#!/usr/bin/env ruby

# © 2002 Jos Backus <jos@catnook.com>
#
# 2002-01-22 Initial version
# 2002-06-02 Updates inspired by comments by Jack Herrington
#
# This script is a reimplementation of most of the xxd utility that ships with
# vim. It can create an editable text dump of a file, and (when the -r option
# is specified) recreate a file based on a text dump. It sends its output to
# stdout.
# The dump line format looks like this:
# 0000000: 7f45 4c46 0101 0109 0000 0000 0000 0000  .ELF............

$progname = File.basename($0)

def usage
    STDERR.puts "usage: #$progname [-r] [file]"
    exit 64
end

class Fixnum
    def even?
	self % 2 == 0
    end
    def printable
	case self
	    when 0..037, 0177..0377 then "."
	    else self.chr
	end
    end
end

def printline(n, c, chars)
    i = 0
    line = chars.map {|ch| i += 1; sprintf "%02x%s", ch, i.even? ? ' ' : '' }
    text = chars.map {|ch| ch.printable }
    printf "%07x: %-40s %-#{n}s\n", c - c % n, line, text
end

revert = nil
while ARGV[0] =~ /^-/
    case ARGV[0]
	when "-r"
	    revert = 1
	else
	    STDERR.puts "#$progname: illegal option -- #{ARGV[0]}"
 	    usage
    end
    ARGV.shift
end

if revert
    $stdout.binmode # when running under DOS/Windows
    pat = /^[\da-f]{7}:(( [\da-f]{4}){1,8})/
    while line = ARGF.gets
	if m = pat.match(line)
	    print m[1].split(' ').map {|h| h.hex}.pack("n*")
	end
    end
else
    n = 16
    c = 0
    chars = []
    while ch = ARGF.getc
	chars << ch
	if (c += 1) % n == 0
	    printline(n, c - n, chars)
	    chars.clear
	end
    end
    # Print remaining bytes, if any
    printline(n, c, chars) unless chars.empty?
end

exit