add the Mut<> type

sub/core/src/lib.rs

@@ -50,7 +50,7 @@ pub mod prelude {
     pub use crate::time::dur;
     pub use crate::fnv1::*;
     pub use crate::pstruct::struct_offset;
-    pub use crate::pod::Pod;
+    pub use crate::pod::{Pod,Mut};
 }
 
 pub mod public {

sub/core/src/pod.rs

@@ -1,4 +1,5 @@
 use core::mem::MaybeUninit;
+use core::ops::{Deref, DerefMut};
 
 /// Plain Old data type
 pub trait Pod: Copy + 'static {
@@ -18,3 +19,32 @@ primitive!(f32, f64, usize, isize);
 primitive!(());
 
 impl<const LEN: usize, T: Pod> Pod for [T;LEN] {}
+
+
+/// Type with unsafe interior mutability
+/// but also with Send+Sync
+///
+/// internally just wraps UnsafeCell
+#[repr(transparent)]
+pub struct Mut<T>(core::cell::UnsafeCell<T>);
+unsafe impl<T> Sync for Mut<T> {}
+unsafe impl<T> Send for Mut<T> {}
+
+impl<T: Sized> Mut<T> {
+    pub const fn new(value: T) -> Self {
+        Self(core::cell::UnsafeCell::new(value))
+    }
+    pub const fn as_ptr(&self) -> *mut T {
+        self.0.get()
+    }
+}
+
+impl<T: Pod> Mut<T> {
+    pub fn set(&self, value: T) { unsafe { core::ptr::write(self.as_ptr(), value) } }
+    pub fn get(&self) -> T { unsafe { core::ptr::read(self.as_ptr()) } }
+}
+
+impl<T> Deref for Mut<T> {
+    type Target = core::cell::UnsafeCell<T>;
+    fn deref(&self) -> &Self::Target { &self.0 }
+}