Re^5: How to convert binary to hexadecimal

[roboticus]

Anonymonk:

Here's another way to do it:

$ cat bin2hex.pl
#!/usr/bin/perl
use strict; use warnings;

for my $b (qw(101101110101001010010100101000101011101010101010101010
              1  10 101 1010 10101 101010 11010011 000000000000001 000
+1111
              11111 11000011
)) {
    print "$b --> ", bin2hex($b), "\n";
}

sub bin2hex {
    my $bin = shift;

    # Make input bit string a multiple of 4
    $bin = substr("0000",length($bin)%4) . $bin if length($bin)%4;

    my ($hex, $nybble) = ("");
    while (length($bin)) {
        ($nybble,$bin) = (substr($bin,0,4), substr($bin,4));
        $nybble = eval "0b$nybble";
        $hex .= substr("0123456789ABCDEF", $nybble, 1);
    }
    return $hex;
}

$ perl bin2hex.pl
101101110101001010010100101000101011101010101010101010 --> 2DD4A528AEA
+AAA
1 --> 1
10 --> 2
101 --> 5
1010 --> A
10101 --> 15
101010 --> 2A
11010011 --> D3
000000000000001 --> 0001
0001111 --> 0F
11111 --> 1F
11000011 --> C3

It uses an old^[1] trick: Since each "nybble"^[2] represents a decimal value from 0 to 15, you can build a 16 character string of digits, and use the nybble value as the index of a character.

Then, to simplify things, we ensure that the string is a multiple of four characters long. That way, we simply chop off four characters, turn it into a hex digit, repeating until the string is consumed.

Notes:

[1] How old? It was old when I learned it, roughly 35 years ago.

[2] Four bits == half a byte, thus, a nybble.

...roboticus

When your only tool is a hammer, all problems look like your thumb.