Number of arguments in function -- Extended with number of upvalues

args.lua

function int(t)
	return t:byte(1)+t:byte(2)*0x100+t:byte(3)*0x10000+t:byte(4)*0x1000000
end

function num_args(func)
	local ok, dump = pcall(string.dump,func)
	if (not ok) then return -1 end
	local cursor = 13
	local offset = int(dump:sub(cursor))
	cursor = cursor + offset + 13
	--Get the Parameters
	local params= dump:sub(cursor):byte()
	cursor = cursor + 1
	--Get the Variable Args flag (whether there's a ... in the param)
	local varargs= dump:sub(cursor):byte()

	return params, varargs
end

-- Usage:
num_args(function(a,b,c,d, ...) end) -- return 4, 7

--
-- Saw this gist today and remembered the following code I partially wrote for someone just a few days ago
--

function has_upvalues(func) -- cross platform by the way
	local dump = ("").dump(func); -- pretty nice, eh? 
	local int_len,size_t_len = dump:byte(8,9) 
	local bytes = {dump:byte(13, 12+size_t_len)}; -- get integer size of the name string 
	local name_len = bytes[1] 
	for i=2,#bytes do -- decode the integer 
	name_len = name_len + bytes[i]*(256^(i-1)-1) 
	end 
	local upvalue_position = 12 + size_t_len + (name_len > 0 and 1 or 0) + name_len + int_len + int_len; 
	local number_upvalues = dump:byte(upvalue_position); -- return the number of upvalues 
	return number_upvalues > 0, number_upvalues; 
end

-- usage:
local a, b;
local f0, f1, f2 = function() end,
 function() return a; end,
 function() return a, b; end

has_upvalues(f0) --> returns false, 0
has_upvalues(f1) --> returns true, 1
has_upvalues(f2) --> returns true, 2