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Lua

--- Brainless serialization library.
--
-- Takes Lua tables and turns them into their string
-- representation. Also takes a Lua table string representation
-- and turns it back into its corresponding table.
-- That is all.
--
-- @module serialize
-- @copyright 2022 The DoubleFourteen Code Forge
-- @author Lorenzo Cogotti
local math = require 'math'
local serialize = {}
local dopack -- forward declare for mutual recursion
local function isfinite(x)
return x ~= math.huge and x ~= -math.huge and x == x
end
local function keys(k, i)
local t = type(k)
if t == 'boolean' then
return k and "[true]" or "[false]"
elseif t == 'string' then
local f = ("%q"):format(k)
if k:find(" ") or f ~= '"'..k..'"' then
return "["..f.."]"
else
return k
end
elseif t == 'number' then
if not isfinite(k) then
error("Can't serialize.pack() table with non-finite key `"..k.."'.")
end
return "["..k.."]"
elseif t == 'table' then
return "["..dopack(k, i+1).."]"
else
error("Can't serialize.pack() table with key `"..tostring(k).."'.")
end
end
local function vals(v, i)
local t = type(v)
if t == 'boolean' then
return v and 'true' or 'false'
elseif t == 'string' then
return ("%q"):format(v)
elseif t == 'number' then
if not isfinite(v) then
error("Can't serialize.pack() table with non-finite value `"..v.."'.")
end
return tostring(v)
elseif t == 'table' then
return dopack(v, i+1)
else
error("Can't serialize.pack() table with value `"..tostring(v).."'.")
end
end
-- local
function dopack(o, i, mode)
local fields = {}
local seen = {}
local is = (" "):rep(i)
local lastis = (" "):rep(i-1)
-- Attempt to encode as array.
for k,v in ipairs(o) do
if mode == 'skip-functions' and type(v) == 'function' then
goto skip
end
fields[#fields + 1] = ("%s%s"):format(is, vals(v, i))
::skip:: seen[k] = true
end
-- Process leftover fields.
for k,v in pairs(o) do
if seen[k] or (mode == 'skip-functions' and type(v) == 'function') then
goto skip
end
local f = ("%s%s = %s"):format(is, keys(k, i), vals(v, i))
fields[#fields + 1] = f
::skip::
end
return "{\n"..table.concat(fields, ",\n").."\n"..lastis.."}"
end
--- Construct string recreating a Lua table.
--
-- @param o (table) a Lua table.
-- @param indent (number|nil) optional initial indent.
-- @param mode (string|nil) one of two modes: 'strict' (default), where
-- attempt to serialize a function is an error, or
-- 'skip-functions', where functions are ignored.
--
-- @return string recreating the table, use serialize.unpack() to do so.
function serialize.pack(o, indent, mode)
if type(o) ~= 'table' then
error("Can't serialize.pack() a `"..type(o).."'.")
end
return dopack(o, indent or 1, mode)
end
--- Reconstruct Lua table from string.
--
-- @param s (string) Lua table in its string form.
-- @param chunk (string|nil) optional string providing a chunk's name
-- for better diagnostics, if left nil a default value
-- of "<serialize.unpack>" is used.
--
-- @return the reconstructed table and an error string, on success
-- the error value is nil, on failure the table is nil.
function serialize.unpack(s, chunk)
if type(s) ~= 'string' then
error("Can only serialize.unpack() strings.")
end
chunk = chunk or "<serialize.unpack>"
local fun, res = load("return "..s, chunk, 't', {})
if not fun then
return nil, res
end
local ok, o = pcall(fun)
if not ok then
return nil, o -- o is now pcall()'s error message
end
if type(o) ~= 'table' then
return nil, "[string \""..chunk.."\"] resulted in a `"..type(o).."'."
end
return o
end
return serialize