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--- Lua module to serialize values as Lua code.
-- From: https://github.com/appgurueu/modlib/blob/master/luon.lua
-- License: MIT
local next, rawget, pairs, pcall, error, type, setfenv, loadstring
= next, rawget, pairs, pcall, error, type, setfenv, loadstring
local table_concat, string_dump, string_format, string_match, math_huge
= table.concat, string.dump, string.format, string.match, math.huge
-- Recursively counts occurences of objects (non-primitives including strings) in a table.
local function count_objects(value)
local counts = {}
if value == nil then
-- Early return for nil; tables can't contain nil
return counts
end
local function count_values(val)
local type_ = type(val)
if type_ == "boolean" or type_ == "number" then
return
end
local count = counts[val]
counts[val] = (count or 0) + 1
if type_ == "table" then
if not count then
for k, v in pairs(val) do
count_values(k)
count_values(v)
end
end
elseif type_ ~= "string" and type_ ~= "function" then
error("unsupported type: " .. type_)
end
end
count_values(value)
return counts
end
-- Build a "set" of Lua keywords. These can't be used as short key names.
-- See https://www.lua.org/manual/5.1/manual.html#2.1
local keywords = {}
for _, keyword in pairs({
"and", "break", "do", "else", "elseif",
"end", "false", "for", "function", "if",
"in", "local", "nil", "not", "or",
"repeat", "return", "then", "true", "until", "while",
"goto" -- LuaJIT, Lua 5.2+
}) do
keywords[keyword] = true
end
local function quote(string)
return string_format("%q", string)
end
local function dump_func(func)
return string_format("loadstring(%q)", string_dump(func))
end
-- Serializes Lua nil, booleans, numbers, strings, tables and even functions
-- Tables are referenced by reference, strings are referenced by value. Supports circular tables.
local function serialize(value, write)
local reference, refnum = "r1", 1
-- [object] = reference string
local references = {}
-- Circular tables that must be filled using `table[key] = value` statements
local to_fill = {}
for object, count in pairs(count_objects(value)) do
local type_ = type(object)
-- Object must appear more than once. If it is a string, the reference has to be shorter than the string.
if count >= 2 and (type_ ~= "string" or #reference + 2 < #object) then
write(reference)
write("=")
if type_ == "table" then
write("{}")
elseif type_ == "function" then
write(dump_func(object))
elseif type_ == "string" then
write(quote(object))
end
write(";")
references[object] = reference
if type_ == "table" then
to_fill[object] = reference
end
refnum = refnum + 1
reference = ("r%X"):format(refnum)
end
end
-- Used to decide whether we should do "key=..."
local function use_short_key(key)
return not references[key] and type(key) == "string" and (not keywords[key]) and string_match(key, "^[%a_][%a%d_]*$")
end
local function dump(value)
-- Primitive types
if value == nil then
return write("nil")
end
if value == true then
return write("true")
end
if value == false then
return write("false")
end
local type_ = type(value)
if type_ == "number" then
return write(string_format("%.17g", value))
end
-- Reference types: table, function and string
local ref = references[value]
if ref then
return write(ref)
end
if type_ == "string" then
return write(quote(value))
end
if type_ == "function" then
return write(dump_func(value))
end
if type_ == "table" then
write("{")
-- First write list keys:
-- Don't use the table length #value here as it may horribly fail
-- for tables which use large integers as keys in the hash part;
-- stop at the first "hole" (nil value) instead
local len = 0
local first = true -- whether this is the first entry, which may not have a leading comma
while true do
local v = rawget(value, len + 1) -- use rawget to avoid metatables like the vector metatable
if v == nil then break end
if first then first = false else write(",") end
dump(v)
len = len + 1
end
-- Now write map keys ([key] = value)
for k, v in next, value do
-- We have written all non-float keys in [1, len] already
if type(k) ~= "number" or k % 1 ~= 0 or k < 1 or k > len then
if first then first = false else write(",") end
if use_short_key(k) then
write(k)
else
write("[")
dump(k)
write("]")
end
write("=")
dump(v)
end
end
write("}")
return
end
end
-- Write the statements to fill circular tables
for table, ref in pairs(to_fill) do
for k, v in pairs(table) do
write(ref)
if use_short_key(k) then
write(".")
write(k)
else
write("[")
dump(k)
write("]")
end
write("=")
dump(v)
write(";")
end
end
write("return ")
dump(value)
end
function core.serialize(value)
local rope = {}
serialize(value, function(text)
-- Faster than table.insert(rope, text) on PUC Lua 5.1
rope[#rope + 1] = text
end)
return table_concat(rope)
end
local function dummy_func() end
local nan = (0/0)^1 -- +nan
function core.deserialize(str, safe)
local func, err = loadstring(str)
if not func then return nil, err end
-- math.huge is serialized to inf, NaNs are serialized to nan by Lua
local env = {inf = math_huge, nan = nan}
if safe then
env.loadstring = dummy_func
else
env.loadstring = function(str, ...)
local func, err = loadstring(str, ...)
if func then
setfenv(func, env)
return func
end
return nil, err
end
end
setfenv(func, env)
local success, value_or_err = pcall(func)
if success then
return value_or_err
end
return nil, value_or_err
end
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