Lua FIFO / QUEUE 文件

local queue_filespec = [[/path/to/your/queue/file]]
-- "queue file" 必须是一个包含单行 "return {}" 的普通文件！

local function operation_with_queue(func)
  local queue = dofile(queue_filespec)
  local result = func(queue)
  for k, v in ipairs(queue) do
    queue[k] = ("%q,\n"):format(v)
  end
  table.insert(queue, "}\n")
  queue[0] = "return {\n"
  queue = table.concat(queue, "", 0)
  local f = assert(io.open(queue_filespec, "w"))
  f:write(queue)
  f:close()
  return result
end

function add_to_queue(some_data)
  operation_with_queue(
    function(queue)
      table.insert(queue, some_data)
    end
  )
end

function extract_from_queue()
  -- 如果队列为空，则返回 nil
  return operation_with_queue(
    function(queue)
      return table.remove(queue, 1)
    end
  )
end

用法示例：

add_to_queue(42)
add_to_queue("Hello")
print(extract_from_queue()) --> 42
print(extract_from_queue()) --> Hello
print(extract_from_queue()) --> nil