From 3248590d18018dcb38afb4af0741c030bf3f8cd3 Mon Sep 17 00:00:00 2001
From: HampusM <hampus@hampusmat.com>
Date: Tue, 27 Aug 2024 20:41:15 +0200
Subject: feat: add function to get slice with fields of all items

---
 src/lib.rs | 45 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 45 insertions(+)

(limited to 'src')

diff --git a/src/lib.rs b/src/lib.rs
index e55d8ec..943ad04 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -116,6 +116,8 @@ where
     }
 
     /// Returns a field of the item with the given index.
+    ///
+    /// This function is equivalant to doing `.get_all().get(index)`
     pub fn get<FieldSel>(
         &self,
         index: usize,
@@ -138,6 +140,18 @@ where
         Some(unsafe { field_ptr.cast().as_ref() })
     }
 
+    /// Returns a slice containing the specified field of all items.
+    pub fn get_all<FieldSel>(&self) -> &[<FieldSel as ItemFieldSelection<ItemT>>::Field]
+    where
+        FieldSel: ItemFieldSelection<ItemT>,
+    {
+        let field_arr_byte_offset = self.field_arr_byte_offsets[FieldSel::INDEX];
+
+        let field_arr_ptr = unsafe { self.ptr.byte_add(field_arr_byte_offset) };
+
+        unsafe { std::slice::from_raw_parts(field_arr_ptr.as_ptr().cast(), self.len()) }
+    }
+
     /// Returns the number of items stored in this `MultiVec`.
     pub fn len(&self) -> usize
     {
@@ -707,4 +721,35 @@ mod tests
             [9090, 2233, u16::MAX - 75, 8182]
         );
     }
+
+    #[test]
+    fn get_all_works()
+    {
+        let mut multi_vec = MultiVec::<Foo>::new();
+
+        #[repr(packed)]
+        #[allow(dead_code)]
+        struct Data
+        {
+            num_a: [u32; 3],
+            num_b: [u16; 3],
+        }
+
+        let data = Data {
+            num_a: [u32::MAX - 3000, 901, 5560000],
+            num_b: [20210, 7120, 1010],
+        };
+
+        multi_vec.ptr = NonNull::from(&data).cast();
+        multi_vec.field_arr_byte_offsets = vec![0, size_of::<u32>() * 3];
+        multi_vec.length = 3;
+        multi_vec.capacity = 3;
+
+        assert_eq!(
+            multi_vec.get_all::<FooFieldNumA>(),
+            [u32::MAX - 3000, 901, 5560000]
+        );
+
+        assert_eq!(multi_vec.get_all::<FooFieldNumB>(), [20210, 7120, 1010]);
+    }
 }
-- 
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