perl-scripts/Encoding/binary_variable_length_run_encoding.pl at master · trizen/perl-scripts · GitHub

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#!/usr/bin/perl

# Implementation of the Variable Length Run Encoding, for a binary string consisting of only 0s and 1s.

# Reference:

# Data Compression (Summer 2023) - Lecture 5 - Basic Techniques

# https://youtube.com/watch?v=TdFWb8mL5Gk

use 5.036;

sub run_length ($arr) {

@$arr || return [];

my @result = [$arr->[0], 1];

my $prev_value = $arr->[0];

foreach my $i (1 .. $#{$arr}) {

my $curr_value = $arr->[$i];

if ($curr_value eq $prev_value) {

++$result[-1][1];

}

else {

push(@result, [$curr_value, 1]);

}

$prev_value = $curr_value;

}

return \@result;

}

sub binary_vrl_encoding ($str) {

my @bits = split(//, $str);

my $bitstring = $bits[0];

foreach my $rle (@{run_length(\@bits)}) {

my ($c, $v) = @$rle;

if ($v == 1) {

$bitstring .= '0';

}

else {

my $t = sprintf('%b', $v - 1);

$bitstring .= join('', '1' x length($t), '0', substr($t, 1));

}

return $bitstring;

}

sub binary_vrl_decoding ($bitstring) {

open my $fh, '<:raw', \$bitstring;

my $decoded = '';

my $bit = getc($fh);

while (!eof($fh)) {

$decoded .= $bit;

my $bl = 0;

while (getc($fh) == 1) {

++$bl;

}

if ($bl > 0) {

$decoded .= $bit x oct('0b1' . join('', map { getc($fh) } 1 .. $bl - 1));

}

$bit = ($bit eq '1' ? '0' : '1');

}

return $decoded;

}

my $bitstring = "101000010000000010000000100000000001001100010000000000000010010100000000000000001";

my $enc = binary_vrl_encoding($bitstring);

my $dec = binary_vrl_decoding($enc);

say $enc;

say $dec;

$dec eq $bitstring or die "error";

__END__

1000110101110110111010011110001010101100011110101010000111101110

101000010000000010000000100000000001001100010000000000000010010100000000000000001

perl-scripts/Encoding/binary_variable_length_run_encoding.pl at master · trizen/perl-scripts · GitHub

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