A ring buffer implementation example for Ruby Discord.

ring_buffer.rb

# frozen_string_literal: true

class RingBuffer
  Nothing = Data.define
  EMPTY = Nothing.new
  
  attr_reader :size
  
  def initialize(capacity:)
    @capacity = capacity
    @buffer = Array.new(capacity, EMPTY)
    reset_counters
  end
  
  def reset_counters
    @head = nil
    @tail = nil
    @looping = false
    @size = 0
  end
  
  def clear
    @buffer.fill(EMPTY)
    reset_counters
  end
  
  def <<(value)
    @head ||= 0
    if @tail
      @tail = @tail.succ.modulo(@capacity)
      @looping = true if @tail.zero?
      @head = @head.succ.modulo(@capacity) if @looping
    else
      @tail = 0
    end
    
    @size = @size.succ.clamp(..@capacity)
    @buffer[@tail] = value
  end
  alias put <<

  def get
    return EMPTY unless @tail
    
    tail = @buffer.fetch(@tail)
    @buffer[@tail] = EMPTY

    if @tail == @head
      clear
      return tail
    end

    if @tail.zero?
      @tail = @capacity - 1
    else
      @tail -= 1
    end

    @size -= 1
    tail
  end
  alias detail get

  def behead
    return EMPTY unless @head

    head = @buffer.fetch(@head)
    @buffer[@head] = EMPTY

    if @head == @tail
      clear
      return head
    end

    @head = @head.succ.modulo(@capacity)
    @size -= 1

    head
  end

  def head
    return EMPTY unless @head

    @buffer.fetch(@head)
  end

  def tail
    return EMPTY unless @tail

    @buffer.fetch(@tail)
  end

  def [](index)
    return EMPTY unless @head

    @buffer.fetch((@head + index) % @capacity)
  end

  def clear
    @head = nil
    @tail = nil
    @looping = false
    @buffer.fill(EMPTY)
    @size = 0
  end
end