diff --git a/unreal-sdk/src/lib.rs b/unreal-sdk/src/lib.rs
index 4f487a5..6ab72b2 100644
--- a/unreal-sdk/src/lib.rs
+++ b/unreal-sdk/src/lib.rs
@@ -16,3 +16,4 @@ pub mod v2_types;
 
 pub mod any_type;
 pub mod types;
+pub mod util;
diff --git a/unreal-sdk/src/util.rs b/unreal-sdk/src/util.rs
new file mode 100644
index 0000000..fccff4c
--- /dev/null
+++ b/unreal-sdk/src/util.rs
@@ -0,0 +1,210 @@
+use std::collections::hash_map::Entry;
+use std::collections::HashMap;
+use std::hash::Hash;
+
+pub struct DedupIdentity;
+
+pub trait DedupGetHash<T> {
+    type Hashed: Hash + Eq;
+    fn get_hash<'a>(&mut self, a: &'a T) -> Self::Hashed;
+}
+
+impl<T> DedupGetHash<T> for DedupIdentity
+where
+    T: Hash + Eq + Clone,
+{
+    type Hashed = T;
+
+    fn get_hash<'a>(&mut self, a: &'a T) -> Self::Hashed {
+        a.clone()
+    }
+}
+
+impl<F, T, H> DedupGetHash<T> for F
+where
+    F: FnMut(&T) -> H,
+    H: Hash + Eq,
+{
+    type Hashed = H;
+
+    fn get_hash<'a>(&mut self, a: &'a T) -> Self::Hashed {
+        self(a)
+    }
+}
+
+pub struct DedupWithBy<I, F, H>
+where
+    I: Iterator,
+    F: FnMut(usize, <I as Iterator>::Item) -> <I as Iterator>::Item,
+    H: DedupGetHash<<I as Iterator>::Item>,
+{
+    iter: I,
+    /// makes item unique, is told how many elements of this equality.
+    cb_fn: F,
+    /// returns the borrowed element by which to compare the iterators elements
+    hash_fn: H,
+    cache: HashMap<H::Hashed, usize>,
+}
+
+pub trait DedupIter: Iterator {
+    fn dedup_with<'a, F>(self, f: F) -> DedupWithBy<Self, F, DedupIdentity>
+    where
+        F: FnMut(usize, <Self as Iterator>::Item) -> <Self as Iterator>::Item,
+        Self: Sized,
+        <Self as Iterator>::Item: Eq + Hash + Clone,
+    {
+        DedupWithBy {
+            iter: self,
+            cb_fn: f,
+            hash_fn: DedupIdentity,
+            cache: HashMap::new(),
+        }
+    }
+
+    fn dedup_with_by<'a, F, H>(self, f: F, h: H) -> DedupWithBy<Self, F, H>
+    where
+        F: FnMut(usize, <Self as Iterator>::Item) -> <Self as Iterator>::Item,
+        H: DedupGetHash<<Self as Iterator>::Item>,
+        Self: Sized,
+    {
+        DedupWithBy {
+            iter: self,
+            cb_fn: f,
+            hash_fn: h,
+            cache: HashMap::new(),
+        }
+    }
+}
+
+impl<I> DedupIter for I where I: Iterator {}
+
+impl<I, F, H> Iterator for DedupWithBy<I, F, H>
+where
+    I: Iterator,
+    F: FnMut(usize, <I as Iterator>::Item) -> <I as Iterator>::Item,
+    H: DedupGetHash<<I as Iterator>::Item>,
+{
+    type Item = <I as Iterator>::Item;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        let mut next = self.iter.next()?;
+
+        let next = loop {
+            let hash = self.hash_fn.get_hash(&next);
+
+            match self.cache.entry(hash) {
+                Entry::Occupied(mut entry) => {
+                    *entry.get_mut() += 1;
+
+                    next = (self.cb_fn)(*entry.get(), next);
+                }
+                Entry::Vacant(entry) => {
+                    entry.insert(0);
+                    break next;
+                }
+            };
+        };
+
+        Some(next)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn numbers() {
+        let numbers = [1, 2, 2, 2, 3, 4, 5, 6, 22];
+
+        let unique = numbers
+            .into_iter()
+            .dedup_with(|n, i| (i * 10 + n) as usize)
+            .collect::<Vec<_>>();
+
+        assert_eq!(&unique, &[1, 2, 21, 22, 3, 4, 5, 6, 221]);
+    }
+
+    #[derive(Debug, PartialEq, Clone)]
+    struct Key {
+        number: usize,
+        other: f32,
+    }
+
+    #[test]
+    fn keys() {
+        let keys = [
+            Key {
+                number: 1,
+                other: 1.0,
+            },
+            Key {
+                number: 2,
+                other: 1.0,
+            },
+            Key {
+                number: 2,
+                other: 1.0,
+            },
+            Key {
+                number: 2,
+                other: 1.0,
+            },
+            Key {
+                number: 3,
+                other: 1.0,
+            },
+            Key {
+                number: 4,
+                other: 1.0,
+            },
+            Key {
+                number: 5,
+                other: 1.0,
+            },
+        ];
+        let expected = [
+            Key {
+                number: 1,
+                other: 1.0,
+            },
+            Key {
+                number: 2,
+                other: 1.0,
+            },
+            Key {
+                number: 21,
+                other: 1.0,
+            },
+            Key {
+                number: 22,
+                other: 1.0,
+            },
+            Key {
+                number: 3,
+                other: 1.0,
+            },
+            Key {
+                number: 4,
+                other: 1.0,
+            },
+            Key {
+                number: 5,
+                other: 1.0,
+            },
+        ];
+
+        let unique = keys
+            .into_iter()
+            .dedup_with_by(
+                |n, key| Key {
+                    number: (key.number * 10 + n),
+                    ..key
+                },
+                |key: &Key| -> usize { key.number },
+            )
+            .collect::<Vec<_>>();
+
+        assert_eq!(&unique, &expected);
+    }
+}