[Python-Dev] [Python-checkins] cpython (2.7): Issue #10276: test_zlib checks that inputs of 2 GB are handled correctly by

[Ethan Furman]

Victor Stinner wrote:
> Le mardi 03 mai 2011 à 16:22 +0200, Nadeem Vawda a écrit :
>> On Tue, May 3, 2011 at 3:19 PM, victor.stinner
>> <python-checkins at python.org> wrote:
>>> +# Issue #10276 - check that inputs of 2 GB are handled correctly.
>>> +# Be aware of issues #1202, #8650, #8651 and #10276
>>> +class ChecksumBigBufferTestCase(unittest.TestCase):
>>> +    int_max = 0x7FFFFFFF
>>> +
>>> +    @unittest.skipUnless(mmap, "mmap() is not available.")
>>> +    def test_big_buffer(self):
>>> +        if sys.platform[:3] == 'win' or sys.platform == 'darwin':
>>> +            requires('largefile',
>>> +                     'test requires %s bytes and a long time to run' %
>>> +                     str(self.int_max))
>>> +        try:
>>> +            with open(TESTFN, "wb+") as f:
>>> +                f.seek(self.int_max-4)
>>> +                f.write("asdf")
>>> +                f.flush()
>>> +                try:
>>> +                    m = mmap.mmap(f.fileno(), 0, access=mmap.ACCESS_READ)
>>> +                    self.assertEqual(zlib.crc32(m), 0x709418e7)
>>> +                    self.assertEqual(zlib.adler32(m), -2072837729)
>>> +                finally:
>>> +                    m.close()
>>> +        except (IOError, OverflowError):
>>> +            raise unittest.SkipTest("filesystem doesn't have largefile support")
>>> +        finally:
>>> +            unlink(TESTFN)
>>> +
>>> +
>> 0x7FFFFFFF is (2G-1) bytes. For a 2GB buffer, int_max should be
>> 0x80000000. However, if you make this change, crc32() and adler32()
>> raise OverflowErrors (see changeset a0681e7a6ded).
> 
> I don't want to check OverflowError: the test is supposed to compute the
> checksum of a buffer of 0x7FFFFFFF bytes

The comment says 'check that inputs of 2 GB are handled correctly' but 
the file created is 1 byte short of 2Gb.  Is the test wrong, or just 
wrongly commented?  Or am I not understanding?

~Ethan~