Re: Saving a table in file

[Tony Finch <dot@...>]

On Sun, 7 Mar 2010, Doug Rogers wrote:
>
> Why not just use two named functions for the API?

You only need one function, since you can use loadstring() to deserialize.

Tony.
-- 
f.anthony.n.finch  <dot@dotat.at>  http://dotat.at/
GERMAN BIGHT HUMBER: SOUTHWEST 5 TO 7. MODERATE OR ROUGH. SQUALLY SHOWERS.
MODERATE OR GOOD.

local szt = {}

local function char(c) return ("\\%03d"):format(c:byte()) end
local function szstr(s) return ('"%s"'):format(s:gsub("[^ !#-~]", char)) end
local function szfun(f) return "loadstring"..szstr(string.dump(f)) end
local function szany(...) return szt[type(...)](...) end

local function sztbl(t,code,var)
  for k,v in pairs(t) do
    local ks = szany(k,code,var)
    local vs = szany(v,code,var)
    code[#code+1] = ("%s[%s]=%s"):format(var[t],ks,vs)
  end
  return "{}"
end

local function memo(sz)
  return function(d,code,var)
    if var[d] == nil then
      var[1] = var[1] + 1
      var[d] = ("_[%d]"):format(var[1])
      local index = #code+1
      code[index] = "" -- reserve place during recursion
      code[index] = ("%s=%s"):format(var[d],sz(d,code,var))
    end
    return var[d]
  end
end

szt["nil"]      = tostring
szt["boolean"]  = tostring
szt["number"]   = tostring
szt["string"]   = szstr
szt["function"] = memo(szfun)
szt["table"]    = memo(sztbl)

local function serialize(d)
  local code = { "local _ = {}" }
  local value = szany(d,code,{0})
  code[#code+1] = "return "..value
  if #code == 2 then return code[2]
  else return table.concat(code, "\n")
  end
end

return serialize