Implement new BeaconStateTypes trait in types

eth2/utils/fixed_len_vec/src/lib.rs

@@ -0,0 +1,111 @@
+use serde_derive::{Deserialize, Serialize};
+use std::marker::PhantomData;
+use std::ops::{Index, IndexMut};
+use std::slice::SliceIndex;
+use typenum::Unsigned;
+
+pub use typenum;
+
+mod impls;
+
+#[derive(Debug, PartialEq, Clone, Serialize, Deserialize)]
+pub struct FixedLenVec<T, N>
+where
+    N: Unsigned,
+{
+    vec: Vec<T>,
+    _phantom: PhantomData<N>,
+}
+
+impl<T: Default, N: Unsigned> From<Vec<T>> for FixedLenVec<T, N> {
+    fn from(mut vec: Vec<T>) -> Self {
+        dbg!(Self::capacity());
+        vec.resize_with(Self::capacity(), Default::default);
+
+        Self {
+            vec,
+            _phantom: PhantomData,
+        }
+    }
+}
+
+impl<T, N: Unsigned> Into<Vec<T>> for FixedLenVec<T, N> {
+    fn into(self) -> Vec<T> {
+        self.vec
+    }
+}
+
+impl<T, N: Unsigned> Default for FixedLenVec<T, N> {
+    fn default() -> Self {
+        Self {
+            vec: Vec::default(),
+            _phantom: PhantomData,
+        }
+    }
+}
+
+impl<T, N: Unsigned> FixedLenVec<T, N> {
+    pub fn capacity() -> usize {
+        N::to_usize()
+    }
+}
+
+impl<T, N: Unsigned, I: SliceIndex<[T]>> Index<I> for FixedLenVec<T, N> {
+    type Output = I::Output;
+
+    #[inline]
+    fn index(&self, index: I) -> &Self::Output {
+        Index::index(&self.vec, index)
+    }
+}
+
+impl<T, N: Unsigned, I: SliceIndex<[T]>> IndexMut<I> for FixedLenVec<T, N> {
+    #[inline]
+    fn index_mut(&mut self, index: I) -> &mut Self::Output {
+        IndexMut::index_mut(&mut self.vec, index)
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    use typenum::*;
+
+    #[test]
+    fn indexing() {
+        let vec = vec![1, 2];
+
+        let mut fixed: FixedLenVec<u64, U8192> = vec.clone().into();
+
+        assert_eq!(fixed[0], 1);
+        assert_eq!(&fixed[0..1], &vec[0..1]);
+        assert_eq!((&fixed[..]).len(), 8192);
+
+        fixed[1] = 3;
+        assert_eq!(fixed[1], 3);
+    }
+
+    #[test]
+    fn length() {
+        let vec = vec![42; 5];
+        let fixed: FixedLenVec<u64, U4> = FixedLenVec::from(vec.clone());
+        assert_eq!(&fixed[..], &vec[0..4]);
+
+        let vec = vec![42; 3];
+        let fixed: FixedLenVec<u64, U4> = FixedLenVec::from(vec.clone());
+        assert_eq!(&fixed[0..3], &vec[..]);
+        assert_eq!(&fixed[..], &vec![42, 42, 42, 0][..]);
+
+        let vec = vec![];
+        let fixed: FixedLenVec<u64, U4> = FixedLenVec::from(vec.clone());
+        assert_eq!(&fixed[..], &vec![0, 0, 0, 0][..]);
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn it_works() {
+        assert_eq!(2 + 2, 4);
+    }
+}