Rav1dTaskContext::a: Make into offset and give BlockContext inter…

…ior mutability (#958)

src/align.rs

@@ -100,6 +100,18 @@ macro_rules! def_align {
         }
 
         impl AlignedByteChunk for $name<[u8; $align]> {}
+
+        unsafe impl<V, const N: usize> AsMutPtr for $name<[V; N]> {
+            type Target = V;
+
+            unsafe fn as_mut_ptr(ptr: *mut Self) -> *mut V {
+                (*ptr).0.as_mut_ptr()
+            }
+
+            fn len(&self) -> usize {
+                N
+            }
+        }
     };
 }
 

src/ctx.rs

@@ -37,6 +37,8 @@
 //! * is far simpler than the `case_set*` implementation, consisting of a `match` and array writes
 //!
 //! [`BlockContext`]: crate::src::env::BlockContext
+use crate::src::disjoint_mut::AsMutPtr;
+use crate::src::disjoint_mut::DisjointMut;
 use std::iter::zip;
 
 /// Perform a `memset` optimized for lengths that are small powers of 2.
@@ -83,6 +85,20 @@ impl<const UP_TO: usize, const WITH_DEFAULT: bool> CaseSetter<UP_TO, WITH_DEFAUL
     pub fn set<T: Clone + Copy>(&self, buf: &mut [T], val: T) {
         small_memset::<T, UP_TO, WITH_DEFAULT>(&mut buf[self.offset..][..self.len], val);
     }
+
+    /// # Safety
+    ///
+    /// Caller must ensure that no elements of the written range are concurrently
+    /// borrowed (immutably or mutably) at all during the call to `set_disjoint`.
+    #[inline]
+    pub unsafe fn set_disjoint<T, V>(&self, buf: &DisjointMut<T>, val: V)
+    where
+        T: AsMutPtr<Target = V>,
+        V: Clone + Copy,
+    {
+        let mut buf = unsafe { buf.index_mut(self.offset..self.offset + self.len) };
+        small_memset::<V, UP_TO, WITH_DEFAULT>(&mut *buf, val);
+    }
 }
 
 /// The entrypoint to the [`CaseSet`] API.