python: expose Corrade's utility.copy().

Because having to pull in the whole numpy just to efficiently copy some
data around is *silly*.

doc/python/corrade.utility.rst

@@ -23,6 +23,9 @@
     DEALINGS IN THE SOFTWARE.
 ..
 
+.. py:function:: corrade.utility.copy
+    :raise AssertionError: If :p:`src` and :p:`dst` sizes, type sizes or types are different
+
 .. py:function:: corrade.utility.ConfigurationGroup.group
     :raise KeyError: If group :p:`name` doesn't exist
 

doc/python/pages/changelog.rst

@@ -135,6 +135,8 @@ Changelog
 -   Exposed :ref:`Color3.red()` and other convenience constructors (see
     :gh:`mosra/magnum-bindings#12`)
 -   Exposed the :ref:`scenetools` and :ref:`text` libraries
+-   Exposed :ref:`utility.copy()` for convenient, fast and safe copying of
+    multi-dimensional strided arrays
 -   Exposed the minimal interface of :ref:`utility.ConfigurationGroup` and
     :ref:`utility.Configuration`
 -   Exposed :ref:`pluginmanager.AbstractManager.set_preferred_plugins()`,

src/python/corrade/test/test_utility.py

@@ -30,6 +30,9 @@ import unittest
 
 from corrade import utility
 
+# The copy() algorithms can't be tested here as there's nothing that would
+# return a StridedArrayView. A test is in magnum/test/test.py instead.
+
 # Tests also the ConfigurationGroup bindings, as a ConfigurationGroup cannot be
 # constructed as a standalone type
 class Configuration(unittest.TestCase):

src/python/corrade/utility.cpp

@@ -24,16 +24,45 @@
 */
 
 #include <pybind11/pybind11.h>
+#include <Corrade/Utility/Algorithms.h>
 #include <Corrade/Utility/Assert.h>
 #include <Corrade/Utility/Configuration.h>
 
 #include "corrade/bootstrap.h"
 
+#include "Corrade/Containers/StridedArrayViewPythonBindings.h"
+
 namespace corrade {
 
+template<unsigned dimensions> void algorithmsCopy(py::module_& m) {
+    m.def("copy", [](const Containers::PyStridedArrayView<dimensions, const char>& src, const Containers::PyStridedArrayView<dimensions, char>& dst) {
+        if(src.size() != dst.size()) {
+            PyErr_SetString(PyExc_AssertionError, "sizes don't match");
+            throw py::error_already_set{};
+        }
+        if(src.itemsize != dst.itemsize) {
+            PyErr_SetString(PyExc_AssertionError, "type sizes don't match");
+            throw py::error_already_set{};
+        }
+        if(Containers::StringView{src.format} != Containers::StringView{dst.format}) {
+            PyErr_SetString(PyExc_AssertionError, "types don't match");
+            throw py::error_already_set{};
+        }
+
+        Utility::copy(
+            Containers::arrayCast<dimensions + 1, const char>(Containers::StridedArrayView<dimensions, const void>{src}, src.itemsize),
+            Containers::arrayCast<dimensions + 1, char>(Containers::StridedArrayView<dimensions, void>{dst}, dst.itemsize));
+    }, "Copy a strided array view to another", py::arg("src"), py::arg("dst"));
+}
+
 void utility(py::module_& m) {
     m.doc() = "Utilities";
 
+    algorithmsCopy<1>(m);
+    algorithmsCopy<2>(m);
+    algorithmsCopy<3>(m);
+    algorithmsCopy<4>(m);
+
     py::class_<Utility::ConfigurationGroup>{m, "ConfigurationGroup", "Group of values in a configuration file"}
         .def_property_readonly("has_groups", &Utility::ConfigurationGroup::hasGroups, "Whether this group has any subgroups")
         .def("group", [](Utility::ConfigurationGroup& self, const std::string& name) {

src/python/magnum/test/test.py

@@ -27,8 +27,11 @@ import array
 import sys
 import unittest
 
+from corrade import utility
 from magnum import *
 
+# tests also corrade.utility.copy() in UtilityCopy
+
 class PixelStorage_(unittest.TestCase):
     def test_init(self):
         a = PixelStorage()
@@ -447,3 +450,64 @@ class ImageView(unittest.TestCase):
 
         with self.assertRaisesRegex(NotImplementedError, "access to this pixel format is not implemented yet, sorry"):
             a.pixels
+
+class UtilityCopy(unittest.TestCase):
+    def test_1d(self):
+        a_data = array.array('f', [1.0, 2.0, 3.0, 4.0, 5.0, 6.0])
+        a = ImageView1D(PixelFormat.RGB32F, 2, a_data)
+
+        b_data = array.array('f', [0.0]*6)
+        b = MutableImageView1D(PixelFormat.RGB32F, 2, b_data)
+
+        utility.copy(a.pixels, b.pixels)
+        self.assertEqual(list(b_data), [1.0, 2.0, 3.0, 4.0, 5.0, 6.0])
+
+    def test_2d(self):
+        a_data = array.array('f', [1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0])
+        a = ImageView2D(PixelFormat.RG32F, (2, 2), a_data)
+
+        b_data = array.array('f', [0.0]*8)
+        b = MutableImageView2D(PixelFormat.RG32F, (2, 2), b_data)
+
+        utility.copy(a.pixels, b.pixels)
+        self.assertEqual(list(b_data), [1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0])
+
+    def test_3d(self):
+        a_data = array.array('f', [1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0])
+        a = ImageView3D(PixelFormat.R32F, (3, 1, 3), a_data)
+
+        b_data = array.array('f', [0.0]*9)
+        b = MutableImageView3D(PixelFormat.R32F, (3, 1, 3), b_data)
+
+        utility.copy(a.pixels, b.pixels)
+        self.assertEqual(list(b_data), [1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0])
+
+    def test_size_mismatch(self):
+        a_data = array.array('f', [0.0]*12)
+        a = ImageView2D(PixelFormat.RG32F, (3, 2), a_data)
+
+        b_data = array.array('f', [0.0]*12)
+        b = MutableImageView2D(PixelFormat.RG32F, (2, 3), b_data)
+
+        with self.assertRaisesRegex(AssertionError, "sizes don't match"):
+            utility.copy(a.pixels, b.pixels)
+
+    def test_itemsize_mismatch(self):
+        a_data = array.array('f', [0.0]*12)
+        a = ImageView2D(PixelFormat.RG32F, (3, 2), a_data)
+
+        b_data = array.array('f', [0.0]*18)
+        b = MutableImageView2D(PixelFormat.RGB32F, (3, 2), b_data)
+
+        with self.assertRaisesRegex(AssertionError, "type sizes don't match"):
+            utility.copy(a.pixels, b.pixels)
+
+    def test_format_mismatch(self):
+        a_data = array.array('f', [0.0]*12)
+        a = ImageView2D(PixelFormat.RG32F, (3, 2), a_data)
+
+        b_data = array.array('I', [0]*18)
+        b = MutableImageView2D(PixelFormat.RG32UI, (3, 2), b_data)
+
+        with self.assertRaisesRegex(AssertionError, "types don't match"):
+            utility.copy(a.pixels, b.pixels)