[ python-Bugs-1678102 ] zlib.crc32() not cross-platform

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Bugs item #1678102, was opened at 2007-03-10 18:07
Message generated for change (Settings changed) made by tjreedy
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Category: Python Library
Group: Python 2.5
>Status: Closed
>Resolution: Invalid
Priority: 5
Private: No
Submitted By: Ben Collver (bencollver)
Assigned to: Nobody/Anonymous (nobody)
Summary: zlib.crc32() not cross-platform

Initial Comment:
The zlib.crc32() function sometimes produces different results for the same input on big and little-endian processors.  Same for zlib.adler32().

sparc64:
>>> import zlib
>>> print zlib.adler32("--------------------------------------------------", 1)
> 3763407051
>>> print zlib.crc32("--------------------------------------------------", 1)
3044228349

i386:
>>> import zlib
>>> print zlib.adler32("--------------------------------------------------", 1)
> -531560245
>>> print zlib.crc32("--------------------------------------------------", 1)
-1250738947


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Comment By: Gabriel Genellina (gagenellina)
Date: 2007-03-13 18:52

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py> -531560245 & 0xffffffff
3763407051L

It's the same number (actually, the same bit pattern). The i386 version is
signed, the other unsigned. The i386 platform uses a 32 bit "int"; the
sparc64 uses 64 bits (I presume). 3763407051 doesnt fit in 31bits, so it's
seen as a negative number.



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Comment By: Ben Collver (bencollver)
Date: 2007-03-10 18:13

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The extra > characters before the first results come from me pasting the
results to my irc client, then copying from there and pasting here.  Sorry
for any confusion.

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