Re: bit wise math? Is there a function to easily return the bits?

[Roman Neuhauser <neuhauser@xxxxxxxxxx>]

# jon@xxxxxxxxxxxxxxxxxx / 2007-01-25 14:34:51 -0500:
> function bits($num) {
>        $bit_array = str_split(strrev(decbin(intval($num))));
>        $val_array = array();
>        foreach ($bit_array as $pow => $bit) {
>                if ($val = $bit * pow(2,$pow))
>                        $val_array[] = $val;
>        }
>        return($val_array);
> }
> 
> (I wanted to see if I could write it in few LOC.) I wonder if there's a 
> faster way...

I didn't time either version, and I'm no mathematician either, so this
is prolly a stupid solution.

<?php

function bitarray($ored)
{
    $rv = array();
    for ($v = 1; $v <= $ored; $v *= 2) {
        if ($ored & $v) {
            array_push($rv, $v);
        }
    }
    return $rv;
}

class SingleBitTest extends Tence_TestCase
{
    private function doTest($int)
    {
        return $this->assertEquals(
            array($int),
            bitarray($int)
        );
    }
    function testE_ERROR()
    {
        return $this->doTest(E_ERROR);
    }
    function testE_WARNING()
    {
        return $this->doTest(E_WARNING);
    }
    function testE_NOTICE()
    {
        return $this->doTest(E_NOTICE);
    }
    function testE_USER_ERROR()
    {
        return $this->doTest(E_USER_ERROR);
    }
    function testE_USER_WARNING()
    {
        return $this->doTest(E_USER_WARNING);
    }
    function testE_USER_NOTICE()
    {
        return $this->doTest(E_USER_NOTICE);
    }
}

class BitArrayTest extends Tence_TestCase
{
    private function doTest(array $expected, $int)
    {
        return $this->assertEquals(
            $expected,
            bitarray($int)
        );
    }
    function test7()
    {
        return $this->doTest(array(1, 2, 4), 7);
    }
    function test8()
    {
        return $this->doTest(array(8), 8);
    }
    function testERROR_WARNING_NOTICE_STRICT()
    {
        return $this->doTest(
            array(E_ERROR, E_WARNING, E_NOTICE, E_STRICT),
            E_ERROR|E_WARNING|E_NOTICE|E_STRICT
        );
    }
}

class bttests extends Tence_TestSuite
{
    function __construct()
    {
        $this
            ->add(new SingleBitTest)
            ->add(new BitArrayTest)
        ;
    }
}

?>

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