From e377e825e114abe2ba6f70f1bb5e4864af86162b Mon Sep 17 00:00:00 2001
From: bluss <bluss@users.noreply.github.com>
Date: Sat, 27 Mar 2021 14:05:13 +0100
Subject: [PATCH] FIX: Fix .windows() producer for negative stride arrays

Avoid using ArrayView::from_shape_ptr (public constructor) because it
does not allow negative stride arrays.

Use the internal constructor ArrayView::new, which is easier.
---
 src/iterators/windows.rs |  2 +-
 tests/windows.rs         | 36 ++++++++++++++++++++++++++++++++++++
 2 files changed, 37 insertions(+), 1 deletion(-)

diff --git a/src/iterators/windows.rs b/src/iterators/windows.rs
index 2d9095303..4538f7abb 100644
--- a/src/iterators/windows.rs
+++ b/src/iterators/windows.rs
@@ -41,7 +41,7 @@ impl<'a, A, D: Dimension> Windows<'a, A, D> {
 
         unsafe {
             Windows {
-                base: ArrayView::from_shape_ptr(size.strides(a.strides), a.ptr.as_ptr()),
+                base: ArrayView::new(a.ptr, size, a.strides),
                 window,
                 strides: window_strides,
             }
diff --git a/tests/windows.rs b/tests/windows.rs
index 9fb8cc8ae..87fdf6ecb 100644
--- a/tests/windows.rs
+++ b/tests/windows.rs
@@ -116,3 +116,39 @@ fn test_window_zip() {
         }
     }
 }
+
+#[test]
+fn test_window_neg_stride() {
+    let array = Array::from_iter(1..10).into_shape((3, 3)).unwrap();
+
+    // window neg/pos stride combinations
+    
+    // Make a 2 x 2 array of the windows of the 3 x 3 array
+    // and compute test answers from here
+    let mut answer = Array::from_iter(array.windows((2, 2)).into_iter().map(|a| a.to_owned()))
+        .into_shape((2, 2)).unwrap();
+
+    answer.invert_axis(Axis(1));
+    answer.map_inplace(|a| a.invert_axis(Axis(1)));
+
+    itertools::assert_equal(
+        array.slice(s![.., ..;-1]).windows((2, 2)),
+        answer.iter().map(|a| a.view())
+    );
+
+    answer.invert_axis(Axis(0));
+    answer.map_inplace(|a| a.invert_axis(Axis(0)));
+
+    itertools::assert_equal(
+        array.slice(s![..;-1, ..;-1]).windows((2, 2)),
+        answer.iter().map(|a| a.view())
+    );
+
+    answer.invert_axis(Axis(1));
+    answer.map_inplace(|a| a.invert_axis(Axis(1)));
+
+    itertools::assert_equal(
+        array.slice(s![..;-1, ..]).windows((2, 2)),
+        answer.iter().map(|a| a.view())
+    );
+}