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DataDumper is a Lua table serialization, slow but mostly complete
--[[ DataDumper.lua
Copyright (c) 2007 Olivetti-Engineering SA
Permission is hereby granted, free of charge, to any person
obtaining a copy of this software and associated documentation
files (the "Software"), to deal in the Software without
restriction, including without limitation the rights to use,
copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the
Software is furnished to do so, subject to the following
conditions:
The above copyright notice and this permission notice shall be
included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
OTHER DEALINGS IN THE SOFTWARE.
]]
local dumplua_closure = [[
local closures = {}
local function closure(t)
closures[#closures+1] = t
t[1] = assert(loadstring(t[1]))
return t[1]
end
for _,t in pairs(closures) do
for i = 2,#t do
debug.setupvalue(t[1], i-1, t[i])
end
end
]]
local lua_reserved_keywords = {
'and', 'break', 'do', 'else', 'elseif', 'end', 'false', 'for',
'function', 'if', 'in', 'local', 'nil', 'not', 'or', 'repeat',
'return', 'then', 'true', 'until', 'while' }
local function keys(t)
local res = {}
local oktypes = { stringstring = true, numbernumber = true }
local function cmpfct(a,b)
if oktypes[type(a)..type(b)] then
return a < b
else
return type(a) < type(b)
end
end
for k in pairs(t) do
res[#res+1] = k
end
table.sort(res, cmpfct)
return res
end
local c_functions = {}
for _,lib in pairs{'_G', 'string', 'table', 'math',
'io', 'os', 'coroutine', 'package', 'debug'} do
local t = _G[lib] or {}
lib = lib .. "."
if lib == "_G." then lib = "" end
for k,v in pairs(t) do
if type(v) == 'function' and not pcall(string.dump, v) then
c_functions[v] = lib..k
end
end
end
function DataDumper(value, varname, fastmode, ident)
local defined, dumplua = {}
-- Local variables for speed optimization
local string_format, type, string_dump, string_rep =
string.format, type, string.dump, string.rep
local tostring, pairs, table_concat =
tostring, pairs, table.concat
local keycache, strvalcache, out, closure_cnt = {}, {}, {}, 0
setmetatable(strvalcache, {__index = function(t,value)
local res = string_format('%q', value)
t[value] = res
return res
end})
local fcts = {
string = function(value) return strvalcache[value] end,
number = function(value) return value end,
boolean = function(value) return tostring(value) end,
['nil'] = function(value) return 'nil' end,
['function'] = function(value)
return string_format("loadstring(%q)", string_dump(value))
end,
userdata = function() error("Cannot dump userdata") end,
thread = function() error("Cannot dump threads") end,
}
local function test_defined(value, path)
if defined[value] then
if path:match("^getmetatable.*%)$") then
out[#out+1] = string_format("s%s, %s)\n", path:sub(2,-2), defined[value])
else
out[#out+1] = path .. " = " .. defined[value] .. "\n"
end
return true
end
defined[value] = path
end
local function make_key(t, key)
local s
if type(key) == 'string' and key:match('^[_%a][_%w]*$') then
s = key .. "="
else
s = "[" .. dumplua(key, 0) .. "]="
end
t[key] = s
return s
end
for _,k in ipairs(lua_reserved_keywords) do
keycache[k] = '["'..k..'"] = '
end
if fastmode then
fcts.table = function (value)
-- Table value
local numidx = 1
out[#out+1] = "{"
for key,val in pairs(value) do
if key == numidx then
numidx = numidx + 1
else
out[#out+1] = keycache[key]
end
local str = dumplua(val)
out[#out+1] = str..","
end
if string.sub(out[#out], -1) == "," then
out[#out] = string.sub(out[#out], 1, -2);
end
out[#out+1] = "}"
return ""
end
else
fcts.table = function (value, ident, path)
if test_defined(value, path) then return "nil" end
-- Table value
local sep, str, numidx, totallen = " ", {}, 1, 0
local meta, metastr = (debug or getfenv()).getmetatable(value)
if meta then
ident = ident + 1
metastr = dumplua(meta, ident, "getmetatable("..path..")")
totallen = totallen + #metastr + 16
end
for _,key in pairs(keys(value)) do
local val = value[key]
local s = ""
local subpath = path
if key == numidx then
subpath = subpath .. "[" .. numidx .. "]"
numidx = numidx + 1
else
s = keycache[key]
if not s:match "^%[" then subpath = subpath .. "." end
subpath = subpath .. s:gsub("%s*=%s*$","")
end
s = s .. dumplua(val, ident+1, subpath)
str[#str+1] = s
totallen = totallen + #s + 2
end
if totallen > 80 then
sep = "\n" .. string_rep(" ", ident+1)
end
str = "{"..sep..table_concat(str, ","..sep).." "..sep:sub(1,-3).."}"
if meta then
sep = sep:sub(1,-3)
return "setmetatable("..sep..str..","..sep..metastr..sep:sub(1,-3)..")"
end
return str
end
fcts['function'] = function (value, ident, path)
if test_defined(value, path) then return "nil" end
if c_functions[value] then
return c_functions[value]
elseif debug == nil or debug.getupvalue(value, 1) == nil then
return string_format("loadstring(%q)", string_dump(value))
end
closure_cnt = closure_cnt + 1
local res = {string.dump(value)}
for i = 1,math.huge do
local name, v = debug.getupvalue(value,i)
if name == nil then break end
res[i+1] = v
end
return "closure " .. dumplua(res, ident, "closures["..closure_cnt.."]")
end
end
function dumplua(value, ident, path)
return fcts[type(value)](value, ident, path)
end
if varname == nil then
varname = "return "
elseif varname:match("^[%a_][%w_]*$") then
varname = varname .. " = "
end
if fastmode then
setmetatable(keycache, {__index = make_key })
out[1] = varname
table.insert(out,dumplua(value, 0))
return table.concat(out)
else
setmetatable(keycache, {__index = make_key })
local items = {}
for i=1,10 do items[i] = '' end
items[3] = dumplua(value, ident or 0, "t")
if closure_cnt > 0 then
items[1], items[6] = dumplua_closure:match("(.*\n)\n(.*)")
out[#out+1] = ""
end
if #out > 0 then
items[2], items[4] = "local t = ", "\n"
items[5] = table.concat(out)
items[7] = varname .. "t"
else
items[2] = varname
end
return table.concat(items)
end
end
@prapin

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prapin commented Jan 5, 2011

This is basically a copy from http://lua-users.org/wiki/DataDumper

Here is one of the multiple ways to implement the serialization of a table. See http://lua-users.org/wiki/TableSerialization for a list of many other solutions. This version is written for Lua 5.1 and is quite long, because it tries to be as generic as possible and to keep its output string human readable. The drawback is that it is not the fastest one, mainly because it returns a string and does not write to a temporarily file. Still, there is a "fast" mode with fewer features, when execution time (or memory) is important. The function is copyrighted on MIT license, so is is free to use even in a commercial product.

DataDumper consists of a single Lua function, which could easily be put in a separate module or integrated into a bigger one. The function has four parameters, but only the first one is mandatory. It always returns a string value, which is valid Lua code. Simply executing this chunk will import back to a variable the complete structure of the original variable. For simple structures, there is only one Lua instruction like a table constructor, but some more complex features will output a script with more instructions.

All the following language features are supported:

* Simple Lua types: nil, boolean, number, string
* Tables are dumped recursively
* Table metatables are also dumped recursively
* Simple Lua functions (no upvalue) are dumped with loadstring
* Lua closures with upvalues are also supported, using the debug library!
* Known C functions are output using their original name
* Complex tables structures with internal references are supported 

What is not supported since it seems to be impossible, are these types:

* Both light and full userdata
* Coroutines
* Other C functions 

Here is the function declaration:

function DataDumper(value[, varname, fastmode, indent])

* value can be of any supported type
* varname: optional variable name. Depending on its form, the output will look like:
      o nil: "return value"
      o identifier: "varname = value"
      o other: "varname".."value" 
* fastmode is a boolean value:
      o true: optimizes for speed. Metatables, closures, C functions and references are not supported. Returns a code chunk without any space or new line!
      o false: supports all advanced features and favors readable code with good indentation. 
* indent: the number of additional indentation level. Default is 0. 
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