1 files changed, 131 insertions, 0 deletions
diff --git a/ecs/src/util/array_vec.rs b/ecs/src/util/array_vec.rs
new file mode 100644
index 0000000..a37b1f9
--- /dev/null
+++ b/ecs/src/util/array_vec.rs
@@ -0,0 +1,131 @@
+use std::mem::MaybeUninit;
+use std::ops::{Deref, DerefMut};
+
+#[derive(Debug)]
+pub struct ArrayVec<Item, const CAPACITY: usize>
+{
+    items: [MaybeUninit<Item>; CAPACITY],
+    len: usize,
+}
+
+impl<Item, const CAPACITY: usize> ArrayVec<Item, CAPACITY>
+{
+    #[inline]
+    #[must_use]
+    pub fn len(&self) -> usize
+    {
+        self.len
+    }
+
+    #[inline]
+    #[must_use]
+    pub fn is_empty(&self) -> bool
+    {
+        self.len == 0
+    }
+
+    pub fn push(&mut self, item: Item)
+    {
+        assert!(self.len < CAPACITY);
+
+        self.items[self.len].write(item);
+
+        self.len += 1;
+    }
+
+    pub fn insert(&mut self, index: usize, item: Item)
+    {
+        assert!(index <= self.len);
+        assert!(self.len < CAPACITY);
+
+        if index == self.len {
+            self.push(item);
+            return;
+        }
+
+        unsafe {
+            std::ptr::copy(
+                &self.items[index],
+                &mut self.items[index + 1],
+                self.len - index,
+            );
+        }
+
+        self.items[index].write(item);
+
+        self.len += 1;
+    }
+}
+
+impl<Item, const CAPACITY: usize> Extend<Item> for ArrayVec<Item, CAPACITY>
+{
+    fn extend<IntoIter: IntoIterator<Item = Item>>(&mut self, iter: IntoIter)
+    {
+        for item in iter {
+            self.push(item);
+        }
+    }
+}
+
+impl<Item, const CAPACITY: usize> AsRef<[Item]> for ArrayVec<Item, CAPACITY>
+{
+    fn as_ref(&self) -> &[Item]
+    {
+        let ptr = &raw const self.items[..self.len];
+
+        unsafe { &*(ptr as *const [Item]) }
+    }
+}
+
+impl<Item, const CAPACITY: usize> AsMut<[Item]> for ArrayVec<Item, CAPACITY>
+{
+    fn as_mut(&mut self) -> &mut [Item]
+    {
+        let ptr = &raw mut self.items[..self.len];
+
+        unsafe { &mut *(ptr as *mut [Item]) }
+    }
+}
+
+impl<Item, const CAPACITY: usize> Deref for ArrayVec<Item, CAPACITY>
+{
+    type Target = [Item];
+
+    fn deref(&self) -> &Self::Target
+    {
+        self.as_ref()
+    }
+}
+
+impl<Item, const CAPACITY: usize> DerefMut for ArrayVec<Item, CAPACITY>
+{
+    fn deref_mut(&mut self) -> &mut Self::Target
+    {
+        self.as_mut()
+    }
+}
+
+impl<Item, const CAPACITY: usize> Default for ArrayVec<Item, CAPACITY>
+{
+    fn default() -> Self
+    {
+        Self {
+            items: [const { MaybeUninit::uninit() }; CAPACITY],
+            len: 0,
+        }
+    }
+}
+
+impl<Item, const CAPACITY: usize> Drop for ArrayVec<Item, CAPACITY>
+{
+    fn drop(&mut self)
+    {
+        for item in &mut self.items[..self.len] {
+            // SAFETY: The items from index 0 to the length index will always be
+            // initialized and satisfy all the invariants of the Item type.
+            unsafe {
+                item.assume_init_drop();
+            }
+        }
+    }
+}