gistfile1.rb

#!/usr/bin/env ruby
 
class Brainfuck
# Ruby Brainfuck interpreter
# (C) Scott Olson <scott@scott-olson.org>
# MIT License
  attr_accessor :script, :stdin, :stdout
 
  @@allowed = '<>+-.,[]#'
 
  # script is the brainfuck program
  # stdin and stdout are the input and output, respectively
  # they can be String, IO, or something else that accepts putc/getc
  def initialize(script, stdout=nil, stdin=nil)
    @script = script
    @stdout = stdout || ''
    @stdin = stdin || ''
  end
 
  def run
    ptr = 0
    stack = [0]
    script = @script.split('')
    script_ptr = 0
 
    while script_ptr < script.length
      debug_msg = "%0#{script.length.to_s.length}i: (#{ptr}=#{stack[ptr]}) #{script[script_ptr]}" % script_ptr
      case script[script_ptr]
      when '>'
        ptr += 1
        stack[ptr] ||= 0 # set the cell to 0 if it is nil
 
      when '<'
        ptr -= 1
        stack[ptr] ||= 0 # set the cell to 0 if it is nil
 
      when '+'
        stack[ptr] += 1
 
      when '-'
        stack[ptr] -= 1
 
      when '.'
        debug_msg << " outputting #{stack[ptr].chr.inspect}"
        case @stdout
        when String
          @stdout << stack[ptr]
        else
          @stdout.putc stack[ptr]
        end
 
      when ','
        case @stdin
        when String
          stack[ptr] = (/^1\.8/ === RUBY_VERSION ? @stdin.first[0] : @stdin.first.ord) # grab first char as int
          @stdin[0] = '' # remove the char from the string
        else
          stack[ptr] = @stdin.getc
          stack[ptr] ||= 0 # our EOF if @stdin is at the end
        end
 
      when '['
        came_from = script_ptr # never forget where you came from
        # this code jumps to the next ']' if our current byte is 0
        script_ptr += script[script_ptr..-1].index(']') if stack[ptr] == 0
 
      when ']'
        raise "unmatched ] encountered" unless defined? :came_from
        script_ptr = came_from - 1 # go back to the start of the loop
        
      when '#'
        debug_msg << " dumping info for debugging purposes\n"
        stack_dump = []
        stack.each_with_index do |v,i|
          stack_dump << "*#{i}=#{v}" && next if ptr == i # put a * next to the cell the pointer is at
          stack_dump << "#{i}=#{v}"
        end
        debug_msg << "[" << stack_dump.join(', ') << "]\n"
        
      else # not a brainfuck character; treated as a comment
        comment ||= [script_ptr]
        comment[1] = script_ptr
 
      end
      if @@allowed.include?(script[script_ptr]) and comment
        debug_msg = ("%0#{script.length.to_s.length}i-%0#{script.length.to_s.length}i: comments\n" % [comment[0], comment[1]]) + debug_msg
        comment = nil
      end
      
      script_ptr += 1
      $stderr.puts debug_msg if @@debug unless comment
    end
  end
 
  @@debug = false
  def self.debug=(val)
    @@debug = val
  end
end

class BSP
  def call(env)
    #Brainfuck.debug = true
    req = Rack::Request.new env
    headers = {"Content-Type" => "text/html"}
    filename = env["PATH_INFO"][1..-1]
    
    input = req.params.map{|k,v|"#{k}=#{v}"}.join("&")
    output = ""
    
    Brainfuck.new(File.read(filename), output, input).run
    headers["Content-Length"] = output.length.to_s
    [200,headers,output]
  end
end

run BSP.new