add OffsetDimensionedSlice, with basic indexing operations

crates/cross/src/dim/mod.rs

@@ -1,5 +1,7 @@
 mod dim_slice;
+mod offset_dim_slice;
 pub use dim_slice::{
     DimensionedSlice,
     DimIter,
 };
+pub use offset_dim_slice::OffsetDimensionedSlice;

crates/cross/src/dim/offset_dim_slice.rs

@@ -0,0 +1,80 @@
+use core::ops::{Index, IndexMut};
+
+use crate::dim::DimensionedSlice;
+use crate::vec::Vec3u;
+
+
+pub struct OffsetDimensionedSlice<T> {
+    offset: Vec3u,
+    inner: DimensionedSlice<T>,
+}
+
+impl<T> OffsetDimensionedSlice<T> {
+    pub fn new(offset: Vec3u, dim: Vec3u, items: T) -> Self {
+        Self { offset, inner: DimensionedSlice::new(dim, items) }
+    }
+}
+
+impl<T> Index<Vec3u> for OffsetDimensionedSlice<T>
+where
+    DimensionedSlice<T>: Index<Vec3u>
+{
+    type Output=<DimensionedSlice<T> as Index<Vec3u>>::Output;
+
+    fn index(&self, idx: Vec3u) -> &Self::Output {
+        &self.inner[idx - self.offset]
+    }
+}
+
+impl<T> IndexMut<Vec3u> for OffsetDimensionedSlice<T>
+where
+    DimensionedSlice<T>: IndexMut<Vec3u>
+{
+    fn index_mut(&mut self, idx: Vec3u) -> &mut Self::Output {
+        &mut self.inner[idx - self.offset]
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn offset_dim_slice_index() {
+        let data = [
+            0, 1, 2,
+            3, 4, 5,
+
+            0, 10,20,
+            30,40,50,
+        ];
+        let s = OffsetDimensionedSlice::new(Vec3u::new(1, 2, 3), Vec3u::new(3, 2, 2), &data);
+        assert_eq!(s[Vec3u::new(1, 2, 3)], 0);
+        assert_eq!(s[Vec3u::new(2, 2, 3)], 1);
+        assert_eq!(s[Vec3u::new(2, 3, 3)], 4);
+        assert_eq!(s[Vec3u::new(2, 3, 4)], 40);
+        assert_eq!(s[Vec3u::new(3, 3, 4)], 50);
+    }
+
+    #[test]
+    fn offset_dim_slice_index_mut() {
+        let mut data = [
+            0, 1, 2,
+            3, 4, 5,
+
+            0, 10,20,
+            30,40,50,
+        ];
+        let mut s = OffsetDimensionedSlice::new(Vec3u::new(1, 2, 3), Vec3u::new(3, 2, 2), &mut data);
+        s[Vec3u::new(1, 2, 3)] = 100;
+        s[Vec3u::new(1, 3, 4)] = 300;
+
+        assert_eq!(data, [
+            100,1, 2,
+            3,  4, 5,
+
+            0, 10, 20,
+            300,40,50,
+        ]);
+    }
+}