diff --git a/src/dimension/broadcast.rs b/src/dimension/broadcast.rs
index dc1513f04..6470dd58b 100644
--- a/src/dimension/broadcast.rs
+++ b/src/dimension/broadcast.rs
@@ -34,6 +34,57 @@ where
Ok(out)
}
+/// Return new stride when trying to grow `from` into shape `to`
+///
+/// Broadcasting works by returning a "fake stride" where elements
+/// to repeat are in axes with 0 stride, so that several indexes point
+/// to the same element.
+///
+/// **Note:** Cannot be used for mutable iterators, since repeating
+/// elements would create aliasing pointers.
+pub(crate) fn upcast<D: Dimension, E: Dimension>(to: &D, from: &E, stride: &E) -> Option<D> {
+ // Make sure the product of non-zero axis lengths does not exceed
+ // `isize::MAX`. This is the only safety check we need to perform
+ // because all the other constraints of `ArrayBase` are guaranteed
+ // to be met since we're starting from a valid `ArrayBase`.
+ let _ = size_of_shape_checked(to).ok()?;
+
+ let mut new_stride = to.clone();
+ // begin at the back (the least significant dimension)
+ // size of the axis has to either agree or `from` has to be 1
+ if to.ndim() < from.ndim() {
+ return None;
+ }
+
+ {
+ let mut new_stride_iter = new_stride.slice_mut().iter_mut().rev();
+ for ((er, es), dr) in from
+ .slice()
+ .iter()
+ .rev()
+ .zip(stride.slice().iter().rev())
+ .zip(new_stride_iter.by_ref())
+ {
+ /* update strides */
+ if *dr == *er {
+ /* keep stride */
+ *dr = *es;
+ } else if *er == 1 {
+ /* dead dimension, zero stride */
+ *dr = 0
+ } else {
+ return None;
+ }
+ }
+
+ /* set remaining strides to zero */
+ for dr in new_stride_iter {
+ *dr = 0;
+ }
+ }
+ Some(new_stride)
+}
+
pub trait DimMax<Other: Dimension> {
/// The resulting dimension type after broadcasting.
type Output: Dimension;
diff --git a/src/impl_methods.rs b/src/impl_methods.rs
index 115cd2d71..ad9e11685 100644
--- a/src/impl_methods.rs
+++ b/src/impl_methods.rs
@@ -22,7 +22,7 @@ use crate::dimension::{
abs_index, axes_of, do_slice, merge_axes, move_min_stride_axis_to_last,
offset_from_low_addr_ptr_to_logical_ptr, size_of_shape_checked, stride_offset, Axes,
};
-use crate::dimension::broadcast::co_broadcast;
+use crate::dimension::broadcast::{co_broadcast, upcast};
use crate::dimension::reshape_dim;
use crate::error::{self, ErrorKind, ShapeError, from_kind};
use crate::math_cell::MathCell;
@@ -2036,56 +2036,6 @@ where
E: IntoDimension,
S: Data,
{
- /// Return new stride when trying to grow `from` into shape `to`
- ///
- /// Broadcasting works by returning a "fake stride" where elements
- /// to repeat are in axes with 0 stride, so that several indexes point
- /// to the same element.
- ///
- /// **Note:** Cannot be used for mutable iterators, since repeating
- /// elements would create aliasing pointers.
- fn upcast<D: Dimension, E: Dimension>(to: &D, from: &E, stride: &E) -> Option<D> {
- // Make sure the product of non-zero axis lengths does not exceed
- // `isize::MAX`. This is the only safety check we need to perform
- // because all the other constraints of `ArrayBase` are guaranteed
- // to be met since we're starting from a valid `ArrayBase`.
- let _ = size_of_shape_checked(to).ok()?;
-
- let mut new_stride = to.clone();
- // begin at the back (the least significant dimension)
- // size of the axis has to either agree or `from` has to be 1
- if to.ndim() < from.ndim() {
- return None;
- }
-
- {
- let mut new_stride_iter = new_stride.slice_mut().iter_mut().rev();
- for ((er, es), dr) in from
- .slice()
- .iter()
- .rev()
- .zip(stride.slice().iter().rev())
- .zip(new_stride_iter.by_ref())
- {
- /* update strides */
- if *dr == *er {
- /* keep stride */
- *dr = *es;
- } else if *er == 1 {
- /* dead dimension, zero stride */
- *dr = 0
- } else {
- return None;
- }
- }
-
- /* set remaining strides to zero */
- for dr in new_stride_iter {
- *dr = 0;
- }
- }
- Some(new_stride)
- }
let dim = dim.into_dimension();
// Note: zero strides are safe precisely because we return an read-only view
diff --git a/src/impl_views/methods.rs b/src/impl_views/methods.rs
new file mode 100644
index 000000000..a34247165
--- /dev/null
+++ b/src/impl_views/methods.rs
@@ -0,0 +1,34 @@
+// Copyright 2014-2016 bluss and ndarray developers.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use crate::imp_prelude::*;
+use crate::dimension::IntoDimension;
+use crate::dimension::broadcast::upcast;
+
+impl<'a, A, D> ArrayView<'a, A, D>
+where
+ D: Dimension,
+{
+ /// Broadcasts an `ArrayView`. See [`ArrayBase::broadcast`].
+ ///
+ /// This is a specialized version of [`ArrayBase::broadcast`] that transfers
+ /// the view's lifetime to the output.
+ pub fn broadcast_ref<E>(&self, dim: E) -> Option<ArrayView<'a, A, E::Dim>>
+ where
+ E: IntoDimension,
+ {
+ let dim = dim.into_dimension();
+
+ // Note: zero strides are safe precisely because we return an read-only view
+ let broadcast_strides = match upcast(&dim, &self.dim, &self.strides) {
+ Some(st) => st,
+ None => return None,
+ };
+ unsafe { Some(ArrayView::new(self.ptr, dim, broadcast_strides)) }
+ }
+}
diff --git a/src/impl_views/mod.rs b/src/impl_views/mod.rs
index 487cc3cb2..fda58242a 100644
--- a/src/impl_views/mod.rs
+++ b/src/impl_views/mod.rs
@@ -1,6 +1,7 @@
mod constructors;
mod conversions;
mod indexing;
+mod methods;
mod splitting;
pub use constructors::*;