Victor Stinner wrote:
Le mercredi 04 mai 2011 à 15:40 -0700, Ethan Furman a écrit :
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-check...@python.org> wrote:

+    int_max = 0x7FFFFFFF

+            with open(TESTFN, "wb+") as f:
+                f.seek(self.int_max-4)
+                f.write("asdf")
+                f.flush()

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?

If you write a byte after 2 GB of zeros, the file size is 2 GB+the few
bytes. This trick is to create quickly a large file: some OSes support
sparse files, zeros are not written on disk. But on Mac OS X and
Windows, you really write 2 GB+some bytes.

True, but that's not what's happening -- four bytes are being written at
int_max - 4, and int_max is one less that 2GB; hence the resulting file is one less than 2GB.

~Ethan~
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