Revert "Fix _wraparound on 64-bit windows without using ctypes."

This reverts commit 358cd618.

The _wraparound function is still broken on PyPy3 (both the old version
on Travis and the latest available) if we don't use ctypes.

CHANGES.rst

 ``persistent`` Changelog
 ========================
 
+4.2.3 (unreleased)
+------------------
+
+- Fix the hashcode of Python ``TimeStamp`` objects on 64-bit Python on
+  Windows. See https://github.com/zopefoundation/persistent/pull/55
+
 4.2.2 (2016-11-29)
 ------------------
 

persistent/tests/test_timestamp.py

@@ -280,13 +280,26 @@ class PyAndCComparisonTests(unittest.TestCase):
 
         is_32_bit_hash = orig_maxint == MAX_32_BITS
 
+        orig_c_long = None
+        c_int64 = None
+        c_int32 = None
+        if hasattr(MUT, 'c_long'):
+            import ctypes
+            orig_c_long = MUT.c_long
+            c_int32 = ctypes.c_int32
+            c_int64 = ctypes.c_int64
+            # win32, even on 64-bit long, has funny sizes
+            is_32_bit_hash = c_int32 == ctypes.c_long
+
         try:
             MUT._MAXINT = MAX_32_BITS
+            MUT.c_long = c_int32
 
             py = self._makePy(*self.now_ts_args)
             self.assertEqual(hash(py), bit_32_hash)
 
             MUT._MAXINT = int(2 ** 63 - 1)
+            MUT.c_long = c_int64
             # call __hash__ directly to avoid interpreter truncation
             # in hash() on 32-bit platforms
             if not self._is_jython:
@@ -303,6 +316,10 @@ class PyAndCComparisonTests(unittest.TestCase):
                     384009219096809580920179179233996861765753210540033)
         finally:
             MUT._MAXINT = orig_maxint
+            if orig_c_long is not None:
+                MUT.c_long = orig_c_long
+            else:
+                del MUT.c_long
 
         # These are *usually* aliases, but aren't required
         # to be (and aren't under Jython 2.7).
@@ -317,7 +334,7 @@ class PyAndCComparisonTests(unittest.TestCase):
         import persistent.timestamp as MUT
         # We get 32-bit hash values on 32-bit platforms, or on the JVM
         # OR on Windows (whether compiled in 64 or 32-bit mode)
-        is_32_bit = MUT._MAXINT == (2**31 - 1) or self._is_jython
+        is_32_bit = MUT._MAXINT == (2**31 - 1) or self._is_jython or sys.platform == 'win32'
 
         c, py = self._make_C_and_Py(b'\x00\x00\x00\x00\x00\x00\x00\x00')
         self.assertEqual(hash(c), 8)

persistent/timestamp.py

@@ -19,8 +19,7 @@ import struct
 import sys
 
 _RAWTYPE = bytes
-# On win32, long is 4 bytes even on a 64-bit platform.
-_MAXINT = sys.maxsize if not sys.platform == 'win32' else (2 ** 31 - 1)
+_MAXINT = sys.maxsize
 
 def _makeOctets(s):
     if sys.version_info < (3,):
@@ -30,11 +29,22 @@ def _makeOctets(s):
 
 _ZERO = _makeOctets('\x00' * 8)
 
-def _wraparound(x):
+try:
     # Make sure to overflow and wraparound just
-    # like the C code does. This is more compactly expressed
-    # as ctypes.c_long(x).value
-    return int(((x + (_MAXINT + 1)) & ((_MAXINT << 1) + 1)) - (_MAXINT + 1))
+    # like the C code does.
+    from ctypes import c_long
+except ImportError: # pragma: no cover
+    # XXX: This is broken on 64-bit windows, where
+    # sizeof(long) != sizeof(Py_ssize_t)
+    # sizeof(long) == 4, sizeof(Py_ssize_t) == 8
+    # It can be fixed by setting _MAXINT = 2 ** 31 - 1 on all
+    # win32 platforms, but then that breaks PyPy3 64 bit for an unknown
+    # reason.
+    def _wraparound(x):
+        return int(((x + (_MAXINT + 1)) & ((_MAXINT << 1) + 1)) - (_MAXINT + 1))
+else:
+    def _wraparound(x):
+        return c_long(x).value
 
 class _UTC(datetime.tzinfo):
     def tzname(self):