byte_array.rb

class ByteArray
  include Enumerable

  def initialize(n)
    @size = n
    @char_count = (n / 8.0).ceil
    @store = String.new("\0" * @char_count, encoding: "ASCII-8BIT")
  end

  def [](n)
    return nil if n >= @size
    return nil if n < (@size * -1)
    return self[@size + n] if n < 0

    char_nr, bit_nr = n.divmod(8)
    access(char_nr, bit_nr)
  end

  def []=(n, value)
    return nil if n >= @size
    return nil if n < (@size * -1)
    return self[@size + n] = value if n < 0

    char_nr, reverse_bit_nr = n.divmod(8)
    bit_nr = 7 - reverse_bit_nr

    new_int = @store[char_nr].getbyte(0)
    if value
      new_int = new_int | (1 << bit_nr)
    else
      new_int = new_int & (~0 ^ (1 << bit_nr))
    end

    @store[char_nr] = [new_int].pack('c')
  end

  def each
    unless block_given?
      return to_enum(__method__) { @size }
    end

    (0...@char_count).each do |char_nr|
      (0...8).each do |bit_nr|
        return if (char_nr + 1) * (bit_nr + 1) > @size

        yield access(char_nr, bit_nr)
      end
    end
    nil
  end

  private

  def access(char_nr, reverse_bit_nr)
    bit_nr = 7 - reverse_bit_nr
    1 == (@store[char_nr].getbyte(0)[bit_nr])
  end
end