jbfc.rb

# jbfc.rb - Josh Sandlin - 7:27PM - 1/18/2010
# Takes brainfuck source and compiles it to exe

# converts brainfuck code into C code
class BFToC

  attr_accessor :source, :memory

  def initialize( source, memory=30000 )
    if !File.exists? source
      abort "The supplied source file doesn't appear to exist."
    else
      @source_file = File.open( source )
      @instructions = Array.new
      @memory = memory
    end
  end
 
  # takes BF program source and converts it
  # into C instructions
  private
  def parse_to_c_instructions
    instructions = Array.new
    @source_file.each_byte do |byte|
      case byte.chr
      when "+"
        # increment value of stack pointer
        instructions += ['++*ptr;']
      when "-"
        # decrement value of stack pointer
        instructions += ['--*ptr;']
      when ">"
        # increment index of stack pointer
        instructions += ['++ptr;']
      when "<"
        # decrement index of stack pointer
        instructions += ['--ptr;']
      when "."
        # value of stack pointer to stdout
        instructions += ['putchar(*ptr);']
      when ","
        # value of stack pointer from stdin
        instructions += ['*ptr = getchar();']
      when "["
        # begin `while' loop
        instructions += ['while(*ptr) {']
      when "]"
        # end `while' loop
        instructions += ['}']
      else
        # ignore instruction (comment, etc.)
      end
    end
    instructions
  end

  # tacks on a valid header and the return statement.
  private
  def build_c_source
    "#include <stdio.h>\n" +
      "int main( void ) {\n" +
      "  unsigned char memory[#{@memory}];\n" +
      "  unsigned char *ptr = memory;\n" +
      "  #{parse_to_c_instructions.join('')}\n" +
      "  return 0;\n" +
      "}\n"
  end

  # BFToC.new('bf_source.bf').to_c -> C source code
  public
  def to_c
    build_c_source
  end

end

# compiles brainfuck code into a binary via converting
# to C first and then compiling that.
class BFCompiler

  attr_accessor :filename, :c_translation
  
  def initialize( source_file, memory=30000 )
    @filename = source_file.split('.')[0] # get name
    @c_translation = BFToC.new( source_file ).to_c
  end

  def compile
    # create C source file
    if !File.exists? "#{@filename}.c"
      File.open( "#{@filename}.c", 'w' ) do |f|
        f << @c_translation
      end
    end
    # compile C source file
    if !File.exists? "#{@filename}"
      system( "gcc #{@filename}.c -o #{@filename}" )
    end
    File.unlink( "#{@filename}.c" )
  end

end

# `frontend' to the script. Allows the user to call the
# compiler from the command prompt and supply a file.
source_file = ARGV.shift
if source_file.split('.')[1] != 'bf'
  puts "The supplied file was not a valid Brainfuck source file"
else
  compiler = BFCompiler.new( source_file ).compile
end