Simple ring buffer

ringbuf.lua

ringbuf={}
ringbuf.eof=0
ringbuf.size=0
ringbuf.__index=ringbuf

function ringbuf:new(size)
  size=tonumber(size)
  if not size then
    return nil, "arg must be an number"
  elseif size<1 then
    return nil, "out of range"
  end
  return setmetatable({size=size},self)
end

function ringbuf:add(value)
  self.eof=self.eof<self.size and self.eof+1 or 1
  self[self.eof]=tostring(value)
end

function ringbuf:get(index)
  index=tonumber(index)
  if not index then
    return nil, "arg must be an number"
  elseif index<1 or index>self.size then
    return nil, "out of range"
  end
  if not self[self.size] then
    return self[index]
  end
  index=self.eof+index
  index=index>self.size and index-self.size or index
  return self[index]
end

function ringbuf:concat()
  local buf={}
  local len=0
  for value in self:iterator() do
    len=len+1
    buf[len]=value
  end
  return table.concat(buf)
end

function ringbuf:iterator()
  local i=0
  return function()
    if i<=self.size then
      i=i+1
      return self:get(i)
    end
  end
end

t=ringbuf:new(5)
t:add(1)
t:add(2)
print(t:concat())
t:add(3)
t:add(4)
print(t:get(1), t:get(2))
print(t:concat())
for value in t:iterator() do
  print(value)
end
t:add(5)
print(t:get(1), t:get(2))
print(t:concat())
t:add(6)
print(t:get(1), t:get(2), t:get(5))
print(t:concat())
t:add(7)
t:add(8)
print(t:get(1), t:get(2), t:get(5))
print(t:concat())
t:add(9)
t:add(10)
t:add(11)
print(t:get(1), t:get(2), t:get(5))
print(t:concat())
for value in t:iterator() do
  print(value)
end