Tserial.lua

--- Tserial v1.5, a simple table serializer which turns tables into Lua script
-- @author Taehl (SelfMadeSpirit@gmail.com)
Tserial = {}
TSerial = Tserial	-- for backwards-compatibility

--- Serializes a table into a string, in form of Lua script.
-- @param t table to be serialized (may not contain any circular reference)
-- @param drop if true, unserializable types will be silently dropped instead of raising errors
-- if drop is a function, it will be called to serialize unsupported types
-- if drop is a table, it will be used as a serialization table (where {[value] = serial})
-- @param indent if true, output "human readable" mode with newlines and indentation (for debug)
-- @return string recreating given table
function Tserial.pack(t, drop, indent)
	assert(type(t) == "table", "Can only Tserial.pack tables.")
	local s, empty, indent = "{"..(indent and "\n" or ""), true, indent and math.max(type(indent)=="number" and indent or 0,0)
	local function proc(k,v, omitKey)	-- encode a key/value pair
		empty = nil	-- helps ensure empty tables return as "{}"
		local tk, tv, skip = type(k), type(v)
		if type(drop)=="table" and drop[k] then k = "["..drop[k].."]"
		elseif tk == "boolean" then k = k and "[true]" or "[false]"
		elseif tk == "string" then local f = string.format("%q",k) if f ~= '"'..k..'"' then k = '['..f..']' end
		elseif tk == "number" then k = "["..k.."]"
		elseif tk == "table" then k = "["..Tserial.pack(k, drop, indent and indent+1).."]"
		elseif type(drop) == "function" then k = "["..string.format("%q",drop(k)).."]"
		elseif drop then skip = true
		else error("Attempted to Tserial.pack a table with an invalid key: "..tostring(k))
		end
		if type(drop)=="table" and drop[v] then v = drop[v]
		elseif tv == "boolean" then v = v and "true" or "false"
		elseif tv == "string" then v = string.format("%q", v)
		elseif tv == "number" then	-- no change needed
		elseif tv == "table" then v = Tserial.pack(v, drop, indent and indent+1)
		elseif type(drop) == "function" then v = string.format("%q",drop(v))
		elseif drop then skip = true
		else error("Attempted to Tserial.pack a table with an invalid value: "..tostring(v))
		end
		if not skip then return string.rep("\t",indent or 0)..(omitKey and "" or k.."=")..v..","..(indent and "\n" or "") end
		return ""
	end
	local l=-1 repeat l=l+1 until t[l+1]==nil	-- #t "can" lie!
	for i=1,l do s = s..proc(i, t[i], true) end	-- use ordered values when possible for better string
	for k, v in pairs(t) do if not (type(k)=="number" and k<=l) then s = s..proc(k, v) end end
	if not empty then s = string.sub(s,1,string.len(s)-1) end
	if indent then s = string.sub(s,1,string.len(s)-1).."\n" end
	return s..string.rep("\t",(indent or 1)-1).."}"
end

--- Loads a table into memory from a string (like those output by Tserial.pack)
-- @param s a string of Lua defining a table, such as "{2,4,8,ex='ample'}"
-- @param safe if true, all extraneous parts of the string will be removed, leaving only a table (prevents running anomalous code when unpacking untrusted strings). Will also cause malformed tables to quietly return nil and an error message, instead of throwing an error (so your program can't be crashed with a bad string)
-- @return a table recreated from the given string.
function Tserial.unpack(s, safe)
	if safe then s = string.match(s, "(%b{})") end
	assert(type(s) == "string", "Can only Tserial.unpack strings.")
	local f, result = loadstring("Tserial.table="..s)
	if not safe then assert(f,result) elseif not f then return nil, result end
	result = f()
	local t = Tserial.table
	Tserial.table = nil
	return t, result
end