[eclipse-iceoryx#497] Introduce SlotMap::next_free_key

Author: elfenpiff

iceoryx2-bb/container/src/slotmap.rs

@@ -274,6 +274,12 @@ pub mod details {
             }
         }
 
+        pub(crate) unsafe fn next_free_key_impl(&self) -> Option<SlotMapKey> {
+            self.idx_to_data_next_free_index
+                .peek_impl()
+                .map(|v| SlotMapKey::new(*v))
+        }
+
         pub(crate) fn len_impl(&self) -> usize {
             self.len
         }
@@ -386,6 +392,12 @@ pub mod details {
             unsafe { self.remove_impl(key) }
         }
 
+        /// Returns the [`SlotMapKey`] that will be used when the user calls
+        /// [`SlotMap::insert()`]. If the [`SlotMap`] is full it returns [`None`].
+        pub fn next_free_key(&self) -> Option<SlotMapKey> {
+            unsafe { self.next_free_key_impl() }
+        }
+
         /// Returns the number of stored values.
         pub fn len(&self) -> usize {
             self.len_impl()
@@ -493,6 +505,17 @@ pub mod details {
             self.remove_impl(key)
         }
 
+        /// Returns the [`SlotMapKey`] that will be used when the user calls
+        /// [`SlotMap::insert()`]. If the [`SlotMap`] is full it returns [`None`].
+        ///
+        /// # Safety
+        ///
+        ///  * [`RelocatableSlotMap::init()`] must be called once before
+        ///
+        pub unsafe fn next_free_key(&self) -> Option<SlotMapKey> {
+            self.next_free_key_impl()
+        }
+
         /// Returns the number of stored values.
         pub fn len(&self) -> usize {
             self.len_impl()
@@ -607,6 +630,12 @@ impl<T, const CAPACITY: usize> FixedSizeSlotMap<T, CAPACITY> {
         unsafe { self.state.remove_impl(key) }
     }
 
+    /// Returns the [`SlotMapKey`] that will be used when the user calls
+    /// [`SlotMap::insert()`]. If the [`SlotMap`] is full it returns [`None`].
+    pub fn next_free_key(&self) -> Option<SlotMapKey> {
+        unsafe { self.state.next_free_key_impl() }
+    }
+
     /// Returns the number of stored values.
     pub fn len(&self) -> usize {
         self.state.len_impl()

iceoryx2-bb/container/tests/slotmap_tests.rs

@@ -171,4 +171,31 @@ mod slot_map {
             assert_that!(*value, eq 5 * key.value() + 3);
         }
     }
+
+    #[test]
+    fn next_free_key_returns_key_used_for_insert() {
+        let mut sut = FixedSizeSut::new();
+        let mut keys = vec![];
+
+        for _ in 0..SUT_CAPACITY / 2 {
+            keys.push(sut.insert(0).unwrap());
+        }
+
+        let next_key = sut.next_free_key();
+        assert_that!(next_key, is_some);
+        assert_that!(sut.insert(0), eq next_key);
+    }
+
+    #[test]
+    fn next_free_key_returns_none_when_full() {
+        let mut sut = FixedSizeSut::new();
+        let mut keys = vec![];
+
+        for _ in 0..SUT_CAPACITY {
+            keys.push(sut.insert(0).unwrap());
+        }
+
+        let next_key = sut.next_free_key();
+        assert_that!(next_key, is_none);
+    }
 }