bit operation

[Anon]

Hello everyone,

I'm desperatly trying to do the following:

I have an int which I use to hold 4 pairs of bits. I want to be able to set the pairs of bits within the int like this:

setpair($stuff, $i, $bits)

where $stuff is an int,
$i is an index (0, 1, 2 or 3)
and $bits is a two bit value: 00, 01, 10, or 11.

For example:

$stuff = 10 01 10 01
$i = 2
$bits = 10

setpair($stuff, $i, $bits) would set $stuff to 10 10 10 01 (the second pair of bits starting from 0 is set to the value of $bits).

I tried different things but I'm not getting the results I want. Any help would be appreciated!

Thanks,

Matt.

[Anon]

I assume

$stuff == 153;
not
$stuff == "10 0110 01";

and

$bits == 3 OR $bits == 2 OR $bits == 1 OR $bits = 0
not
$bits == '11' OR $bits == '10' OR $bits == '01' OR $bits == '00';

this should work.

$stuff = 153;
$i = 2;
$bits = 2;

function setpair($stuff, $i, $bits)
{
$a[0] = (($stuff - 0) >> 6) << 6;
$a[1] = (($stuff - $a[0]) >> 4) << 4;
$a[2] = (($stuff - $a[0] - $a[1]) >> 2) << 2;
$a[3] = (($stuff - $a[0] - $a[1] - $a[2]) >> 0) << 0;

$a[(3 - $i)] = $bits << ($i * 2);
$stuff = $a[0] + $a[1] + $a[2] + $a[3];

return $stuff
}

echo "$stuff <br>\n";

$stuff = setpair($stuff, $i, $bits);

echo "$stuff <br>\n";

Hope this helps.

Chris Lee

[Anon]

Chris,
that f*cking helped!!!!!!! Works perfectly!!

Thanks very much!

Matt.

[Anon]

No problem 🙂

Chris Lee