Issue #23319: Fix ctypes.BigEndianStructure, swap correctly bytes. Patch
written by Matthieu Gautier.
diff --git a/Lib/ctypes/test/test_bitfields.py b/Lib/ctypes/test/test_bitfields.py
index 991dbe8..a854d2b 100644
--- a/Lib/ctypes/test/test_bitfields.py
+++ b/Lib/ctypes/test/test_bitfields.py
@@ -259,5 +259,33 @@
x.a = 0xFEDCBA9876543211
self.assertEqual(x.a, 0xFEDCBA9876543211)
+ @need_symbol('c_uint32')
+ def test_uint32_swap_little_endian(self):
+ # Issue #23319
+ class Little(LittleEndianStructure):
+ _fields_ = [("a", c_uint32, 24),
+ ("b", c_uint32, 4),
+ ("c", c_uint32, 4)]
+ b = bytearray(4)
+ x = Little.from_buffer(b)
+ x.a = 0xabcdef
+ x.b = 1
+ x.c = 2
+ self.assertEqual(b, b'\xef\xcd\xab\x21')
+
+ @need_symbol('c_uint32')
+ def test_uint32_swap_big_endian(self):
+ # Issue #23319
+ class Big(BigEndianStructure):
+ _fields_ = [("a", c_uint32, 24),
+ ("b", c_uint32, 4),
+ ("c", c_uint32, 4)]
+ b = bytearray(4)
+ x = Big.from_buffer(b)
+ x.a = 0xabcdef
+ x.b = 1
+ x.c = 2
+ self.assertEqual(b, b'\xab\xcd\xef\x12')
+
if __name__ == "__main__":
unittest.main()
diff --git a/Misc/NEWS b/Misc/NEWS
index e861175..65bb837 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -34,6 +34,9 @@
Library
-------
+- Issue #23319: Fix ctypes.BigEndianStructure, swap correctly bytes. Patch
+ written by Matthieu Gautier.
+
- Issue #23254: Document how to close the TCPServer listening socket.
Patch from Martin Panter.
diff --git a/Modules/_ctypes/cfield.c b/Modules/_ctypes/cfield.c
index 76c72f8..85b5ad2 100644
--- a/Modules/_ctypes/cfield.c
+++ b/Modules/_ctypes/cfield.c
@@ -769,6 +769,7 @@
if (get_ulong(value, &val) < 0)
return NULL;
memcpy(&field, ptr, sizeof(field));
+ field = SWAP_INT(field);
field = SET(unsigned int, field, (unsigned int)val, size);
field = SWAP_INT(field);
memcpy(ptr, &field, sizeof(field));