readwrite.lua

local source, level = ...
level = (level or 0) + 2

local _load
local _pack
local _unpack
if _VERSION == "Lua 5.1" then
	_load = loadstring
	_pack = function (...)
		local t = {...}
		t.n = select("#", ...)
		return t
	end
	_unpack = unpack
else
	_load = load
	_pack = table.pack
	_unpack = table.unpack
end

local f = assert(debug.getinfo(level,"f").func, "can't find function")
local args_name = {}
local args_value = {}
local updates = {}
local env
do
	local i = 1
	while true do
		local name, value = debug.getupvalue(f, i)
		if name == nil then
			break
		end
		if #name > 0 then
			if name == "_ENV" then
				env = value
			else
				args_name[#args_name+1] = name
				args_value[name] = value
				updates[#updates+1] = ("{'u',name=%q,idx=%d,val=%s}"):format(name, i, name)
			end
		end
		i = i + 1
	end
end
if not env and getfenv then
	env = getfenv(f)
end
do
	local i = 1
	while true do
		local name, value = debug.getlocal(level, i)
		if name == nil then
			break
		end
		if name:byte() ~= 40 then	-- '('
			args_name[#args_name+1] = name
			args_value[name] = value
			updates[#updates+1] = ("{'l',name=%q,idx=%d,val=%s}"):format(name, i, name)
		end
		i = i + 1
	end
end

local full_source
if #args_name > 0 then
	full_source = ([[
local $ARGS
return function(...)
$SOURCE
end,
function()
return {$UPDATES}
end
]]):gsub("%$(%w+)", {
	ARGS = table.concat(args_name, ","),
	SOURCE = source,
	UPDATES = table.concat(updates, ','),
})
else
	full_source = ([[
return function(...)
$SOURCE
end,
function()
return {$UPDATES}
end
]]):gsub("%$(%w+)", {
	SOURCE = source,
	UPDATES = table.concat(updates, ','),
})
end

local compiled = env
	and assert(_load(full_source, '=(EVAL)', "t", env))
	or  assert(_load(full_source, '=(EVAL)'))
if env and setfenv then
	setfenv(compiled, env)
end
local func, update = compiled()
local found = {}
do
	local i = 1
	while true do
		local name = debug.getupvalue(func, i)
		if name == nil then
			break
		end
		if name ~= "_ENV" then
			debug.setupvalue(func, i, args_value[name])
		end
		found[name] = true
		i = i + 1
	end
end
local rets
do
	local vararg, v = debug.getlocal(level, -1)
	if vararg then
		local vargs = { v }
		local i = 2
		while true do
			vararg, v = debug.getlocal(level, -i)
			if vararg then
				vargs[i] = v
			else
				break
			end
			i = i + 1
		end
		rets = _pack(func(_unpack(vargs)))
	else
		rets = _pack(func())
	end
end
for _, info in ipairs(update()) do
	if found[info.name] then
		if info[1] == 'l' then
			debug.setlocal(level, info.idx, info.val)
		else
			debug.setupvalue(f, info.idx, info.val)
		end
	end
end
return _unpack(rets)