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Builtin: Redo serialize.lua (#11427)
Features: * Support for arbitrary references, including self-referencing * Short output, references "long" strings as a bonus * Around the same speed, potentially slower if long, short keys are present * Properly works with NaN and inf
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Lars Müller
GitHub
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3 changed files with 352 additions and 216 deletions
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@ -1,205 +1,214 @@
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--- 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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-- From: https://github.com/appgurueu/modlib/blob/master/luon.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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local next, rawget, pairs, pcall, error, type, setfenv, loadstring
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= next, rawget, pairs, pcall, error, type, setfenv, loadstring
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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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local table_concat, string_dump, string_format, string_match, math_huge
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= table.concat, string.dump, string.format, string.match, math.huge
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-- Recursively counts occurences of objects (non-primitives including strings) in a table.
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local function count_objects(value)
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local counts = {}
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if value == nil then
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-- Early return for nil; tables can't contain nil
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return counts
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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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local function count_values(val)
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local type_ = type(val)
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if type_ == "boolean" or type_ == "number" then
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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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local count = counts[val]
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counts[val] = (count or 0) + 1
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if type_ == "table" then
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if not count then
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for k, v in pairs(val) do
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count_values(k)
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count_values(v)
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end
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end
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nested[x] = nil
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elseif type_ ~= "string" and type_ ~= "function" then
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error("unsupported type: " .. type_)
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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 numbers reversibly with string.format
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return string.format("%.17g", x)
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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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count_values(value)
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return counts
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end
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-- Deserialization
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-- Build a "set" of Lua keywords. These can't be used as short key names.
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-- See https://www.lua.org/manual/5.1/manual.html#2.1
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local keywords = {}
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for _, keyword in pairs({
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"and", "break", "do", "else", "elseif",
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"end", "false", "for", "function", "if",
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"in", "local", "nil", "not", "or",
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"repeat", "return", "then", "true", "until", "while",
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"goto" -- LuaJIT, Lua 5.2+
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}) do
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keywords[keyword] = true
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end
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local function safe_loadstring(...)
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local func, err = loadstring(...)
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if func then
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setfenv(func, {})
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return func
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local function quote(string)
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return string_format("%q", string)
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end
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local function dump_func(func)
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return string_format("loadstring(%q)", string_dump(func))
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end
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-- Serializes Lua nil, booleans, numbers, strings, tables and even functions
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-- Tables are referenced by reference, strings are referenced by value. Supports circular tables.
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local function serialize(value, write)
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local reference, refnum = "r1", 1
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-- [object] = reference string
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local references = {}
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-- Circular tables that must be filled using `table[key] = value` statements
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local to_fill = {}
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for object, count in pairs(count_objects(value)) do
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local type_ = type(object)
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-- Object must appear more than once. If it is a string, the reference has to be shorter than the string.
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if count >= 2 and (type_ ~= "string" or #reference + 2 < #object) then
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write(reference)
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write("=")
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if type_ == "table" then
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write("{}")
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elseif type_ == "function" then
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write(dump_func(object))
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elseif type_ == "string" then
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write(quote(object))
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end
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write(";")
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references[object] = reference
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if type_ == "table" then
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to_fill[object] = reference
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end
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refnum = refnum + 1
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reference = ("r%X"):format(refnum)
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end
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end
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return nil, err
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-- Used to decide whether we should do "key=..."
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local function use_short_key(key)
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return not references[key] and type(key) == "string" and (not keywords[key]) and string_match(key, "^[%a_][%a%d_]*$")
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end
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local function dump(value)
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-- Primitive types
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if value == nil then
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return write("nil")
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end
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if value == true then
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return write("true")
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end
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if value == false then
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return write("false")
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end
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local type_ = type(value)
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if type_ == "number" then
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return write(string_format("%.17g", value))
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end
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-- Reference types: table, function and string
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local ref = references[value]
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if ref then
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return write(ref)
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end
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if type_ == "string" then
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return write(quote(value))
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end
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if type_ == "function" then
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return write(dump_func(value))
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end
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if type_ == "table" then
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write("{")
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-- First write list keys:
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-- Don't use the table length #value here as it may horribly fail
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-- for tables which use large integers as keys in the hash part;
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-- stop at the first "hole" (nil value) instead
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local len = 0
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local first = true -- whether this is the first entry, which may not have a leading comma
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while true do
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local v = rawget(value, len + 1) -- use rawget to avoid metatables like the vector metatable
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if v == nil then break end
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if first then first = false else write(",") end
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dump(v)
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len = len + 1
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end
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-- Now write map keys ([key] = value)
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for k, v in next, value do
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-- We have written all non-float keys in [1, len] already
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if type(k) ~= "number" or k % 1 ~= 0 or k < 1 or k > len then
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if first then first = false else write(",") end
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if use_short_key(k) then
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write(k)
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else
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write("[")
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dump(k)
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write("]")
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end
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write("=")
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dump(v)
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end
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end
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write("}")
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return
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end
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end
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-- Write the statements to fill circular tables
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for table, ref in pairs(to_fill) do
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for k, v in pairs(table) do
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write(ref)
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if use_short_key(k) then
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write(".")
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write(k)
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else
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write("[")
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dump(k)
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write("]")
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end
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write("=")
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dump(v)
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write(";")
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end
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end
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write("return ")
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dump(value)
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end
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function core.serialize(value)
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local rope = {}
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serialize(value, function(text)
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-- Faster than table.insert(rope, text) on PUC Lua 5.1
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rope[#rope + 1] = text
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end)
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return table_concat(rope)
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end
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local function dummy_func() end
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local nan = (0/0)^1 -- +nan
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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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local func, err = loadstring(str)
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if not func then return nil, err end
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-- The environment is recreated every time so deseralized code cannot
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-- pollute it with permanent references.
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setfenv(f, {loadstring = safe and dummy_func or safe_loadstring})
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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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-- math.huge is serialized to inf, NaNs are serialized to nan by Lua
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local env = {inf = math_huge, nan = nan}
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if safe then
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env.loadstring = dummy_func
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else
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return nil, data
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env.loadstring = function(str, ...)
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local func, err = loadstring(str, ...)
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if func then
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setfenv(func, env)
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return func
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end
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return nil, err
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end
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end
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setfenv(func, env)
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local success, value_or_err = pcall(func)
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if success then
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return value_or_err
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end
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return nil, value_or_err
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end
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