1 files changed, 131 insertions, 1 deletions
diff --git a/ecs/src/util.rs b/ecs/src/util.rs
index 71021cd..fbd33fa 100644
--- a/ecs/src/util.rs
+++ b/ecs/src/util.rs
@@ -1,8 +1,138 @@
 use std::hash::Hash;
-use std::ops::BitAnd;
+use std::mem::transmute;
+use std::ops::{BitAnd, Deref};
 
 use hashbrown::HashMap;
 
+pub trait VecExt<Item>
+{
+    fn insert_at_partition_point_by_key<Key>(
+        &mut self,
+        item: Item,
+        func: impl FnMut(&Item) -> Key,
+    ) where
+        Key: Ord;
+}
+
+impl<Item> VecExt<Item> for Vec<Item>
+{
+    fn insert_at_partition_point_by_key<Key>(
+        &mut self,
+        item: Item,
+        mut func: impl FnMut(&Item) -> Key,
+    ) where
+        Key: Ord,
+    {
+        let key = func(&item);
+
+        let insert_index = self.partition_point(|other_item| func(other_item) <= key);
+
+        self.insert(insert_index, item);
+    }
+}
+
+pub trait StreamingIterator
+{
+    type Item<'a>
+    where
+        Self: 'a;
+
+    fn streaming_next(&mut self) -> Option<Self::Item<'_>>;
+
+    fn streaming_map<NewItem, Func>(self, func: Func) -> StreamingMap<Self, Func>
+    where
+        Self: Sized,
+        Func: FnMut(Self::Item<'_>) -> NewItem,
+    {
+        StreamingMap { iter: self, func }
+    }
+
+    fn streaming_find<'this, Predicate>(
+        &'this mut self,
+        mut predicate: Predicate,
+    ) -> Option<Self::Item<'this>>
+    where
+        Self: Sized,
+        Predicate: FnMut(&Self::Item<'this>) -> bool,
+    {
+        while let Some(item) =
+            unsafe { transmute::<_, Option<Self::Item<'_>>>(self.streaming_next()) }
+        {
+            if predicate(&item) {
+                return Some(item);
+            }
+        }
+
+        None
+    }
+}
+
+pub struct StreamingMap<Iter, Func>
+{
+    iter: Iter,
+    func: Func,
+}
+
+impl<Iter, Func, Item> StreamingIterator for StreamingMap<Iter, Func>
+where
+    Iter: StreamingIterator,
+    Func: FnMut(Iter::Item<'_>) -> Item,
+{
+    type Item<'a>
+        = Item
+    where
+        Iter: 'a,
+        Func: 'a;
+
+    fn streaming_next(&mut self) -> Option<Self::Item<'_>>
+    {
+        Some((self.func)(self.iter.streaming_next()?))
+    }
+}
+
+#[derive(Debug)]
+pub enum BorrowedOrOwned<'a, Value>
+{
+    Borrowned(&'a Value),
+    Owned(Value),
+}
+
+impl<'a, Value> Deref for BorrowedOrOwned<'a, Value>
+{
+    type Target = Value;
+
+    fn deref(&self) -> &Self::Target
+    {
+        match self {
+            Self::Borrowned(value) => value,
+            Self::Owned(value) => value,
+        }
+    }
+}
+
+#[derive(Debug, Clone)]
+pub enum Either<A, B>
+{
+    A(A),
+    B(B),
+}
+
+impl<A, B> Iterator for Either<A, B>
+where
+    A: Iterator,
+    B: Iterator<Item = A::Item>,
+{
+    type Item = A::Item;
+
+    fn next(&mut self) -> Option<Self::Item>
+    {
+        match self {
+            Self::A(a) => a.next(),
+            Self::B(b) => b.next(),
+        }
+    }
+}
+
 pub trait HashMapExt<Key, Value>
 {
     /// Returns true if the keys are a subset of another [`HashMap`]'s keys, i.e., `other`