Serializing Lua objects into Lua Code

The following little snippet allows you to ‘pickle’ Lua objects directly into Lua code (with the exception of functions, which are serialized as raw bytecode). Metatable support is on the way, but for now, it should be useful enough.

Example code:

 view sourceprint? 
dofile "pickle.lua" 
  
users = { 
user1 = {pass = "abcdef", start = 10230}, 
user2 = {pass = "cdefba", start = 12032} 
} 
  
userdump = pickle.dumps(users) 
print(userdump) 

Outputs

 view sourceprint? 
return { 
["user1"] = { 
["pass"] = "abcdef", 
["start"] = 10230, 
}, 
["user2"] = { 
["pass"] = "cdefba", 
["start"] = 12032, 
}, 
} 

Pickle API:

pickle.dumps(object) -> String
Pickles an object and returns it.
pickle.dump(object, filename) -> String
Pickles an object and saves it as :filename, afterwards, returns the dump.
pickle.loads(object) -> Lua Object
Loads a string dump of lua object and returns the object. The returned object will not injected into the global table.
pickle.load(filename) -> Lua Object
Loads a pickled object from a file and returns it. The returned object will not be injected into the global table.

Full Source:

 view sourceprint? 
local objects = {} 
setmetatable(objects, {__index={["subset"]=function(object, proxies) 
for _,o in ipairs(proxies) do 
if object == o then return true end 
end 
end}}) 
  
function _pickle(object, seen, indent) 
---if not seen then seen = {} end 
if not indent then indent = "" end 
  
local serialize_key = function(key) 
if type(key) == "string" then 
return "[\""..key.."\"]" 
elseif type(key) == "table" then 
return "[".._pickle(key):gsub("\n"," ").."]" 
else 
return "["..key.."]" 
end 
return key 
end 
  
local escape = function(o) 
return o:gsub("\\","\\\\"):gsub("'","\\'"):gsub('"','\\"') 
end 
  
---Switch Object type: 
if type(object) == "table" then 
local serialize = "{\n" 
for key, value in pairs(object) do 
serialize = serialize .. indent.."\t" .. serialize_key(key) .. " = " ..tostring(_pickle(value, seen, indent.."\t")) .. ",\n" 
end 
serialize = serialize .. indent .. "}" 
  
return serialize 
elseif type(object) == "string" then 
return '"' .. escape(object) .. '"' 
elseif type(object) == "function" then 
return "loadstring([["..string.dump(object).."]])" 
elseif objects.subset(object, {"userdata"}) then 
return nil 
end 
return tostring(object) 
end 
  
pickle = {} 
  
function pickle.dumps(object) 
return "return ".. _pickle(object) 
end 
  
function pickle.dump(object, filename) 
local dump = pickle.dumps(object) 
local _file = io.open(filename, "wb") 
_file:write(dump) 
_file:close() 
return dump 
end 
  
function pickle.loads(object) 
local fn = loadstring(object) 
if fn then 
return fn() 
end 
end 
  
function pickle.load(filename) 
local _file = io.open(filename, "rb") 
local dump = _file:read("*all") 
local object = pickle.loads(dump) 
_file:close() 
return object 
end 