Merge pull request #734 from rust-ndarray/raw-view-cast

Simplify ArrayView construction from NonNull<T> and add RawView .cast() method

Author: bluss

src/impl_methods.rs

@@ -139,7 +139,7 @@ where
         S: Data,
     {
         debug_assert!(self.pointer_is_inbounds());
-        unsafe { ArrayView::new_(self.ptr.as_ptr(), self.dim.clone(), self.strides.clone()) }
+        unsafe { ArrayView::new(self.ptr, self.dim.clone(), self.strides.clone()) }
     }
 
     /// Return a read-write view of the array
@@ -148,7 +148,7 @@ where
         S: DataMut,
     {
         self.ensure_unique();
-        unsafe { ArrayViewMut::new_(self.ptr.as_ptr(), self.dim.clone(), self.strides.clone()) }
+        unsafe { ArrayViewMut::new(self.ptr, self.dim.clone(), self.strides.clone()) }
     }
 
     /// Return an uniquely owned copy of the array.
@@ -1313,7 +1313,7 @@ where
     /// Return a raw view of the array.
     #[inline]
     pub fn raw_view(&self) -> RawArrayView<A, D> {
-        unsafe { RawArrayView::new_(self.ptr.as_ptr(), self.dim.clone(), self.strides.clone()) }
+        unsafe { RawArrayView::new(self.ptr, self.dim.clone(), self.strides.clone()) }
     }
 
     /// Return a raw mutable view of the array.
@@ -1323,7 +1323,7 @@ where
         S: RawDataMut,
     {
         self.try_ensure_unique(); // for RcArray
-        unsafe { RawArrayViewMut::new_(self.ptr.as_ptr(), self.dim.clone(), self.strides.clone()) }
+        unsafe { RawArrayViewMut::new(self.ptr, self.dim.clone(), self.strides.clone()) }
     }
 
     /// Return the array’s data as a slice, if it is contiguous and in standard order.
@@ -1620,7 +1620,7 @@ where
             Some(st) => st,
             None => return None,
         };
-        unsafe { Some(ArrayView::new_(self.ptr.as_ptr(), dim, broadcast_strides)) }
+        unsafe { Some(ArrayView::new(self.ptr, dim, broadcast_strides)) }
     }
 
     /// Swap axes `ax` and `bx`.

src/impl_raw_views.rs

@@ -1,3 +1,6 @@
+use std::mem;
+use std::ptr::NonNull;
+
 use crate::dimension::{self, stride_offset};
 use crate::extension::nonnull::nonnull_debug_checked_from_ptr;
 use crate::imp_prelude::*;
@@ -11,16 +14,20 @@ where
     ///
     /// Unsafe because caller is responsible for ensuring that the array will
     /// meet all of the invariants of the `ArrayBase` type.
-    #[inline(always)]
-    pub(crate) unsafe fn new_(ptr: *const A, dim: D, strides: D) -> Self {
+    #[inline]
+    pub(crate) unsafe fn new(ptr: NonNull<A>, dim: D, strides: D) -> Self {
         RawArrayView {
             data: RawViewRepr::new(),
-            ptr: nonnull_debug_checked_from_ptr(ptr as *mut _),
+            ptr,
             dim,
             strides,
         }
     }
 
+    unsafe fn new_(ptr: *const A, dim: D, strides: D) -> Self {
+        Self::new(nonnull_debug_checked_from_ptr(ptr as *mut A), dim, strides)
+    }
+
     /// Create an `RawArrayView<A, D>` from shape information and a raw pointer
     /// to the elements.
     ///
@@ -76,7 +83,7 @@ where
     /// ensure that all of the data is valid and choose the correct lifetime.
     #[inline]
     pub unsafe fn deref_into_view<'a>(self) -> ArrayView<'a, A, D> {
-        ArrayView::new_(self.ptr.as_ptr(), self.dim, self.strides)
+        ArrayView::new(self.ptr, self.dim, self.strides)
     }
 
     /// Split the array view along `axis` and return one array pointer strictly
@@ -105,6 +112,32 @@ where
 
         (left, right)
     }
+
+    /// Cast the raw pointer of the raw array view to a different type
+    ///
+    /// **Panics** if element size is not compatible.
+    ///
+    /// Lack of panic does not imply it is a valid cast. The cast works the same
+    /// way as regular raw pointer casts.
+    ///
+    /// While this method is safe, for the same reason as regular raw pointer
+    /// casts are safe, access through the produced raw view is only possible
+    /// in an unsafe block or function.
+    pub fn cast<B>(self) -> RawArrayView<B, D> {
+        assert_eq!(
+            mem::size_of::<B>(),
+            mem::size_of::<A>(),
+            "size mismatch in raw view cast"
+        );
+        let ptr = self.ptr.cast::<B>();
+        debug_assert!(
+            is_aligned(ptr.as_ptr()),
+            "alignment mismatch in raw view cast"
+        );
+        /* Alignment checked with debug assertion: alignment could be dynamically correct,
+         * and we don't have a check that compiles out for that. */
+        unsafe { RawArrayView::new(ptr, self.dim, self.strides) }
+    }
 }
 
 impl<A, D> RawArrayViewMut<A, D>
@@ -115,16 +148,20 @@ where
     ///
     /// Unsafe because caller is responsible for ensuring that the array will
     /// meet all of the invariants of the `ArrayBase` type.
-    #[inline(always)]
-    pub(crate) unsafe fn new_(ptr: *mut A, dim: D, strides: D) -> Self {
+    #[inline]
+    pub(crate) unsafe fn new(ptr: NonNull<A>, dim: D, strides: D) -> Self {
         RawArrayViewMut {
             data: RawViewRepr::new(),
-            ptr: nonnull_debug_checked_from_ptr(ptr),
+            ptr,
             dim,
             strides,
         }
     }
 
+    unsafe fn new_(ptr: *mut A, dim: D, strides: D) -> Self {
+        Self::new(nonnull_debug_checked_from_ptr(ptr), dim, strides)
+    }
+
     /// Create an `RawArrayViewMut<A, D>` from shape information and a raw
     /// pointer to the elements.
     ///
@@ -176,7 +213,7 @@ where
     /// Converts to a non-mutable `RawArrayView`.
     #[inline]
     pub(crate) fn into_raw_view(self) -> RawArrayView<A, D> {
-        unsafe { RawArrayView::new_(self.ptr.as_ptr(), self.dim, self.strides) }
+        unsafe { RawArrayView::new(self.ptr, self.dim, self.strides) }
     }
 
     /// Converts to a read-only view of the array.
@@ -186,7 +223,7 @@ where
     /// ensure that all of the data is valid and choose the correct lifetime.
     #[inline]
     pub unsafe fn deref_into_view<'a>(self) -> ArrayView<'a, A, D> {
-        ArrayView::new_(self.ptr.as_ptr(), self.dim, self.strides)
+        ArrayView::new(self.ptr, self.dim, self.strides)
     }
 
     /// Converts to a mutable view of the array.
@@ -196,7 +233,7 @@ where
     /// ensure that all of the data is valid and choose the correct lifetime.
     #[inline]
     pub unsafe fn deref_into_view_mut<'a>(self) -> ArrayViewMut<'a, A, D> {
-        ArrayViewMut::new_(self.ptr.as_ptr(), self.dim, self.strides)
+        ArrayViewMut::new(self.ptr, self.dim, self.strides)
     }
 
     /// Split the array view along `axis` and return one array pointer strictly
@@ -207,9 +244,35 @@ where
         let (left, right) = self.into_raw_view().split_at(axis, index);
         unsafe {
             (
-                Self::new_(left.ptr.as_ptr(), left.dim, left.strides),
-                Self::new_(right.ptr.as_ptr(), right.dim, right.strides),
+                Self::new(left.ptr, left.dim, left.strides),
+                Self::new(right.ptr, right.dim, right.strides),
             )
         }
     }
+
+    /// Cast the raw pointer of the raw array view to a different type
+    ///
+    /// **Panics** if element size is not compatible.
+    ///
+    /// Lack of panic does not imply it is a valid cast. The cast works the same
+    /// way as regular raw pointer casts.
+    ///
+    /// While this method is safe, for the same reason as regular raw pointer
+    /// casts are safe, access through the produced raw view is only possible
+    /// in an unsafe block or function.
+    pub fn cast<B>(self) -> RawArrayViewMut<B, D> {
+        assert_eq!(
+            mem::size_of::<B>(),
+            mem::size_of::<A>(),
+            "size mismatch in raw view cast"
+        );
+        let ptr = self.ptr.cast::<B>();
+        debug_assert!(
+            is_aligned(ptr.as_ptr()),
+            "alignment mismatch in raw view cast"
+        );
+        /* Alignment checked with debug assertion: alignment could be dynamically correct,
+         * and we don't have a check that compiles out for that. */
+        unsafe { RawArrayViewMut::new(ptr, self.dim, self.strides) }
+    }
 }

src/impl_views/constructors.rs

@@ -6,6 +6,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+use std::ptr::NonNull;
+
 use crate::dimension;
 use crate::error::ShapeError;
 use crate::extension::nonnull::nonnull_debug_checked_from_ptr;
@@ -200,11 +202,11 @@ where
 
     /// Convert the view into an `ArrayViewMut<'b, A, D>` where `'b` is a lifetime
     /// outlived by `'a'`.
-    pub fn reborrow<'b>(mut self) -> ArrayViewMut<'b, A, D>
+    pub fn reborrow<'b>(self) -> ArrayViewMut<'b, A, D>
     where
         'a: 'b,
     {
-        unsafe { ArrayViewMut::new_(self.as_mut_ptr(), self.dim, self.strides) }
+        unsafe { ArrayViewMut::new(self.ptr, self.dim, self.strides) }
     }
 }
 
@@ -217,14 +219,24 @@ where
     ///
     /// Unsafe because: `ptr` must be valid for the given dimension and strides.
     #[inline(always)]
-    pub(crate) unsafe fn new_(ptr: *const A, dim: D, strides: D) -> Self {
+    pub(crate) unsafe fn new(ptr: NonNull<A>, dim: D, strides: D) -> Self {
+        if cfg!(debug_assertions) {
+            assert!(is_aligned(ptr.as_ptr()), "The pointer must be aligned.");
+            dimension::max_abs_offset_check_overflow::<A, _>(&dim, &strides).unwrap();
+        }
         ArrayView {
             data: ViewRepr::new(),
-            ptr: nonnull_debug_checked_from_ptr(ptr as *mut A),
+            ptr,
             dim,
             strides,
         }
     }
+
+    /// Unsafe because: `ptr` must be valid for the given dimension and strides.
+    #[inline]
+    pub(crate) unsafe fn new_(ptr: *const A, dim: D, strides: D) -> Self {
+        Self::new(nonnull_debug_checked_from_ptr(ptr as *mut A), dim, strides)
+    }
 }
 
 impl<'a, A, D> ArrayViewMut<'a, A, D>
@@ -235,17 +247,24 @@ where
     ///
     /// Unsafe because: `ptr` must be valid for the given dimension and strides.
     #[inline(always)]
-    pub(crate) unsafe fn new_(ptr: *mut A, dim: D, strides: D) -> Self {
+    pub(crate) unsafe fn new(ptr: NonNull<A>, dim: D, strides: D) -> Self {
         if cfg!(debug_assertions) {
-            assert!(!ptr.is_null(), "The pointer must be non-null.");
-            assert!(is_aligned(ptr), "The pointer must be aligned.");
+            assert!(is_aligned(ptr.as_ptr()), "The pointer must be aligned.");
             dimension::max_abs_offset_check_overflow::<A, _>(&dim, &strides).unwrap();
         }
         ArrayViewMut {
             data: ViewRepr::new(),
-            ptr: nonnull_debug_checked_from_ptr(ptr),
+            ptr,
             dim,
             strides,
         }
     }
+
+    /// Create a new `ArrayView`
+    ///
+    /// Unsafe because: `ptr` must be valid for the given dimension and strides.
+    #[inline(always)]
+    pub(crate) unsafe fn new_(ptr: *mut A, dim: D, strides: D) -> Self {
+        Self::new(nonnull_debug_checked_from_ptr(ptr), dim, strides)
+    }
 }

src/impl_views/conversions.rs

@@ -26,7 +26,7 @@ where
     where
         'a: 'b,
     {
-        unsafe { ArrayView::new_(self.as_ptr(), self.dim, self.strides) }
+        unsafe { ArrayView::new(self.ptr, self.dim, self.strides) }
     }
 
     /// Return the array’s data as a slice, if it is contiguous and in standard order.
@@ -53,7 +53,7 @@ where
 
     /// Converts to a raw array view.
     pub(crate) fn into_raw_view(self) -> RawArrayView<A, D> {
-        unsafe { RawArrayView::new_(self.ptr.as_ptr(), self.dim, self.strides) }
+        unsafe { RawArrayView::new(self.ptr, self.dim, self.strides) }
     }
 }
 
@@ -161,12 +161,12 @@ where
 {
     // Convert into a read-only view
     pub(crate) fn into_view(self) -> ArrayView<'a, A, D> {
-        unsafe { ArrayView::new_(self.ptr.as_ptr(), self.dim, self.strides) }
+        unsafe { ArrayView::new(self.ptr, self.dim, self.strides) }
     }
 
     /// Converts to a mutable raw array view.
     pub(crate) fn into_raw_view_mut(self) -> RawArrayViewMut<A, D> {
-        unsafe { RawArrayViewMut::new_(self.ptr.as_ptr(), self.dim, self.strides) }
+        unsafe { RawArrayViewMut::new(self.ptr, self.dim, self.strides) }
     }
 
     #[inline]

src/lib.rs

@@ -1517,7 +1517,7 @@ where
         let ptr = self.ptr;
         let mut strides = dim.clone();
         strides.slice_mut().copy_from_slice(self.strides.slice());
-        unsafe { ArrayView::new_(ptr.as_ptr(), dim, strides) }
+        unsafe { ArrayView::new(ptr, dim, strides) }
     }
 
     fn raw_strides(&self) -> D {

src/zip/mod.rs

@@ -73,7 +73,7 @@ where
     type Output = ArrayView<'a, A, E::Dim>;
     fn broadcast_unwrap(self, shape: E) -> Self::Output {
         let res: ArrayView<'_, A, E::Dim> = (&self).broadcast_unwrap(shape.into_dimension());
-        unsafe { ArrayView::new_(res.ptr.as_ptr(), res.dim, res.strides) }
+        unsafe { ArrayView::new(res.ptr, res.dim, res.strides) }
     }
     private_impl! {}
 }