全局变量相关

function declare_global(name, value)
  rawset(_G, name, value or false)
end

function delete_global(name)
  rawset(_G, name, nil)
end

function get_global(name)
  return rawget(_G, name)
end

function unrequire(name)
  if package.loaded[name] then
    package.loaded[name] = nil
    if get_global(name) then
      delete_global(name)
    end
  end
end

只读 table

-- 设置记录 error 的 traceback 深度
local function _traceback()
  return '\\n' .. traceback('lua traceback', 3)
end

function readonly_table(t)
  assert(type(t) == 'table', 'invalid type')
  setmetatable(t, {
    __newindex = function(_, n)
      log.error('attempt to write to undeclared global variable: ' .. n .. _traceback())
    end,
    __index = function(_, n)
      log.error('attempt to read undeclared global variable: ' .. n .. _traceback())
    end,
  })
end

设置继承关系/创建类的实例

---@param parent table
---@param child table?
function new_instance(parent, child)
  child = child or {}
  for k, v in pairs(parent) do
    if type(v) == 'table' then
      child[k] = {}
    end
  end
  setmetatable(child, {__index = parent})
  return child
end

遍历

function switch(case)
  return function(cases)
    local f = cases[case] or cases.default
    if f then
      return f(case)
    end
  end
end

---@param tbl table
---@param func fun(k:any, v:any)
function foreach(tbl, func)
  if tbl == nil or type(tbl) ~= 'table' then return end
  for k, v in pairs(tbl) do
    func(k, v)
  end
end

一个简单的高精度计时器（需要 socket 库）

socket = require 'socket'
local __timer_t = 0
local __timer_s = nil

---@param str string?
function start_timer(str)
  __timer_t = socket.gettime()
  __timer_s = str or 'timer'
end

---@param str string?
function stop_timer(str)
  local t = socket.gettime() - __timer_t
  log.error(__timer_s, string.format('%.3f ms', t * 1000), str)
end