thanks, it does seem simpler without 'pack' and I can even count the set bits with a for loop to test each in turn.

I'd been hoping to use this fragment from Programming Perl (ch.29.2.189. unpack):
"The following efficiently counts the number of set bits in a bitstring:
$setbits = unpack "%32b*", $selectmask;

but for me 

    $value = 5242880;
    $value = $value | 0x0011;
    $setbits = unpack "%32b*", $value;
    printf "$setbits bits are set in %#.8x\n", $value;

[download]
gives
25 bits are set in 0x00500011

so my understanding is still inadequate. If you can bear to explain, it would be much appreciated (though I can use the for loop to count bits instead)

thanks

In reply to Re^2: how to pack bits, flags and masks by anadem
in thread how to pack bits, flags and masks by anadem

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