Re: unpacking 6-bit values

my $buf;
my @out = ();
while ( length( $bigstring )) {
    $buf = '';
    $buf = $buf . chop $bigstring for (0..2);
    for (0..3) { 
        push @out, ($buf & 64); # update: Perl didn't accept this bit 
+op
        $buf >>= 6; # but is happy with this one
    }
}
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update: Grr if only all perl bitwise operators worked on strings! Pity - it would be pointless fixing this by unpacking the "offending" byte because I was deliberately trying to avoid any unpacking in this attempt at a quickie solution.

One world, one people

Comment on Re: unpacking 6-bit values Download Code

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Re^2: unpacking 6-bit values by BrowserUk (Patriarch) on Dec 16, 2010 at 15:07 UTC
#! perl -slw use strict; sub doit { my $in = shift; my $buf; my @out = (); while( length( $in ) ) { $buf = ''; $buf = $buf . chop $in for (0..2); for( 0 .. 3 ) { push @out, ($buf & 64); $buf >>= 6; } } return @out } our $packed = pack 'C*', qw[ 00 16 131 16 81 135 32 146 139 48 211 143 65 20 147 81 85 151 97 1 +50 155 113 215 159 ]; print join ' ', map sprintf( "%02d", $_ ), doit( $packed ); __END__ C:\test>junk10 Argument "ƒÎq" isn't numeric in bitwise and (&) at C:\test\junk10.pl l +ine 12. Argument "øûa" isn't numeric in bitwise and (&) at C:\test\junk10.pl l +ine 12. Argument "ùUQ" isn't numeric in bitwise and (&) at C:\test\junk10.pl l +ine 12. Argument "ô^TA" isn't numeric in bitwise and (&) at C:\test\junk10.pl +line 12. Argument "M-^OË0" isn't numeric in bitwise and (&) at C:\test\junk10.p +l line 12. Argument "ïÆ " isn't numeric in bitwise and (&) at C:\test\junk10.pl l +ine 12. Argument "çQ^P" isn't numeric in bitwise and (&) at C:\test\junk10.pl +line 12. Argument "â^P\0" isn't numeric in bitwise and (&) at C:\test\junk10.pl + line 12. 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0 +0 00 00 00 00 00 00 00 00 [download] 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.	[reply] [d/l]

Replies are listed 'Best First'.

Re^2: unpacking 6-bit values
by BrowserUk (Patriarch) on Dec 16, 2010 at 15:07 UTC

#! perl -slw
use strict;

sub doit {
    my $in = shift;
    my $buf;
    my @out = ();
    while( length( $in ) ) {
        $buf = '';
        $buf = $buf . chop $in for (0..2);
        for( 0 .. 3 ) {
            push @out, ($buf & 64);
            $buf >>= 6;
        }
    }
    return @out
}

our  $packed = pack 'C*', qw[
    00 16 131 16 81 135 32 146 139 48 211 143 65 20 147 81 85 151 97 1
+50 155 113 215 159
];

print join ' ', map sprintf( "%02d", $_ ),    doit( $packed );

__END__
C:\test>junk10
Argument "ƒÎq" isn't numeric in bitwise and (&) at C:\test\junk10.pl l
+ine 12.
Argument "øûa" isn't numeric in bitwise and (&) at C:\test\junk10.pl l
+ine 12.
Argument "ùUQ" isn't numeric in bitwise and (&) at C:\test\junk10.pl l
+ine 12.
Argument "ô^TA" isn't numeric in bitwise and (&) at C:\test\junk10.pl 
+line 12.
Argument "M-^OË0" isn't numeric in bitwise and (&) at C:\test\junk10.p
+l line 12.
Argument "ïÆ " isn't numeric in bitwise and (&) at C:\test\junk10.pl l
+ine 12.
Argument "çQ^P" isn't numeric in bitwise and (&) at C:\test\junk10.pl 
+line 12.
Argument "â^P\0" isn't numeric in bitwise and (&) at C:\test\junk10.pl
+ line 12.
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0
+0 00 00 00 00 00 00 00 00
[download]

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.

[reply]
[d/l]