diff --git a/src/_macros.rs b/src/_macros.rs
index 748f8ba3b..9947d401c 100644
--- a/src/_macros.rs
+++ b/src/_macros.rs
@@ -1016,14 +1016,7 @@ macro_rules! build_table_column_slice_getter {
     ($(#[$attr:meta])* => $column: ident, $name: ident, $cast: ty) => {
         $(#[$attr])*
         pub fn $name(&self) -> &[$cast] {
-            // Caveat: num_rows is u64 but we need usize
-            // The conversion is fallible but unlikely.
-            let num_rows =
-                usize::try_from(self.num_rows()).expect("conversion of num_rows to usize failed");
-            let ptr = self.as_ref().$column as *const $cast;
-            // SAFETY: tables are initialzed, num rows comes
-            // from the C back end.
-            unsafe { std::slice::from_raw_parts(ptr, num_rows) }
+            $crate::sys::generate_slice(self.as_ref().$column, self.num_rows())
         }
     };
 }
@@ -1032,14 +1025,7 @@ macro_rules! build_table_column_slice_mut_getter {
     ($(#[$attr:meta])* => $column: ident, $name: ident, $cast: ty) => {
         $(#[$attr])*
         pub fn $name(&mut self) -> &mut [$cast] {
-            // Caveat: num_rows is u64 but we need usize
-            // The conversion is fallible but unlikely.
-            let num_rows =
-                usize::try_from(self.num_rows()).expect("conversion of num_rows to usize failed");
-            let ptr = self.as_ref().$column as *mut $cast;
-            // SAFETY: tables are initialzed, num rows comes
-            // from the C back end.
-            unsafe { std::slice::from_raw_parts_mut(ptr, num_rows) }
+            $crate::sys::generate_slice_mut(self.as_ref().$column, self.num_rows())
         }
     };
 }
diff --git a/src/node_table.rs b/src/node_table.rs
index e2c6d5b68..84127ab92 100644
--- a/src/node_table.rs
+++ b/src/node_table.rs
@@ -224,22 +224,12 @@ impl NodeTable {
 
     #[deprecated(since = "0.12.0", note = "use flags_slice_mut instead")]
     pub fn flags_array_mut(&mut self) -> &mut [NodeFlags] {
-        unsafe {
-            std::slice::from_raw_parts_mut(
-                self.as_ref().flags.cast::<NodeFlags>(),
-                usize::try_from(self.as_ref().num_rows).unwrap_or(0),
-            )
-        }
+        sys::generate_slice_mut(self.as_ref().flags, self.num_rows())
     }
 
     #[deprecated(since = "0.12.0", note = "use time_slice_mut instead")]
     pub fn time_array_mut(&mut self) -> &mut [Time] {
-        unsafe {
-            std::slice::from_raw_parts_mut(
-                self.as_ref().time.cast::<Time>(),
-                usize::try_from(self.as_ref().num_rows).unwrap_or(0),
-            )
-        }
+        sys::generate_slice_mut(self.as_ref().flags, self.num_rows())
     }
 
     /// Return the ``population`` value from row ``row`` of the table.
diff --git a/src/sys.rs b/src/sys.rs
index 05523ad8d..6a2d0b24d 100644
--- a/src/sys.rs
+++ b/src/sys.rs
@@ -134,11 +134,20 @@ pub fn tsk_ragged_column_access<
         .map(|(p, n)| unsafe { std::slice::from_raw_parts(p.cast::<O>(), n) })
 }
 
-pub fn tree_array_slice<'a, L: Into<bindings::tsk_size_t>>(
-    data: *const bindings::tsk_id_t,
+pub fn generate_slice<'a, L: Into<bindings::tsk_size_t>, I, O>(
+    data: *const I,
     length: L,
-) -> &'a [crate::NodeId] {
+) -> &'a [O] {
     assert!(!data.is_null());
     // SAFETY: pointer is not null, length comes from C API
-    unsafe { std::slice::from_raw_parts(data.cast::<crate::NodeId>(), length.into() as usize) }
+    unsafe { std::slice::from_raw_parts(data.cast::<O>(), length.into() as usize) }
+}
+
+pub fn generate_slice_mut<'a, L: Into<bindings::tsk_size_t>, I, O>(
+    data: *mut I,
+    length: L,
+) -> &'a mut [O] {
+    assert!(!data.is_null());
+    // SAFETY: pointer is not null, length comes from C API
+    unsafe { std::slice::from_raw_parts_mut(data.cast::<O>(), length.into() as usize) }
 }
diff --git a/src/tree_interface.rs b/src/tree_interface.rs
index 23e1b1517..b8dd54ada 100644
--- a/src/tree_interface.rs
+++ b/src/tree_interface.rs
@@ -69,7 +69,7 @@ impl TreeInterface {
     /// }
     /// ```
     pub fn parent_array(&self) -> &[NodeId] {
-        sys::tree_array_slice(self.as_ref().parent, self.array_len)
+        sys::generate_slice(self.as_ref().parent, self.array_len)
     }
 
     /// # Failing examples
@@ -107,7 +107,7 @@ impl TreeInterface {
             unsafe { ll_bindings::tsk_treeseq_get_num_samples((*self.as_ptr()).tree_sequence) };
         err_if_not_tracking_samples!(
             self.flags,
-            sys::tree_array_slice(self.as_ref().samples, num_samples)
+            sys::generate_slice(self.as_ref().samples, num_samples)
         )
     }
 
@@ -144,7 +144,7 @@ impl TreeInterface {
     pub fn next_sample_array(&self) -> Result<&[NodeId], TskitError> {
         err_if_not_tracking_samples!(
             self.flags,
-            sys::tree_array_slice(self.as_ref().next_sample, self.array_len)
+            sys::generate_slice(self.as_ref().next_sample, self.array_len)
         )
     }
 
@@ -181,7 +181,7 @@ impl TreeInterface {
     pub fn left_sample_array(&self) -> Result<&[NodeId], TskitError> {
         err_if_not_tracking_samples!(
             self.flags,
-            sys::tree_array_slice(self.as_ref().left_sample, self.array_len)
+            sys::generate_slice(self.as_ref().left_sample, self.array_len)
         )
     }
 
@@ -218,7 +218,7 @@ impl TreeInterface {
     pub fn right_sample_array(&self) -> Result<&[NodeId], TskitError> {
         err_if_not_tracking_samples!(
             self.flags,
-            sys::tree_array_slice(self.as_ref().right_sample, self.array_len)
+            sys::generate_slice(self.as_ref().right_sample, self.array_len)
         )
     }
 
@@ -239,7 +239,7 @@ impl TreeInterface {
     /// }
     /// ```
     pub fn left_sib_array(&self) -> &[NodeId] {
-        sys::tree_array_slice(self.as_ref().left_sib, self.array_len)
+        sys::generate_slice(self.as_ref().left_sib, self.array_len)
     }
 
     /// # Failing examples
@@ -259,7 +259,7 @@ impl TreeInterface {
     /// }
     /// ```
     pub fn right_sib_array(&self) -> &[NodeId] {
-        sys::tree_array_slice(self.as_ref().right_sib, self.array_len)
+        sys::generate_slice(self.as_ref().right_sib, self.array_len)
     }
 
     /// # Failing examples
@@ -279,7 +279,7 @@ impl TreeInterface {
     /// }
     /// ```
     pub fn left_child_array(&self) -> &[NodeId] {
-        sys::tree_array_slice(self.as_ref().left_child, self.array_len)
+        sys::generate_slice(self.as_ref().left_child, self.array_len)
     }
 
     /// # Failing examples
@@ -299,7 +299,7 @@ impl TreeInterface {
     /// }
     /// ```
     pub fn right_child_array(&self) -> &[NodeId] {
-        sys::tree_array_slice(self.as_ref().right_child, self.array_len)
+        sys::generate_slice(self.as_ref().right_child, self.array_len)
     }
 
     // error if we are not tracking samples,
@@ -405,7 +405,7 @@ impl TreeInterface {
     pub fn sample_nodes(&self) -> &[NodeId] {
         let num_samples =
             unsafe { ll_bindings::tsk_treeseq_get_num_samples((*self.as_ptr()).tree_sequence) };
-        sys::tree_array_slice(self.as_ref().samples, num_samples)
+        sys::generate_slice(self.as_ref().samples, num_samples)
     }
 
     /// Return an [`Iterator`] from the node `u` to the root of the tree,
diff --git a/src/trees.rs b/src/trees.rs
index 14f4a35f9..24d146508 100644
--- a/src/trees.rs
+++ b/src/trees.rs
@@ -396,7 +396,7 @@ impl TreeSequence {
     /// Get the list of sample nodes as a slice.
     pub fn sample_nodes(&self) -> &[NodeId] {
         let num_samples = unsafe { ll_bindings::tsk_treeseq_get_num_samples(self.as_ptr()) };
-        sys::tree_array_slice(self.as_ref().samples, num_samples)
+        sys::generate_slice(self.as_ref().samples, num_samples)
     }
 
     /// Get the number of trees.