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-- Minetest: builtin/serialize.lua
-- https://github.com/fab13n/metalua/blob/no-dll/src/lib/serialize.lua
-- Copyright (c) 2006-2997 Fabien Fleutot <metalua@gmail.com>
-- License: MIT
--------------------------------------------------------------------------------
-- Serialize an object into a source code string. This string, when passed as
-- an argument to deserialize(), returns an object structurally identical
-- to the original one. The following are currently supported:
-- * strings, numbers, booleans, nil
-- * tables thereof. Tables can have shared part, but can't be recursive yet.
-- Caveat: metatables and environments aren't saved.
--------------------------------------------------------------------------------
local no_identity = { number=1, boolean=1, string=1, ['nil']=1 }
function core.serialize(x)
local gensym_max = 0 -- index of the gensym() symbol generator
local seen_once = { } -- element->true set of elements seen exactly once in the table
local multiple = { } -- element->varname set of elements seen more than once
local nested = { } -- transient, set of elements currently being traversed
local nest_points = { }
local nest_patches = { }
local function gensym()
gensym_max = gensym_max + 1 ; return gensym_max
end
-----------------------------------------------------------------------------
-- nest_points are places where a table appears within itself, directly or not.
-- for instance, all of these chunks create nest points in table x:
-- "x = { }; x[x] = 1", "x = { }; x[1] = x", "x = { }; x[1] = { y = { x } }".
-- To handle those, two tables are created by mark_nest_point:
-- * nest_points [parent] associates all keys and values in table parent which
-- create a nest_point with boolean `true'
-- * nest_patches contain a list of { parent, key, value } tuples creating
-- a nest point. They're all dumped after all the other table operations
-- have been performed.
--
-- mark_nest_point (p, k, v) fills tables nest_points and nest_patches with
-- informations required to remember that key/value (k,v) create a nest point
-- in table parent. It also marks `parent' as occuring multiple times, since
-- several references to it will be required in order to patch the nest
-- points.
-----------------------------------------------------------------------------
local function mark_nest_point (parent, k, v)
local nk, nv = nested[k], nested[v]
assert (not nk or seen_once[k] or multiple[k])
assert (not nv or seen_once[v] or multiple[v])
local mode = (nk and nv and "kv") or (nk and "k") or ("v")
local parent_np = nest_points [parent]
local pair = { k, v }
if not parent_np then parent_np = { }; nest_points [parent] = parent_np end
parent_np [k], parent_np [v] = nk, nv
table.insert (nest_patches, { parent, k, v })
seen_once [parent], multiple [parent] = nil, true
end
-----------------------------------------------------------------------------
-- First pass, list the tables and functions which appear more than once in x
-----------------------------------------------------------------------------
local function mark_multiple_occurences (x)
if no_identity [type(x)] then return end
if seen_once [x] then seen_once [x], multiple [x] = nil, true
elseif multiple [x] then -- pass
else seen_once [x] = true end
if type (x) == 'table' then
nested [x] = true
for k, v in pairs (x) do
if nested[k] or nested[v] then mark_nest_point (x, k, v) else
mark_multiple_occurences (k)
mark_multiple_occurences (v)
end
end
nested [x] = nil
end
end
local dumped = { } -- multiply occuring values already dumped in localdefs
local localdefs = { } -- already dumped local definitions as source code lines
-- mutually recursive functions:
local dump_val, dump_or_ref_val
--------------------------------------------------------------------
-- if x occurs multiple times, dump the local var rather than the
-- value. If it's the first time it's dumped, also dump the content
-- in localdefs.
--------------------------------------------------------------------
function dump_or_ref_val (x)
if nested[x] then return 'false' end -- placeholder for recursive reference
if not multiple[x] then return dump_val (x) end
local var = dumped [x]
if var then return "_[" .. var .. "]" end -- already referenced
local val = dump_val(x) -- first occurence, create and register reference
var = gensym()
table.insert(localdefs, "_["..var.."]="..val)
dumped [x] = var
return "_[" .. var .. "]"
end
-----------------------------------------------------------------------------
-- Second pass, dump the object; subparts occuring multiple times are dumped
-- in local variables which can be referenced multiple times;
-- care is taken to dump locla vars in asensible order.
-----------------------------------------------------------------------------
function dump_val(x)
local t = type(x)
if x==nil then return 'nil'
elseif t=="number" then return tostring(x)
elseif t=="string" then return string.format("%q", x)
elseif t=="boolean" then return x and "true" or "false"
elseif t=="function" then
return string.format("loadstring(%q)", string.dump(x))
elseif t=="table" then
local acc = { }
local idx_dumped = { }
local np = nest_points [x]
for i, v in ipairs(x) do
if np and np[v] then
table.insert (acc, 'false') -- placeholder
else
table.insert (acc, dump_or_ref_val(v))
end
idx_dumped[i] = true
end
for k, v in pairs(x) do
if np and (np[k] or np[v]) then
--check_multiple(k); check_multiple(v) -- force dumps in localdefs
elseif not idx_dumped[k] then
table.insert (acc, "[" .. dump_or_ref_val(k) .. "] = " .. dump_or_ref_val(v))
end
end
return "{ "..table.concat(acc,", ").." }"
else
error ("Can't serialize data of type "..t)
end
end
local function dump_nest_patches()
for _, entry in ipairs(nest_patches) do
local p, k, v = unpack (entry)
assert (multiple[p])
local set = dump_or_ref_val (p) .. "[" .. dump_or_ref_val (k) .. "] = " ..
dump_or_ref_val (v) .. " -- rec "
table.insert (localdefs, set)
end
end
mark_multiple_occurences (x)
local toplevel = dump_or_ref_val (x)
dump_nest_patches()
if next (localdefs) then
return "local _={ }\n" ..
table.concat (localdefs, "\n") ..
"\nreturn " .. toplevel
else
return "return " .. toplevel
end
end
-- Deserialization.
-- http://stackoverflow.com/questions/5958818/loading-serialized-data-into-a-table
--
local env = {
loadstring = loadstring,
}
local function noop() end
local safe_env = {
loadstring = noop,
}
local function stringtotable(sdata, safe)
if sdata:byte(1) == 27 then return nil, "binary bytecode prohibited" end
local f, message = assert(loadstring(sdata))
if not f then return nil, message end
if safe then
setfenv(f, safe_env)
else
setfenv(f, env)
end
return f()
end
function core.deserialize(sdata, safe)
local table = {}
local okay, results = pcall(stringtotable, sdata, safe)
if okay then
return results
end
core.log('error', 'core.deserialize(): '.. results)
return nil
end
-- Run some unit tests
local function unit_test()
function unitTest(name, success)
if not success then
error(name .. ': failed')
end
end
unittest_input = {cat={sound="nyan", speed=400}, dog={sound="woof"}}
unittest_output = core.deserialize(core.serialize(unittest_input))
unitTest("test 1a", unittest_input.cat.sound == unittest_output.cat.sound)
unitTest("test 1b", unittest_input.cat.speed == unittest_output.cat.speed)
unitTest("test 1c", unittest_input.dog.sound == unittest_output.dog.sound)
unittest_input = {escapechars="\n\r\t\v\\\"\'", noneuropean="θשׁ٩∂"}
unittest_output = core.deserialize(core.serialize(unittest_input))
unitTest("test 3a", unittest_input.escapechars == unittest_output.escapechars)
unitTest("test 3b", unittest_input.noneuropean == unittest_output.noneuropean)
end
unit_test() -- Run it
unit_test = nil -- Hide it
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