feat: add swap_remove fn

1 files changed, 117 insertions, 0 deletions

diff --git a/src/lib.rs b/src/lib.rs
index 8fd5ee4..007cf82 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -260,6 +260,75 @@ impl MultiVec
         Some(item_fields)
     }
 
+    pub fn swap_remove(&mut self, item_index: usize) -> Option<Vec<Field<'static, '_>>>
+    {
+        if item_index >= self.length {
+            return None;
+        }
+
+        let prev_length = self.length;
+
+        self.length -= 1;
+
+        let mut item_fields = Vec::<Field<'static, '_>>::with_capacity(self.field_cnt());
+
+        for field_index in 0..self.field_cnt() {
+            let field_metadata = &self.get_field_metadata()?.get(field_index)?;
+
+            let field_arr_ptr = unsafe { self.ptr.byte_add(field_metadata.array_offset) };
+
+            let bytes = unsafe {
+                std::slice::from_raw_parts_mut(
+                    field_arr_ptr.as_ptr().cast(),
+                    prev_length * field_metadata.size,
+                )
+            };
+
+            let field_slice = FieldSliceMut {
+                bytes,
+                len: prev_length,
+                field_metadata,
+            };
+
+            let mut item_field_bytes = AnonUnique::new_uninit(
+                Layout::from_size_align(field_metadata.size, field_metadata.alignment)
+                    .unwrap(),
+            );
+
+            item_field_bytes.as_slice_mut().copy_from_slice(
+                field_slice
+                    .get_item(item_index)
+                    .expect("Not possible")
+                    .bytes
+                    .as_a()
+                    .expect("Not possible"),
+            );
+
+            let item_field = Field {
+                bytes: Either::B(item_field_bytes),
+                field_metadata,
+            };
+
+            item_fields.push(item_field);
+
+            let item_field_offset = field_slice
+                .get_item_offset(item_index)
+                .expect("Not possible");
+
+            let last_item_field_offset = field_slice
+                .get_item_offset(prev_length - 1)
+                .expect("Not possible");
+
+            field_slice.bytes.copy_within(
+                last_item_field_offset
+                    ..last_item_field_offset + field_slice.field_metadata.size,
+                item_field_offset,
+            );
+        }
+
+        Some(item_fields)
+    }
+
     ///// Returns a field of the item with the given index.
     /////
     ///// This function is equivalant to doing `.get_all().get(index)`
@@ -1454,6 +1523,54 @@ mod tests
     }
 
     #[test]
+    fn swap_remove_in_middle_works()
+    {
+        let mut data;
+        let mut multi_vec = multi_vec_with_data!(
+            data = &mut data,
+            {
+                _a: u32 = [u32::MAX - 3000, 901, 5560000, 123123],
+                _b: u16 = [20210u16, 7120, 1010, 9009],
+            },
+            length = 4
+        );
+
+        let removed = multi_vec.swap_remove(1).expect("Should be Some");
+
+        assert_eq!(&data._a[0..3], [u32::MAX - 3000, 123123, 5560000]);
+        assert_eq!(&data._b[0..3], [20210u16, 9009, 1010]);
+
+        assert_eq!(removed.len(), 2);
+
+        assert_eq!(*removed[0].cast::<u32>(), 901);
+        assert_eq!(*removed[1].cast::<u16>(), 7120);
+    }
+
+    #[test]
+    fn swap_remove_at_end_works()
+    {
+        let mut data;
+        let mut multi_vec = multi_vec_with_data!(
+            data = &mut data,
+            {
+                _a: u32 = [u32::MAX - 3000, 901, 5560000, 123123],
+                _b: u16 = [20210u16, 7120, 1010, 9009],
+            },
+            length = 4
+        );
+
+        let removed = multi_vec.swap_remove(3).expect("Should be Some");
+
+        assert_eq!(&data._a[0..3], [u32::MAX - 3000, 901, 5560000]);
+        assert_eq!(&data._b[0..3], [20210u16, 7120, 1010]);
+
+        assert_eq!(removed.len(), 2);
+
+        assert_eq!(*removed[0].cast::<u32>(), 123123);
+        assert_eq!(*removed[1].cast::<u16>(), 9009);
+    }
+
+    #[test]
     fn fields_are_dropped()
     {
         static THING_DROPPED_CNT: AtomicUsize = AtomicUsize::new(0);