Add index traits

Author: mangelats

src/lib.rs

@@ -168,6 +168,53 @@ pub trait StructOfArray {
     type Type;
 }
 
+
+mod private_soa_indexs {
+    // From [`std::slice::SliceIndex`](https://doc.rust-lang.org/std/slice/trait.SliceIndex.html) code.
+    // Limits the types that may implement the SoA index traits.
+    // It's also helpful to have the exaustive list of all accepted types.
+
+    use ::std::ops;
+
+    pub trait Sealed {}
+
+    impl Sealed for usize {}                        // [a]
+    impl Sealed for ops::Range<usize> {}            // [a..b]
+    impl Sealed for ops::RangeTo<usize> {}          // [..b]
+    impl Sealed for ops::RangeFrom<usize> {}        // [a..]
+    impl Sealed for ops::RangeFull {}               // [..]
+    impl Sealed for ops::RangeInclusive<usize> {}   // [a..=b]
+    impl Sealed for ops::RangeToInclusive<usize> {} // [..=b]
+}
+
+/// Helper trait used for indexing operations.
+/// Inspired by [`std::slice::SliceIndex`](https://doc.rust-lang.org/std/slice/trait.SliceIndex.html).
+pub trait SoaIndex<T>: private_soa_indexs::Sealed {
+    /// The output for the non-mutable functions
+    type RefOutput;
+
+    /// Returns the reference output in this location if in bounds. None otherwise.
+    fn get(self, soa: T) -> Option<Self::RefOutput>;
+    /// Returns the reference output in this location withotu performing any bounds check.
+    unsafe fn get_unchecked(self, soa: T) -> Self::RefOutput;
+    /// Returns the reference output in this location. Panics if it is not in bounds.
+    fn index(self, soa: T) -> Self::RefOutput;
+}
+
+/// Helper trait used for indexing operations returning mutable.
+/// Inspired by [`std::slice::SliceIndex`](https://doc.rust-lang.org/std/slice/trait.SliceIndex.html).
+pub trait SoaMutIndex<T>: private_soa_indexs::Sealed {
+    /// The output for the mutable functions
+    type MutOutput;
+
+    /// Returns the mutable reference output in this location if in bounds. None otherwise.
+    fn get_mut(self, soa: T) -> Option<Self::MutOutput>;
+    /// Returns the mutable reference output in this location withotu performing any bounds check.
+    unsafe fn get_unchecked_mut(self, soa: T) -> Self::MutOutput;
+    /// Returns the mutable reference output in this location. Panics if it is not in bounds.
+    fn index_mut(self, soa: T) -> Self::MutOutput;
+}
+
 /// Create an iterator over multiple fields in a Struct of array style vector.
 ///
 /// This macro takes two main arguments: the array/slice container, and a list