Posted by writeson on 12/28/05 19:33

Hi all,

I have PHP version 4.4 installed on a Soaris 2.6 system and I'm getting
strange results doing math/boolean operators. I have a hashing
algorithm that does multiplication, bitwise operations and mod() calls
interatively on the characters of a filename. On a linux platform the
multiplications start to overflow (as I expect) and the overflow is
just dropped. The lower three bytes are masked off like this:

$result = $result & 0x00FFFFFF;

and the loop continues. On the Solaris platform the multiplication
fails very quickly in the loop, and it looks like the overflow bits are
wrapped around onto the lower order bytes, eventually I end up with an
interger value of 0x00FFFFFF because of the masking above. To solve the
problem I had to compile the gmp_* function support into PHP and work
with the gmp_* family of functions.

Has anyone ever seen this behavior before, and if so can you enlighten
me about it?

Thanks,
Doug

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