OCR-safe four-symbol binary encoding

Encodes every byte from standard input as four OCR-safe characters, wrapping at 32 encoded characters per line. Mapping: 00=A, 01=M, 10=3, 11=7.

Perl script

#!/usr/bin/env perl

'ocr4_encode.pl';

=head1 NAME

ocr4_encode.pl - encode binary input using four OCR-safe characters

=head1 SYNOPSIS

  producer | perl ocr4_encode.pl

=head1 DESCRIPTION

Reads a binary stream from standard input. Each byte is written as four
characters using C<00=A>, C<01=M>, C<10=3>, and C<11=7>.

=cut

use strict;
use warnings;

binmode STDIN;
binmode STDOUT;

my @symbol = qw(A M 3 7);
my $buffer;
my $column = 0;

while (read(STDIN, $buffer, 64 * 1024)) {
    for my $byte (unpack 'C*', $buffer) {
        print $symbol[($byte >> 6) & 3],
              $symbol[($byte >> 4) & 3],
              $symbol[($byte >> 2) & 3],
              $symbol[$byte & 3];
        $column += 4;
        if ($column == 32) {
            print "\n";
            $column = 0;
        }
    }
}

die "Error reading standard input: $!\n" if $!;
print "\n" if $column;

Usage

some_binary_command | perl ocr4_encode.pl