bpo-32011: Revert "Issue GH-15480: Remove the deprecated and unused TYPE_INT64 code from marshal." (GH-4381) (#4405)

Simplify the reverted code.

This reverts commit e9bbe8b87ba2874efba0474af5cc7d5941dbf742.
(cherry picked from commit 00987f6230fcdbecc8d9ab4b2b9fae8f99a1a4a9)

1 files changed, 23 insertions, 0 deletions

diff --git a/Lib/test/test_marshal.py b/Lib/test/test_marshal.py
index b378ffe..29dda98 100644
--- a/Lib/test/test_marshal.py
+++ b/Lib/test/test_marshal.py
@@ -34,6 +34,29 @@ class IntTestCase(unittest.TestCase, HelperMixin):
                 self.helper(expected)
             n = n >> 1
 
+    def test_int64(self):
+        # Simulate int marshaling with TYPE_INT64.
+        maxint64 = (1 << 63) - 1
+        minint64 = -maxint64-1
+        for base in maxint64, minint64, -maxint64, -(minint64 >> 1):
+            while base:
+                s = b'I' + int.to_bytes(base, 8, 'little', signed=True)
+                got = marshal.loads(s)
+                self.assertEqual(base, got)
+                if base == -1:  # a fixed-point for shifting right 1
+                    base = 0
+                else:
+                    base >>= 1
+
+        got = marshal.loads(b'I\xfe\xdc\xba\x98\x76\x54\x32\x10')
+        self.assertEqual(got, 0x1032547698badcfe)
+        got = marshal.loads(b'I\x01\x23\x45\x67\x89\xab\xcd\xef')
+        self.assertEqual(got, -0x1032547698badcff)
+        got = marshal.loads(b'I\x08\x19\x2a\x3b\x4c\x5d\x6e\x7f')
+        self.assertEqual(got, 0x7f6e5d4c3b2a1908)
+        got = marshal.loads(b'I\xf7\xe6\xd5\xc4\xb3\xa2\x91\x80')
+        self.assertEqual(got, -0x7f6e5d4c3b2a1909)
+
     def test_bool(self):
         for b in (True, False):
             self.helper(b)