p64 and p64 are faster and create more informative exceptions.

Fixes #216.

CHANGES.rst

@@ -17,6 +17,11 @@
 
 - Add support for Python 3.7.
 
+- Make the internal support functions for dealing with OIDs (``p64``
+  and ``u64``) somewhat faster and raise more informative
+  exceptions on certain types of bad input. See `issue 216
+  <https://github.com/zopefoundation/ZODB/issues/216>`_.
+
 5.4.0 (2018-03-26)
 ==================
 

src/ZODB/tests/testUtils.py

@@ -128,12 +128,34 @@ class TestUtils(unittest.TestCase):
             self.assertEqual(get_pickle_metadata(pickle),
                             (__name__, ExampleClass.__name__))
 
+    def test_p64_bad_object(self):
+        with self.assertRaises(ValueError) as exc:
+            p64(2 ** 65)
+
+        e = exc.exception
+        # The args will be whatever the struct.error args were,
+        # which vary from version to version and across implementations,
+        # followed by the bad value
+        self.assertEqual(e.args[-1], 2 ** 65)
+
+    def test_u64_bad_object(self):
+        with self.assertRaises(ValueError) as exc:
+            u64(b'123456789')
+
+        e = exc.exception
+        # The args will be whatever the struct.error args were,
+        # which vary from version to version and across implementations,
+        # followed by the bad value
+        self.assertEqual(e.args[-1], b'123456789')
+
+
 
 class ExampleClass(object):
     pass
 
 def test_suite():
-    return unittest.TestSuite((
-        unittest.makeSuite(TestUtils),
-        doctest.DocFileSuite('../utils.txt', checker=checker),
-    ))
+    suite = unittest.defaultTestLoader.loadTestsFromName(__name__)
+    suite.addTest(
+        doctest.DocFileSuite('../utils.txt', checker=checker)
+    )
+    return suite

src/ZODB/utils.py

@@ -18,10 +18,10 @@ import sys
 import time
 import threading
 from binascii import hexlify, unhexlify
-from struct import pack, unpack
+
 from tempfile import mkstemp
 
-from persistent.TimeStamp import TimeStamp
+from persistent.timestamp import TimeStamp
 
 from ZODB._compat import Unpickler
 from ZODB._compat import BytesIO
@@ -84,13 +84,24 @@ assert sys.hexversion >= 0x02030000
 # The distinction between ints and longs is blurred in Python 2.2,
 # so u64() are U64() really the same.
 
+_OID_STRUCT = struct.Struct('>Q')
+_OID_PACK = _OID_STRUCT.pack
+_OID_UNPACK = _OID_STRUCT.unpack
+
+
 def p64(v):
-    """Pack an integer or long into a 8-byte string"""
-    return pack(">Q", v)
+    """Pack an integer or long into a 8-byte string."""
+    try:
+        return _OID_PACK(v)
+    except struct.error as e:
+        raise ValueError(*(e.args + (v,)))
 
 def u64(v):
     """Unpack an 8-byte string into a 64-bit long integer."""
-    return unpack(">Q", v)[0]
+    try:
+        return _OID_UNPACK(v)[0]
+    except struct.error as e:
+        raise ValueError(*(e.args + (v,)))
 
 U64 = u64