Problems using bitwise &

#1 March 28th, 2008, 12:25 PM

I'm trying to perform some basic mathematics on IP Addresses. IP's are
normally represented as 32 bit unsigned integers. However I am getting
strange results when using the operators in PHP.

If you run this is a mysql query browser: select (3388826209 &
4294867288) as val; it will tell you the correct answer is:
3388760128. This is the answer I want. My snippet of PHP code is here:

$ip = $networkObjectRow['sipv4addr'];
$subnet = $networkObjectRow['eipv4addr'];

//make php treats these likes numbers and not strings

$ip += (int)0;
$subnet += (int)0;

if ($ip == 0)
return "NOT SET";

$ans = $ip & $subnet; //Bitwise AND.

print("\n");
return ($ans);

However my output is like this:



<!-- sip F (ip=3388826225,subnet=4294967280) returned is -906141072 --

Quote:

>

<!-- sip F (ip=3388826225,subnet=4294967280) returned is -906141072 --

Quote:

>

Where the IP starts 17... the answer is correct. When the value starts
3388 the value is wrong.

I guess this is because PHP is treating the number as a 64 bit one
rather than an unsigned 32 bit one but I'm not really sure. Can anyone
help please?

#2 March 28th, 2008, 02:35 PM

Philluminati wrote:

Quote:

>
$ip = $networkObjectRow['sipv4addr'];
$subnet = $networkObjectRow['eipv4addr'];
>
//make php treats these likes numbers and not strings
>
$ip += (int)0;
$subnet += (int)0;

$ip = (int)$networkObjectRow['sipv4addr'];
$subnet = (int)$networkObjectRow['eipv4addr'];

Quote:

>
print("\n");
return ($ans);
>
However my output is like this:
>



>

>
Where the IP starts 17... the answer is correct. When the value starts
3388 the value is wrong.

PHP _outputs_ it as signed integer. Try formatted output to clear
this question:

printf("\n",$ip,$subnet,$ans);

What is Bytes?

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