1 files changed, 152 insertions, 0 deletions

diff --git a/crates/arena/src/lib.rs b/crates/arena/src/lib.rs
new file mode 100644
index 000000000..3169aa5b8
--- /dev/null
+++ b/crates/arena/src/lib.rs
@@ -0,0 +1,152 @@
+//! Yet another index-based arena.
+
+use std::{
+    fmt,
+    hash::{Hash, Hasher},
+    iter::FromIterator,
+    marker::PhantomData,
+    ops::{Index, IndexMut},
+};
+
+pub mod map;
+
+#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct RawId(u32);
+
+impl From<RawId> for u32 {
+    fn from(raw: RawId) -> u32 {
+        raw.0
+    }
+}
+
+impl From<u32> for RawId {
+    fn from(id: u32) -> RawId {
+        RawId(id)
+    }
+}
+
+impl fmt::Debug for RawId {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        self.0.fmt(f)
+    }
+}
+
+impl fmt::Display for RawId {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        self.0.fmt(f)
+    }
+}
+
+pub struct Idx<T> {
+    raw: RawId,
+    _ty: PhantomData<fn() -> T>,
+}
+
+impl<T> Clone for Idx<T> {
+    fn clone(&self) -> Self {
+        *self
+    }
+}
+impl<T> Copy for Idx<T> {}
+
+impl<T> PartialEq for Idx<T> {
+    fn eq(&self, other: &Idx<T>) -> bool {
+        self.raw == other.raw
+    }
+}
+impl<T> Eq for Idx<T> {}
+
+impl<T> Hash for Idx<T> {
+    fn hash<H: Hasher>(&self, state: &mut H) {
+        self.raw.hash(state)
+    }
+}
+
+impl<T> fmt::Debug for Idx<T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let mut type_name = std::any::type_name::<T>();
+        if let Some(idx) = type_name.rfind(':') {
+            type_name = &type_name[idx + 1..]
+        }
+        write!(f, "Idx::<{}>({})", type_name, self.raw)
+    }
+}
+
+impl<T> Idx<T> {
+    pub fn from_raw(raw: RawId) -> Self {
+        Idx { raw, _ty: PhantomData }
+    }
+    pub fn into_raw(self) -> RawId {
+        self.raw
+    }
+}
+
+#[derive(Clone, PartialEq, Eq)]
+pub struct Arena<T> {
+    data: Vec<T>,
+}
+
+impl<T: fmt::Debug> fmt::Debug for Arena<T> {
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        fmt.debug_struct("Arena").field("len", &self.len()).field("data", &self.data).finish()
+    }
+}
+
+impl<T> Arena<T> {
+    pub const fn new() -> Arena<T> {
+        Arena { data: Vec::new() }
+    }
+    pub fn clear(&mut self) {
+        self.data.clear();
+    }
+
+    pub fn len(&self) -> usize {
+        self.data.len()
+    }
+    pub fn is_empty(&self) -> bool {
+        self.data.is_empty()
+    }
+    pub fn alloc(&mut self, value: T) -> Idx<T> {
+        let id = RawId(self.data.len() as u32);
+        self.data.push(value);
+        Idx::from_raw(id)
+    }
+    pub fn iter(
+        &self,
+    ) -> impl Iterator<Item = (Idx<T>, &T)> + ExactSizeIterator + DoubleEndedIterator {
+        self.data.iter().enumerate().map(|(idx, value)| (Idx::from_raw(RawId(idx as u32)), value))
+    }
+    pub fn shrink_to_fit(&mut self) {
+        self.data.shrink_to_fit();
+    }
+}
+
+impl<T> Default for Arena<T> {
+    fn default() -> Arena<T> {
+        Arena { data: Vec::new() }
+    }
+}
+
+impl<T> Index<Idx<T>> for Arena<T> {
+    type Output = T;
+    fn index(&self, idx: Idx<T>) -> &T {
+        let idx = idx.into_raw().0 as usize;
+        &self.data[idx]
+    }
+}
+
+impl<T> IndexMut<Idx<T>> for Arena<T> {
+    fn index_mut(&mut self, idx: Idx<T>) -> &mut T {
+        let idx = idx.into_raw().0 as usize;
+        &mut self.data[idx]
+    }
+}
+
+impl<T> FromIterator<T> for Arena<T> {
+    fn from_iter<I>(iter: I) -> Self
+    where
+        I: IntoIterator<Item = T>,
+    {
+        Arena { data: Vec::from_iter(iter) }
+    }
+}