Pickle Table

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The following is a table serialization utility for Lua.

VersionNotice: table.getn is deprecated in Lua 5.1.

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-- Pickle.lua

-- A table serialization utility for lua

-- Steve Dekorte, http://www.dekorte.com, Apr 2000

-- Freeware

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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 == "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



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-- unpickle

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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

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-- 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