222 lines
6.7 KiB
Lua
222 lines
6.7 KiB
Lua
--- Lua module to serialize values as Lua code.
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-- From: https://github.com/fab13n/metalua/blob/no-dll/src/lib/serialize.lua
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-- License: MIT
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-- @copyright 2006-2997 Fabien Fleutot <metalua@gmail.com>
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-- @author Fabien Fleutot <metalua@gmail.com>
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-- @author ShadowNinja <shadowninja@minetest.net>
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--------------------------------------------------------------------------------
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--- Serialize an object into a source code string. This string, when passed as
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-- an argument to deserialize(), returns an object structurally identical to
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-- the original one. The following are currently supported:
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-- * Booleans, numbers, strings, and nil.
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-- * Functions; uses interpreter-dependent (and sometimes platform-dependent) bytecode!
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-- * Tables; they can cantain multiple references and can be recursive, but metatables aren't saved.
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-- This works in two phases:
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-- 1. Recursively find and record multiple references and recursion.
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-- 2. Recursively dump the value into a string.
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-- @param x Value to serialize (nil is allowed).
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-- @return load()able string containing the value.
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function core.serialize(x)
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local local_index = 1 -- Top index of the "_" local table in the dump
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-- table->nil/1/2 set of tables seen.
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-- nil = not seen, 1 = seen once, 2 = seen multiple times.
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local seen = {}
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-- nest_points are places where a table appears within itself, directly
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-- or not. For instance, all of these chunks create nest points in
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-- table x: "x = {}; x[x] = 1", "x = {}; x[1] = x",
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-- "x = {}; x[1] = {y = {x}}".
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-- To handle those, two tables are used by mark_nest_point:
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-- * nested - Transient set of tables being currently traversed.
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-- Used for detecting nested tables.
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-- * nest_points - parent->{key=value, ...} table cantaining the nested
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-- keys and values in the parent. They're all dumped after all the
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-- other table operations have been performed.
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--
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-- mark_nest_point(p, k, v) fills nest_points with information required
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-- to remember that key/value (k, v) creates a nest point in table
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-- parent. It also marks "parent" and the nested item(s) as occuring
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-- multiple times, since several references to it will be required in
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-- order to patch the nest points.
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local nest_points = {}
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local nested = {}
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local function mark_nest_point(parent, k, v)
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local nk, nv = nested[k], nested[v]
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local np = nest_points[parent]
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if not np then
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np = {}
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nest_points[parent] = np
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end
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np[k] = v
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seen[parent] = 2
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if nk then seen[k] = 2 end
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if nv then seen[v] = 2 end
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end
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-- First phase, list the tables and functions which appear more than
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-- once in x.
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local function mark_multiple_occurences(x)
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local tp = type(x)
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if tp ~= "table" and tp ~= "function" then
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-- No identity (comparison is done by value, not by instance)
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return
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end
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if seen[x] == 1 then
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seen[x] = 2
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elseif seen[x] ~= 2 then
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seen[x] = 1
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end
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if tp == "table" then
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nested[x] = true
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for k, v in pairs(x) do
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if nested[k] or nested[v] then
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mark_nest_point(x, k, v)
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else
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mark_multiple_occurences(k)
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mark_multiple_occurences(v)
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end
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end
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nested[x] = nil
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end
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end
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local dumped = {} -- object->varname set
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local local_defs = {} -- Dumped local definitions as source code lines
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-- Mutually recursive local functions:
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local dump_val, dump_or_ref_val
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-- If x occurs multiple times, dump the local variable rather than
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-- the value. If it's the first time it's dumped, also dump the
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-- content in local_defs.
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function dump_or_ref_val(x)
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if seen[x] ~= 2 then
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return dump_val(x)
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end
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local var = dumped[x]
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if var then -- Already referenced
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return var
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end
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-- First occurence, create and register reference
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local val = dump_val(x)
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local i = local_index
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local_index = local_index + 1
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var = "_["..i.."]"
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local_defs[#local_defs + 1] = var.." = "..val
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dumped[x] = var
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return var
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end
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-- Second phase. Dump the object; subparts occuring multiple times
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-- are dumped in local variables which can be referenced multiple
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-- times. Care is taken to dump local vars in a sensible order.
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function dump_val(x)
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local tp = type(x)
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if x == nil then return "nil"
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elseif tp == "string" then return string.format("%q", x)
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elseif tp == "boolean" then return x and "true" or "false"
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elseif tp == "function" then
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return string.format("loadstring(%q)", string.dump(x))
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elseif tp == "number" then
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-- Serialize integers with string.format to prevent
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-- scientific notation, which doesn't preserve
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-- precision and breaks things like node position
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-- hashes. Serialize floats normally.
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if math.floor(x) == x then
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return string.format("%d", x)
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else
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return tostring(x)
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end
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elseif tp == "table" then
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local vals = {}
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local idx_dumped = {}
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local np = nest_points[x]
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for i, v in ipairs(x) do
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if not np or not np[i] then
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vals[#vals + 1] = dump_or_ref_val(v)
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end
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idx_dumped[i] = true
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end
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for k, v in pairs(x) do
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if (not np or not np[k]) and
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not idx_dumped[k] then
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vals[#vals + 1] = "["..dump_or_ref_val(k).."] = "
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..dump_or_ref_val(v)
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end
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end
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return "{"..table.concat(vals, ", ").."}"
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else
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error("Can't serialize data of type "..tp)
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end
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end
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local function dump_nest_points()
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for parent, vals in pairs(nest_points) do
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for k, v in pairs(vals) do
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local_defs[#local_defs + 1] = dump_or_ref_val(parent)
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.."["..dump_or_ref_val(k).."] = "
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..dump_or_ref_val(v)
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end
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end
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end
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mark_multiple_occurences(x)
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local top_level = dump_or_ref_val(x)
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dump_nest_points()
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if next(local_defs) then
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return "local _ = {}\n"
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..table.concat(local_defs, "\n")
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.."\nreturn "..top_level
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else
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return "return "..top_level
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end
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end
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-- Deserialization
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local env = {
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loadstring = loadstring,
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}
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local safe_env = {
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loadstring = function() end,
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}
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function core.deserialize(str, safe)
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if type(str) ~= "string" then
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return nil, "Cannot deserialize type '"..type(str)
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.."'. Argument must be a string."
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end
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if str:byte(1) == 0x1B then
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return nil, "Bytecode prohibited"
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end
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local f, err = loadstring(str)
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if not f then return nil, err end
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setfenv(f, safe and safe_env or env)
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local good, data = pcall(f)
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if good then
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return data
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else
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return nil, data
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end
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end
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-- Unit tests
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local test_in = {cat={sound="nyan", speed=400}, dog={sound="woof"}}
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local test_out = core.deserialize(core.serialize(test_in))
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assert(test_in.cat.sound == test_out.cat.sound)
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assert(test_in.cat.speed == test_out.cat.speed)
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assert(test_in.dog.sound == test_out.dog.sound)
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test_in = {escape_chars="\n\r\t\v\\\"\'", non_european="θשׁ٩∂"}
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test_out = core.deserialize(core.serialize(test_in))
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assert(test_in.escape_chars == test_out.escape_chars)
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assert(test_in.non_european == test_out.non_european)
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