<dyn Any>
+    {
+        self
+    }
+}