From 99b54465c7b6c67330593b77f81a765b74ecf66a Mon Sep 17 00:00:00 2001
From: sebcrozet <developer@crozet.re>
Date: Thu, 13 Sep 2018 05:38:57 +0200
Subject: [PATCH] Add a copy_from_slice method.

Fix #381.
---
 CHANGELOG.md         |  5 +++++
 src/base/matrix.rs   | 21 +++++++++++++++++++++
 tests/core/matrix.rs | 15 +++++++++++++++
 3 files changed, 41 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index f3c09964..e03b90e4 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,11 @@ documented here.
 
 This project adheres to [Semantic Versioning](http://semver.org/).
 
+## [0.17.0] - WIP
+
+### Added
+  * Add `.copy_from_slice` to copy matrix components from a slice in column-major order.
+
 ## [0.16.0]
 All dependencies have been updated to their latest versions.
 
diff --git a/src/base/matrix.rs b/src/base/matrix.rs
index fae56d70..2c7c673a 100644
--- a/src/base/matrix.rs
+++ b/src/base/matrix.rs
@@ -475,6 +475,27 @@ impl<N: Scalar, R: Dim, C: Dim, S: StorageMut<N, R, C>> Matrix<N, R, C, S> {
         unsafe { self.swap_unchecked(row_cols1, row_cols2) }
     }
 
+    /// Fills this matrix with the content of a slice. Both must hold the same number of elements.
+    ///
+    /// The components of the slice are assumed to be ordered in column-major order.
+    #[inline]
+    pub fn copy_from_slice(&mut self, slice: &[N]) {
+        let (nrows, ncols) = self.shape();
+
+        assert!(
+            nrows * ncols == slice.len(),
+            "The slice must contain the same number of elements as the matrix."
+        );
+
+        for j in 0..ncols {
+            for i in 0..nrows {
+                unsafe {
+                    *self.get_unchecked_mut(i, j) = *slice.get_unchecked(i + j * nrows);
+                }
+            }
+        }
+    }
+
     /// Fills this matrix with the content of another one. Both must have the same shape.
     #[inline]
     pub fn copy_from<R2, C2, SB>(&mut self, other: &Matrix<N, R2, C2, SB>)
diff --git a/tests/core/matrix.rs b/tests/core/matrix.rs
index d515d0ac..1b08acca 100644
--- a/tests/core/matrix.rs
+++ b/tests/core/matrix.rs
@@ -239,6 +239,21 @@ fn from_rows_with_different_dimensions() {
     let _ = DMatrix::from_columns(columns);
 }
 
+#[test]
+fn copy_from_slice() {
+    let mut a = Matrix3::zeros();
+    let data = [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0 ];
+    let expected_a = Matrix3::new(
+        1.0, 4.0, 7.0,
+        2.0, 5.0, 8.0,
+        3.0, 6.0, 9.0
+    );
+
+    a.copy_from_slice(&data);
+
+    assert_eq!(a, expected_a);
+}
+
 #[test]
 fn to_homogeneous() {
     let a = Vector3::new(1.0, 2.0, 3.0);