circular_buffer.rb

class CircularBuffer
  attr_accessor :buffer, :read_index, :write_index

  def initialize(length)
    @buffer = Array.new(length)
    @read_index = 0
    @write_index = 0
  end

  def read
    raise BufferEmptyException if buffer_empty?
    element = buffer[read_index]
    buffer[read_index] = nil
    self.read_index = circulate_index(read_index)
    element
  end

  def write(element)
    return if element.nil?
    raise BufferFullException if buffer_full?
    buffer[write_index] = element
    self.write_index = circulate_index(write_index)
  end   

  def write!(element)
    return if element.nil?
    read if buffer_full?
    write(element)
  end

  def clear
    initialize(buffer.length)
  end

  private

  def circulate_index(index)
     index == buffer.length - 1 ? 0 : index.next
  end

  def buffer_full?
    buffer.all?
  end

  def buffer_empty?
    buffer.all? { |element| element.nil? }
  end

  class BufferEmptyException < Exception; end
  class BufferFullException < Exception; end
end