bpo-15913: Implement PyBuffer_SizeFromFormat() (GH-13873)

Implement PyBuffer_SizeFromFormat() function (previously
documented but not implemented): call struct.calcsize().

1 files changed, 12 insertions, 0 deletions

diff --git a/Lib/test/test_buffer.py b/Lib/test/test_buffer.py
index 47413c03d6..5fa52bffc2 100644..100755
--- a/Lib/test/test_buffer.py
+++ b/Lib/test/test_buffer.py
@@ -43,6 +43,11 @@ try:
 except ImportError:
     numpy_array = None
 
+try:
+    import _testcapi
+except ImportError:
+    _testcapi = None
+
 
 SHORT_TEST = True
 
@@ -4412,6 +4417,13 @@ class TestBufferProtocol(unittest.TestCase):
         x = ndarray([1,2,3], shape=[3], flags=ND_GETBUF_FAIL)
         self.assertRaises(BufferError, memoryview, x)
 
+    @support.cpython_only
+    def test_pybuffer_size_from_format(self):
+        # basic tests
+        for format in ('', 'ii', '3s'):
+            self.assertEqual(_testcapi.PyBuffer_SizeFromFormat(format),
+                             struct.calcsize(format))
+
 
 if __name__ == "__main__":
     unittest.main()