Issue #15944: memoryview: Allow arbitrary formats when casting to bytes.

Original patch by Martin Panter.

1 files changed, 21 insertions, 0 deletions

diff --git a/Lib/test/test_memoryview.py b/Lib/test/test_memoryview.py
index 6fe61a4..da01a84 100644
--- a/Lib/test/test_memoryview.py
+++ b/Lib/test/test_memoryview.py
@@ -492,5 +492,26 @@ class ArrayMemorySliceSliceTest(unittest.TestCase,
     pass
 
 
+class OtherTest(unittest.TestCase):
+    def test_ctypes_cast(self):
+        # Issue 15944: Allow all source formats when casting to bytes.
+        ctypes = test.support.import_module("ctypes")
+        p6 = bytes(ctypes.c_double(0.6))
+
+        d = ctypes.c_double()
+        m = memoryview(d).cast("B")
+        m[:2] = p6[:2]
+        m[2:] = p6[2:]
+        self.assertEqual(d.value, 0.6)
+
+        for format in "Bbc":
+            with self.subTest(format):
+                d = ctypes.c_double()
+                m = memoryview(d).cast(format)
+                m[:2] = memoryview(p6).cast(format)[:2]
+                m[2:] = memoryview(p6).cast(format)[2:]
+                self.assertEqual(d.value, 0.6)
+
+
 if __name__ == "__main__":
     unittest.main()