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Diffstat (limited to 'src/libs/intertrait/mod.rs')
| -rw-r--r-- | src/libs/intertrait/mod.rs | 282 |
1 files changed, 0 insertions, 282 deletions
diff --git a/src/libs/intertrait/mod.rs b/src/libs/intertrait/mod.rs deleted file mode 100644 index d2ace67..0000000 --- a/src/libs/intertrait/mod.rs +++ /dev/null @@ -1,282 +0,0 @@ -//! A library providing direct casting among trait objects implemented by a type. -//! -//! In Rust, an object of a sub-trait of [`Any`] can be downcast to a concrete type -//! at runtime if the type is known. But no direct casting between two trait objects -//! (i.e. without involving the concrete type of the backing value) is possible -//! (even no coercion from a trait object to that of its super-trait yet). -//! -//! With this crate, any trait object with [`CastFrom`] as its super-trait can be cast -//! directly to another trait object implemented by the underlying type if the target -//! traits are registered beforehand with the macros provided by this crate. -//! -//! -//! 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::rc::Rc; -use std::sync::Arc; - -use ahash::AHashMap; -use linkme::distributed_slice; -use once_cell::sync::Lazy; - -pub mod cast; - -pub type BoxedCaster = Box<dyn Any + Send + Sync>; - -/// A distributed slice gathering constructor functions for [`Caster`]s. -/// -/// A constructor function returns `TypeId` of a concrete type involved in the casting -/// and a `Box` of a type or trait backed by a [`Caster`]. -#[distributed_slice] -pub static CASTERS: [fn() -> (TypeId, BoxedCaster)] = [..]; - -/// A `HashMap` mapping `TypeId` of a [`Caster`] to an instance of it. -static CASTER_MAP: Lazy<AHashMap<(TypeId, TypeId), BoxedCaster>> = Lazy::new(|| { - CASTERS - .iter() - .map(|caster_fn| { - let (type_id, caster) = caster_fn(); - - ((type_id, (*caster).type_id()), caster) - }) - .collect() -}); - -type CastBoxFn<Dest> = fn(from: Box<dyn Any>) -> Result<Box<Dest>, CasterError>; - -type CastRcFn<Dest> = fn(from: Rc<dyn Any>) -> Result<Rc<Dest>, CasterError>; - -type CastArcFn<Dest> = - fn(from: Arc<dyn Any + Sync + Send + 'static>) -> Result<Arc<Dest>, CasterError>; - -/// A `Caster` knows how to cast a type or trait to the type or trait `Dest`. Each -/// `Caster` instance is specific to a concrete type. That is, it knows how to cast to -/// single specific type or trait implemented by single specific type. -pub struct Caster<Dest: ?Sized + 'static> -{ - /// Casts a `Box` holding a type or trait object for `Any` to another `Box` holding a - /// type or trait `Dest`. - pub cast_box: CastBoxFn<Dest>, - - /// Casts an `Rc` holding a type or trait for `Any` to another `Rc` holding a type or - /// trait `Dest`. - pub cast_rc: CastRcFn<Dest>, - - /// Casts an `Arc` holding a type or trait for `Any + Sync + Send + 'static` to - /// another `Arc` holding a type or trait for `Dest`. - pub opt_cast_arc: Option<CastArcFn<Dest>>, -} - -impl<Dest: ?Sized + 'static> Caster<Dest> -{ - pub fn new(cast_box: CastBoxFn<Dest>, cast_rc: CastRcFn<Dest>) -> Caster<Dest> - { - Caster::<Dest> { - cast_box, - cast_rc, - opt_cast_arc: None, - } - } - - #[allow(clippy::similar_names)] - pub fn new_sync( - cast_box: CastBoxFn<Dest>, - cast_rc: CastRcFn<Dest>, - cast_arc: CastArcFn<Dest>, - ) -> Caster<Dest> - { - Caster::<Dest> { - cast_box, - cast_rc, - opt_cast_arc: Some(cast_arc), - } - } -} - -#[derive(Debug, thiserror::Error)] -pub enum CasterError -{ - #[error("Failed to cast Box")] - CastBoxFailed, - - #[error("Failed to cast Rc")] - CastRcFailed, - - #[error("Failed to cast Arc")] - CastArcFailed, -} - -/// Returns a `Caster<Dest>` from a concrete type with the id `type_id` to a type or trait -/// `Dest`. -fn get_caster<Dest: ?Sized + 'static>( - type_id: TypeId, -) -> Result<&'static Caster<Dest>, GetCasterError> -{ - let any_caster = CASTER_MAP - .get(&(type_id, TypeId::of::<Caster<Dest>>())) - .ok_or(GetCasterError::NotFound)?; - - any_caster - .downcast_ref::<Caster<Dest>>() - .ok_or(GetCasterError::DowncastFailed) -} - -#[derive(Debug, thiserror::Error)] -pub enum GetCasterError -{ - #[error("Caster not found")] - NotFound, - - #[error("Failed to downcast caster")] - DowncastFailed, -} - -/// `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>; -} - -/// `CastFromSync` must be extended by a trait that is `Any + Sync + Send + 'static` -/// and wants to allow for casting into another trait behind references and smart pointers -/// especially including `Arc`. -/// -/// It is used for obtaining a trait object for [`Any + Sync + Send + 'static`] from an -/// object for its sub-trait, and blanket implemented for all `Sized + Sync + Send + -/// 'static` types. -/// -/// # Examples -/// ```ignore -/// trait Source: CastFromSync { -/// ... -/// } -/// ``` -pub trait CastFromSync: CastFrom + Sync + Send + 'static -{ - fn arc_any(self: Arc<Self>) -> Arc<dyn Any + Sync + Send + 'static>; -} - -impl<Source: Sized + Any + 'static> CastFrom for Source -{ - 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<Source: Sized + Sync + Send + 'static> CastFromSync for Source -{ - fn arc_any(self: Arc<Self>) -> Arc<dyn Any + Sync + Send + 'static> - { - 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 - } -} - -impl CastFromSync for dyn Any + Sync + Send + 'static -{ - fn arc_any(self: Arc<Self>) -> Arc<dyn Any + Sync + Send + 'static> - { - self - } -} - -#[cfg(test)] -mod tests -{ - use std::any::TypeId; - use std::fmt::Debug; - - use linkme::distributed_slice; - - use super::*; - use crate::test_utils::subjects; - - #[distributed_slice(super::CASTERS)] - static TEST_CASTER: fn() -> (TypeId, BoxedCaster) = create_test_caster; - - fn create_test_caster() -> (TypeId, BoxedCaster) - { - let type_id = TypeId::of::<subjects::Ninja>(); - - let caster = Box::new(Caster::<dyn Debug> { - cast_box: |from| { - let concrete = from - .downcast::<subjects::Ninja>() - .map_err(|_| CasterError::CastBoxFailed)?; - - Ok(concrete as Box<dyn Debug>) - }, - cast_rc: |from| { - let concrete = from - .downcast::<subjects::Ninja>() - .map_err(|_| CasterError::CastRcFailed)?; - - Ok(concrete as Rc<dyn Debug>) - }, - opt_cast_arc: Some(|from| { - let concrete = from - .downcast::<subjects::Ninja>() - .map_err(|_| CasterError::CastArcFailed)?; - - Ok(concrete as Arc<dyn Debug>) - }), - }); - (type_id, caster) - } -} |