Pickle Table

wiki

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