serialize.lua

local type, next, tostring = type, next, tostring
local byte, find, format, gsub, concat = string.byte, string.find, string.format, string.gsub, table.concat
local function ctlsub(c)
	if c == "\t" then return "\\t"
	elseif c == "\n" then return "\\n"
	elseif c == "\r" then return "\\r"
	else return byte(c) end
end
local function serialize_push(b, v, q)
	local t = type(v)
	if t == "table" then
		if next(v) == nil then b[#b+1] = "{}" return end
		if b[v] then b[#b+1] = '"table: loops_to#'..b[v]..'"' return end
		b[v], b.l =  b.l, b.l + 1
		b[#b+1] = "{\n"
		local i, qq = 1, q.."  "
		for k, w in next, v do
			b[#b+1] = qq
			if k ~= i then
				if type(k) == "string" and find(k, "^[%a_][%w_]*$") then
					b[#b+1] = k
					b[#b+1] = " = "
				else
					b[#b+1] = "["
					serialize_push(b, k, qq)
					b[#b+1] = "] = "
				end
			else
				i = i + 1
			end
			serialize_push(b, w, qq)
			b[#b+1] = ",\n"
		end
		b[#b+1] = q.."}"
	elseif t == "boolean" or t == "number" or t == "nil" then b[#b+1] = tostring(v)
	else b[#b+1] = gsub(format("%q", tostring(v)), "%c", ctlsub)
	end
end
local function serialize(v)
	local b = {nil,nil,nil,nil,nil,nil,nil,nil,l=1}
	serialize_push(b, v, "")
	return concat(b)
end

print(serialize(_G))