[Api] Proper Serialization

This is like textutils.serialize, but it handles self-referencing tables, handles all datatypes except coroutines, userdata (I don't think CC uses userdata anywhere though) and functions.

You may use this under the terms of the WTFPL.

Usage:

-- Set up a complicated table
local a = {b={c={d={test=1}}}}
a.b.c.d.e = a
a[a.b.c] = {[a]=a,test=2}

print(a.b.c.d.test) -- prints 1
print(a[a.b.c][a][a.b.c].test) -- prints 2

-- Serialize it
local s = serialize(a)
print(s) -- prints gibberish

-- s is a string here - you can send it over modems or whatever (might not work with bundled cable rednet as I'm not sure if that preserves bit 7)

-- Deserialize it
local a2 = deserialize(s)
print(a2.b.c.d.test) -- should print 1
print(a2[a2.b.c][a2][a2.b.c].test) -- should print 2

Code:

local function serializeInt(i)
	local s = ""
	repeat
		s = s .. string.char((i % 128) + ((i >= 128) and 128 or 0))
		i = math.floor(i / 128)
	until i == 0
	return s
end
-- returns int, next position
local function deserializeInt(s,pos)
	local k = pos
	local i = 0
	local m = 1
	while true do
		local b = string.byte(s:sub(k,k))
		i = i + m * (b % 128)
		m = m * 128
		k = k + 1
		if b < 128 then break end
	end
	return i, k
end

local nextid_key = {}
local function serializeInternal(obj, seen)
	if obj ~= nil and seen[obj] then
		return "06" .. serializeInt(seen[obj])
	end
	if type(obj) == "table" then
		local id = seen[nextid_key]
		seen[nextid_key] = id + 1
		seen[obj] = id

		local s = "05"
		local ikeys = {}
		for k,v in ipairs(obj) do
			ikeys[k] = v
			s = s .. serializeInternal(v, seen)
		end
		s = s .. serializeInternal(nil, seen)
		for k,v in pairs(obj) do
			if ikeys[k] == nil then
				s = s .. serializeInternal(k, seen) .. serializeInternal(v, seen)
			end
		end
		s = s .. serializeInternal(nil, seen)
		return s
	elseif type(obj) == "number" then
		local ns = tostring(obj)
		return "04" .. serializeInt(ns:len()) .. ns
	elseif type(obj) == "string" then
		return "03" .. serializeInt(obj:len()) .. obj
	elseif type(obj) == "boolean" then
		if obj then
			return "01"
		else
			return "02"
		end
	elseif type(obj) == "nil" then
		return "00"
	elseif type(obj) == "userdata" then
		error("cannot serialize userdata")
	elseif type(obj) == "thread" then
		error("cannot serialize threads")
	elseif type(obj) == "function" then
		error("cannot serialize functions")
	else
		error("unknown type: " .. type(obj))
	end
end
function serialize(obj)
	return serializeInternal(obj, {[nextid_key] = 0})
end
function deserialize(s)
	local pos = 1
	local seen = {}
	local nextid = 0
	local function internal()
		local tch = s:sub(pos,pos)
		local len
		pos = pos + 1
		if tch == "00" then
			return nil
		elseif tch == "01" then
			return true
		elseif tch == "02" then
			return false
		elseif tch == "03" then
			len, pos = deserializeInt(s, pos)
			local rv = s:sub(pos, pos+len-1)
			pos = pos + len
			return rv
		elseif tch == "04" then
			len, pos = deserializeInt(s, pos)
			local rv = s:sub(pos, pos+len-1)
			pos = pos + len
			return tonumber(rv)
		elseif tch == "05" then
			local id = nextid
			nextid = id + 1
			local t = {}
			seen[id] = t

			local k = 1
			while true do
				local v = internal()
				if v == nil then break end
				t[k] = v
				k = k + 1
			end

			while true do
				local k = internal()
				if k == nil then break end
				local v = internal()
				if v == nil then break end
				t[k] = v
			end
			return t
		elseif tch == "06" then
			local id
			id, pos = deserializeInt(s, pos)
			return seen[id]
		else
			return nil
		end
	end
	return internal()
end

edit: fixed typo in example (s instead of a2)

Excelent :D/>/>

Great code! It even fixed the problem with control characters in strings in tables. :D/>/>

Should be default in CC

Having a bit of a problem. Whenever I attempt to use the serialize function, I always get an error.

lua:43: attempt to call table

Fixed a pretty serious typo, which made it not save the boolean value false properly.

dmillerw, whch line is line 43 and what's your code?

You can also serialize (some) functions with string.dump and restore them with loadstring

This should be default in computercraft an it solves a bug that i have seen!

(How fun is make a topic back to life :D/>)

*facepam*
I have never seen someone mention that they are gravedigging a thread.

*slow sarcastic clap*

Preventing further necromancy, by locking this thread. I may have to investigate this upwelling of dark magic into our peaceful forums….