in reply to Re: Split any number into string of 8-bit hex values (=1 byte)
in thread Split any number into string of 8-bit hex values (=1 byte)

log(0) is undefined, so I designed a custom function hexbytes which returns a list of 0 padded bytes and special casing '00'.

Please note how I kept the reverse and join outside for generic flexibility of use.

NB: you must still take care of negative $n!

use strict;
use warnings;
use feature "say";

sub hexbytes {
    my ($n)=@_;

    my $nibbles = $n
      ? int( log($n)/log 256 )+1
        : 1  ;                          # 00 has no log

    $nibbles *= 2;                      # 2 nibbles = 1 byte

    return sprintf( '%0*x', $nibbles, $n ) =~ /(..)/g;
}


say "$_ => ", join " ", reverse hexbytes($_) for 0,2,20,200,2000,20000
+,200000;

[download]

C:/Strawberry/perl/bin\perl.exe -w d:/tmp/pm/hex_reverse.pl 
0 => 00
2 => 02
20 => 14
200 => c8
2000 => d0 07
20000 => 20 4e
200000 => 40 0d 03

Compilation finished at Mon Aug 30 15:57:08

[download]

Cheers Rolf
(addicted to the Perl Programming Language :)
Wikisyntax for the Monastery

Replies are listed 'Best First'.
Re^3: Split any number into string of 8-bit hex values (=1 byte)
by LanX (Saint) on Aug 30, 2021 at 14:29 UTC
    Here a more generic solution, the grouping is free now

    (left the reverse out for better testing) 

    use strict;
use warnings;
use feature "say";

sub hexgroups {
    my ( $n, $group ) = @_;

    die "Can't handle negative $n" if $n <0;

    $group //= 2;                       # default 1 byte = 2 nibbles

    my $nibbles = $n
      ? int( log($n)/log 16**$group ) +1
        : 1  ;                          # 00 has no log

    $nibbles *= $group;                 # zero padding

    my @list = sprintf( '%0*x', $nibbles, $n ) =~ /(.{$group})/g;

    return @list;
}



for my $n (0, map { 2*"1e$_"} 0..10) {
    say "$n => ";
    say "\t"x2, join " ",  hexgroups($n, $_) for 1,2,3,4;
}

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