Pickle Table

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The following is a table serialization utility for Lua.

VersionNotice: table.getn is deprecated in Lua 5.1.

----------------------------------------------
-- Pickle.lua
-- A table serialization utility for lua
-- Steve Dekorte, http://www.dekorte.com, Apr 2000
-- Freeware
----------------------------------------------
function pickle(t)
 return Pickle:clone():pickle_(t)
end
Pickle = {
 clone = function (t) local nt={}; for i, v in pairs(t) do nt[i]=v end return nt end 
}
function Pickle:pickle_(root)
 if type(root) ~= "table" then 
 error("can only pickle tables, not ".. type(root).."s")
 end
 self._tableToRef = {}
 self._refToTable = {}
 local savecount = 0
 self:ref_(root)
 local s = ""
 while table.getn(self._refToTable) > savecount do
 savecount = savecount + 1
 local t = self._refToTable[savecount]
 s = s.."{\n"
 for i, v in pairs(t) do
 s = string.format("%s[%s]=%s,\n", s, self:value_(i), self:value_(v))
 end
 s = s.."},\n"
 end
 return string.format("{%s}", s)
end
function Pickle:value_(v)
 local vtype = type(v)
 if vtype == "string" then return string.format("%q", v)
 elseif vtype == "number" then return v
 elseif vtype == "boolean" then return tostring(v)
 elseif vtype == "table" then return "{"..self:ref_(v).."}"
 else --error("pickle a "..type(v).." is not supported")
 end 
end
function Pickle:ref_(t)
 local ref = self._tableToRef[t]
 if not ref then 
 if t == self then error("can't pickle the pickle class") end
 table.insert(self._refToTable, t)
 ref = table.getn(self._refToTable)
 self._tableToRef[t] = ref
 end
 return ref
end
----------------------------------------------
-- unpickle
----------------------------------------------
function unpickle(s)
 if type(s) ~= "string" then
 error("can't unpickle a "..type(s)..", only strings")
 end
 local gentables = loadstring("return "..s)
 local tables = gentables()
 
 for tnum = 1, table.getn(tables) do
 local t = tables[tnum]
 local tcopy = {}; for i, v in pairs(t) do tcopy[i] = v end
 for i, v in pairs(tcopy) do
 local ni, nv
 if type(i) == "table" then ni = tables[i[1]] else ni = i end
 if type(v) == "table" then nv = tables[v[1]] else nv = v end
 t[i] = nil
 t[ni] = nv
 end
 end
 return tables[1]
end

And here is some testcode to see that after loading the table it is not the same anymore

----------------------------------------------
-- PickleTest.lua
-- Testing code for Pickle.lua
-- Steve Dekorte, http://www.dekorte.com, Apr 2000
----------------------------------------------
--dofile("Pickle.lua")
function test()
 local t = {
 name = "foo", 
 ssn=123456789, 
 contact = { phone = "555-1\r\n212", email = "foo@foo.com"},
 }
 t.t = { 1 }
 t.contact.loop = t
 t["a b"] = "zzz"
 t[10] = 11
 t[t] = 5
 t[t.t] = 10
 local s = pickle(t)
 print("pickled string:\n\n"..s)
 local ut = unpickle(s) 
print("pickled string:\n\n"..pickle( ut ))
 print("loop test: "); eq(ut == ut.contact.loop)
 print("subitem test:"); eq(ut.contact.phone == t.contact.phone)
 print("number value:"); eq(ut.ssn == t.ssn)
 print("number index:"); eq(ut[10] == 11)
 print("table index: "); eq(ut[ut] == 5)
end
function eq(b)
 if b then print(" succeeded") else print(" failed") end
end
test()

Pickle Table

See Also