Converter between byte string and number

number_bytes.lua

-- Lua 5.1 or 5.2 table unpacker
local unpack = table.unpack or unpack

-- Bytes to unsigned integer
local function bton(s)
	local bytes, n = {s:byte(1,-1)}, 0
	for i=0, #s-1 do
		n = n + bytes[1+i] * 256^i
	end
	return n
end

-- Unsigned integer to bytes
local function ntob(n, len)
	local bytes = {}
	for i=1, len do
		bytes[i] = n % 256
		n = math.floor(n / 256)
	end
	return string.char(unpack(bytes))
end

-- Test
print(
	bton(ntob(32767, 2))
)