factorio/data/core/lualib/dataloader.lua

-- all the prototypes will be collected here
data = {}
-- raw data
data.raw = {}
-- this will be overwritten in the c++ based on whether we are in demo or not
-- careful: using this flag to change the number prototypes that are created will make saves not load between demo/retail
data.is_demo = false
local table_string = "table"

function data.extend(self, otherdata)
  if type(otherdata) ~= table_string or #otherdata == 0 then
    error("Invalid prototype array " .. serpent.block(otherdata, {maxlevel= 1}))
  end

  for _, e in ipairs(otherdata) do

    if not e.type then
      error("Missing type in the following prototype definition " .. serpent.block(e))
    end

    if not e.name then
      error("Missing name in the following prototype definition " .. serpent.block(e))
    end

    local t = self.raw[e.type]
    if t == nil then
      t = {}
      self.raw[e.type] = t
    end
    t[e.name] = e
  end
end