From: James Edward Gray II <james@...>
Date: 2006-08-01T04:15:24+09:00
Subject: Fwd: Please Forward: Ruby Quiz Submission (88)

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Begin forwarded message:

> From: afalcone@tinymonkey.net
> Date: July 31, 2006 2:13:15 PM CDT
> To: afalcone@tinymonkey.net
> Cc: submission@rubyquiz.com
> Subject: Re: Please Forward: Ruby Quiz Submission (88)
>
> Sorry to email you again, but there's a tiny bug in my original  
> program.
> Please submit the one attached to this mail.
>
> Thanks,
> -A
>
>> Hi James. Please forward my solution on to the board.
>>
>> Thanks,
>> -Adrian
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class UnsignedFixedWidthInt
#code for this class taken from Hank Lords' solution to ruby quiz #85
#http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-talk/199907
#
#to_bin_string is mine

  #Direct access to @value added to assist carry and certain quicker assignments.
  #Kinda defeats the purpose of using this class, but I save on object creation in certain places
  # -AF
  attr_accessor :value

  def initialize(value, bits)
    raise ArgumentError.new('number of bits must be > 0') if bits <= 0
    @bits = bits
    @value = value % 2**@bits
  end

  # operators returning a new FixedWidthInt
  %w{& ^ | << >> + - * / +@ -@ ~@}.each do |operator|
    define_method operator do |*other|
      self.class.new(@value.send(operator, *other), @bits)
    end
  end

  # methods forwarded to @value
  %w{== < > <=> inspect to_s to_i to_int}.each do |meth|
    define_method meth do |*other|
    @value.send(meth, *other)
    end
  end

  #this method was not in the original UFWI class
  # -AF
  def to_bin_string
    s = ""
    (@bits - 1).downto(0) { |i| s << @value[i].to_s }
    s
  end

  #modified from original because I never need Floats
  # -AF
  def coerce(other)
    [other, @value]
  end
end

class Integer
  def to_1_digit_hex
    #simplified to_hex method because I'll only ever need one digit
    raise ArgumentError, "doesn't work on negatives" if self < 0
    raise ArgumentError, "#{self.to_s} is greater than 15" if self > 15
    self < 10 ? self.to_s : (self - 10 + ?A).chr
  end
end

class InvalidOpCodeError < StandardError
  def initialize( io )
    puts "Invalid Op Code starting at byte #{io.pos - 2}."
  end
end

class Chip8

  def initialize( io=STDIN, carry_on_op7=1 )
    raise ArgumentError, "Need an IO object" unless io.kind_of?( IO )
    @code = io
    @v = Array.new( 16 ) { UnsignedFixedWidthInt.new( 0, 8 ) }
    @carry_on_op7 = carry_on_op7
  end

  def parse
    hob = @code.getc
    lob = @code.getc
    raise EOFError, "File ends before opcode x0000" unless hob && lob
    case hob & 0xF0
      when 0x00
	if ( hob == 0 && lob == 0 )
	  @code.close rescue IOError
	  return nil
	else
	  raise InvalidOpCodeError.new( @code )
	end
      when 0x10
	@code.seek( ( ( hob & 0x0F ) << 8 ) + lob, IO::SEEK_SET )
      when 0x30
	@code.seek( 2, IO::SEEK_CUR ) if ( @v[ hob & 0x0F ] == lob )
      when 0x60
	@v[ hob & 0x0F ].value = lob
      when 0x70
	@v[ 0 ].value = ( @carry_on_op7 && ( @v[ hob & 0x0F ].value + lob > 255 ) ) ? 1 : 0
	@v[ hob & 0x0F ] += lob
      when 0x80
	x = hob % 16
	y = lob >> 4
	case lob & 0x0F
	  when 0x00 : @v[x].value = @v[y].value
	  when 0x01 : @v[x] |= @v[y]
	  when 0x02 : @v[x] &= @v[y]
	  when 0x03 : @v[x] ^= @v[y]
	  when 0x04
	    @v[ 0 ].value = @v[x].value + @v[y].value > 255 ? 1 : 0
	    @v[x] += @v[y]
	  when 0x05
	    @v[ 0 ].value = @v[x].value < @v[y].value ? 1 : 0
	    @v[x] -= @v[y]
	  when 0x06
	    if y == 0
	      @v[0].value = @v[x].value % 2
	      @v[x].value = @v[x].value >> 1
	    else
	      raise InvalidOpCodeError.new( @code )
	    end
	  when 0x07
	    @v[0].value = @v[y].value < @v[x].value ? 1 : 0
	    @v[x] = @v[y] - @v[x]
	  when 0x0E
	    if y == 0
	      @v[0].value = @v[x].value / 128
	      @v[x].value = ( @v[x].value << 1 ) % 256
	    else
	      raise InvalidOpCodeError.new( @code )
	    end
	  else
	    raise InvalidOpCodeError.new( @code )
	end
      when 0xC0
	@v[ hob & 0x0F ].value = rand( 256 ) & lob
      else
	raise InvalidOpCodeError.new( @code )
    end
    self
  end

  def dump_all
    16.times { |i| puts "V#{i.to_1_digit_hex}:#{@v[i].to_bin_string}" }
    self
  end

end

if $0 == __FILE__
  begin
    f=File.open( ARGV[0], "r" )
    a=Chip8.new( f )
    while( a.parse ) do; end
    a.dump_all
  rescue IOError
    puts "Please enter a valid Chip8 file name.\nExample: ruby chip8.rb Chip8Test"
  end
end

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