Add pod option type

src/types/mod.rs

@@ -1,5 +1,7 @@
 mod pod_bool;
+mod pod_option;
 mod pod_str;
 
 pub use pod_bool::*;
+pub use pod_option::*;
 pub use pod_str::*;

src/types/pod_option.rs

@@ -0,0 +1,41 @@
+use bytemuck::{Pod, Zeroable};
+
+/// Used for "pod-enabled" types that can have a `None` value.
+pub trait Nullable: Pod {
+    /// Indicates if the value is `Some`.
+    fn is_some(&self) -> bool;
+
+    /// Indicates if the value is `None`.
+    fn is_none(&self) -> bool;
+}
+
+/// A "pod-enabled" type that can be used as an `Option<T>` without
+/// requiring extra space to indicate if the value is `Some` or `None`.
+///
+/// This can be used when a specific value of `T` indicates that its
+/// value is `None`.
+#[repr(C)]
+#[derive(Clone, Copy)]
+pub struct PodOption<T: Nullable>(T);
+
+unsafe impl<T: Nullable> Pod for PodOption<T> {}
+
+unsafe impl<T: Nullable> Zeroable for PodOption<T> {}
+
+impl<T: Nullable> PodOption<T> {
+    pub fn value(&self) -> Option<&T> {
+        if self.0.is_some() {
+            Some(&self.0)
+        } else {
+            None
+        }
+    }
+
+    pub fn value_mut(&mut self) -> Option<&mut T> {
+        if self.0.is_some() {
+            Some(&mut self.0)
+        } else {
+            None
+        }
+    }
+}