Init Commit

Monorepo for Rust support of VA416XX family of radiation hardened MCUs

va416xx-hal/src/typelevel.rs

@@ -0,0 +1,155 @@
+//! Module supporting type-level programming
+//!
+//! This module is identical to the
+//! [atsamd typelevel](https://docs.rs/atsamd-hal/latest/atsamd_hal/typelevel/index.html).
+
+use core::ops::{Add, Sub};
+
+use typenum::{Add1, Bit, Sub1, UInt, Unsigned, B1, U0};
+
+mod private {
+    /// Super trait used to mark traits with an exhaustive set of
+    /// implementations
+    pub trait Sealed {}
+
+    impl Sealed for u8 {}
+    impl Sealed for i8 {}
+    impl Sealed for u16 {}
+    impl Sealed for i16 {}
+    impl Sealed for u32 {}
+    impl Sealed for i32 {}
+    impl Sealed for f32 {}
+
+    /// Mapping from an instance of a countable type to its successor
+    pub trait Increment {
+        /// Successor type of `Self`
+        type Inc;
+        /// Consume an instance of `Self` and return its successor
+        fn inc(self) -> Self::Inc;
+    }
+
+    /// Mapping from an instance of a countable type to its predecessor
+    pub trait Decrement {
+        /// Predecessor type of `Self`
+        type Dec;
+        /// Consume an instance of `Self` and return its predecessor
+        fn dec(self) -> Self::Dec;
+    }
+}
+
+pub(crate) use private::Decrement as PrivateDecrement;
+pub(crate) use private::Increment as PrivateIncrement;
+pub(crate) use private::Sealed;
+
+/// Type-level version of the [`None`] variant
+#[derive(Default)]
+pub struct NoneT;
+
+impl Sealed for NoneT {}
+
+//==============================================================================
+// Is
+//==============================================================================
+
+/// Marker trait for type identity
+///
+/// This trait is used as part of the [`AnyKind`] trait pattern. It represents
+/// the concept of type identity, because all implementors have
+/// `<Self as Is>::Type == Self`. When used as a trait bound with a specific
+/// type, it guarantees that the corresponding type parameter is exactly the
+/// specific type. Stated differently, it guarantees that `T == Specific` in
+/// the following example.
+///
+/// ```ignore
+/// where T: Is<Type = Specific>
+/// ```
+///
+/// Moreover, the super traits guarantee that any instance of or reference to a
+/// type `T` can be converted into the `Specific` type.
+///
+/// ```ignore
+/// fn example<T>(mut any: T)
+/// where
+///     T: Is<Type = Specific>,
+/// {
+///     let specific_mut: &mut Specific = any.as_mut();
+///     let specific_ref: &Specific = any.as_ref();
+///     let specific: Specific = any.into();
+/// }
+/// ```
+///
+/// [`AnyKind`]: #anykind-trait-pattern
+pub trait Is
+where
+    Self: Sealed,
+    Self: From<IsType<Self>>,
+    Self: Into<IsType<Self>>,
+    Self: AsRef<IsType<Self>>,
+    Self: AsMut<IsType<Self>>,
+{
+    type Type;
+}
+
+/// Type alias for [`Is::Type`]
+pub type IsType<T> = <T as Is>::Type;
+
+impl<T> Is for T
+where
+    T: Sealed + AsRef<T> + AsMut<T>,
+{
+    type Type = T;
+}
+
+//==============================================================================
+// Counting
+//==============================================================================
+
+/// Implement `Sealed` for [`U0`]
+impl Sealed for U0 {}
+
+/// Implement `Sealed` for all type-level, [`Unsigned`] integers *except* [`U0`]
+impl<U: Unsigned, B: Bit> Sealed for UInt<U, B> {}
+
+/// Trait mapping each countable type to its successor
+///
+/// This trait maps each countable type to its corresponding successor type. The
+/// actual implementation of this trait is contained within `PrivateIncrement`.
+/// Access to `PrivateIncrement` is restricted, so that safe HAL APIs can be
+/// built with it.
+pub trait Increment: PrivateIncrement {}
+
+impl<T: PrivateIncrement> Increment for T {}
+
+/// Trait mapping each countable type to its predecessor
+///
+/// This trait maps each countable type to its corresponding predecessor type.
+/// The actual implementation of this trait is contained within
+/// `PrivateDecrement`. Access to `PrivateDecrement` is restricted, so that safe
+/// HAL APIs can be built with it.
+pub trait Decrement: PrivateDecrement {}
+
+impl<T: PrivateDecrement> Decrement for T {}
+
+impl<N> PrivateIncrement for N
+where
+    N: Unsigned + Add<B1>,
+    Add1<N>: Unsigned,
+{
+    type Inc = Add1<N>;
+    #[inline]
+    fn inc(self) -> Self::Inc {
+        Self::Inc::default()
+    }
+}
+
+impl<N> PrivateDecrement for N
+where
+    N: Unsigned + Sub<B1>,
+    Sub1<N>: Unsigned,
+{
+    type Dec = Sub1<N>;
+    #[inline]
+    fn dec(self) -> Self::Dec {
+        Self::Dec::default()
+    }
+}