Brainfuck in Ruby (Fixed an Faster)

#!/usr/bin/ruby1.9.1
# Brainfuck Interpreter
# (C) Sebastian Kaspari 2009
# Usage: bf4 [FILE]

# This code is much much faster than the last one, which did
# a lot of unnecessary loops which could also lead to bugs
#
# There's now a bracket map which stores starting and ending
# brackets for direct "jumps", that should speed up things too

require 'rubygems'
require "highline/system_extensions"
include HighLine::SystemExtensions

msec = Time.now.to_f * 1000;

code = ARGF.read
le   = code.length
cp   = -1        # code pointer
p    = 0         # cell pointer
c    = [0]       # cells
bm   = {}        # bracket map, jump directly to matching brackets! :)
bc   = 0         # bracket counter
s    = []        # bracket stack
ccp  = 0         # code pointer for cleaned code

# valid commands
commands = [">", "<", "+", "-", ".", "[", "]", ","]

cleaned = [] # code goes here

# Only select valid commands and build bracket map
# Now there's also some time for bracket syntax checking :)
until (cp+=1) == le
  case code[cp]
    when ?[ then s.push(ccp) && bc += 1
    when ?] then (bm[s.pop] = ccp) && bc -= 1
  end
  bc < 0 && puts("Ending Bracket without opening, mismatch at #{cp}") && exit
  commands.include? code[cp] && (cleaned.push code[cp]) && ccp += 1
end

!s.empty? && puts("Opening Bracket without closing, mismatch at #{s.pop}") && exit

# reset defaults
cp = -1

# now lets interprete the code :)
until (cp+=1) == le
  case cleaned[cp]
    when ?> then (p += 1) && c[p].nil? && c[p] = 0
    when ?< then p <= 1 ? p = 0 : p -= 1
    when ?+ then c[p] <= 254 ? c[p] += 1 : c[p] = 0
    when ?- then c[p] >= 1 ? c[p] -= 1 : c[p] = 255
    when ?[ then c[p] == 0 && cp = bm[cp]
    when ?] then c[p] != 0 && cp = bm.key(cp)
    when ?. then print c[p].chr
    when ?, then c[p] = get_character.to_i
  end
end

# and finally some benchmarking

runtime = Time.now.to_f * 1000 - msec

puts ""
puts ""
puts "#{runtime} msecs [Used #{c.length} cells]"

The interpreter is now part of this "project": http://github.com/pocmo/Ruby-Brainfuck