Const generics Improvements

.github/workflows/ci.yml

@@ -21,7 +21,7 @@ jobs:
           - stable
           - beta
           - nightly
-          - 1.49.0  # MSRV
+          - 1.51.0  # MSRV
 
     steps:
       - uses: actions/checkout@v2

src/arraytraits.rs

@@ -6,20 +6,20 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use std::hash;
-use std::iter::FromIterator;
+use alloc::boxed::Box;
+use alloc::vec::Vec;
 use std::iter::IntoIterator;
 use std::mem;
 use std::ops::{Index, IndexMut};
-use alloc::boxed::Box;
-use alloc::vec::Vec;
+use std::{hash, mem::size_of};
+use std::{iter::FromIterator, slice};
 
 use crate::imp_prelude::*;
-use crate::iter::{Iter, IterMut};
-use crate::NdIndex;
-
-use crate::numeric_util;
-use crate::{FoldWhile, Zip};
+use crate::{
+    dimension,
+    iter::{Iter, IterMut},
+    numeric_util, FoldWhile, NdIndex, Zip,
+};
 
 #[cold]
 #[inline(never)]
@@ -323,6 +323,30 @@ where
     }
 }
 
+/// Implementation of ArrayView2::from(&S) where S is a slice to a 2D array
+///
+/// **Panics** if the product of non-zero axis lengths overflows `isize` (This can only occur if A
+/// is zero-sized because slices cannot contain more than `isize::MAX` number of bytes).
+impl<'a, A, const N: usize> From<&'a [[A; N]]> for ArrayView<'a, A, Ix2> {
+    /// Create a two-dimensional read-only array view of the data in `slice`
+    fn from(xs: &'a [[A; N]]) -> Self {
+        let cols = N;
+        let rows = xs.len();
+        let dim = Ix2(rows, cols);
+        if size_of::<A>() == 0 {
+            dimension::size_of_shape_checked(&dim)
+                .expect("Product of non-zero axis lengths must not overflow isize.");
+        }
+
+        // `cols * rows` is guaranteed to fit in `isize` because we checked that it fits in
+        // `isize::MAX`
+        unsafe {
+            let data = slice::from_raw_parts(xs.as_ptr() as *const A, cols * rows);
+            ArrayView::from_shape_ptr(dim, data.as_ptr())
+        }
+    }
+}
+
 /// Implementation of `ArrayView::from(&A)` where `A` is an array.
 impl<'a, A, S, D> From<&'a ArrayBase<S, D>> for ArrayView<'a, A, D>
 where
@@ -355,6 +379,30 @@ where
     }
 }
 
+/// Implementation of ArrayViewMut2::from(&S) where S is a slice to a 2D array
+///
+/// **Panics** if the product of non-zero axis lengths overflows `isize` (This can only occur if A
+/// is zero-sized because slices cannot contain more than `isize::MAX` number of bytes).
+impl<'a, A, const N: usize> From<&'a mut [[A; N]]> for ArrayViewMut<'a, A, Ix2> {
+    /// Create a two-dimensional read-write array view of the data in `slice`
+    fn from(xs: &'a mut [[A; N]]) -> Self {
+        let cols = N;
+        let rows = xs.len();
+        let dim = Ix2(rows, cols);
+        if size_of::<A>() == 0 {
+            dimension::size_of_shape_checked(&dim)
+                .expect("Product of non-zero axis lengths must not overflow isize.");
+        }
+
+        // `cols * rows` is guaranteed to fit in `isize` because we checked that it fits in
+        // `isize::MAX`
+        unsafe {
+            let data = slice::from_raw_parts_mut(xs.as_mut_ptr() as *mut A, cols * rows);
+            ArrayViewMut::from_shape_ptr(dim, data.as_mut_ptr())
+        }
+    }
+}
+
 /// Implementation of `ArrayViewMut::from(&mut A)` where `A` is an array.
 impl<'a, A, S, D> From<&'a mut ArrayBase<S, D>> for ArrayViewMut<'a, A, D>
 where

src/dimension/ndindex.rs

@@ -140,50 +140,6 @@ macro_rules! ndindex_with_array {
                 0
             }
         }
-
-        // implement NdIndex<IxDyn> for Dim<[Ix; 2]> and so on
-        unsafe impl NdIndex<IxDyn> for Dim<[Ix; $n]> {
-            #[inline]
-            fn index_checked(&self, dim: &IxDyn, strides: &IxDyn) -> Option<isize> {
-                debug_assert_eq!(strides.ndim(), $n,
-                              "Attempted to index with {:?} in array with {} axes",
-                              self, strides.ndim());
-                stride_offset_checked(dim.ix(), strides.ix(), self.ix())
-            }
-
-            #[inline]
-            fn index_unchecked(&self, strides: &IxDyn) -> isize {
-                debug_assert_eq!(strides.ndim(), $n,
-                              "Attempted to index with {:?} in array with {} axes",
-                              self, strides.ndim());
-                $(
-                stride_offset(get!(self, $index), get!(strides, $index)) +
-                )*
-                0
-            }
-        }
-
-        // implement NdIndex<IxDyn> for [Ix; 2] and so on
-        unsafe impl NdIndex<IxDyn> for [Ix; $n] {
-            #[inline]
-            fn index_checked(&self, dim: &IxDyn, strides: &IxDyn) -> Option<isize> {
-                debug_assert_eq!(strides.ndim(), $n,
-                              "Attempted to index with {:?} in array with {} axes",
-                              self, strides.ndim());
-                stride_offset_checked(dim.ix(), strides.ix(), self)
-            }
-
-            #[inline]
-            fn index_unchecked(&self, strides: &IxDyn) -> isize {
-                debug_assert_eq!(strides.ndim(), $n,
-                              "Attempted to index with {:?} in array with {} axes",
-                              self, strides.ndim());
-                $(
-                stride_offset(self[$index], get!(strides, $index)) +
-                )*
-                0
-            }
-        }
         )+
     };
 }
@@ -198,6 +154,64 @@ ndindex_with_array! {
     [6, Ix6 0 1 2 3 4 5]
 }
 
+// implement NdIndex<IxDyn> for Dim<[Ix; 2]> and so on
+unsafe impl<const N: usize> NdIndex<IxDyn> for Dim<[Ix; N]> {
+    #[inline]
+    fn index_checked(&self, dim: &IxDyn, strides: &IxDyn) -> Option<isize> {
+        debug_assert_eq!(
+            strides.ndim(),
+            N,
+            "Attempted to index with {:?} in array with {} axes",
+            self,
+            strides.ndim()
+        );
+        stride_offset_checked(dim.ix(), strides.ix(), self.ix())
+    }
+
+    #[inline]
+    fn index_unchecked(&self, strides: &IxDyn) -> isize {
+        debug_assert_eq!(
+            strides.ndim(),
+            N,
+            "Attempted to index with {:?} in array with {} axes",
+            self,
+            strides.ndim()
+        );
+        (0..N)
+            .map(|i| stride_offset(get!(self, i), get!(strides, i)))
+            .sum()
+    }
+}
+
+// implement NdIndex<IxDyn> for [Ix; 2] and so on
+unsafe impl<const N: usize> NdIndex<IxDyn> for [Ix; N] {
+    #[inline]
+    fn index_checked(&self, dim: &IxDyn, strides: &IxDyn) -> Option<isize> {
+        debug_assert_eq!(
+            strides.ndim(),
+            N,
+            "Attempted to index with {:?} in array with {} axes",
+            self,
+            strides.ndim()
+        );
+        stride_offset_checked(dim.ix(), strides.ix(), self)
+    }
+
+    #[inline]
+    fn index_unchecked(&self, strides: &IxDyn) -> isize {
+        debug_assert_eq!(
+            strides.ndim(),
+            N,
+            "Attempted to index with {:?} in array with {} axes",
+            self,
+            strides.ndim()
+        );
+        (0..N)
+            .map(|i| stride_offset(self[i], get!(strides, i)))
+            .sum()
+    }
+}
+
 impl<'a> IntoDimension for &'a [Ix] {
     type Dim = IxDyn;
     fn into_dimension(self) -> Self::Dim {