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Re^2: emulate 32-bit on perl 64

by loofort (Initiate)
on Jan 11, 2012 at 15:17 UTC ( #947360=note: print w/ replies, xml ) Need Help??


in reply to Re: emulate 32-bit on perl 64
in thread emulate 32-bit on perl 64

I'm not sure that example brings any clearence. I'm not the author and I use it as black box. here is little part::

for ($h = 16; $h < 80; $h++) { $i[$h] = a2 ($i[$h - 3] ^ $i[$h - 8] ^ $i[$h - 14] ^ $i[$h - 16], +1); } sub a2 { my ($b, $a) = @_; my $c = $b >> 32 - $a; my $e = (1 << 32 - $a) - 1; my $d = $b & $e; return tos($d << $a | $c); } sub tos { my ($num) = @_; $num = $num - 4294967296 if $num > 4294967295; $num = $num + 4294967296 if $num < -2147483648; if ($num >= 0) { $num = $num - 2 ** 32 if ($num >> 31); } return $num; }


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Re^3: emulate 32-bit on perl 64
by Corion (Pope) on Jan 11, 2012 at 15:24 UTC

    There is no magic to sprinkle over an algorithm that relies on 32-bit integers to make it behave with other integer sizes. The hardcoded numbers here are magic for 32-bit numbers:

    $num = $num - 4294967296 if $num > 4294967295; $num = $num + 4294967296 if $num < -2147483648;

    You will have to understand the algorithm involved to be able to make the required changes. Alternatively, you can run the program under a Perl compiled with 32-bit integers.

Re^3: emulate 32-bit on perl 64
by BrowserUk (Pope) on Jan 11, 2012 at 15:54 UTC

    Try this -- 'scuse the formatting, but there's no good way to format it. It produces the same results on 32-bit and 64-bit Perls for one randomly generated set of input data:

    for( my $h = 16; $h < 80; $h++ ) { $i[$h] = a2( ( ( ( ( ( $i[$h - 3] ^ $i[$h - 8] ) & 0xffffffff ) ^ $i[$h - 14] ) & 0xffffffff ) ^ $i[$h - 16] ) & 0xffffffff , 1 ); } print "@i"; sub a2 { my ($b, $a) = @_; my $c = $b >> 32 - $a; my $e = (1 << 32 - $a) - 1; my $d = $b & $e; return tos($d << $a | $c); } sub tos { my ($num) = @_; $num = $num - 4294967296 if $num > 4294967295; $num = $num + 4294967296 if $num < -2147483648; if ($num >= 0) { $num = $num - 2 ** 32 if ($num >> 31); } return $num; }

    With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
    Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
    "Science is about questioning the status quo. Questioning authority".
    In the absence of evidence, opinion is indistinguishable from prejudice.

    The start of some sanity?

Re^3: emulate 32-bit on perl 64
by BrowserUk (Pope) on Jan 11, 2012 at 16:06 UTC

    This is slightly more readable:

    sub fix32{ $_[0] & 0xffffffff } for( my $h = 16; $h < 80; $h++ ) { $i[$h] = a2( fix32( fix32( fix32( $i[$h - 3] ^ $i[$h - 8] ) ^ $i[$h - 14] ) + ^ $i[$h - 16] ) , 1 ); }

    With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
    Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
    "Science is about questioning the status quo. Questioning authority".
    In the absence of evidence, opinion is indistinguishable from prejudice.

    The start of some sanity?

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