Question

How to extract N bits from a given position in a number with PHP

Answer 1

function extract_bits($number, $N, $pos) {
    return (((1 << $N) - 1) & ($number >> ($pos - 1)));
}

$number = 441;
$N = 6;
$pos = 5;


/*
 str_replace(
    array|string $search,
    array|string $replace,
    string|array $subject,
    int &$count = null
): string|array
*/


echo str_replace(" ", "0", sprintf("%16s", decbin($number))) . "\n";

$extracted_bits = extract_bits($number, $N, $pos);

echo str_replace(" ", "0", sprintf("%16s", decbin($extracted_bits)));





/*
run:
     
0000000110111001
0000000000011011
     
*/

 

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