I need to calculate the two’s complement of a HEX value, but am struggling using dechex, hexbin etc. and not getting the correct result.
How do i do this in PHP ?
For example: The two’s complement of E2 is 1E.
Hi,
[php]<?php
$tests = [
‘E2’, ‘1e’, ‘aab’, ‘f32d’,
];
foreach ($tests as $hex) {
echo "$hex => ", hex_complement($hex), PHP_EOL;
}
function hex_complement($hex) {
$dec = hexdec($hex);
$clear = dechex($dec);
$big = ‘1’. str_repeat(‘0’, strlen($clear));
$comp = hexdec($big) - $dec;
return strtoupper(dechex($comp));
}[/php] results E2 => 1E
1e => E2
aab => 555
f32d => CD3
Is this the correct result?
thx,
what i an wondering, would this do the same, or would i run into troubles somehow?
[php]
$dec = (int) 226;
$negative = $dec * -1;
echo dechex( bindec( ltrim( decbin( $negative ) , ‘1’) ) );
[/php]
hi,
would i run into troubles somehow?i suppose yes
[php]$dec = hexdec(‘1E’);
$negative = $dec * -1;
echo dechex( bindec( ltrim( decbin( $negative ) , ‘1’) ) ); // outputs ‘2’ instead of ‘E2’[/php]
ltrim too greedy and removes extra bits