feat: make MultiVec implement FromIterator

1 files changed, 60 insertions, 0 deletions

diff --git a/src/lib.rs b/src/lib.rs
index 1fc7803..e55d8ec 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -271,6 +271,33 @@ where
     }
 }
 
+impl<ItemT> FromIterator<ItemT> for MultiVec<ItemT>
+where
+    ItemT: Item,
+{
+    fn from_iter<ItemIter: IntoIterator<Item = ItemT>>(iter: ItemIter) -> Self
+    {
+        let iter = iter.into_iter();
+
+        let initial_capacity =
+            max(Self::MIN_NON_ZERO_CAP, iter.size_hint().0.saturating_add(1));
+
+        let mut this = Self::with_capacity(initial_capacity);
+
+        for item in iter {
+            if this.capacity == this.length {
+                this.grow_amortized(1);
+            }
+
+            this.write_item(this.length, item);
+
+            this.length += 1;
+        }
+
+        this
+    }
+}
+
 impl<ItemT> Drop for MultiVec<ItemT>
 where
     ItemT: Item,
@@ -647,4 +674,37 @@ mod tests
         assert_eq!(multi_vec.get::<FooFieldNumA>(2).copied(), Some(5560000));
         assert_eq!(multi_vec.get::<FooFieldNumB>(2).copied(), Some(1010));
     }
+
+    #[test]
+    fn from_iter_works()
+    {
+        let multi_vec = MultiVec::<Foo>::from_iter([
+            Foo { num_a: 456456, num_b: 9090 },
+            Foo { num_a: 79541, num_b: 2233 },
+            Foo { num_a: 1761919, num_b: u16::MAX - 75 },
+            Foo { num_a: u32::MAX / 9, num_b: 8182 },
+        ]);
+
+        assert_eq!(multi_vec.length, 4);
+        assert_eq!(multi_vec.capacity, 5);
+
+        assert_eq!(multi_vec.field_arr_byte_offsets, [0, size_of::<u32>() * 5]);
+
+        assert_eq!(
+            unsafe {
+                std::slice::from_raw_parts::<u32>(multi_vec.ptr.as_ptr().cast(), 4)
+            },
+            [456456, 79541, 1761919, u32::MAX / 9]
+        );
+
+        assert_eq!(
+            unsafe {
+                std::slice::from_raw_parts::<u16>(
+                    multi_vec.ptr.as_ptr().byte_add(size_of::<u32>() * 5).cast(),
+                    4,
+                )
+            },
+            [9090, 2233, u16::MAX - 75, 8182]
+        );
+    }
 }