Revert "Fix hardbyte#1376 (hardbyte#1412)"

This reverts commit a344a13.

Author: j-c-cook

test/test_socketcan.py

@@ -3,10 +3,13 @@
 """
 Test functions in `can.interfaces.socketcan.socketcan`.
 """
-import ctypes
-import struct
 import unittest
+
+from unittest.mock import Mock
 from unittest.mock import patch
+from unittest.mock import call
+
+import ctypes
 
 from can.interfaces.socketcan.socketcan import (
     bcm_header_factory,
@@ -237,25 +240,51 @@ def side_effect_ctypes_alignment(value):
         ]
         self.assertEqual(expected_fields, BcmMsgHead._fields_)
 
-    def test_build_bcm_header(self):
-        def _find_u32_fmt_char() -> str:
-            for _fmt in ("H", "I", "L", "Q"):
-                if struct.calcsize(_fmt) == 4:
-                    return _fmt
+    @unittest.skipIf(
+        not (
+            ctypes.sizeof(ctypes.c_long) == 4 and ctypes.alignment(ctypes.c_long) == 4
+        ),
+        "Should only run on platforms where sizeof(long) == 4 and alignof(long) == 4",
+    )
+    def test_build_bcm_header_sizeof_long_4_alignof_long_4(self):
+        expected_result = (
+            b"\x02\x00\x00\x00\x00\x00\x00\x00"
+            b"\x00\x00\x00\x00\x00\x00\x00\x00"
+            b"\x00\x00\x00\x00\x00\x00\x00\x00"
+            b"\x00\x00\x00\x00\x01\x04\x00\x00"
+            b"\x01\x00\x00\x00\x00\x00\x00\x00"
+        )
 
-        def _standard_size_little_endian_to_native(data: bytes) -> bytes:
-            std_le_fmt = "<IIIllllII"
-            native_fmt = "@" + std_le_fmt[1:].replace("I", _find_u32_fmt_char())
-            aligned_data = struct.pack(native_fmt, *struct.unpack(std_le_fmt, data))
-            padded_data = aligned_data + b"\x00" * ((8 - len(aligned_data) % 8) % 8)
-            return padded_data
+        self.assertEqual(
+            expected_result,
+            build_bcm_header(
+                opcode=CAN_BCM_TX_DELETE,
+                flags=0,
+                count=0,
+                ival1_seconds=0,
+                ival1_usec=0,
+                ival2_seconds=0,
+                ival2_usec=0,
+                can_id=0x401,
+                nframes=1,
+            ),
+        )
 
-        expected_result = _standard_size_little_endian_to_native(
+    @unittest.skipIf(
+        not (
+            ctypes.sizeof(ctypes.c_long) == 8 and ctypes.alignment(ctypes.c_long) == 8
+        ),
+        "Should only run on platforms where sizeof(long) == 8 and alignof(long) == 8",
+    )
+    def test_build_bcm_header_sizeof_long_8_alignof_long_8(self):
+        expected_result = (
             b"\x02\x00\x00\x00\x00\x00\x00\x00"
             b"\x00\x00\x00\x00\x00\x00\x00\x00"
             b"\x00\x00\x00\x00\x00\x00\x00\x00"
-            b"\x00\x00\x00\x00\x01\x04\x00\x00"
-            b"\x01\x00\x00\x00"
+            b"\x00\x00\x00\x00\x00\x00\x00\x00"
+            b"\x00\x00\x00\x00\x00\x00\x00\x00"
+            b"\x00\x00\x00\x00\x00\x00\x00\x00"
+            b"\x01\x04\x00\x00\x01\x00\x00\x00"
         )
 
         self.assertEqual(