1 files changed, 59 insertions, 0 deletions

diff --git a/src/entity_iterator.rs b/src/entity_iterator.rs
new file mode 100644
index 0000000..58cd2a9
--- /dev/null
+++ b/src/entity_iterator.rs
@@ -0,0 +1,59 @@
+use crate::*;
+
+pub struct EntityIterator<'tok, 'brand, 'arena, T>(Option<(lens_t!(T), lens_t!(T))>);
+
+impl<'tok, 'brand, 'arena, T> Clone for EntityIterator<'tok, 'brand, 'arena, T> {
+    fn clone(&self) -> Self {
+        Self(self.0)
+    }
+}
+
+impl<'tok, 'brand, 'arena, T> Copy for EntityIterator<'tok, 'brand, 'arena, T> {}
+
+impl<'tok, 'brand, 'arena, T: Entity<'brand, 'arena>> EntityIterator<'tok, 'brand, 'arena, T> {
+    pub(crate) fn new(
+        start: Option<ptr_t!(T)>,
+        token: &'tok impl ReflAsRef<GhostToken<'brand>>,
+    ) -> Self {
+        Self(start.map(|s| {
+            let l = Lens::new(s, token);
+            (l, l.prev())
+        }))
+    }
+}
+
+impl<'tok, 'brand, 'arena, T: Entity<'brand, 'arena>> Iterator
+    for EntityIterator<'tok, 'brand, 'arena, T>
+{
+    type Item = lens_t!(T);
+
+    fn next(&mut self) -> Option<Self::Item> {
+        let range = self.0.as_mut()?;
+        let ret = range.0;
+
+        if range.0 == range.1 {
+            self.0 = None;
+        } else {
+            range.0 = range.0.next();
+        }
+
+        Some(ret)
+    }
+}
+
+impl<'tok, 'brand, 'arena, T: Entity<'brand, 'arena>> DoubleEndedIterator
+    for EntityIterator<'tok, 'brand, 'arena, T>
+{
+    fn next_back(&mut self) -> Option<Self::Item> {
+        let range = self.0.as_mut()?;
+        let ret = range.1;
+
+        if range.0 == range.1 {
+            self.0 = None;
+        } else {
+            range.1 = range.1.prev();
+        }
+
+        Some(ret)
+    }
+}