You say you have a data stream coming from a device. This which may mean there is some structure to the data stream. unpack() is a great tool and will go down to the single bit level with "B" and "b" specs. It can be used along with the tools already mentioned to do pretty much anything you want.

Remember that you can use successive unpack()s to pick things apart and leave some, as in 

use strict;

my $str = '567';
my ($ch, $rest);

($ch, $rest) = unpack('a a*', $str);
while (length $ch) {
   my $high_nib= ord($ch)>>4;
   my $low_nib = ord($ch) & 15;
   my ($high_bit,$case,$alpha,$rangel,$bit3,$bit2,$bit1,$bit0)
      = split '', unpack('B*',$ch);
   my @bits 
      = split '', unpack('B*',$ch);

   print "$ch == @bits   ...   ";
   printf "%d, %d, %d, %d : %d/%d\n",
      $high_bit,$case,$alpha,$rangel,$high_nib,$low_nib;   
   ($ch, $rest) = unpack('a a*', $rest);
}
     
# prints
# 5 == 0 0 1 1 0 1 0 1   ...   0, 0, 1, 1 : 3/5
# 6 == 0 0 1 1 0 1 1 0   ...   0, 0, 1, 1 : 3/6
# 7 == 0 0 1 1 0 1 1 1   ...   0, 0, 1, 1 : 3/7

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In reply to Re: Handling bits in Perl by rodion
in thread Handling bits in Perl by LittleGreyCat

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